Cold storage and temperature management of olive fruit: The impact on fruit physiology and olive oil quality—a review

p ocesses Re iew Cold S o age and Tempe a u e Managemen o Oli e F ui : The Impac on F ui Physiology and Oli e Oil Quali y—A Re iew Eddy Plasquy 1,* , JoséMa ía Ga cía Ma os 1, Ma ía C. Flo ido 2, Ra ael Rubén Sola-Gui ado 3 and Juan F ancisco Ga cía Ma ín4,*   Ci a ion: Plasquy, E.; Ga cía Ma os, J.M.; Flo ido, M.C.; Sola-Gui ado, R.R.; Ga cía Ma ín, J.F. Cold S o age and Tempe a u e Managemen o Oli e F ui : The Impac on F ui Physiology and Oli e Oil Quali y—A Re iew. P ocesses 2021,9, 1543. h ps://doi.o g/10.3390/p 9091543 Academic Edi o : Elwi a Sieniawska Recei ed: 4 Augus 2021 Accep ed: 27 Augus 2021 Published: 30 Augus 2021 Publishe ’s No e: MDPI s ays neu al wi h ega d o ju isdic ional claims in published maps and ins i u ional a il- ia ions. Copy igh : © 2021 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). 1 Depa men o Biochemis y and Molecula Biology o Plan P oduc s, Ins i u o de la G asa Spanish Na ional Resea ch Council, 41013 Se ille, Spain; jmga [email p o ec ed] 2Depa men o C ys allog aphy, Mine alogy and Ag icul u al Chemis y, Escuela Técnica Supe io de Ingenie ía Ag onómica, Uni e sidad de Se illa, 41013 Se ille, Spain; [email p o ec ed] 3Depa men o Mechanics, Uni e si y o Co doba, 14014 Co doba, Spain; [email p o ec ed] 4Depa amen o de Ingenie ía Química, Uni e sidad de Se illa, 41012 Se ille, Spain *Co espondence: eddy[email p o ec ed] (E.P.); [email p o ec ed] (J.F.G.M.) Abs ac : Cold s o age o oli e ui has been he subjec o s udy o o e mo e han 50 yea s. F om he 1990s on, an inc easing amoun o knowledge is build-up abou he impac o he conse a ion on he physiological esponse o he ui as well as on he quali y o he ex ac ed oil he e om. This e iew o e s a comp ehensi e synopsis o his esea ch, discusses he mos impo an in luen ial ac o s and summa izes he esul s on he in luence o he s udied pa ame e s on bo h he ui and he oil. Cu en ly, changing clima ic condi ions, new ha es ing echniques and a mo e demanding consume ma ke a e igge ing he need o b oaden his s ic ocus on conse a ion. A mo e dynamic iew on he e ec s o empe a u e om he momen he ui is ha es ed up o he oil ex ac ion p ocess, e eals he necessi y o manage his c ucial in luen ial ac o mo e di e sely. An o e iew o how his managemen can ake o m is s uc u ed h ough a ocus on he di e en phases o he pos ha es p ocessing and he widely di e en ha es ing scales. Fu u e p ospec s o esea ch a e p esen ed based on he ac ual s a e o he a o cold s o age esea ch as well as on he necessi ies ha come o wa d om a b oade ui empe a u e managemen pe spec i e. Keywo ds: oli e ui ; hea ans e ; physicochemical analysis; pos ha es ; he mal ea men ; empe a u e managemen 1. In oduc ion The In e na ional Oli e Council (IOC) de ines i gin oli e oils as “ he oils ob ained om he ui o he oli e ee (Olea eu opaea L.) solely by mechanical o o he physical means unde condi ions, pa icula ly he mal condi ions, ha do no lead o al e a ions in he oil, and which ha e no unde gone any ea men o he han washing, decan a ion, cen i uga ion and il a ion.” [ 1 ]. This de ini ion unde lines he impo ance and he s ic ela ion be ween he ui on he one side, and he ob ained oil on he o he . The quali y o he la e depends o a la ge ex en on he quali y o he o me . A he same ime, he de ini ion speci ies he need o es ic o a minimum he ea men s ha can be applied be o e and du ing he ex ac ion p ocess and explici ly poin s o he impo ance o con olling he empe a u e du ing he p ocessing. Vi gin oli e oils a e di e en ia ed in o Ex a i gin oli e oil (EVOO), i gin oli e oil (VOO), o dina y i gin oli e oil (OVOO) and lamp oil (LOO) [ 1 ]. EVOO is ega ded as he oli e oil wi h he highes quali y. I has a ee acidi y, exp essed as oleic acid, o no mo e han 0.8 g pe 100 g (0.8%) besides o he cha ac e is ics ha co espond o hose ixed o each ca ego y in he IOC s anda ds. In he case o VOO, a maximum le el o 2.0% ee a y acids (FFA) is ole a ed and 3.5% in he case o OVO. LOO’s ha e a FFA o mo e han 3.3%. Mo eo e , an e alua ion by skilled as e s is manda o y and based on he absence P ocesses 2021,9, 1543. h ps://doi.o g/10.3390/p 9091543 h ps://www.mdpi.com/jou nal/p ocesses P ocesses 2021,9, 1543 2 o 34 (ex a i gin) o he weak p esence ( i gin) o senso y de ec s and p esence o h ee posi i e a ibu es: ui iness, bi e ness and pungency. The applied ha es ing me hod and he en i onmen al condi ions du ing he p e- p ocessing s o age o oli e ui a e c ucial ac o s in main aining he quali y o he ui . Fo mo e han 30 yea s, bo h aspec s ha e been s udied in ensi ely using he o icial physicochemical pa ame e s and senso y e alua ions ha de e mine he quali y o he oils and he impac o he applied ea men s. The g owing economic impo ance o p emium oli e oils u he igge ed ine- uned s udies in which mo e sophis ica ed a iables and analyses we e in oduced o di e en ia e be ween oli e oils ha comply wi h he o icial EVOO s anda ds and hose ha aspi e o an e en highe quali y. The s o age o oli e ui has been in es iga ed using di e en a ie ies, empe a u es, conse a ion imes and con olled a mosphe es. The ocus on he cold s o age o oli e ui was ini ially d i en by he need o inding a solu ion o a logis ic p oblem, namely he managing o an inc easing amoun o ui ha needed o be p ocessed as quickly as possible. S o ing he ui unde op imum condi ions was p esen ed as an al e na i e ha allows he use o he a ailable equipmen , a oiding signi ican in es men s. La e , a ious s udies p obed he possibili y o modi ying he speci ic cha ac e is ics o he oli e oil, such as he bi e ness and con en o polyphenols, by cooling o hea ing he ui jus be o e o a e being g ound. Mo e ecen ly, a en ion is b ough o he possibili ies o ine- une he empe a u e o he pas e be o e en e ing he malaxe o op imize no only he malaxing p ocess bu also o co ec oo high o oo low ui empe a u es. The la e necessi y is becoming mo e and mo e ele an as he indus y copes wi h ui ha es ed a ield empe a u es ha a e oo high o ideal ex ac ion. A he same ime, high ield empe a u es can induce e men a ion p ocesses du ing anspo , especially when en ila ion wi hin he con aine is educed. The published s udies in which he con ol o he empe a u e du ing he pos -ha es and p e-p ocessing s ages came o play a c ucial ole hus no only inc eased du ing he las decade bu also b ough he possibili ies o he mal modi ica ion mo e o he o e. Shi ing om cold s o age o se e al weeks o he necessi y o con ol and co ec he ui o pas e empe a u e du ing i s p ocessing, opened a ious lines o esea ch in which he possibili ies o dynamically modi y he ui empe a u e be o e hei p ocessing a e a cen al ocus. Simul aneously, new echnologies a e needed o inco po a e his new challenge in he ac ual oli e ui ha es ing and p ocessing. This e iew aims o p esen a comp ehensi e o e iew o he a ailable li e a u e conce ning cold s o age o oli e ui along wi h an ou line o he ad an ages ha dy- namic con ol o he oli e ui empe a u e can o e and he una oidable echnological challenges such a shi ine i ably implies. A e a his o ical o e iew o he p og ess in his ield, he mos impo an independen a iables ha in e e e in he cold s o age o oli e ui a e discussed as well as he ac ual s a e o he a conce ning he chemical and physiological esponses o oli e ui and he physicochemical cha ac e is ics o he oil ex ac ed om cold-s o ed oli es. In a hi d chap e , he ocus is b ough owa ds ui empe a u e managemen as a no el amewo k o es ablish new echnological challenges and oppo uni ies. 2. Cold S o age: An His o ical O e iew The i s s udies conce ning he conse a ion o oli e ui we e published in he 1960s. Resea che s o he Uni e si y o Cali o nia en isioned he p ocessing o able oli es and s udied he ipening and he s o age o his ui [ 2 – 4 ]. Thei i s aim was o de ine he lowes pe missible empe a u e o s o age while a oiding chilling inju ies. Secondly, hey explo ed he possibili ies o apply a con olled a mosphe e du ing s o age. The expe imen s led o he conclusion ha al e ing he oxygen and ca bon dioxide concen a ions a ound he ui inc eased hei suscep ibili y o chilling inju y [ 3 ]. F om 1965 on, he s o age o oli e ui o oil ex ac ion was ackled by I alian esea che s wo king in he Ins i u o di Indus ie Ag a ie dell’Uni e si ádi Pe ugia [ 5 , 6 ]. Awa e o he de e io a ion o he P ocesses 2021,9, 1543 3 o 34 oli e ui du ing s o age hey ocused on wo causes: he ui cons i uen s and he con amina ion by lipoly ic mic oo ganisms. The ola ile and phenolic compounds o oli e ui p ocessed immedia ely a e ha es and s o ed a ambien empe a u e o 10 days we e compa ed [ 7 ] and poin ed o he loss o hese componen s because o hyd oly ic enzyma ic mechanisms. The po en ial solu ions a ied om inac i a ion o ui enzymes, dehyd a ion, he use o ine gas a mosphe es o ammonia; imme sion in o sal and acidic solu ions, o ea men wi h ungicides o an ibio ics [ 5 – 8 ]. Howe e , and qui e ema kably gi en he ea lie published wo k [ 2 – 4 ], cold s o age was no men ioned as a possible ea men . Meanwhile, a he Uni e si y o Cali o nia, he use o Con olled A mosphe es (CA) a a ious empe a u es was u he e alua ed in o de o main ain he quali y o he ui o ex end he pos -ha es li e o ‘Manzanillo’ oli es and unde lined he po en ial o s o e oli e ui a 5 ◦C a 2% O2 o up o abou 12 weeks [9]. I is only om he 1990s ha an inc easing in e es in he cold s o age o oli e ui o oil ex ac ion ook o m, esul ing in a con inuous inc easing in published pape s on he opic om he 90s up o da e (Figu e 1). P ocesses 2021, 9, x FOR PEER REVIEW 3 o 34 Ins i u o di Indus ie Ag a ie dell’Uni e si á di Pe ugia [5,6]. Awa e o he de e io a ion o he oli e ui du ing s o age hey ocused on wo causes: he ui cons i uen s and he con amina ion by lipoly ic mic oo ganisms. The ola ile and phenolic compounds o oli e ui p ocessed immedia ely a e ha es and s o ed a ambien empe a u e o 10 days we e compa ed [7] and poin ed o he loss o hese componen s because o hyd oly ic en- zyma ic mechanisms. The po en ial solu ions a ied om inac i a ion o ui enzymes, dehyd a ion, he use o ine gas a mosphe es o ammonia; imme sion in o sal and acidic solu ions, o ea men wi h ungicides o an ibio ics [5–8]. Howe e , and qui e ema ka- bly gi en he ea lie published wo k [2–4], cold s o age was no men ioned as a possible ea men . Meanwhile, a he Uni e si y o Cali o nia, he use o Con olled A mosphe es (CA) a a ious empe a u es was u he e alua ed in o de o main ain he quali y o he ui o ex end he pos -ha es li e o ‘Manzanillo’ oli es and unde lined he po en ial o s o e oli e ui a 5 °C a 2% O2 o up o abou 12 weeks [9]. I is only om he 1990s ha an inc easing in e es in he cold s o age o oli e ui o oil ex ac ion ook o m, esul ing in a con inuous inc easing in published pape s on he opic om he 90s up o da e (Figu e 1). Figu e 1. Numbe and ype o wo ks o analysis, unde ai and con olled a mosphe e, published be ween 1990 and 2021. The pi o al wo k o Ga cía and S ei [10], published in 1991, was ollowed wi h 8 mo e publica ions in he ollowing 4 yea s, all belonging o a esea ch g oup o he Ins i- u o de la G asa (CSIC) o Se illa. Thei ocus included he e ec o cold s o age and CA du ing cold s o age on he ui as well on he ex ac ed oil [11–14]. F ui quali y pa ame- e s and oil quali y pa ame e s (FFA, pe oxides, K232 and K270, oxida i e s abili y and senso y analysis) we e measu ed, while mo e speci ic publica ions indica ed shi s in po- la compound concen a ions [15], and changes in polyphenol con en [16] when s o ed unde di e en condi ions. Whils he ad an ages o cold s o age became mo e and mo e clea a labo a o y scale, a en ion was b ough o he limi a ions o he used s o age sys- em especially when s o age o e mo e han 15 days in con aine s o 400 kg was en i- sioned [17,18]. In he ollowing yea s, he expe imen s we e scaled up o an indus ial le el and ca ied ou on wo di e en a ie ies, ‘Blanque a’ and ‘Villalonga’ [19–22]. The esul s con i med he ad an ages o cold s o age and i s po en ial o imp o ing he p o- cessing. A he same ime, i unde lined he need o speci ic equi emen s, such as an adequa e cooling ins alla ion o s o e he ui ha canno be p ocessed immedia ely, he capabili y o enew he ai o a oid he accumula ion o CO2, speci ic ma e ial, and ma- chine y o handle he boxes and he supply o undamaged ui . In he knowledge ha Figu e 1. Numbe and ype o wo ks o analysis, unde ai and con olled a mosphe e, published be ween 1990 and 2021. The pi o al wo k o Ga cía and S ei [ 10 ], published in 1991, was ollowed wi h 8 mo e publica ions in he ollowing 4 yea s, all belonging o a esea ch g oup o he Ins i u o de la G asa (CSIC) o Se illa. Thei ocus included he e ec o cold s o age and CA du ing cold s o age on he ui as well on he ex ac ed oil [ 11 – 14 ]. F ui quali y pa ame e s and oil quali y pa ame e s (FFA, pe oxides, K232 and K270, oxida i e s abili y and senso y analysis) we e measu ed, while mo e speci ic publica ions indica ed shi s in pola compound concen a ions [ 15 ], and changes in polyphenol con en [ 16 ] when s o ed unde di e en condi ions. Whils he ad an ages o cold s o age became mo e and mo e clea a labo a o y scale, a en ion was b ough o he limi a ions o he used s o age sys em especially when s o age o e mo e han 15 days in con aine s o 400 kg was en isioned [ 17 , 18 ]. In he ollowing yea s, he expe imen s we e scaled up o an indus ial le el and ca ied ou on wo di e en a ie ies, ‘Blanque a’ and ‘Villalonga’ [19–22] . The esul s con i med he ad an ages o cold s o age and i s po en ial o imp o ing he p ocessing. A he same ime, i unde lined he need o speci ic equi emen s, such as an adequa e cooling ins alla ion o s o e he ui ha canno be p ocessed immedia ely, he capabili y o enew he ai o a oid he accumula ion o CO 2 , speci ic ma e ial, and machine y o handle he boxes and he supply o undamaged ui . In he knowledge ha each deg ee highe han 5 ◦ C implies a signi ican educ ion o ene gy cos s, an expe imen a a pilo -scale demons a ed ha b inging he empe a u e om 5 o 8 ◦ C would esul in signi ican di e ences in ui ipening and oli e oil quali y [20]. Meanwhile, I alian esea che s buil on he wo k o [ 7 ] and speci ied ha o op imize he quali y o he oil in ela ion o he le el o ipeness and s o age ime, he la e could P ocesses 2021,9, 1543 4 o 34 be s o ed up o a maximum o 6 days and e en sho e when dealing wi h ipe oli e [ 23 ]. A local a ie y om no heas I aly was used o ocus on he e ec o hypoxic and CO 2 en iched a mosphe es on oli e ipening and oil quali y [ 24 ]. As an al e na i e o cold s o - age, Kop i njak e al. assessed an ancien conse a ion me hod om C oa ia ha consis ed o keeping he oli e ui in seawa e , a me hod ha was p e iously men ioned by o he au ho s [5,6], only o conclude ha al hough he basic physicochemical quali y indica o s did no change signi ican ly, he senso y cha ac e is ics we e a ec ed d ama ically [25]. The pionee ing wo k o he g oup om he Ins i u o de la G asa inspi ed esea che s o design s o age expe imen s wi h o he a ie ies, modi ying he empe a u e and he a mosphe e. Signi ican in e cul i a di e ences we e obse ed be ween ‘Se illa’ and ‘Mission’ cul i a s on he hand, and ‘Manzanillo’ and ‘Ascolano’ on he o he hand [ 26 ]. While he o me could be s o ed up o 8 weeks a 5 ◦ C, he la e only las ed 4 weeks a he same empe a u e. A s udy on he ‘Ko oneiki’ a ie y and designed a ine- uned s udy in which he ui was kep a 0, 5 and 7.5 ◦ C while modi ying he a mosphe e a he same ime [ 27 ]. They con i med he ea lie conclusions ha cold s o age a 7.5 ◦ C esul ed in low quali y and could la gely be a ibu ed o he de elopmen o ungus [ 20 ]. In line wi h he obse a ions o Maxie, s o age a 0 ◦ C was nei he ecommended because o he isk o chilling inju ies [ 3 ]. In he ollowing decades, he po en ial o cold s o age oli e ui was e alua ed and con i med by Cali o nian [ 26 , 28 ], Aus alian [ 29 ]; Is aelian [ 30 ], I al- ian [ 31 – 35 ], Spanish [ 36 – 46 ], Po uguese [ 47 ], Egyp ian [ 48 ], Tunisian [ 49 – 54 ], Tu kish [ 55 ], I anian [ 56 , 57 ] and C oa ian [ 58 ] esea ch cen e s, which used mos o he ime he local cul i a s o hei expe imen s. Thus a , a o al o 38 a ie ies has been he subjec o an expe imen ela ed o he conse a ion and cold s o age o oli es (Figu e 2). P ocesses 2021, 9, x FOR PEER REVIEW 4 o 34 each deg ee highe han 5 °C implies a signi ican educ ion o ene gy cos s, an expe imen a a pilo -scale demons a ed ha b inging he empe a u e om 5 o 8 °C would esul in signi ican di e ences in ui ipening and oli e oil quali y [20]. Meanwhile, I alian esea che s buil on he wo k o [7] and speci ied ha o op imize he quali y o he oil in ela ion o he le el o ipeness and s o age ime, he la e could be s o ed up o a maximum o 6 days and e en sho e when dealing wi h ipe oli e [23]. A local a ie y om no heas I aly was used o ocus on he e ec o hypoxic and CO2 en- iched a mosphe es on oli e ipening and oil quali y [24]. As an al e na i e o cold s o age, Kop i njak e al. assessed an ancien conse a ion me hod om C oa ia ha consis ed o keep- ing he oli e ui in seawa e , a me hod ha was p e iously men ioned by o he au ho s [5,6], only o conclude ha al hough he basic physicochemical quali y indica o s did no change signi ican ly, he senso y cha ac e is ics we e a ec ed d ama ically [25]. The pionee ing wo k o he g oup om he Ins i u o de la G asa inspi ed esea che s o design s o age expe imen s wi h o he a ie ies, modi ying he empe a u e and he a mosphe e. Signi ican in e cul i a di e ences we e obse ed be ween ‘Se illa’ and ‘Mission’ cul i a s on he hand, and ‘Manzanillo’ and ‘Ascolano’ on he o he hand [26]. While he o me could be s o ed up o 8 weeks a 5 °C, he la e only las ed 4 weeks a he same empe a u e. A s udy on he ‘Ko oneiki’ a ie y and designed a ine- uned s udy in which he ui was kep a 0, 5 and 7.5 °C while modi ying he a mosphe e a he same ime [27]. They con i med he ea lie conclusions ha cold s o age a 7.5 °C esul ed in low quali y and could la gely be a ibu ed o he de elopmen o ungus [20]. In line wi h he obse a ions o Maxie, s o age a 0 °C was nei he ecommended because o he isk o chilling inju ies [3]. In he ollowing decades, he po en ial o cold s o age oli e ui was e alua ed and con i med by Cali o nian [26,28], Aus alian [29]; Is aelian [30], I alian [31–35], Spanish [36–46], Po uguese [47], Egyp ian [48], Tunisian [49–54], Tu kish [55], I anian [56,57] and C oa ian [58] esea ch cen e s, which used mos o he ime he local cul i a s o hei expe imen s. Thus a , a o al o 38 a ie ies has been he subjec o an expe imen ela ed o he conse a ion and cold s o age o oli es (Figu e 2). Figu e 2. Va ie ies used in cold s o age expe imen s and he numbe o a ie ies pe s udy. Figu e 2. Va ie ies used in cold s o age expe imen s and he numbe o a ie ies pe s udy. The ‘Picual’ and ‘A bequina’ s and ou as he mos s udied a ie ies wi h 18 and 12 ex- pe imen s, espec i ely, ollowed by ‘Chemlali’ (5), ‘Ché oui’ (4); ‘F an oio’ (4), ‘Ko oneiki’ (4) and ‘Manzanillo’ (4) cul i a s. Mo e han hal o he a ie ies appea ed only in one expe imen (22). 60% o he expe imen s we e ealized wi h 1 cul i a , and 24 and 14% wi h, espec i ely, 2 and 3 cul i a s. Only one s udy ook 4 a ie ies in o accoun (Figu e 2). The mo e han 60 published s udies since he pi o al wo k o Ga cía e al. [ 10 ] a e no e enly dis ibu ed o e ime bu came in h ee wa es (Figu e 1). The i s one was in he 1990s, du ing which he p ospec o cold s o age was e alua ed o ime spans P ocesses 2021,9, 1543 5 o 34 up o 90 days and whe e he majo i y o he s udies assessed he possibili ies o CA. A second boos o s udies a ose om 2005 on, when CA became less p ominen , and he mean maximum s o age ime was educed o 30 days. Be ween 2015 and 2021 he numbe o publica ions doubled, while only ma ginal a en ion was gi en o CA, and he s o age ime was u he educed. F om he second wa e on, he ype o analysis became no only mo e di e en ia ed wi h an inc easing ocus on he phenolic and ola ile compounds (Figu e 1) bu also mo e ocused on he ha es ing me hod. The las is in la ge pa due o he p og essi e mechaniza ion and he in oduc ion o o e head mechanical ha es e s in high-densi y o cha ds. The b oadening and he deepening o he esea ch we e mainly pe o med a he labo a o y le el, dealing wi h small quan i ies o ui o keep he explana o y a iables unde s ic con ol. E en hough a ew expe imen s we e pe o med a a pilo -plan le el and indus ial le el, cold s o age has ne e been inco po a ed in o he daily wo kings o an ac ual mill. The absence o he modynamic s udies o calcula e he ene gy cos and economic s udies o es ima e he ull size o a cold s o age in es men a an indus ial le el is in his espec s iking bu no su p ising. A he ime he al e na i e o e ed by cold s o age was published, new ex ac ion lines we e al eady on he ma ke , allowing mills o inc ease hei milling capaci y easily. The p ospec o modi y he senso y cha ac e is ics o he ex ac ed oil h ough he - mal ea men o he oli e ui was sugges ed once i became clea ha he amoun o polyphenols in he oil was suscep ible o empe a u e. Howe e , expe imen s a labo a o y as well as pilo plan scale, e ealed ha con olling he condi ions o a ain a desi ed le el o bi e ness was ex emely di icul , i no impossible, gi en he in luence o he ui cul i a , hei ipeness and hei o igin. A he same ime, an inadequa e applica ion p o oked a dena u aliza ion o he ui s uc u e and undesi able emulsions du ing he malaxing [38,59–63]. Recen ly, he ad an ages o cold s o age o small p oduce s we e b ough o he a - en ion. Keeping ha es ed oli es a 5 ◦ C o a sho ime, o e ed a solu ion o p ese e he quali y o he ui un il he necessa y quan i y o anspo o he mill was eached. Com- bined wi h a gen le ha es ing me hod, he e ige a ion me hod made i possible o ex ac high-quali y oil wi hou disp opo iona e in es men s [ 45 , 46 ]. Cooling he ui a he a m o a sho e m opens up new possibili ies o e alo ize he ad an ages o cold s o age. Meanwhile, clima ological changes and ea lie ha es s, especially o hose a ie ies ha a e plan ed in high-densi y o cha ds, igge new que ies in which he managemen o he ui empe a u e is coming o he o e as a key ac o . The accumula ed knowledge conce ning cold s o age did o m a c ucial elemen o add ess hese new challenges. 3. Explana o y Va iables 3.1. S o age Tempe a u e In 80% o he s udies, he empe a u e o he cold s o age expe imen s was kep a 4–6 ◦ C, ollowing he ecommenda ion gi en in ea lie wo ks o espec he 5 ◦ C limi o a oid chilling inju ies [ 3 , 4 , 9 ]. Howe e , he con ol empe a u e a ied signi ican ly be ween 15 and 25 ◦C in 75% o he cases, conside ed as ambien empe a u e (Figu e 3). This wide ange is pa ly explained because se e al s udies ook he mean maximum day and nigh empe a u es in o accoun o egis e ed he empe a u es o e longe s o - ages imes. A mino i y o s udies used in e media e empe a u es o 8 ◦ C [ 17 , 18 , 20 ] and 10 ◦C [30,48]. Mos o he published s udies epo ed ha he quali y o he ui and/o ex ac ed oil we e signi ican ly lowe when compa ed o a lowe empe a u e o e he same s o age ime. Ye , i was also sugges ed ha ‘Picual’ and ‘Ko oneiki’ cul i a can be s o ed a 10 ◦ C o e en a oom empe a u e o 9 days wi hou much educ ion in oil quali y [ 30 ]. A ew s udies looked a he possibili ies o keep he ui a lowe empe a u es. Black ‘Manzanillo’ oli es we e s o ed a 0, 2.2 and 5 ◦ C o 6 weeks bu , al hough no chilling inju ies we e obse ed, he oil ex ac ed a e 4 weeks o s o age los i s quali y as EVOO [ 28 ]. Mechanically and P ocesses 2021,9, 1543 6 o 34 manually ha es ed oli es o he ‘A bequina’ a ie y, kep a 3 ◦ C o 21 days nei he p esen ed chilling inju ies [ 39 ]. ‘Manzanilla de Se illa’ and he ‘Manzanilla Cace eña’ a ie ies we e s o ed a 2 ◦ C o 11 days in he bes condi ions wi hou chilling damage [ 43 ]. P ocesses 2021, 9, x FOR PEER REVIEW 6 o 34 Figu e 3. Tempe a u es use du ing se e al expe imen s o cold s o age. This wide ange is pa ly explained because se e al s udies ook he mean maximum day and nigh empe a u es in o accoun o egis e ed he empe a u es o e longe s o - ages imes. A mino i y o s udies used in e media e empe a u es o 8 °C [17,18,20] and 10 °C [30,48]. Mos o he published s udies epo ed ha he quali y o he ui and/o ex ac ed oil we e signi ican ly lowe when compa ed o a lowe empe a u e o e he same s o age ime. Ye , i was also sugges ed ha ‘Picual’ and ‘Ko oneiki’ cul i a can be s o ed a 10 °C o e en a oom empe a u e o 9 days wi hou much educ ion in oil quali y [30]. A ew s udies looked a he possibili ies o keep he ui a lowe empe a u es. Black ‘Man- zanillo’ oli es we e s o ed a 0, 2.2 and 5 °C o 6 weeks bu , al hough no chilling inju ies we e obse ed, he oil ex ac ed a e 4 weeks o s o age los i s quali y as EVOO [28]. Mechanically and manually ha es ed oli es o he ‘A bequina’ a ie y, kep a 3 °C o 21 days nei he p esen ed chilling inju ies [39]. ‘Manzanilla de Se illa’ and he ‘Manza- nilla Cace eña’ a ie ies we e s o ed a 2 °C o 11 days in he bes condi ions wi hou chilling damage [43]. S o age a 0 °C was de imen al due o he des uc ion o he na u al an ioxidan s p esen in he oli e ui , leading o a diminishing o he oxida ion esis ance [27]. In e - es ingly, oils ob ained om ‘A bequina’, ‘Ko oneiki’ and ‘Mission’ cul i a s ha we e kep a −4 °C o up o 3 weeks, main ained he s anda d indices used o assessing i gin oli e oil quali y [64]; howe e , he amoun s o FFA in he s udied samples we e no indi- ca ed in ha s udy. A e 24 h a −18 °C, a nega i e e ec was ound on he oxida i e s abili y o VOO due o oli e ui eezing [65]. I is sugges ed ha wi hou hawing ou he ui be o e malaxa ion, he ac i i y o oxida i e enzymes is educed. Oli e eezing signi ican ly modi ied he phenolic and ola ile p o iles o VOO om ‘Picual’ and ‘A be- quina’ cul i a s [66]. Simila esul s we e ob ained a e s o ing oli e ui a −25 °C o 6 mon hs [67]. Howe e , hey unde lined ha he ex ac ed oils me he s anda d comme - cial pa ame e s o EVOO’s while indica ing ha he senso ial de ec s may also be ela ed o mic obial ac i i y. I was sugges ed ha an oli e sani iza ion ea men could possibly o e come his p oblem. The ‘Ko oneiki’ cul i a was kep o up o 60 days a −18, 5 and 20 °C, showing no nega i e e ec o s o age o oli e samples a −18 °C in he ex ac ed oil based on he le els o acidi y and pe oxide alues [57]. A e 7 days s o ed a 4 °C, he wo C oa ian cul i a s, ‘Is a ska Bjelica’ and ‘Rosinjola’, p ese ed he concen a ion o mos phenolic compounds a le els ha we e compa able wi h esh oil [58]. A dec ease in sen- so y quali y was obse ed a e s o age a oom empe a u e and −20 °C, leading o he Figu e 3. Tempe a u es use du ing se e al expe imen s o cold s o age. S o age a 0 ◦ C was de imen al due o he des uc ion o he na u al an ioxidan s p esen in he oli e ui , leading o a diminishing o he oxida ion esis ance [ 27 ]. In e es - ingly, oils ob ained om ‘A bequina’, ‘Ko oneiki’ and ‘Mission’ cul i a s ha we e kep a − 4 ◦ C o up o 3 weeks, main ained he s anda d indices used o assessing i gin oli e oil quali y [ 64 ]; howe e , he amoun s o FFA in he s udied samples we e no indica ed in ha s udy. A e 24 h a − 18 ◦ C, a nega i e e ec was ound on he oxida i e s abili y o VOO due o oli e ui eezing [ 65 ]. I is sugges ed ha wi hou hawing ou he ui be o e malaxa ion, he ac i i y o oxida i e enzymes is educed. Oli e eezing signi ican ly modi ied he phenolic and ola ile p o iles o VOO om ‘Picual’ and ‘A bequina’ cul i- a s [ 66 ]. Simila esul s we e ob ained a e s o ing oli e ui a − 25 ◦ C o 6 mon hs [ 67 ]. Howe e , hey unde lined ha he ex ac ed oils me he s anda d comme cial pa ame e s o EVOO’s while indica ing ha he senso ial de ec s may also be ela ed o mic obial ac i i y. I was sugges ed ha an oli e sani iza ion ea men could possibly o e come his p oblem. The ‘Ko oneiki’ cul i a was kep o up o 60 days a − 18, 5 and 20 ◦ C, showing no nega i e e ec o s o age o oli e samples a − 18 ◦ C in he ex ac ed oil based on he le els o acidi y and pe oxide alues [ 57 ]. A e 7 days s o ed a 4 ◦ C, he wo C oa ian cul i a s, ‘Is a ska Bjelica’ and ‘Rosinjola’, p ese ed he concen a ion o mos phenolic compounds a le els ha we e compa able wi h esh oil [ 58 ]. A dec ease in senso y quali y was obse ed a e s o age a oom empe a u e and − 20 ◦ C, leading o he conclusion ha , unde p oduc ion condi ions, e ige a ion is he mos sui able op ion when p olonged ui s o age is aken in o conside a ion [58]. 3.2. S o age Time The s o age ime is a a iable o majo impo ance when he e ec s o cold s o age on he physiology o he ui as well as he quali y o he ex ac ed oils he e om a e examined (Figu e 4). The e ec o he s o age ime on he quali y pa ame e s, and especially on he FFA, is p o oundly s udied and con i med o a wide ange o a ie ies. P ocesses 2021,9, 1543 7 o 34 P ocesses 2021, 9, x FOR PEER REVIEW 7 o 34 conclusion ha , unde p oduc ion condi ions, e ige a ion is he mos sui able op ion when p olonged ui s o age is aken in o conside a ion [58]. 3.2. S o age Time The s o age ime is a a iable o majo impo ance when he e ec s o cold s o age on he physiology o he ui as well as he quali y o he ex ac ed oils he e om a e examined (Figu e 4). The e ec o he s o age ime on he quali y pa ame e s, and espe- cially on he FFA, is p o oundly s udied and con i med o a wide ange o a ie ies. When in he 1990’s he in e es in cooling oli e ui ook o m, imespans up o 3 mon hs we e used o ollow he o icial quali y pa ame e s o he oli e oil [10,17,27,68,69]. Once i became clea ha cold s o age o mo e han one mon h esul ed in p oblema ic ui quali y and de icien oils, he maximum s o age ime was educed and he obse a- ions we e made wi hin sho e in e als [29–31,45,46,49,51–53,70]. Moni o ing he amoun o polyphenolic and ola ile compounds in he s o ed oils, igge ed e en mo e p ecise obse a ions o only se e al weeks and be ween days [34,40–42,58]. Mo e e- cen ly, he e ec o sho - e m s o age o less han one day is acqui ing a en ion as a ool o modula e he a oma p o ile o he oil [71]. Figu e 4. Maximum days o s o age conside ed in he expe imen s be ween 1990 and 2021. 3.3. Use o Con olled A mosphe e The p ospec o con ol he a mosphe e o enla ge he s o age ime while gua an ee- ing he quali y o he ui was ex ensi ely es ed o able oli es as well as o mill oli es. Inc easing he concen a ion o CO2 and/o he dec ease o O2 allows, on he one hand, con ol o he de elopmen o ui ma u a ion and pa hogenic p oli e a ion and can delay he physiological changes due o chilling sensi i e c ops on he o he [72]. On he o he hand, hese a mosphe es can a he same ime induce o he physiological diso de s and e en agg a a e chilling inju ies o speci ic commodi ies. The ea ly expe imen s a Da is we e designed o e alua e he e ec s o con olled a mosphe e (CA) on oli e ui . Oli es o he ‘Manzanillo’ and ‘Mission’ cul i a s kep a 3.8 °C (39 °F) s o ed unde low O2 and high CO2 concen a ions we e se e ely inju ed ui due o chilling damage [2]. A he same ime and based on colo change, he e was a clea indica ion o delaying ipening. ‘Manzanillo’ oli es s o ed unde di e en empe a u es and le els o 5% o CO2 caused in e nal inju ies, while s o age a 2% O2 e a ded ui Figu e 4. Maximum days o s o age conside ed in he expe imen s be ween 1990 and 2021. When in he 1990’s he in e es in cooling oli e ui ook o m, imespans up o 3 mon hs we e used o ollow he o icial quali y pa ame e s o he oli e oil [ 10 , 17 , 27 , 68 , 69 ]. Once i became clea ha cold s o age o mo e han one mon h esul ed in p oblema ic ui quali y and de icien oils, he maximum s o age ime was educed and he obse a ions we e made wi hin sho e in e als [ 29 – 31 , 45 , 46 , 49 , 51 – 53 , 70 ]. Moni o ing he amoun o polyphenolic and ola ile compounds in he s o ed oils, igge ed e en mo e p ecise obse a ions o only se e al weeks and be ween days [ 34 , 40 – 42 , 58 ]. Mo e ecen ly, he e ec o sho - e m s o age o less han one day is acqui ing a en ion as a ool o modula e he a oma p o ile o he oil [71]. 3.3. Use o Con olled A mosphe e The p ospec o con ol he a mosphe e o enla ge he s o age ime while gua an eeing he quali y o he ui was ex ensi ely es ed o able oli es as well as o mill oli es. Inc easing he concen a ion o CO 2 and/o he dec ease o O 2 allows, on he one hand, con ol o he de elopmen o ui ma u a ion and pa hogenic p oli e a ion and can delay he physiological changes due o chilling sensi i e c ops on he o he [ 72 ]. On he o he hand, hese a mosphe es can a he same ime induce o he physiological diso de s and e en agg a a e chilling inju ies o speci ic commodi ies. The ea ly expe imen s a Da is we e designed o e alua e he e ec s o con olled a mosphe e (CA) on oli e ui . Oli es o he ‘Manzanillo’ and ‘Mission’ cul i a s kep a 3.8 ◦ C (39 ◦ F) s o ed unde low O 2 and high CO 2 concen a ions we e se e ely inju ed ui due o chilling damage [ 2 ]. A he same ime and based on colo change, he e was a clea indica ion o delaying ipening. ‘Manzanillo’ oli es s o ed unde di e en empe a u es and le els o 5% o CO 2 caused in e nal inju ies, while s o age a 2% O 2 e a ded ui so ening and colo changes [ 9 ]. Two G eek a ie ies o able oli es, s o ed a 5 ◦ C, de eloped skin inju ies a e p olonged s o age a high CO 2 concen a ions, wi h o wi hou low O 2 . A signi ican di e ence was obse ed be ween he a ie ies, wi h ‘Chond olia’ being highly sensi i e o chilling inju y and ‘Conse olea’ ha ing he po en ial o be s o ed a 7.5 ◦C o up o 3 weeks unde CA condi ions [68,69]. The possibili y o applying CA o op imize he cold s o age o mill oli es was one o he main objec i es o he esea ch g oup o he Ins i u o de la G asa o Se ille (Figu e 1) . Thei expe imen s all led o he conclusions ha CA induced physiological diso de s ha acili a ed ui decay [ 10 – 15 ]. Oil ex ac ed om hese ui s esul ed in poo quali y le els, cha ac e ized by high acidy le els and senso ial de ec s. The esul s we e con i med by o he au ho s, epo ing he bes esul s a e 30 days unde ai a 5 ◦ C [ 27 ]; he lowes P ocesses 2021,9, 1543 8 o 34 panel es sco es we e ob ained o oils ex ac ed om ui kep du ing 11 days unde low O 2 and high CO 2 concen a ions [ 62 ]; se e al con en ional and noncon en ional analysis led o he conclusion ha CA did no p oduce any ema kable ad an age o e s o age a 5 ◦ C [ 31 , 32 ]. In he ligh o his e idence, he esul s ob ained a e he s o age o Tu kish ‘Gemlik’ oli es unde CO 2 a e qui e su p ising, as he ea men p o ec ed hei physical p ope ies up o 25 days, whils he quali y pa ame e s we e no a ec ed, and no signi ican e ec on he phenolic and a y acid composi ion o he ex ac ed oil we e de ec ed [55]. 3.4. Cul i a E en hough he in e a ie al compa ison among di e en expe imen s is o en com- plica ed, i no impossible, due o o he in e e ing ac o s such as di e en empe a u e, ipeness o s o age condi ions, su icien s udies do illus a e he signi ican e ec o he gene ic ac o on he quali y o he ui and he oils ex ac ed om oli es ha we e cold- s o ed. ‘Villalonga’ and ‘Blanque a’ a ie ies showed signi ican di e ences be ween de le els o FFA o bo h cul i a s when s o ed o mo e han 20 days a 5 ◦ C [ 19 ]. ‘Manzanillo’ and ‘Ascolano’ could be s o ed up a 5 ◦ C o 2 and 4 weeks, while ‘Mission’ and ‘Se il- lano’ a ie ies could be kep in good ui condi ion up o 6–8 weeks [ 26 ]. Compa ing he Po uguese cul i a s ‘Cob ançosa’, ‘Madu al’ and ‘Ve deal T ansmon ana’, ‘Ve deal T ansmon ana’ de e io a ed he mos apidly, while ‘Cob ançosa’ showed he bes esul s in oil quali y a e cold s o age op 14 days [ 47 ]. A signi ican di e ence in he bi e ness in ensi y was obse ed among he ‘Manzanilla’, ‘Picual’ and ‘Ve dial’ a ie ies when s o ed a 5 ◦ C o 8 weeks [ 38 ]. Di e ences in he le els o decay as well as FFA we e epo ed o h ee I alian cul i a s (‘Co a ina’, ‘Olgia ola leccese’ and ‘Leccino’) [ 32 ], while he e ec o s o age empe a u e and ime on he oil quali y o mechanically ha es ed oli es om h ee a ie ies, ‘Ko eneiki’, ‘Picual’ and Ba nea’ we e compa ed [ 30 ]. Signi ican di e ences be ween he ‘Manzanilla de Se illa’ and he ‘Manzanilla Cace eña’ we e obse ed in a simila s udy [ 43 ]. Di e ences on bo h he ui as well as oil cha ac e is ics o he cul i a s s udied we e con i med be ween he I alian a ie ies ‘Ca olea’ and ‘O ob a ica’ [ 34 ] and he ‘A bequina’, ‘Picual’ and ‘Ve dial’ cul i a s [45,46]. 3.5. Loading Uni The cooling p ocess o esh ui s and ege ables in ol es a complex in e ac ion be- ween he he mophysical p ope ies o he commodi y (hea gene a ion due o espi a ion, speci ic hea and he mal conduc i i y), he kind o packaging and palle iza ion, low ield pa ame e s (ai low a e and cooling empe a u e) and he accessibili y o he cooling ai o he p oduce [ 73 – 77 ]. The s o age o oli es implies keeping he ui in con aine s ha educes he physical and biological de e io a ion o a minimum. The capaci y o hese con aine s, o he quan i y o ui s o ed pe loading uni , plays a c i ical ole in he s o age e iciency o he oli es as he incidence o pos ha es losses inc eased oge he wi h he con aine ’s capaci y [ 18 , 22 ]. A e 15 days a 5 ◦ C, he decay incidence app oached 40% and a 30 days, and hal o he con aine was o en. The empe a u e in he inne zone o a con aine o 400 kg o ‘Picual’ ne e wen below 25 ◦ C. Oli es s o ed in boxes wi h a capaci y o 64 kg, a ained o e he same pe iod an incidence below 20% and showed an in e nal empe a u e o 6 ◦ C. The incidence o he ones s o ed in boxes o 2 and 6 kg, s ayed below 10% a e 45 days o s o age. Oli es kep in 400 kg con aine s ga e oils wi h signi ican ly highe acidi y alues han he ones om con aine s o 2, 6, 64 kg be o e 45 days o s o age. Simila ly, no app eciable di e ences we e epo ed in he senso ial analysis. Based on hese obse a ions, he use o boxes wi h a capaci y o 22 kg o ui was ecommended. The e ec o he laye hickness on he quali y and he composi ion o he mino componen s was equally s udied [ 40 ]. Fo up o 3 weeks, oli e ba ches ( ipening index o 4), we e s o ed a 10 and 20 ◦ C in plas ic boxes (capaci y o 50 kg o oli es) illed in di e en laye s, om monolaye , 10 cm, 20 cm o 60 cm hickness. The VOO quali y pa ame e s we e, besides being a ec ed by he s o age empe a u e and ime, also signi ican ly in luences by P ocesses 2021,9, 1543 9 o 34 he hickness o he laye . A e 5 days o s o age, he ui s o ed wi h a 60 cm hickness eached he uppe limi o he EVOO (0.8%). The sugges ion ha oli es can be s o ed o 15 days when placed in one laye a 10 ◦ C, does no o e a wo kable solu ion bu ins ead, unde line one o he bo lenecks in he cold s o age o oli e ui namely he c ucial impo ance o he loading uni . The handling o many boxes leads o la ge, i no unsu moun able logis ic p oblems once dealing wi h se e al ons. A p ecooling ea men o he ha es ed ui be o e dumping hem in a con aine o conse a ion was sugges ed and in es iga ed [ 77 ]. In a i s expe imen , he e olu ion o he in e nal empe a u e o a con aine o 400 kg was assessed wi h and wi hou a p ecooling ea men a 5 ◦ C. In a second expe imen , he e ec s o a sho cooling ea men a − 18 ◦ C o a ain apidly he desi ed 5 ◦ C was es ed. In he con aine wi h ui a a ield empe a u e o 18 ◦ C, he mean in e nal empe a u e descended owa ds 10 ◦ C du ing he i s week, ollowed by a mo e s abilized pe iod wi h empe a u es be ween 8.8 and 9 ◦ C. The con aine wi h p ecooled ui ollowed an in e se beha io . S a ing a 5 ◦ C a slow ise was se in, amoun ing o 7.6 ◦ C on day 14. The examined pa ame e s o he ex ac ed oils om bo h ea men s showed le els ha co esponded o he EVOO ca ego y, al hough he oli es ha unde wen a p ecooling ea men in small boxes, did no expe ience a signi ican inc ease in he acidi y le el a e 14 days o s o age. A compa ison wi h he published da a [ 50 ] was complica ed as nei he he in ac ness no he s a e o he ipening o he ui was p o ided. No wi hs anding, he obse ed low acidi y le els, sugges ha addi ional ac o s mus ha e exe ed a de imen al e ec on he ui . While ui a a ield empe a u e o 18 ◦ C is a he low as compa ed wi h he day empe a u es a he s a o he ha es ing campaign when ui empe a u es abo e 25 ◦C a e a om unusual. Recen ly, he ocus is b ough o he sho - e m cold s o age (16–18 h) in con aine s (pe o a ed plas ic bins), ei he illed wi h 250 kg, o hal - illed wi h 125 kg, and pe o a ed plas ic boxes wi h 20 kg o ui [ 77 ]. The su ace- o- olume a io (SVR) was 7, 10 and 16, espec i ely. Un o una ely, he used ambien empe a u e was only 13.5 ± 1 ◦ C. Thus, he s udy e alua ed he e ec o a 5–6 ◦ C all in empe a u e. A ambien empe a u e, he co e empe a u e o he boxes wi h an SVR o 10 and 16, a ained equilib ium in 6 h, while he empe a u e in bins wi h 250 kg (SVR 7) showed an inc ease which eached o e 3 ◦ C a e 18 h. Rega ding he cooled con aine s, all h ee eached he mal equilib ium, al hough he cooling a e depended on he SVR. No signi ican di e ences we e epo ed o he oil cha ac e is ics (quali y pa ame e s, phenolic compounds and VOCs). The concen a ion o CO 2 was signi ican ly highe in he e ige a ed s o age cell, while he O 2 was signi ican ly lowe , showing ha al hough he lowe empe a u e educed cellula espi a ion, la ge quan i ies o CO 2 accumula ed in oli es s o ed in con aine s ( ∼ = 1%) while O2dec eased (∼ =20%). 3.6. Ha es ing Sys em In gene al, he published a icles on he e ec s o he cold s o age condi ions on he quali y o he oli e ui and he ex ac ed oil used hand-picked oli es o hei expe imen s o ga e no in o ma ion on he ha es ing me hod used. I is only wi h he ise o mech- aniza ion and speci ically he in oduc ion o s addle machines in supe -in ensi e oli e o cha ds, ha he a en ion was b ough o he deg ee o damage ha he used ha es ing me hod could p o oke (Figu e 5). The e ec o he used ha es ing me hod on he ui cha ac e is ics and he oil quali y was b ough o he o e [ 30 ]. The s udy epo ed quali y pa ame e s o he oil (FFA, pe oxides, polyphenol con en ) a e s o age up o 23 days a 4, 10 ◦ C and ambien empe a u e. I was concluded ha , a leas o ‘Picual’, he mode niza ion did no educe he oli e’s capaci y o s o age when he esul s o [ 20 ] we e aken as a e e ence. The po en ial damage du ing mechanical ha es ing was minimized as well o he ‘Ko oneiki’ a ie y, which kep he alues sui able o EVOO up o 24 days when s o ed a 4 ◦ C. A compa a i e s udy o e alua e he e ec o he ha es ing sys em and cold s o age on P ocesses 2021,9, 1543 16 o 34 he Eu opean Commission [ 87 ], he In e na ional Oli e Council [ 1 ] and he US Depa men o Ag icul u e [ 88 ] comp ising he le el o ee a y acids, exp essed as he % oleic acid; he pe oxide alue (PV), exp essed in mEq O 2 /kg oil; and he abso bance a 232 and 270 nm. Addi ional pa ame e s such as he oxida i e s abili y exp essed as he oxida i e induc ion ime (h), he chlo ophyll and ca o enoid pigmen p o ile, and he bi e ness index a e o en included. A speci ic ocus on he mino componen s o he oil implies he de ec ion and quan i ica ion o he kind and amoun o polyphenols, ocophe ols, ola ile compounds (VOC) and alkyl es e s. 5.1. Le el o F ee Acidi y F ee a y acids (FFA) a e p oduced by he hyd olysis o he oil-induced by lipoly ic enzymes. These enzymes a e no mally p esen in he pulp and seed cells o he oli e. When he in eg i y o he ui is los , he enzymes eac wi h he oil ha is con ained in acuoles. Unheal hy, damaged o b uised oli es, oge he wi h de imen s o age condi ions a e he main sou ces o high alues o FFA. The amoun o FFA is exp essed as he pe cen age o g am o oleic acid pe 100 g o oil. The maximum le el o ex a i gin oli e oil (EVOO) is se a 0.8%. The le el o acidi y is always p esen as one o he key pa ame e s o e alua e and compa e he di e en s o age condi ions. No only because i is one o he decisi e elemen s in enhancing he quali y o he oil, bu also because o i s sensi i i y in de ec ing changes in he in es iga ed oils. The published epo s lea e no doub ha he inc ease in he acidi y le el is posi i ely ela ed o he s o age empe a u e as well as he pe iod o ime [10,11,17–20,26,27,30,31,34,39–44,46,47,49,51,55,57,89]. The combined e ec o mechanized ha es ing o oli es o he mill and he conse a- ion me hod was he subjec o se e al s udies [ 30 , 39 , 43 , 46 ]. The acidi y o he oil p oduced om oli es ha es ed wi h a combine ha es e was, a e 4 days and ega dless o he s o age empe a u e, highe when compa ed wi h he alues o he oil ob ained om ui s ha es ed by hand [ 39 ]. Howe e , i was poin ed ou ha he mechaniza ion o he ha es does no comp omise he quali y o he oil p oduced om oli es o he ‘Picual’ a ie y, al hough i is also no denied ha an e ec on ce ain o he a ie ies such as ‘Ko oneiki’ and ‘Ba nea’ is possible [ 30 ]. Gen ly ha es ed oli es main ained low FFA alues o e he s o age pe iod; howe e , hand-held combs, inc eased signi ican ly a e 1 week and hand-held machines e en e ol ed abo e he 0.8% limi a e 1 week. F ui ha es ed wi h a s addle machine e en a ained 1.16% a e 48 h [ 35 ]. The high incidence o decay is b ough o wa d as he main eason why he acidi y le els we e signi ican ly highe in oils ex ac ed om mechanically ha es ed oli es, al hough a a ie al di e ence was no iced be ween he s udied a ie ies [43]. When he ime i akes o exceed he le el o 0.80% is compa ed, he a ie y ‘Picual’, p e- se ed a 5 ◦ C needed be ween 23 [ 30 ], mo e han 30 [ 38 ] and up o 45 days a 1.00% [17,18] . The ‘Co a ina’ a ie y was main ained o up o 30 days a 5 ◦ C a FFA le el below 0.8% [ 31 ]. Oli es o he ‘A bequina’ a ie y, s o ed a 3 ◦ C and ha es ed wi h a ha es e , exceed ha h eshold a e 10 days, while when hand-picked, hey each up o 3 weeks [ 39 ]. The ‘Ve dial’ a ie y was s o ed o mo e han 30 days a 5 ◦C be o e i exceeded 0.8% [38]. The in e a ie al di e ences conce ning he le el o acidi y we e also no iced among h ee Po uguese a ie ies [ 47 ], among he ‘Picual’, ‘Ba nea’ and ‘Ko oneiki’ a ie ies [ 30 ], and be ween ‘A bequina’ and ‘A bosana’ [ 42 ]. Rega ding he e ec o he used ha es ing and conse a ion me hod o he ‘A bequina’ a ie y, conse a ion became p ominen a e ou days o s o age, while he ‘Picual’ cul i a showed o be mo e esis an o a ise in FFA. The ‘Ve dial’ o e ed a mo e con using p o ile. While in he i s yea an inc eased impo ance o he conse a ion me hod was measu ed, his e ec was absen in he second yea while he ha es ing me hod was esponsible o 30–60% o he a iance [46]. Di e ences be ween he ipening s age we e also obse ed. Compa ing g een ma u e, e aison and black oli es o he ‘Picual’ cul i a du ing a s o age pe iod o 4 weeks a 5 ◦ C, he g een ma u e s ayed below 0.8% up o 4 weeks, he e aison and black oli es a ained le els abo e 0.8% a e , espec i ely, 3 and 2 weeks [44]. P ocesses 2021,9, 1543 17 o 34 5.2. Pe oxides Pe oxides a e he p ima y p oduc s o he oxida ion o oli e oil. Pe oxide alue (PV) is a measu e o o al pe oxides in oli e oil exp essed as mEq O 2 kg −1 oil and hence a majo guide o quali y. None o he published s udies exceeded de maximum alue o 20 mEq/kg oil when cold-s o ed. No wi hs anding, signi ican di e ences we e obse ed due o he speci ic condi ions o conse a ion. A e one week, a sha p ise in he pe oxide alue was obse ed up o 30 days a ambien empe a u e and 8 ◦ C, ollowed by a dec ease un il 60 days. A 5 ◦ C, he inc ease was lowe and sp ead o e 45 days [ 19 ]. O he au ho s epo ed an inc ease o he PV only o oli es s o ed a 7.5 ◦ C a e 30 days [ 27 ]. Values highe han 20 mEq we e egis e ed in oli es s o ed a 2 weeks a e which a decline se in, p obably due o he consump ion o mino compounds as phenols and ocophe ols ha make he o ma ion o pe oxides di icul [ 47 ]. The ini ial inc ease ollowed by a dec ease was a ibu ed o he o ma ion o seconda y ca bonyl compounds [ 89 ]. The s o age condi ions do play a signi ican ole. A doubling o he PV was obse ed a e 11 days when s o ed in plas ic bags, while only a e 25 days in plas ic con aine s [ 51 ]. The e ec o he ipeness o he ui on he PV alues was also epo ed [ 44 ]. A clea di e ence be ween on he one hand ‘A bequina’ and ‘Picual’, and on he o he ‘Ve dial’ was no iced [ 46 ]. The la e a ained he PV limi in one week when ecollec ed wi h ne s. The ha es ing me hod s ood ou as he mos in luen ial ac o o all a ie ies. 5.3. K270 and K232 UV-speci ic ex inc ion de e mina ion pe mi s an app oxima ion o he oxida ion p o- cess in unsa u a ed oils. A 232 nm, p ima y oxida ion p oduc s show abso p ion (conju- ga ed pe oxides) which inc ease due o inapp op ia e s o age o oli e ui s o a de ec i e ex ac ion. A 270 nm seconda y oxida ion p oduc s, such as ca bolynic compounds (alde- hydes and ke ones) a e de ec ed which indica es an ad anced oxida ion p ocess. The maximum pe mi ed alues a e 2.5 o K232 and 0.20 o K270. The esul s ob ained in ela ion o he deg ee o oxida ion as measu ed by hese pa ame e s a e in line wi h he one obse ed wi h he pe oxide alues, wi h only a ew s udies epo ing alues ha exceeded he se limi s e en when he ui was cold-s o ed o mo e han a mon h. The alues o K232 and K270 emained p ac ically cons an when s o ed a 5◦C [10,26,27,31,34,40–42,55] . An inc ease in K232 and K270 a 15 days a ambien empe - a u e was obse ed, su passing he limi s a 30 days [ 11 ]. ‘Picual’ oli es, s o ed in plas ic con aine s o 64 kg o ui o wo mon hs, a ained he maximum limi a e 14 days when s o ed a ambien empe a u e, 33 days a 8 ◦ C. A 5 ◦ C he limi was no ye eached a he end o he expe imen . simila alues o K232 we e ob ained a di e en empe a u es up o 30 days [ 19 ]. F om hen on, he samples di e ed signi ican ly wi h he lowes alues ound in oils om oli es s o ed a 5 ◦ C. A 270 nm, and in con as wi h he ea lie pub- lished s udy [ 10 ], he s o age empe a u e showed o signi ican ly a ec he p esence o ca bonylic compounds. [ 29 ] on he o he hand, obse ed a signi ican e ec o he K232 bu no on he K270. In he same manne , [ 89 ] egis e ed an inc ease o K232 a e 7 days, ega dless o he s o age empe a u e, and all alues su passing he limi excep when s o ed a 5% and kep a low O 2 concen a ion. The alues o K270 showed a signi ican e ec o s o age empe a u e bu all alues we e abo e maximum. Mechanical ha es ing exe ed a signi ican e ec on he K232 and K270 alues o he ex ac ed oils. The highe alues obse ed led o an inc ease in he amoun o conjuga ed a y acids, meanwhile his p ocess was accele a ed a a s o age empe a u e o 18 ◦ C [ 39 ]. Fo he alues o K270, no signi ican di e ences we e ound ini ially. Howe e , in oils om mechanically ha es ed oli es an inc ease ook o a e 4 days o s o age a 3 ◦ C, while no di e ence was obse ed in he oils ex ac ed om manually ha es ed ui . This was a ibu ed o he in e nal up u e o he oli e du ing he c ushing in he cou se o he ha es . Simila changes we e no epo ed in a ecen esea ch [ 46 ] as no signi ican e ec o K232 was de ec ed. A 270 nm, he e ec o he ha es ing me hod was signi ican in all P ocesses 2021,9, 1543 18 o 34 he a ie ies. These esul s indica e ha he damages p o oked by a ha es e a e e en mo e se e e han hose ha occu when oli es a e picked om he g ound. Howe e , o he au ho s did no obse e he K232 and K270 alues o be a ec ed by he a ie y, ype o ha es ing and s o age ime [ 30 , 43 ]. Opposed esul s we e epo ed, poin ing o a a ie al di e ence in he Po uguese cul i a s o K232, bu ob aining a 270 nm simila alues [ 47 ]. Oli es in open pe o a ed boxes beha ed be e , as only a e 17 days he limi alue o K232 was a ained [ 51 ]. In plas ic bags, a d as ic inc ease was obse ed, wi hou o he limi alues a e 11 o K232 and 25 days o K270. Signi ican changes in he K270 due o he ime o s o age we e showed [ 44 ]. A e one week, g een ma u e ui s exhibi ed highe alues, while no changes we e ound in ipe oli es. The alues o K232 on he o he hand emained cons an . 5.4. Oxida i e S abili y The oxida i e s abili y, measu ed wi h he Rancima sys em, al hough i is no consid- e ed as one o he legally es ablished pa ame e s o e alua e he quali y o he oils, p o ides an in e es ing es ima e o he shel li e o he oil. A wide ange o s udies shows ha he le els o oxida i e s abili y a e highly in luenced by he gene ics o he ui . I is also accep ed ha no only he alues wi hin each a ie y a e educed du ing i s conse a ion, bu also ha his p ocess slows down when he ui s a e subjec ed o low empe a u es. Se e al s udies ha e poin ed ou ha up o a leas 21 days, he alues ob ained wi h he Rancima me hod did no change. Oils s o ed a 5 ◦ C los 35% o s abili y a e 60 days o s o age, while a 8 ◦ C and ambien empe a u e, 70 and 93%, espec i ely [ 19 ]. The esis ance o ‘Ko oneiki’ oil o oxida ion did no change a 5 ◦ C in ai du ing 30 days o s o age [ 27 ]. I was epo ed ha he s abili y was sligh ly educed (<10) a e 6 weeks o s o age, which was seen as no mal because ui ma u ed, and he s abili y dec eases wi h oli e ma u a ion [ 38 ]. A educ ion o 7% was also obse ed a e 3 weeks o s o age a 5 ◦ C wi h he Tunisian cul i a s ‘Chemlali’ and ‘Che oui’ [ 49 ]. A sligh ly de ian esul was ob ained by Pe ei a e al., epo ing a signi ican dec ease du ing he i s week o s o age a 5 ◦ C, al hough a di e ence be ween he a ie ies ‘Cob ançosa’ on he one hand and ‘Madu al’ and ‘Ve deal T ansmon ana’ on he o he was also no ed [ 47 ]. Simila in e a- ie al di e ences we e obse ed by Rinaldi e al. and Plasquy e al. [ 32 , 46 ]. In he la e s udy, he ha es ing me hod showed o be o majo impo ance o up o 4 days. O e 14 days , he s eng h o he used conse a ion me hod inc eased, al hough he maximum and a e a ied along wi h he cul i a s. In ‘A bequina’ i a ained almos 80% on day 14, in ‘Ve dial’ 40% and ‘Picual’ 20%. In he same line, a ie al di e ences wi h he lowes alues o he mechanically ha es ed oli es we e epo ed [39,43]. A bad co ela ion be ween PV and s abili y was obse ed [ 11 ], sugges ing he exis ence o o he ac o s in addi ion o oxida ion s a e ha in luence s abili y. The high concen a ion o ee a y acid oils ex ac ed om ui s o ed a ambien empe a u e unde wen a ema kable dec ease a e 30 days while a 5 ◦ C he s abili y was cons an . The empe a u e- dependen loss o s abili y was a ibu ed o he moca alyzed hyd aulic and oxida i e p ocesses, which ac on he oil con ained in he oli es du ing hei ipening, ei he as a consequence o hei own me abolism o as a esul o a pa hogenic ac i i y [ 19 ]. Meanwhile, he de ec ed co ela ion be ween he o al amoun o phenols and he induc ion imes poin s o he an ioxidan ac i i y o hyd ophilic phenols [31,65]. 5.5. Chlo ophyll and Ca o enoid Pigmen P o ile The spec ome ic de ec ion o ca o enoid and chlo ophyll pigmen s a 460 and 670 nm, espec i ely, was no epo ed sys ema ically. The main in e es o s udy hei e olu ion du ing cold s o age consis o hem being ac i e as an an ioxidan and hei key ole in he oil colo , a ac o ha in luences he choice o he consume [90]. The in e p e a ion o he esul s u ned ou o be e y di icul gi en he complexi y o ac o s ha a e in ol ed and he a ie al di e ences. A s able ca o enoids con en in he oils ex ac ed om he ‘Manzanilla’ cul i a s o ed du ing 5 weeks a 5 ◦ C was egis e ed, P ocesses 2021,9, 1543 19 o 34 while he ‘Picual’ and ‘Ve dial’ cul i a s p esen ed a clea educ ion o ca o enoids du ing he i s 3 weeks [38]. In he ollowing 2 weeks, he le el o he ‘Picual’ inc eased o a ain he ini ial alues, while he ‘Ve dial’ inc eased only sligh ly. The chlo ophyll con en o he ‘Picual’ and ‘Manzanilla’ inc eased con inuously du ing he i s 6 weeks a e which a s eep dec ease was obse ed o he ‘Picual’. On he o he hand, ‘Ve dial’ showed mo e han 40% loss o chlo ophyll con en a e he i s week and om hen on he same le el was main ained. A dec ease o chlo ophyll in ‘Ko oneiki’ oli es was obse ed when s o ed below 7.5 ◦ C, al hough did no egis e any change o e 60 days when s o ed a 5 ◦ C [ 27 ]. In he same line, only a sligh dec ease in ca o enoids as well as chlo ophyll con en o e 3-week s o age a 5 ◦ C was egis e ed [ 49 ], while epo ed an inc easing end du ing he cold s o age ime [ 34 ]. The p o ile o he chlo ophyll ca o enoid con en did no show signi ican di e ences in he C oa ian a ie ies a ambien empe a u e and 4 ◦ C [ 58 ]. Only hose s o ed a − 20 ◦ C showed a signi ican change in bo h pigmen s. As he chlo ophylls dec eased, he le el o ca o enoids inc eased. The e a ic cha ac e o he esul s was also p esen in he s udies ha ocused on he e ec o he ha es ing me hod. A e 3 weeks o s o age, he con en o pho osyn he ic pigmen s became signi ican ly highe in he manually ha es ed ‘A bequina’ oli es [ 39 , 70 ]. The phenomenon was a ibu ed o a possible dec ease in he consis ency o he chlo oplas wall, acili a ing he elease o he pigmen s in he oil. Simila esul s we e ound o he ‘Manzanilla de Se illa’ bu , a he same ime, he ‘Manzanilla Cace eña’ showed a comple ely di e en p o ile [ 43 ]. The quan i ica ion o he e ec o he ha es ing and conse a ion me hod e ealed signi ican di e ences among ‘A bequina’, ‘Picual’ and ‘Ve dial’ cul i a s [ 46 ]. In ‘A bequina’ he imp essi e impo ance o he s o age me hod, explaining 80% o he a iance om day 4 o 14, was placed agains he esul s o he ‘Picual’ a ie y, whe e he impo ance o he conse a ion was only isible in he i s yea , showing a linea g ow h om he onse o he impo ance o 80%. In ‘Ve dial’ he s o age sensi i i y was illus a ed by a s eep inc ease om day 4 o 8, explaining 90% o he a iance o one yea . In he o he yea , a shi owa d he impo ance o he in e ac ion o he ac o s ha es ing and conse a ion (40%) was obse ed om day 8 up o day 14. 5.6. Bi e ness Index (BI) The signi ican co ela ion be ween he in ensi y o bi e ness, as e alua ed in a sen- so ial manne by a panel, and he measu emen o he abso bance a 225 nm [ 82 ], in- spi ed se e al esea ch g oups o ollow he p og ess o his pa ame e h oughou a cold s o age pe iod. A sha p dec ease o BI in he oils ob ained om oli es s o ed a ambien and 8 ◦ C was ound, while he ones s o ed a 5 ◦ C only p esen ed a slow dec ease [ 19 ]. Simila ly, 8-day s o age a 20 ◦ C led o a educ ion in K225 o 58% in he monolaye ed oli es and 4- old in he case o laye s up o 20 cm. A 10 ◦ C he same esul s we e ob ained a e 14 days . No wi hs anding his di e ence, he K225 index was educed by 80% in all s o age condi ions a 20 days o s o age [ 40 ]. The same g adual dec ease was obse ed in ‘Chemlali’ s o ed o 4 weeks a ambien empe a u e. This p og ess was a ibu ed o al e na ions o pa ial o o al inhibi ion o he speci ic enzymes (glycosidases and es ea ases) which downplay he p esence o secoi idoid de i a i es o phenols and consequen ly he bi e - ness in ensi y [ 91 ]. A di e gen esul was also epo ed, indica ing an ini ial inc ease o he K225 alues o ‘Ché oui’ oli es s o ed a 5 ◦ C, in ai o unde CA. A e wo weeks, a dec ease se in and a simila alue was ob ained o bo h condi ions [89]. The magni ude o he e ec o he ha es ing and conse a ion me hods used indica ed a ie al di e ence [ 46 ]. The ‘A bequina’ cul i a showed o be he mos ulne able o he s o age empe a u e om day 4 on, wi h conse a ion being he ac o ha explained up o 71% (yea 1) and 83% (yea 2) a e 14 days. ‘Picual’ main ained a high explana o y powe o he ha es ing me hod o up o 14 days. ‘Ve dial’ exp essed a s eady inc ease o he ac o ‘conse a ion’, which a ained a maximum abo e 60% a he end o he expe imen . P ocesses 2021,9, 1543 20 o 34 5.7. Phenolic Con en The phenolic con en o oli e ui depends g ea ly on he cha ac e is ics o he cul- i a ion zone, he clima ic condi ions and he di e en echniques applied du ing he p oduc ion, he ha es and he pos ha es ea men [ 92 ]. Du ing ipening, hei amoun inc eases o a ain a maximum a e aison a e which a decline s a s. The phenolic com- posi ion o he oli e ui is o e ly complex, al hough h ee secoi idoid glucosides o m he majo pa : oleu opein, ligus oside and deme yloleu opein. When he cell issues a e up u ed du ing g inding, hese hyd ophilic componen s con ac wi h speci ic enzymes ha ca alyze and modula e he o ma ion o hyd olyzed secoi idoid de i a i es. These oil- soluble subs ances play no only an impo an ole as an ioxidan s bu also in he o ma ion o he senso ial a ibu es o he oil. Once again, nume ous phenolic compounds ha e been de ec ed al hough he 4 mos impo an a e he aldehydes o he aglucones o oleu opein and ligus oside (3, 4-pHEA-EA and p-HPEA-EA and, h ough he media ion o speci ic β -glucosidases, dialdehydes o he same dime hylised aglucones (3, 4-pHPEA-EDA and p-HPEA-EDA) [ 93 ]. Du ing ex ac ion, he phenolic compounds unde go p ocesses o oxida ion, ei he by ee adicals o h ough he enzyma ic ac i i y o polyphenol oxidase (PPO) and pe oxidase (POX), ha a e equally libe a ed du ing he g inding. The inal con en o secoi idoids esul s o he equilib ium be ween he p ocesses o hyd olysis, ca alyzed by he β -glucosidases and he oxida ion p ocesses induced by he PPO and POX enzymes [93]. Thei speci ic ole as an ioxidan s and hei c i ical con ibu ion in he bi e and pungen as e o he oils a ained escala ing a en ion wi hin he cold s o age esea ch. In addi ion o an in e es in he e olu ion o he o al phenol con en unde speci ic s o age condi ions, he ocus was b ough owa ds shi s in he polyphenol’s p o iles, he e olu ion in he ac i i y o he di e en enzymes and he p ospec o modi y he bi e ness o he ex ac ed oil h ough a modi ica ion o he empe a u e and/o CA [61]. The epo ed o al amoun o phenols measu ed in he ex ac ed oil was de e mined by a colo ime ic me hod using a Folin-Cical eau eagen and exp essing he amoun as ppm o ca eic acid; gallic acid equi alen s; p-hyd oxyphenolace ic acid and o-couma ic acid. The sepa a ion o oli e oil phenolic compounds has been achie ed by he applica ion o all ypes o liquid ch oma og aphy and gas ch oma og aphy [94]. The majo i y o he s udies obse ed a signi ican delay in he dec ease o o al polyphe- nols [ 16 , 27 , 29 , 31 , 33 , 34 , 39 , 40 , 49 , 57 , 58 , 62 , 95 ]. Ne e heless, a ie al di e ences we e equally epo ed and e en con adic ed he gene al end [ 30 , 46 , 89 ]. The phenolic compounds o ‘Manzanilla de Se illa’ and ‘Manzanilla Cace eña’, e en s o ed a 2 ◦ C, we e s ongly and nega i ely a ec ed, especially hose which we e mechanically ha es ed [ 43 ]. Simila ly, bu less explici ly, a signi ican di e ence in he oils ex ac ed om mechanically ha es ed ui was egis e ed [70]. Measu emen s o he phenols con en in he ui du ing cold s o age elucida ed he impo ance o he oxida ion p ocess o he phenols. Mo e speci ically, changes in oleu opein we e epo ed ha could only be explained by he e ec o exogenous enzymes p oduced by mic obial g ow h [29,40]. Moni o ing POX, PPO and β -glucosidases in c ude p o ein ex ac s du ing ui ipening and s o age e ealed di e en ends o ac i i ies o di e en cul i a s and s o age condi ions [ 53 ]. A signi ican educ ion o he PPO du ing he i s 2 days o s o age was epo ed, and om hen on, a g adual dec ease [ 33 ]. POX showed a g adual dec ease o e he 7 days o s o age a 15 ◦ C. Howe e , he ac ha a mul i ude o ac o s (ae obic condi ions, s o age ime and empe a u e, ipeness, ini ial quali y and mic obiological s a e, a ie al esis ance agains mic obiological a ack) could in luence he p oduc ion o ola ile phenols make i ex emely di icul o isola e and desc ibe hei complex chemical na u e [41,42,93]. P ocesses 2021,9, 1543 21 o 34 5.8. Vola ile Compounds The ola ile compounds o i gin oli e oil a e p ima ily gene a ed du ing he ex- ac ion p ocess. Mos o hem a e aldehydes and alcohols o six and i e s aigh -chain ca bons (C5, C6) oge he wi h he co esponding es e s, and a e syn hesized h ough he enzyma ic lipoxygenase (LOX) pa hway [ 95 ]. Howe e , he handling o oli e ui and consequen s o ing can esul in p og essi e cell dis up ion, inc eased enzyma ic ac i i y and ul ima ely a modi ica ion o he oil senso y quali y. I is sugges ed ha he p ema u e ac i a ion o he LOX pa hway al e s no only he biochemical s a us o he ui bu also he amoun o ola iles p oduced du ing he milling s ep [43]. While he o al amoun o ola iles dec eases h oughou he s o age ime i is equally ue ha he di e en C5 and C6 ola ile compounds showed o e ol e di e en ly o e he s o age pe iod, making a de ailed in e p e a ion di icul i no impossible [ 29 , 40 ]. Mo eo e , nega i e ola ile compounds a e o med om he me abolic ac ion o yeas and molds [40]. F ui damage caused by mechanical ha es ing igge ed he o ma ion and emission o ola ile compounds du ing s o age, leading o a dec ease in he amoun o o al ola iles ound in he oils. A e 24 h o s o age, a signi ican ly lowe con en in C5 and C6 com- pounds be ween he mechanically and hand-ha es ed oli es was ound, howe e , hese di e ences we e minimized a e 11 days [43]. The e olu ion o he ac i i y o LOX-de i ed ola iles unde di e en s o age condi- ions showed o be highly a ie y dependen . No signi ican di e ences we e epo ed in he p esence o C6 aldehydes and alcohols in he oil o ‘Ché oui’ a ie y when ela ed o he oli e ipening and s o age [ 52 ]. Qui e di e en esul s we e ob ained wi h ‘A be- quina’ oli es, whe e he compounds we e much highe in he oil om ui wi h he same ipening bu s o ed a 25 ◦ C when compa ed wi h hose a 5 ◦ C. I is sugges ed ha hese high amoun s a e due o he apid ui deg ada ion and cell dis up ion due o he highe s o age empe a u e [52]. 5.9. Tocophe ols Tocophe ols ( α -, β -, γ -, δ -) belongs, oge he wi h oco ienols ( α -, β -, γ -, δ -), o a g oup o plan soluble lipid compounds known as i amin E. The an ioxidan e ec o ocophe ols depends mainly on he empe a u e and lipid composi ion. α –Tocophe ol is he mos common o m o i amin E wi h he highes biological ac i i y, ep esen ing 95% o he o al ocophe ol con en in oli e oil. The con en o ocophe ols is shown o be cul i a dependen and signi ican ly a ec ed by he ha es ing sys em, ui ipeness, c op yea , he s o age empe a u e and he s o age ime [39,43,46,96]. F ui cold s o age does delay he deg ada ion o he ocophe ols bu canno a oid i . A signi ican dec ease in ocophe ol when ui was s o ed a 3 ◦ C was epo ed as well as signi ican di e ences be ween h ee Po uguese cul i a s [ 47 ]. Simila ly, a signi ican e ec o he cul i a was epo ed, compa ing ‘O ob a ica’ and ‘Ca olea’, as well as o he s o age empe a u e on he o al amoun o ocophe ols [ 34 ]. A ocus on he e ec s o he ha es ing me hods e ealed ha he oil ex ac ed om manually ha es ed ui signi ican ly con ained highe alues when compa ed wi h he mechanically ha es ed, ega dless o he s o age empe a u e [ 39 ]. A he same ime, he ui s o ed a 3 ◦ C esul ed in alues ha we e signi ican ly highe han when s o ed a 18 ◦ C, ega dless he sys em o ha es ing. A signi ican e ec o he ha es ing me hod was epo ed bu speci ied he p esence o an ex eme di e ence a e one day o s o age, al hough his disc epancy equalized a e 6 days [ 43 ]. I was sugges ed ha he in e nal damage caused in he ui du ing mechanical ha es ing, was esponsible o he ex emely apid oxida ion o ocophe ols). A signi ican e ec o he s o age ime and he ha es ing me hod on he amoun o α – ocophe ols in h ee a ie ies (‘A bequina’, ‘Picual’ and ‘Ve dial’) was obse ed [ 46 ]. Howe e , he e ec o he conse a ion me hod was absen in bo h s udied yea s in he ‘A bequina’ and ‘Ve dial’ cul i a s and only in one yea in he ‘Picual’. The s eng h o he ac o ‘ha es ing’ a ied be ween he wo yea s and among he a ie ies. P ocesses 2021,9, 1543 22 o 34 5.10. Alkylic Es e s The ex ac ion o oil om oli es in which e men a i e p ocesses ha e s a ed gi es place o nega i e a ibu es, such as mus y, winey- inega y o muddy sedimen . These senso y classi ica ions we e ela ed o he con en o ee acid alcoholic es e ’s (FAAE) in he oli e oil [ 97 ]. I was u he obse ed ha e y high concen a ions o FAAEs in he oli e oil do e lec e men a i e de ec s o he oli e ui , whe eas o he de ec s, such as oxida i e ones o ozen oli es, do no p oduce FAAEs [ 98 ]. FAAEs a e o med by ans- es e i ica ion o ee a y acids wi h sho -chain alcohols, mainly me hanol and e hanol yielding me hyl (FAME) and e hyl es e s (FAEE), which a e bo h ex ac ed wi h he oil. Howe e , while he me hanol is also o med du ing he pec in deg ada ion o he cell wall du ing he ipening o he oli e ui , he e hanol can only be p oduced by e men a ion, excep speci ic a ie ies ha ha e been shown o p oduce e hanol du ing hei ipening [ 99 ]. Since 2013, FAEE a e conside ed as an impo an ma ke and as such included in he EU Commission Regula ion [100]. Inapp op ia e p ac ices du ing he ha es and s o age o oli es a e impo an ac o s ha do p omo e hei hyd oly ic and oxida i e de e io a ion. The con en o e hanol in g ound-picked oli es was signi ican ly highe compa ed o ui ha es ed om he ee [ 101 ]. Howe e , he amoun o e hyl es e s in he ex ac ed oil emained below he limi es ablished o EVOO and was a ibu ed o he sho ime be ween he ecollec ion and he ex ac ion which impeded he syn hesis o highe concen a ions [ 101 ]. The ype o con aine used du ing pos -ha es s o age showed o be a ele an ac o in explaining he high le els o FAEE when oli es, s o ed in closed plas ic bags, we e compa ed wi h hose kep in pe o a ed plas ic boxes [51]. Thus a , he p esence o FAAE ha e been s udied sca cely. A mani es e ec o he oli e s o age empe a u e on he FAME and FAEE con en was obse ed [ 34 ]. The limi s o FAEE o EVOO (<30 mg/kg) was su passed a e 12 days o s o age a 25 ◦ C. When s o ed a 4 ◦ C, one a ie y, ‘Ca olea’, showed no inc ease o nei he o he es e s. The o he a ie y, ‘O ob a ica’, showed a signi ican di e ence when wo ha es ing momen s we e compa ed. The la e ha es ed ui a ain ed a le el abo e he se maximum, indica ing ha he physical s a e o he d upes was declining and he ap i ude o de e io a ion in- c easing. No signi ican di e ences we e ound in he ea men s in he s udied ‘Rosignola’ a ie y [ 58 ]. In he o he a ie y, ‘Is a ska Bejelica’, only an inc ease in he oils s o ed a oom empe a u e was obse ed [58]. 6. F ui Tempe a u e Managemen 6.1. Ra ionale o Con olling Pos ha es Oli e F ui Tempe a u e The p ima y objec i e o cold s o age o oli e ui was o sp ead he ex ac ion p ocess o e a longe ime o inc ease he p ocessing capaci y. The esea ch was o ien ed o de e mine he maximum s o age ime o he ui wi hou jeopa dizing he quali y o he oils ex ac ed he e om. Howe e , as he oil indus y op ed o ampli y he p oduc ion capaci y, he p oposed conse a ion me hod was in oduced only spo adically. Subsequen ly, he ui empe a u e was modi ied o induce p ecise cha ac e is ics o he ex ac ed oil. Ye , he challenging echnique came along wi h speci ic cons ain s and hwa ed i s inco po a ion a an indus ial le el. Cu en ly, he oli e oil indus y is acing a ious new challenges ha di ec ly ela e o he con ol and he modi ica ion o he ui empe a u e. Clima ological changes a e p o oking a shi in he phenology o he oli e plan and a e o wa ding he op imum ha es ime by se e al weeks [ 102 , 103 ]. Meanwhile, high-densi y o cha ds (HDO) do eques speci ic a ie ies, such as ‘A bequina’, ‘Ko oneiki’ and ‘A bosana’, which need o be ha es ed ea ly in he season [ 104 ]. Finally, he success o esh- la o ed oils o he gou me ma ke , backed up by he g owing impo ance o he in e na ional oli e oil compe i ions, a o s an ea ly ha es [ 105 ]. Consequen ly, a ha es ing campaign ha en isions high-end quali y oli e oil is aking o in Sep embe , wi h day empe a u e ha easily aises abo e 30 ◦C. P ocesses 2021,9, 1543 23 o 34 Fo wa ding he ha es leads una oidably o a high ield empe a u e o he ui . This undesi able si ua ion, when combined wi h a anspo o a couple o hou s in aile s o mo e han 10 , du ing which he ui empe a u e u he inc eases, su ice o c ea e condi ions o asphyxia and induce anae obic espi a ion. Consequen ly, p ocesses o e - men a ion p oduce by-p oduc s ha lead o de ec able senso y de ec s and high le els o alcoholic es e s in he ex ac ed oil and ul ima ely o he ejec ion o he oil as EVOO [ 106 ]. This new si ua ion has al eady ala med he indus y. Noc u nal ha es ing was in o- duced as a possible solu ion bu soon a e p ohibi ed o i s disas ous side e ec s on he bi dli e [107]. Bu e en wi hou de as a ing e men a ion p ocesses du ing he anspo and s o - age, a high ield empe a u e o he ui impedes he ex ac ion o high-quali y oli e oil. I is widely accep ed ha he ideal malaxa ion empe a u e is si ua ed be ween 25 and 30 ◦ C [ 108 , 109 ]. This becomes simply impossible wi h ui a mo e han 25 ◦ C, knowing ha c ushing i sel ises he oli e pas a a leas 5 ◦ C [ 110 ]. Unde hese condi ions a ull con- ol o he malaxing pa ame e s, essen ial o ob ain he desi ed o ganolep ic cha ac e is ics o he oil, simply becomes impossible. Up o now, con olling he empe a u e du ing he anspo o he oli es was ha dly aken in o conside a ion, simila o he necessi y o adjus he empe a u e be o e he ex ac ion p ocess. Once he ui was ha es ed, i was b ough o he mill and ex ac ed immedia ely i possible and s o ed o a sho ime when necessa y. The men ioned en i onmen al, ag onomical and cul u al ac o s a e b inging he exis ing pos ha es model unde s ess and u ge o a mo e dynamic way o con ol he ui empe a u e om he momen i is ha es ed up o i s p ocessing. De eloping speci ic cooling ins alla ions adap ed o he di e en s ages o he pos ha - es s ages and p oduc ion lines, do ha e in common he need o know he speci ic physi- ological and bio he mal cha ac e is ics o he ui . Se e al s udies ha e been published in his espec and do con i m ha oli e ui can be cooled o he desi ed empe a u e in a ime o se e al minu es ei he by wa e o cooled ai , wi hou comp omising i s quali y [111–113]. 6.2. Bio he mal Cha ac e is ics De e mining he cooling ime needed o each he desi ed empe a u es is he i s necessa y s ep in he design and/o implemen a ion o any cooling sys em. Exis ing physical models ha e low applicabili y a he indus ial le el since i is e y di icul o ake in o accoun he physical and biochemical a iabili y o he ui wi h he pa ame e s hey con empla e. The e o e, an e ec i e way o ob ain in o ma ion abou he cooling p ocess is by making physical measu emen s in a eal p ocess. Speci ic da a conce ning he he modynamic p ope ies o oli e ui emains sca ce. Re . [ 111 ] published da a on he he mal conduc i i y (k), speci ic hea (Cp) and he mal di usi i y ( α ) o oli e ui bu did no ake in o accoun he geome ical a iabili y ha exis s among he a ie ies and used simpli ied ma hema ical equa ions o calcula e he cons an s. The calcula ions o he Cp we e based on he chemical composi ion o 4 di e en a ie ies while he he mal conduc i i y was measu ed using he ansien ho -wi e me hod. The he mal di usi i y was calcula ed using he expe imen ally de e mined alues o k and Cp. The esul s showed de ian esul s when compa ing empe a u e- ela ed models wi h empi ical ones. A sophis ica ed ma hema ical model o hea conduc ion in s one ui s was de eloped o calcula e he he mal p ope ies o oli e ui [ 112 ]. The used empi ical da a s emmed in pa om he p ecise measu emen o he dimensions o one oli e (c. . ‘Go dal’) and he in e nal empe a u e change du ing i s cooling in cold wa e . They calcula ed a Bio numbe o 4.43 using wa e as he ans e medium o an oli e ha weighed 10.44 g, which is by all s anda ds an ex eme weigh o oli e ui . The Bio numbe (Bi) exp esses he a io o he in e nal esis ance o conduc ion o he ex e nal esis ance o con ec ion (h). When Bi < 0.1, he in e nal esis ance is conside ed o be negligible in compa ison wi h he su ace esis ance and i is assumed ha he ma e ial o p oduce P ocesses 2021,9, 1543 24 o 34 hea s o cools down uni o mly [ 72 , 114 ]. As he alues o h a e medium-dependen , he ob ained Bio -numbe is no alid when conside ing a p e-cooling ea men wi h cooled ai [ 115 ]. Subme ging picked oli es in a cooled solu ion o dilu ed lye is a ecognized and ecommended ea men o a oid b uise damage o able oli es [ 116 , 117 ]. Howe e , when dealing wi h ui in ended o oil ex ac ion, con ac wi h wa e be o e s o age is no ecommended as i p omp s de e io a ion and e en e men a ion p ocesses [118]. The mal imaging was used o measu e he empe a u e change o indi idual oli es o six di e en cul i a s s o ed unde oom cooling condi ions and ela ed he ob ained esul s o hei physical and geome ical cha ac e is ics [ 113 ]. The modynamic pa ame e s we e u he used o simula e he cooling p ocess o he oli e ui by con ec ion wi hin a ange o ield empe a u es and oom cooling empe a u es. The calcula ed cooling a es e ealed a non-linea ela ion be ween he speci ic su ace a ea and he cooling a e o an oli e, sugges ing ha unde lying ac o s need o be conside ed when calcula ing he speci ic hea o he ui . To explain he obse ed la ening on bo h sides o he cu e, u he esea ch is needed o cla i y he in luence o he s one when dealing wi h small oli e ui , as well as he inc eased Bio numbe o hea ie oli es. Ne e heless, he simula ion cla i ied ha a ela i ely sho ime is needed o cool he ui o a desi able empe a u e when placed in a cold ai en i onmen . In he case o ‘A bequina’ and ‘Ko oneiki’ cul i a s, ui wi h a ield empe a u e o 38 ◦ C would a ain a empe a u e o 22 ◦ C when kep in an en i onmen o − 16 ◦ C o less han 2 min. In he case o ‘Hojiblanca’ and ‘Picual’, he cooling ime unde hese condi ions inc eased o 3 min. Finally, he hea ie ‘Ve dial’ and ‘Go dal’ a ie ies needed up o 5 min o cool down o he desi ed empe a u e. E en hough u he esea ch is needed o disca d nega i e impac s on he ui , he ob ained esul s a e use ul o he de elopmen and he in oduc ion o new echniques based on cooled ai . A ela ed expe imen in which boxes wi h 10 kg o oli es we e b ough o 5 ◦ C by placing hem a a oom empe a u e o − 18 ◦ C, e ealed no de e io a ion in he quali y pa ame e s o he oil [77]. The impo an ole ha o ced ai cooling can play in he ield, a he a m and a he ecep ion ya d o he mill, does ad oca e o ex ensi e s udies on he applica ion o his echnique. Mo e speci ically, expe imen s a he labo a o y le el a e needed o documen he wo king o a cooling unnel and o s udy he e ec o he cooled o ced ai on he ui cha ac e is ics and oil ex ac ed he e om. This implies he design o he labo a o y scale cooling unnel. An example o such a sys em is gi en in Figu e 6. The showed sys em would imply he p elimina y wa ming o he oli e ui in an incuba o a a se empe a u e while he cooled ai can easily be p o ided by a sepa a e cooling g oup. P ocesses 2021, 9, x FOR PEER REVIEW 25 o 34 cha ac e is ics and oil ex ac ed he e om. This implies he design o he labo a o y scale cooling unnel. An example o such a sys em is gi en in Figu e 6. The showed sys em would imply he p elimina y wa ming o he oli e ui in an incuba o a a se empe a- u e while he cooled ai can easily be p o ided by a sepa a e cooling g oup. Figu e 6. Expe imen al se up a labo a o y scale o s udy he e ec o cooled o ced ai on he quali y o he ui and he oil ex ac ed he e om. 6.3. Remo ing Field Hea The e ec o ime and empe a u e on espi a ion has been s udied on a ious in ac ui as well as esh-cu p oduce [75,119–123]. In all o hese s udies, an A henius- ype equa ion showed o be e y eliable o desc ibe he espi a ion a e in unc ion o he em- pe a u e. The s udies on he espi a ion a e o cold-s o ed oli es ui ha e shown ha he espi a ion a e inc eases a a highe empe a u e. In addi ion, damaged o b uised ui do no only accele a e espi a ion [43,84] bu also induces hyd oly ic and oxida i e de e io a ion. The p esence o FAEE in he ex ac ed oil does indica e he o ma ion o e hanol du ing he anspo o s o age because o ui damage as well as anae obic es- pi a ion [51,101]. The a e o gas di usion and espi a ion a ies signi ican ly when he ui is piled up, as is he case when oli es a e collec ed and anspo ed in la ge con aine s. Unde such condi ions, some pa s isk becoming anae obic while o he s emain ae obic. Remo ing ield hea as soon as possible s ands as a compelling ecommenda ion in he pos ha es s udies ha ocus on con olling he quali y o he ui [74,124]. The p o- cess o emo ing ield hea is commonly e e ed o as p ecooling and implies he quick emo al o hea , in a ew minu es o a ew hou s, ei he in he ield o a he p ocessing plan . P omp p ecooling is used o ui and ege ables ha need apid cooling o main- ain he high quali y du ing he holding pe iod. A delayed cooling, implying a lag be- ween he ha es and he p ecooling ea men , gene ally educed he quali y and he s o age li e, al hough i is also epo ed ha o speci ic ui s, such as che y, peach, nec- a ine and apple, a cooling delay may be bene icial. G adual cooling lowe s he empe a- u e o he ui and ege ables o only ce ain deg ees o e hou s o days o induce he cold ole ance in he p oduce. Fo ced ai cooling, hyd o-cooling, liquid ice-cooling and acuum cooling a e he mos commonly used p ecooling echniques [125–127]. All in ol e he as ans e o hea om he p oduce o a cooling medium, such as ai o wa e . Howe e , he cha ac e is ics o he commodi y and he con aine , he a e o cooling and he u he s o age condi ions do de ine he mos app op ia e echnique. Fo ced ai -cooling is u he di e en ia ed in he ci cula ion o cold ai a a high eloci y in e ige a ed ooms, o cing cold ai h ough bulk o s acked p oduce as hey mo e h ough a cooling unnel on a con eye , and using he p essu e di e en ial echnique ha o ces ai h ough p oduce packed in con aine s. Figu e 6. Expe imen al se up a labo a o y scale o s udy he e ec o cooled o ced ai on he quali y o he ui and he oil ex ac ed he e om. P ocesses 2021,9, 1543 25 o 34 6.3. Remo ing Field Hea The e ec o ime and empe a u e on espi a ion has been s udied on a ious in ac ui as well as esh-cu p oduce [ 75 , 119 – 123 ]. In all o hese s udies, an A henius- ype equa ion showed o be e y eliable o desc ibe he espi a ion a e in unc ion o he empe a u e. The s udies on he espi a ion a e o cold-s o ed oli es ui ha e shown ha he espi a ion a e inc eases a a highe empe a u e. In addi ion, damaged o b uised ui do no only accele a e espi a ion [ 43 , 84 ] bu also induces hyd oly ic and oxida i e de e io a ion. The p esence o FAEE in he ex ac ed oil does indica e he o ma ion o e hanol du ing he anspo o s o age because o ui damage as well as anae obic espi a ion [ 51 , 101 ]. The a e o gas di usion and espi a ion a ies signi ican ly when he ui is piled up, as is he case when oli es a e collec ed and anspo ed in la ge con aine s. Unde such condi ions, some pa s isk becoming anae obic while o he s emain ae obic. Remo ing ield hea as soon as possible s ands as a compelling ecommenda ion in he pos ha es s udies ha ocus on con olling he quali y o he ui [ 74 , 124 ]. The p ocess o emo ing ield hea is commonly e e ed o as p ecooling and implies he quick emo al o hea , in a ew minu es o a ew hou s, ei he in he ield o a he p ocessing plan . P omp p ecooling is used o ui and ege ables ha need apid cooling o main ain he high quali y du ing he holding pe iod. A delayed cooling, implying a lag be ween he ha es and he p ecooling ea men , gene ally educed he quali y and he s o age li e, al hough i is also epo ed ha o speci ic ui s, such as che y, peach, nec a ine and apple, a cooling delay may be bene icial. G adual cooling lowe s he empe a u e o he ui and ege ables o only ce ain deg ees o e hou s o days o induce he cold ole ance in he p oduce. Fo ced ai cooling, hyd o-cooling, liquid ice-cooling and acuum cooling a e he mos commonly used p ecooling echniques [ 125 – 127 ]. All in ol e he as ans e o hea om he p oduce o a cooling medium, such as ai o wa e . Howe e , he cha ac e is ics o he commodi y and he con aine , he a e o cooling and he u he s o age condi ions do de ine he mos app op ia e echnique. Fo ced ai -cooling is u he di e en ia ed in he ci cula ion o cold ai a a high eloci y in e ige a ed ooms, o cing cold ai h ough bulk o s acked p oduce as hey mo e h ough a cooling unnel on a con eye , and using he p essu e di e en ial echnique ha o ces ai h ough p oduce packed in con aine s. When con empla ing he possibili ies o emo e he ield hea o ha es ed oli es, a leas h ee di e en ci cums ances need o be aken in o accoun . Fi s ly, when he e is a isk o ui asphyxia ion and e men a ion p ocesses du ing he anspo and/o consequen s o age. Secondly, when sho - ime s o age be o e anspo is necessa y while he eques ed minimum amoun o ui o ex ac ion is ha es ed. Thi dly, when he op imal ex ac ion o he oil becomes impossible when he ui a i es a he mill a a empe a u e al eady abo e he se maximum. I he day empe a u e and anspo a ion ime a e such ha he espi a ion h eshold will be a ained be o e he p ocessing o he ui , p omp p ecooling come o he o e as he only solu ion o a oid de e io a ion in he ba ch o oli e ui . Wa e as a cooling medium can be excluded as we ing he oli es be o e hei anspo will c ea e e en g ea e de e io a ion. Fo ced ai -cooling comes o he o e as a possibili y and mo e speci ically he use o a cooling unnel in which he empe a u e o he ui is lowe ed o a leas 15 ◦ C. The es ima ion o he cooling a es allowed o p edic ha his can be a ained in he ange o a couple o minu es [ 113 ]. Howe e , he cooling mechanism needs o be capable o handle he conside able and con inuous amoun o oli es ha a e ha es ed mechanically. 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