Emulsion-based coatings for preservation of meat and related products

Ci a ion: Gau am, S.; Lapˇcík, L.; Lapˇcíko á, B.; Gál, R. Emulsion-Based Coa ings o P ese a ion o Mea and Rela ed P oduc s. Foods 2023,12, 832. h ps://doi.o g/10.3390/ oods12040832 Academic Edi o : JoséManuel Beni o Recei ed: 2 Janua y 2023 Re ised: 6 Feb ua y 2023 Accep ed: 14 Feb ua y 2023 Published: 15 Feb ua y 2023 Copy igh : © 2023 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/). oods Re iew Emulsion-Based Coa ings o P ese a ion o Mea and Rela ed P oduc s Shwe a Gau am 1, Lubomí Lapˇcík1,2,* , Ba bo a Lapˇcíko á1,2 and Robe Gál1 1Depa men o Foods u Technology, Facul y o Technology, Tomas Ba a Uni e si y in Zlin, Nam. T.G. Masa yka 275, 762 72 Zlin, Czech Republic 2Depa men o Physical Chemis y, Facul y o Science, Palacky Uni e si y in Olomouc, 17. Lis opadu 12, 771 46 Olomouc, Czech Republic *Co espondence: [email p o ec ed] Abs ac : One o he bigges challenges aced by he mea indus y is main aining he eshness o mea while ex ending i s shel li e. Ad anced packaging sys ems and ood p ese a ion echniques a e highly bene icial in his ega d. Howe e , he ene gy c isis and en i onmen al pollu ion demand an economically easible and en i onmen ally sus ainable p ese a ion me hod. Emulsion coa ings (ECs) a e highly ending in he ood packaging indus y. E icien ly de eloped coa ings can p ese e ood, inc ease nu i ional composi ion, and con ol an ioxidan s’ elease simul aneously. Howe e , hei cons uc ion has many challenges, especially o mea . The e o e, he ollowing e iew ocuses on he essen ial aspec s o de eloping ECs o mea . The s udy begins by classi ying emulsions based on composi ion and pa icle size, ollowed by a discussion on he physical p ope ies, such as ing edien sepa a ion, heology, and he mal cha ac e is ics. Fu he mo e, i discusses he lipid and p o ein oxida ion and an imic obial cha ac e is ics o ECs, which a e necessa y o o he aspec s o be ele an . Las ly, he e iew p esen s he limi a ions o he li e a u e while discussing he u u e ends. ECs ab ica ed wi h an imic obial/an ioxidan p ope ies p esen p omising esul s in inc easing he shel li e o mea while p ese ing i s senso y aspec s. In gene al, ECs a e highly sus ainable and e ec i e packaging sys ems o mea indus ies. Keywo ds: emulsion coa ings; heology; phase sepa a ion; he mal analysis; an imic obial agen s; mea 1. In oduc ion F esh mea is a highly pe ishable ood due o i s complex composi ion and animal a i- e y (Table 1). I a ac s a wide a ie y o mic obes and pa hogens. I s eshness is impac ed by he slaugh e ing condi ions, gu mic o lo a, s o age pa ame e s (mois u e, a mosphe ic oxygen, ligh , and empe a u e) and in e nal enzyma ic eac ions o he animal [1]. Table 1. Composi ion o mea om di e en animals. Mea Nu i ional Composi ion (pe 100 g) Ene gy (kJ/100 g) Re e ences Wa e P o ein Fa Ash Bee (lean) 75.0 22.3 1.8 1.2 485 [2] Bee ca cass 54.7 16.5 28.0 0.8 1351 Po k (lean) 75.1 22.8 1.2 1.0 469 Po k ca cass 41.1 11.2 47.0 0.6 1975 Veal (lean) 76.4 21.3 0.8 1.2 410 Chicken 75.0 22.8 0.9 1.2 439 Mu on ca cass 73.9 20.2 4.86 1.18 524 [3] Che on ca cass 75.6 20.3 3.68 4.09 - [4] Bu alo ca cass 76.3 20.4 1.37 0.98 724 [5] Foods 2023,12, 832. h ps://doi.o g/10.3390/ oods12040832 h ps://www.mdpi.com/jou nal/ oods Foods 2023,12, 832 2 o 15 Mea decay is a apid p ocess and begins as soon as he animal is slaugh e ed. The h ee main spoilage mechanisms a e mic obial, enzyma ic, and lipid oxida ion spoilage. The skin, in es inal ac , and he slaugh e ing and s o age condi ions o he animal a e o emos sou ces o mic obial spoilage. Spoilage bac e ia mos ound include species o Pseudomonas and S ep ococcus, among o he classes, whe eas he mos commonly ound spoilage molds a e Cladospo ium and Spo o ichum, among o he classes. The in es inal enzymes ha chemically combine wi h o ganic compounds and ini ia e de e io a ion eac ions in mea cause enzyma ic spoilage [ 6 , 7 ]. Lipid au oxida ion begins when blood ci cula ion and me abolic p ocesses cease. Mea p ese a ion aims o p e en de imen al eac ions (lipid and p o ein oxida ion and mic obial decay) inc ease mea ’s shel -li e and eshness, conse e nu ien s, and mos impo an ly, p o ec consume s. Fu he mo e, i aims o p oduce mea ha mee s and exceeds consume expec a ions [ 8 ]. Mul iple p ese a ion me hods ha e been ho oughly esea ched, including smoking, chilling, modi ied a mosphe e packaging, ac i e packaging, chemical p ese a i es, eezing, pickling, and edible packaging, all o which a e ad an- ageous acco ding o he equi emen s o he consume ma ke . The inc ease in pollu ion demands en i onmen ally sus ainable me hods and no el packaging sys ems o mea and associa ed p oduc s. Edible ilms (EFs) and coa ings (ECs) a e ood-based packaging sys ems applied o ood o sa egua d i om de imen al changes and ensu e p ese a ion. The concep o EFs and ECs can be da ed back o ancien China, whe e lipid coa ing was applied on lemons and o anges. Lipid coa ing was also used simila ly in he six een h cen u y in he US o p ese e ui s. Since hen, he idea o edible ilms and coa ings has achie ed inc edible ad ancemen s. The p incipal di e ence be ween EFs and ECs lies in he applica ion me hod. EFs a e i s p epa ed as a lamina e in one o mul iple laye s, d ied, and hen applied on he ood p oduc s, whe eas ECs a e ei he sp ayed on he p oduc s, o he p oduc s a e imme sed in he EC and hen d ied. The majo challenge in p epa ing he ilms and coa ings is he selec ion o app op ia e aw ma e ials ha will se e all he equi ed mechanical and ba ie p ope ies and hei op imum a io. Su ice i o say ha one composi ion canno be gene alized o a ood class, c ea ing a spacious a ea o he esea che s o explo e. An EC is a blend o wo o mo e immiscible liquids made miscible by adding an emulsi ie . Emulsions can be classi ied con en ionally based on hei composi ion as O/W (oil-in-wa e ) o W/O (wa e -in-oil). They can also be classi ied based on he numbe o phases as a double phase/mul iple phase emulsion, whe ein one emulsion is dispe sed in o ano he liquid o ano he emulsion, o example, O/W/O (oil-in wa e in-oil), o W/O/W (wa e -in oil in-wa e ) emulsion. F om he ood packaging aspec , mul iple emulsions a e mo e ad an ageous han con en ional ones. Mul iple emulsions can be used e icien ly o hold mo e han one unc ional ing edien , o mula ed s a egically o he con olled elease o ce ain ing edien s, and hey can be de eloped o isola e ce ain ing edien s ha migh eac o he wise. The ood indus y exploi s hese quali ies o mul iple emulsions o make complex ood ECs. The ollowing e iew p esen s a b ie classi ica ion o ECs based on he composi ion o he emulsions and on he pa icle size, ollowed by a comp ehensi e s udy o he h ee mos essen ial physical p ope ies (ing edien sepa a ion, heology, and he mal s abili y) o conside a ion o p epa e an e icien emulsion. Las ly, he ad an ages o ECs, limi a ions in cu en esea ch, and scopes o u u e p ospec s a e b ie ly discussed. The da a collec ed ha e been limi ed o hose om he pas 12 yea s, i.e., 2010 o 2022, om p ominen esea ch websi es, namely Web o Science, Scopus, and Google Schola . ECs o o he ood ca ego ies ha e no been co e ed he e. 2. Classi ica ion o ECs 2.1. Based on Composi ion The p ope ies (physical and mechanical) a e exclusi ely dependen on he ing edi- en o choice. P o eins p o ide ba ie p o ec ion ha is dis inc om ha p o ided by Foods 2023,12, 832 3 o 15 polysaccha ides o lipids. Thei combina ion in coa ings (composi es) may o e a a ie y o p ope ies. Polysaccha ides, p o eins, and/o hei blends o m he base wi h some included unc ional ing edien s such as an imic obial agen s. In some cases, he coa ing is made wi h essen ial oils (EOs) as he main ing edien and he polysaccha ide o ( a ely) p o ein ac s as a ca ie in he emulsion. The complexi y o mea demands a packaging ma e ial capable o se ing mul iple unc ions a once. The e o e, no single ing edien can sa is y all he pu poses and he e mus be a blend o ing edien s o mee he needs o an ideal packaging ma e ial. 2.1.1. Polysaccha ide Coa ings Cellulose, na i e and modi ied s a ch, pec ins, seaweed ex ac s (algina es, ca ageenan, and aga ), gums (acacia, agacan h, and gua ), pullulan, and chi osan a e p ima ily used o make coa ings [ 9 ]. These compounds impa ha dness, c ispness, compac ness, iscosi y, ad- hesi eness, and gel- o ming abili y while p e en ing dehyd a ion, oxida i e ancidi y, and su ace b owning. Al hough some gums ha e a nega i e cha ge, mos a e neu al [ 10 , 11 ]. Hyd ogen bonds play a c ucial ole in o ming ilms and hei inal cha ac e is ic due o he p esence o se e al hyd oxyl and o he pola g oups in hei s uc u es. Nega i ely cha ged gums such as algina e, pec in, and ca boxyme hyl cellulose (CMC) ypically ha e pH-dependen p ope ies [ 12 , 13 ]. Hyd ophobici y and poo mechanical s eng h a e he wo signi ican downsides o ha ing a pu ely polysaccha ide-based coa ing. 2.1.2. P o ein Coa ings Casein, whey p o ein (concen a e and isola e), collagen, gela in, egg albumin, co n, soybean, whea , co onseed, peanu , and ice a e he mos popula examples o p o eins used o coa ings [ 14 – 16 ]. P o eins p o ide good gas ba ie p ope ies bu poo mois- u e di usion esis ance. Thei duc ili y is ano he p oblem which can be imp o ed by gela iniza ion o p o ein. S udies on he e ec o dena u a ion deg ee on he physical and mechanical p ope ies o he edible ilm ha e epo ed ha p o ein dena u a ion educes he apo and oxygen pe meabili y; howe e , he p o ein o ien a ion a he molecula le el emains unclea . In con as , he ins abili y o p o ein-based ilms poses isks in package b eakage du ing anspo a ion, handling, and sale, esul ing in limi ed packaging applica ions [14,17,18]. 2.1.3. Lipid Coa ings Lipids o coa ings can be di ided in o ege able a s and oil, waxes, na u al esins, and EOs. Howe e , all o hem a e no sui able o mea due o he spoilage caused by lipid oxida ion. Pu e lipids wi h p o eins o polysaccha ides as a ca ie a e a mo e e ec i e me hod o ob ain gas ba ie and mois u e ba ie p ope ies. This can u he imp o e he colo , appea ance, ex u e, a oma, and simul aneously p e en mic obial spoilage [19]. 2.2. Based on Pa icle Size Emulsions can be ca ego ized as mac oemulsions (0.1–0.5 µ m), nanoemulsions (20–100 nm) , and mic oemulsions (5–50 nm). The pa icle size o he emulsion d ople s in luences he p ope ies o beha io o he emulsions. Fo emulsions o unc ion as a coa ing, i is c ucial o conside he ela ion o pa icle size o he elease mechanism and he a e o he d ople s h oughou he s o age li e. Homogeniza ion de ices a e bes sui ed o ob ain an emulsion o pa icula pa icle size. Du ing homogeniza ion, he la ge d ople s unde go size educ ion upon applying mechanical shee o ce. This yields uni o mly dis ibu ed d ople s in he dispe sed medium. Since he emulsion is he modynamically uns able, su ac an s a e in oduced o educe he in e acial ension be ween he dispe sed phase and he dispe sed medium [ 20 ]. This implies ha he pa icle size (in luenced by homogeniza ion and he p ocess condi ions) impac s he emulsion s abili y and, he eby, i s encapsula ion e iciency [ 21 ], mo e o which will be co e ed in he subsequen sec ions. An example o his co ela ion is he s udy o O/W sys em wi h d ople size <200 nm, Foods 2023,12, 832 4 o 15 encapsula ing es e a ol. I was ound ha he emulsion sys em was s able o 4 weeks while p ese ing es e a ol om lipid oxida ion and i s an imic obial p ope ies [22]. 3. The Complexi y o ECs o Mea s: Essen ial P ope ies o Conside a ion 3.1. Ing edien Sepa a ion The mos common phenomenon dis up ing he emulsion is he ing edien sepa a ion occu ing due o g a i a ion, coalescence, loccula ion, o phase sepa a ion. The phases o ien hemsel es acco ding o hei concen a ion and pola i y [ 23 – 25 ]. Sepa a ion may also occu due o en i onmen al changes such as empe a u e, p essu e, and pH. Ing edien sepa a ion can be moni o ed by c eaming s abili y analysis and he mal analysis ia DSC; i is also e lec ed in he mic os uc u e analysis o he coa ing. A a molecula le el, he sepa a ion occu s due o he di e ence in he ype o chemical bond ha an ing edien can make. Emulsions sepa a e due o he di e ence in he ype o bonds hey can make wi h each o he . Wa e can make s ong hyd ogen bonds, whe eas he oil phase makes only ela i ely weak an de Waals bonds [ 26 , 27 ]. This c ea es a he modynamically uns able en i onmen ha can be s abilized by p o iding ee ene gy o inc ease he a ea o in e ac ion be ween he ing edien s. This ene gy can be es ima ed by he ollowing equa ion [28]: ∆G=γi∆A whe e ∆ Gis he ee ene gy equi ed o inc ease he a ea o con ac be ween wo im- miscible liquids by ∆ A(a cons an empe a u e and p essu e) and γi is he cons an o p opo ionali y called as he in e acial ension. McClemen s [ 23 ] claims ha he magni ude o imbalance in he molecula in e ac ion ac oss he in e ace de e mines he in e acial ension; he g ea e he imbalance, he highe he in e acial ension. In his way, emulsi ie s a e used o ac as a bo de be ween he wo phases and c ea e uni o mi y. The mos common emulsi ie s epo edly used a e ween 80 [ 29 – 32 ] (concen a ion a ying om 0.2–25 w % o oil/ , ween 20 [ 30 , 33 , 34 ] (concen a ion same as ween 80), polyglyce yl-6-diolea e (3–7% w/w) [ 35 ] and leci hin (10% w/ ) [ 29 , 36 ] wi h ween 80 being he mos common one epo ed. Some esea che s ha e skipped using an emulsi ie and ins ead used a high- eloci y homogenize o ob ain a uni o m emulsion [37,38]. The emulsion’s low beha io (lamina o u bulen ) a ec s he pa icle coalescence. The pa i ion and blending o he dispe sed phase and dispe sed medium o achie e uni o m mixing is he i s s ep o homogeniza ion [ 39 , 40 ]. The emaining pa o he p ocess in ol es dis up ion o la ge d ople s in o smalle ones. The e o e, an unde s anding o he o ces esponsible o he d ople dis up ion du ing homogeniza ion is impo an . Acco ding o Mc Clemen s [ 23 ] he a e o he d ople s o med du ing homogeniza ion depends on he balance be ween he in e acial o ces holding he d ople s oge he and dis up i e o ces gene a ed in he homogenize sepa a ing hem [41,42]. The li e a u e indica ed ha emulsions p epa ed using a homogenize p oduced ex- emely uni o m emulsion in he pa icle size ange o 250–2000 nm. Some expe imen s ha e also used an ul asonica o o p epa e emulsions; howe e , he pa icle sizes we e lowe han hose p oduced by homogenize s (pa icle size ange: 50–300 nm) [ 30 , 43 – 45 ]. The selec ion o a homogenize depends on he desi ed pa icle size, he amoun o p oduc o be homogenized, he physicochemical p ope ies o he componen s and he cha ac e s e- qui ed in inished p oduc , and mos impo an ly, he ene gy cos s. Table 2summa izes he pa icle size in nanome e s (nm) as epo ed by some o he au ho s in hei s udies. Since homogenize s ha e high ene gy cos s, esea che s ha e ied o achie e simila ly s able emulsions using low-ene gy-cos me hods such as spon aneous emulsi ica ion, he phase in e sion me hod, he phase in e sion empe a u e me hod, spon aneous ul asonica ion, e c. [ 46 , 47 ]. Despi e being low ene gy me hods, hey ha e he majo disad an age o using a high a io o emulsi ie and oil. Foods 2023,12, 832 5 o 15 Table 2. Summa y o he composi ion, pa icle size, an imic obial/an ioxidan compound, a ge mic oo ganisms, p oduc ion, and shel li e condi ions s udied in he li e a u e. P oduc Coa ing Ma e ial Pa icle Size (nm) An imic obial/An ioxiadn Compound Ta ge Mic oo ganisms Condi ions Re e ence Chicken Gela in and chi osan nanoemulsion coa ing 1122.4 Rosema y ex ac in co n ge m oil and ε-poly-L-lysine Coli o ms, E-coli, molds, yeas 4◦C, 16 days (d) Coa ed by soaking, co e ed wi h cling ilm and s o ed [43] Eggs Chi osan 1483–983 Beeswax-basil EO E-coli, S. au eus Room empe a u e, 35 d 2 mL coa ing sp ayed and d ied. [44] Tu key b eas ille s Chi osan 342–5149 Za a ia Mul i lo a Boiss EO and Bunium pe sicum Boiss EO Salmonella en e i idis, Lis e ia monocy ogenes, TVC ( o al iable coun ), o al Pseudomonas spp., En e obac e iaceae, LAB (lac ic acid bac e ia), and yeas and mold coun 4◦C, 18 d Coa ed wi h nano-emulsion o 2 min, d ained o 1 h, and packed in zip lock bags. [29] Chicken b eas ille Sodium caseina e 57.4 Ginge EO Lis e ia monocy ogenes and Salmonella yphimu ium 4◦C, 12 d Coa ing by di ec imme sion and packed in LDPE [30] Raw goa mea Gum a abic 220–260 ge aniol and ca ac ol Bacillus ce eus and E-coli 4◦C, 9 d Coa ing by di ec dipping. [45] Po k loin Pec in 48.5–335.9 O egano EO and es e a ol TVC 4◦C, 20 d Coa ing by di ec imme sion o 30 s, ai d ying, and sealed he me ically in plas ic ays wi h 20% CO2 and 80% O2. [31] Sh imps Oil-in-wa e nanoemulsion 10.2–11 Sa on EO E-coli and S au eus 4◦C and 8 ◦C 14 d Coa ing by di ec imme sion, d aining, and sealing in PE (polye hylene) bags. [34] Red sea b eam Oil-in-wa e nanoemulsion 799.5–114.7 Ginge EO E-coli and S au eus 4◦C, 10 d Coa ing by di ec dipping. [48] F esh po k ende loin Gela in 4000–6000 Eugenol EO TVC, En e obac e iaceae lac ic acid bac e ia, Pseudomonas spp. 4◦C, 15 d Coa ing by soaking o 30 s and co e ed wi h cling ilms. [49] Chicken ille s Basil seed gum - Shi azi hyme EO and summe y sa o y EO Mesophilic, psych o ophic and LAB 4◦C, 12 d Coa ing by soaking o 120 s, d ain o 2 min ×2. [32] Scop halmus Maximus Locus bean gum and sodium algina e - Daphne in TVC, psych ophiles, and Pseudomonas spp. 4◦C, 18 d Coa ing by di ec dipping o 20 min a 4◦C, d ying o 60 min in ai low a 4◦C and hen indi idually packed in PE. [36] Chicken ille Konjac glucoman- nan/ca ageenan - Camellia EO TVC, psych ophiles, and LAB 4◦C, 10 d Coa ing by di ec imme sion o 10 s, d ying a ambien emp. o 10 min, and co e ing wi h plas ic w ap. [50] Tu key ille s Algina e 156.2 T achyspe mum ammi EO Lis e ia monocy ogenes 4◦C, 12 d Coa ing by di ec dipping, dipping in 2% CaCl2solu ion o 30 s and, packed in s e ile zippe packs. [51] Sliced bolognas Pec in - Thymus ulga is and Thymb a spica a EO Mesophilic and LAB 4◦C, 21 d Coa ing by dipping o 2 min and d aining o 3 min be o e s o age. [52] Foods 2023,12, 832 6 o 15 Table 2. Con . P oduc Coa ing Ma e ial Pa icle Size (nm) An imic obial/An ioxiadn Compound Ta ge Mic oo ganisms Condi ions Re e ence Po k mea Chi osan - Thyme EO Pseudomonas, Lac ococcus, and Acine obac e 4◦C, 12 d Coa ing by alcohol sp aying, ai d ying o 5 min, and packed in plas ic bags. [53] Ready o ea chicken pa ies Chicken bone gela in–chi osan 1370.8–183.6 Cinnamon EO and osema y ex ac E. coli,Bacillus sub ilis, and S au eus 4◦C, 16 d Coa ing by di ec dipping o 3 min, d ained o 10 min and sealed in PE bags. [38] C ay ish mea Chi osan - P opolis ex ac To al ae obic mesophilic, psych o ophic and H2S-p oducing bac e ia, yeas s- molds 4◦C, 16 d Coa ing by di ec dipping o 2 min, d ying o 60 min in ai low a 10 ◦C and hen indi idually packed in s e ile PE. [54] Chicken mea Chi osan - Duck a TVC and Lis e ia spp. 4◦C, 15 d Coa ing by di ec dipping o 2 min unde magne ic s i ing a 800 pm, d ied in lamina hood a 25 ◦C o 2 h and packed in PE bags. [55] Po k Chi osan 389.7–45.3 Schizonepe a enui olia EO TVC, Pseudomonas spp., LAB, and En e obac e iaceae 4◦C, 16 d Coa ing by di ec dipping o 30 s) ×2 wi h 2 min b eak, d aining o 10 min, and packed in oxygen-pe meable PE ilm. [56] F esh mea Chi osan >1000 Eugenol EO E. coli and S. au eus 4◦C, 14 d Coa ing by di ec dipping o 1 min and d aining. [57] Chicken b eas Calcium algina e - A emisia ag ance EO TVC, coli o ms, molds and yeas 4◦C, 12 d Coa ing by di ec dipping o 60 min a 4◦C, d aining and packing in PE bags. [58] Sil e ca p ille Sodiumalgina e– ca boxyme hyl cellulose - Zizipho a clinopodioides EO, apple peel ex ac , and zinc oxide nanopa icles (alone and in combina ion) Lis e ia monocy ogenes 4◦C, 14 d Coa ing by di ec imme sion a oom empe a u e o 30 s, d ained o 15 min, and d ied unde e ige a ion o 2 h. [59] Chicken b eas Whey p o ein isola e - O egano and clo e EO To al ae obic mesophilic bac e ia, En e obac e iaceae, o al ae obic psych o ophic bac e ia, LAB, and Pseudomonas spp. 4◦C, 13 d Coa ing by imme sion, d aining, and d ying unde s e ilized condi ions. [15] Paínho and alhei a Po uguese sausage Whey p o ein - O iganum i ens EO Salmonella spp. And L. monocy ogenes 4◦C, 106–126 d Coa ing by applying 1 mL o emulsion by silicone b ush and packing in LDPE ilms by he mal acuum sealing (30 s a 120 ◦C) [16] Chicken b eas Pomeg ana e juice–chi osan -Za a ia mul i lo a EO TVC, Pseudomonas spp., lac ic acid bac e ia, En e obac e iaceae, Psych o ophic bac e ia and yeas s– molds 4◦C, 20 d Coa ing by di ec imme sion o 2 min wice wi h a sho in e al, d ained o 5 h a 10 ◦C, and packing in s e ilized LDPE packages. [60] Rainbow ou ille Chi osan - Men ha spica a EO TVC, psych o ophic bac e ia, Pseudomonas spp. and En e obac e iaceae 4◦C, 14 d Coa ing by di ec imme sion o 1 min, d aining o 5 min, and packing in s e ile s omache bags. [61] Foods 2023,12, 832 7 o 15 Table 2. Con . P oduc Coa ing Ma e ial Pa icle Size (nm) An imic obial/An ioxiadn Compound Ta ge Mic oo ganisms Condi ions Re e ence Sil e ca p ille Me hylcellulose - Pimpinella a inis EO TVC and psych o ophic bac e ia 4◦C, 20 d Coa ing by di ec imme sion o 30 s ×2, and d ained o 5 h a 10 ◦C. [62] Bighead ca p ille Sodium Algina e - Ho semin (Men ha longi olia) EO TVC and psych o ophic bac e ia 4◦C, 16 d Coa ing by di ec imme sion o 30 s and d ained o 30 min a ambien condi ions, [63] Rainbow ou ille Fish gela in - O egano EO TVC 4◦C, 16 d Coa ing by di ec imme sion o 2 min ×2 wi h 1 min d aining in e al and d ying o 1 h unde s e ile lamina hood. [64] Sh imp Chi osan - Ga lic EO Ae obic pla e coun 4◦C, 11 d Coa ing by di ec imme sion o 5 min, d ained and d ied o 4ha 4◦C, and packed in plas ic w ap. [65] Lamb mea Chi osan 96–93 Sa u eja plan EO TVC, Pseudomonas spp. and LAB 4◦C, 20 d Coa ing by di ec imme sion o one min) ×2, d ained and d ied o 15 min a 25 ◦C [66] Rainbow ou ille Ca boxyme hyl cellulose -Za a ia mul i lo a Boiss EO and g apeseed ex ac TVC, Pseudomonas spp. and LAB 4◦C, 20 d Coa ing by di ec imme sion and d ained. [67] Re ige a ed b eam (Megalob ama amblycephala) Sodium algina e - Vi amin C and ea polyphenols TVC 4◦C, 20 d Coa ing by di ec imme sion o 1 min, ai d ied o 1 min, and imme sed in CaCl2and packed in PE bags. [68] T ou (Onco hync- husmykiss) ille s Ca ageenan - Lemon EO TVC, Pseudomonas spp. and En e obac e iaceae 4◦C, 15 d Coa ing by di ec imme sion. [69] 3.2. Rheology The s udy o an emulsion’s heological p ope ies is c ucial in unde s anding he p o ec i e abili y o he coa ings o mea o any o he ood p oduc . The luidi y and sp eadabili y o he emulsions a e he mos consequen ial heological cha ac e is ics o conside a ion. I was su p ising o he au ho s o ind ha only 13% o esea ch (as pe he p e iously men ioned c i e ia) conduc ed heological s udies o he coa ing emulsions o mea . Since mea has an i egula su ace, i becomes highly pe inen o in es iga e he iscosi y and sp eadabili y index o he emulsions. The li e a u e indica ed ha he coa ing emulsions manu ac u ed o mea and p oduc s exhibi ed a dec ease in iscosi y wi h inc easing shea a e and shea hinning p ope ies [ 44 , 49 , 69 , 70 ]. Coa ings p epa ed wi h EOs e ealed an inc ease in appa en iscosi y wi h inc easing oil concen a ions. I was also obse ed ha he iscosi y o he coa ings educed signi ican ly a e 30–32 days o s o age o he samples p epa ed wi h he highes amoun s o gelling agen and a (beeswax and animal a in a a blend) [37,70]. On a much deepe le el, one mus unde s and he heological beha io o he in- e acial laye ha su ounds he emulsion d ople s [ 71 , 72 ]. Acco ding o Mu ay and Dickenson [ 73 ], in e acial heology is de ined as he “s udy o he mechanical and low p ope ies o adso ben laye s a luid in e aces” whe eas he s esses esponsible o he mo emen o he in e acial egions ( ela i e o one ano he ) wi hou dis up ion o o e all su ace a e called in e acial shea de o ma ion. Howe e , hey may cause he su ace a ea o expand o con ac , which is e med he in e acial dila ional de o ma ion [ 27 , 74 , 75 ]. Foods 2023,12, 832 8 o 15 The in e acial heology is, consequen ially, con olled by he ac o s (emulsi ie concen a- ion, pH, empe a u e, and ionic s eng h) ha in luence he cha ac e and s eng h o he in e ac ions be ween he molecules abso bed a he in e ace [76,77]. 3.3. The mal S abili y The mal analysis is no a usual echnique chosen by esea che s; howe e , he da a gi e signi ican esul s conce ning he a e o emulsion d ople s and hei na u e. Emulsion sys ems a e known o be uns able, and he e o e hey unwind i e e sibly in o espec i e bulk phases. Howe e , one can ob ain a kine ically s able sys em ha enables analysis ia calo ime y, bu only i i accompanies he adso p ion and elease o ene gy. The p ima y pu pose o he mal analysis is o s udy he mel ing and c ys alliza ion beha io o emulsion d ople s, which is possible by di e en ial scanning calo ime y (DSC) and di e en ial he mal analysis (DTA) [ 23 ]. The analysis akes place based on de ec ing he ene gy adso bed (mel ing) o eleased (c ys alliza ion) by he emulsion sys ems unde he speci ied empe a u e condi ions. These measu emen s help moni o he in luence o ing edien s and expe imen condi ions on he mel ing and c ys alliza ion beha io o he bulk phases [ 70 , 78 ]. Fu he mo e, he mal analysis also gi es a de ailed insigh in o he polymo phic o ms o he iacylglyce ols and he glass ansi ion s a e o he polysaccha ides and p o eins. I also helps de e mine he d ople s’ s abili y o coalescence when he bulk phases mel o c ys allize; his is because he d ople c ys alliza ion empe a u e is di ec ly p opo ional o i s size owing o he supe cooling e ec s. A d ople ’s ene gy elease du ing c ys alliza ion is ins an aneous because i occu s a om he modynamic equilib ium, whe eas he ene gy abso p ion occu s a he ixed empe a u e o mel ing and i s kine ics a e de e mined by in e ac ions wi h he medium su ounding i [79]. 3.4. An ioxidan and An imic obial P ope ies Essen ial equi emen s o ECs in enhancing he shel li e o mea and p oduc s a e an imic obial and an ioxidan p ope ies. The impo ance o discussing he pa ame e s o he a o emen ioned p ope ies lies in he ac ha hey in luence he e icacy o ECs o mea conside ably and ECs wi hou hem a e ende ed less e ec i e. As p e iously es ablished, he high suscep ibili y o mea o spoilage demands ha i s shel li e be conside ed he highes p io i y. Since esh mea is highly suscep ible o oxida ion (lipid and p o ein), i is one o he majo pa ame e s o conce n. Hyd ope oxides a e p oduced h ough lipid pe oxida ion, and when hese compounds a e b oken down, seconda y oxida i e p oduc s a e p oduced, esul ing in unpleasan odo s and la o s in mea [ 32 , 80 , 81 ]. Oxida i e damages due o un- con olled o ma ion o ee adicals esul in quali y decay, loss o la o , ex u e, colo , and nu i i e alues o he mea due o PUFA (polyunsa u a ed a y acids) deg ading [1,82–84]. Na u al an ioxidan s om plan s and ex ac s he eo ha e been o in e es o esea che s; howe e , ECs’ e ec i eness agains lipid and p o ein oxida ion has no ye been s udied ex ensi ely. Na u al an ioxidan s p e en he o ma ion and sp ead o eac i e species and ee adicals by ac ing as hyd ogen dono s and sca enge s o ee adicals [85]. S ep 1 Ini ia ion: Hea , me al ions, and i adia ion ac as ca alys s and o m lipid ee adicals ha eac wi h oxygen o p oduce pe oxy adicals. R+O2→R•+•OOH (1) S ep 2 P opaga ion: Pe oxide adicals eac wi h o he lipid molecules o p oduce hyd ope oxides and mo e ee adicals as ollows: R•+O2→ROO•(2) RH +ROO• → ROOH +R•(3) ROOH →RO•+•OH (4) Foods 2023,12, 832 9 o 15 S ep 3 Te mina ion: Reac ion be ween wo ee adicals esul s in he e mina ion o he eac ion. R•+R• → R–R (5) R+ROO• → ROOR (6) ROO•+ROO• → ROOR +O2(7) Lobo e al. [ 84 ] explained he h ee dis inc me hods o oxida i e p o ein modi ica ion: h ough a speci ic amino acid’s oxida i e modi ica ion; by b eaking he pep ide caused by ee adicals; and by he eac ion wi h he p oduc s o lipid pe oxida ion, which esul s in he o ma ion o he ans e se binding p o ein. The p o ein’s suscep ibili y o oxida ion and enzyma ic p o eolysis inc eases wi h he p esence o amino acids such as cys eine, his idine, me hionine, and a ginine, which a e modi ied by ee adicals [ 86 – 89 ]. Ca bonyl o ma ion is a common eac ion pa hway in he oxida ion p ocess, and he same oxidan s ha s a lipid oxida ion also cause and p opaga e p o ein oxida ion. Ca bonyl de i a i es and p o ein–lipid and p o ein–p o ein complexes a e also p oduced when p o eins eac wi h seconda y lipid pe oxida ion p oduc s such as ke ones and aldehydes [ 90 – 93 ]. • OH is eadily p oduced in mea s when hyd ogen pe oxide o lipid pe oxide eac s wi h coppe o i on o modi y amino acids such as lysine and me hionine in speci ic loca ions. H2O2+ Fe(II)/Cu(I) → •OH + OH−+ Fe(III)/Cu(II) (8) •OH + P o ein (lysine)-NH2→P o ein-COH (ca bonyl) (9) Cu en ly he EOs om plan s, hei ex ac s, and by-p oduc s a e gaining much a en ion. Typically, EOs a e a sou ce o phenolic and polyphenolic subs ances wi h po en an ioxidan p ope ies [ 92 ]. The unc ional p ope ies o emulsions can be imp o ed by he syne gis ic e ec s o he EOs and hei cons i uen s, which in u n can success ully ex end he shel li e o mea , pa icula ly ha high in a such as po k. Due o he s ong adical sca enging p ope ies o phenolic compounds, he an ioxidan ac i i y o EOs is associa ed wi h mechanisms such as in e ac ion wi h ee adicals, hyd ope oxide decomposi ion, inhibi ion o chain eac ions, and ansi ional binding o me als [ 93 , 94 ]. The he modynamic s abili y o phenolic adicals can be a ibu ed o hei esonan s uc u es, acco ding o Majdinasab [ 32 ]. This implies ha he CHO ac ion o EOs is a mo e e ec i e an ioxidan han he phenolic con en [84]. The oxida ion ex en can be e alua ed by pe oxide alue (PV) de e mina ion o by he hioba bi u ic acid eac i e subs ances (TBARS) me hod. In a s udy, sh imp samples ea ed wi h 3% and 5% sa on EO emulsions we e ound o ha e signi ican ly low PV in compa ison o he un ea ed samples, especially a he end o he 14 h day o he s udy. A TBARS assay also e ealed a huge di e ence in he TBA alue o he emulsion coa ed samples and he uncoa ed ones [ 34 ]. Simila esul s we e disco e ed in a s udy on nanoemulsion p epa ed om o egano EO and es e a ol in PEc in EC. I was ound ha he coa ed po k loin samples eached close o he h eshold spoilage alue (4.20 mg MDA (malonaldehyde)/kg) on day 20 o he s udy, whe eas he uncoa ed samples c ossed he h eshold alue on he 5 h day o s udy [ 31 ]. Emulsions p epa ed om lipopep ides and BHA in sun lowe coa ing o aw bee pa ies e ealed ha he TBARS alue o he uncoa ed samples inc eased apidly on s o age and eached a alue o 2.8 mg MDA/kg on he 12 h day o s o age. The alue was much lowe o he emulsion-coa ed samples (0.35 and 0.25 o lipopep ides and BHA coa ing, espec i ely) [ 33 ]. The TBARS alue o chicken mea coa ed wi h osema y ex ac and ε -poly-L-lysine was ound o be signi ican ly lowe (1.523–1.97 mg MDA/kg) han ha o he uncoa ed samples (2.27 mg MDA/kg) [ 48 ]. Chicken ille s coa ed wi h BSG-based coa ings had a pe oxide alue o 5 meq ac i e O 2 /kg lipid a e 12 days whe eas he uncoa ed samples had a alue o 8.07 meq ac i e O 2 /kg lipid. The au ho s epo ed ha he o ma ion o hyd ope oxides was low due o he an ioxidan p ope ies o hyme EO and summe sa o y EO. They a ibu ed his o hyme’s highe amoun s o phenolic compounds, such as ca ac ol and hymol, and hei