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