冻食品保质测定方法Word文档格式.docx
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FXC$E2mepzE5^0frozenfoodsdeteriorateduringstoragebydifferentmodesormechanisms,as
Te#xap-}0l0summarizedinTable1.Microbesusuallyarenotaproblemsincetheycannotgrowat食品伙伴个性空间SRtl;
p{5|}-k6]
freezingtemperaturesunlesssubjectedtoextensivetemperatureabuseabovethe
L;
gB（ov0freezingpoint.Enzymesareabigconcernforfrozenfoods,whichcancauseflavor食品伙伴个性空间f+?
`-myy,U
change（lipoxygenase）innon-blanchedfruitsandvegetablesandaccelerated食品伙伴个性空间`（?
）zhJ
deteriorationreactionsinmeatandpoultry（enzymesreleasedfromdisrupted食品伙伴个性空间:
naKp@/Z$V
membranesduringprecooking）.Celldamageorproteinandstarchinteractionsduring食品伙伴个性空间0mL{yE1K"
[F3y&
N:
~
freezingcausedripandmushinessuponthawing.Discolorationcouldoccurbynonenzymatic食品伙伴个性空间Zh6@NoTp4XF7F
browning,bleaching,andfreezerburn.VitaminClossisoftenamajor
BS~5i'
biS0concernforfrozenvegetables.Physicalchanges,suchaspackageiceformation,食品伙伴个性空间H#JI"
xdl
moistureloss,emulsiondestabilization,recrystallizationofsugarsandiceoffrozen
&
Te0l8n,P）DT.v.d:
R0dessertsareoftenacceleratedbyfluctuatingtemperatures.
2d（Pp/Ya0Foranyspecificfrozenproduct,whichmodedeterminesitsshelflife,depends
8?
cE7U0G;
A0ontheproductcharacteristics（rawmaterials,ingredients,formulation）,pre-freezing
$[8[）~DZ,uR0treatment,freezingprocess,packagingfilmandprocesses,andofcoursestorage食品伙伴个性空间.kxA\ao
conditions.Allofthequalitydeteriorationandpotentialhazardsareusually食品伙伴个性空间（^XaGM7B
exaggeratedorcomplicatedbyafluctuatingtime-temperatureenvironment（e.g.
（n8^（y}O3bbK\0freeze/thawcycle）duringstorage.Ontheotherhand,theshelflifeofafrozenfood食品伙伴个性空间O
{K*QyR+m;
Y"
i
canbeextendedthroughingredientselection,processmodificationandchangeof食品伙伴个性空间*Q|"
y#Jes_
packageorstorageconditions,asdiscussedinSection3ofthisbook.食品伙伴个性空间6nuk/~o%~（?
2|F!
h
Thischapterwillfocusonshelflifetestingoffrozenfoodsforproduct
C_-^C#U}GP0developmentandmarketpractices.Shelflifetestingconsistsbasicallyofselectingthe食品伙伴个性空间:
@NT^）I5j%nn
qualitycharacteristicswhichdeterioratemostrapidlyintimeandthemathematical食品伙伴个性空间~$e"
f3wL
modelingofthechange.Table19.1canbeusedasareferencefortheselectionof
js+v#MTjX;
F5uy&
r0qualitycharacteristics,whichdependsonthespecificproductandusuallyrequires食品伙伴个性空间+~oi3Vy$}]
professionaljudgment.Mathematicalmodelingofqualitydeteriorationwillbe
1ON（Ns;
M*N）[}D9T0discussednext.
q0pg6Xzv4v03
（[Q$O]'
Y-Q:
F0Table19.1Deteriorationmodesoffrozenfoods
X!
q（lu,^%l~0FrozenFoodsDeteriorationModes
kQTMU0Frozenmeats,poultryandseafoodRancidity食品伙伴个性空间mx（G）R~-|
Toughening（proteindenaturation）食品伙伴个性空间oVWnK
Y
_
Discoloration食品伙伴个性空间|-{K6FCKE
Desiccation（freezerburn）
1RJ2T$T8M'
Hqf0FrozenfruitsandvegetablesLossofnutrients（vitamins）食品伙伴个性空间1T[cX2}r
Lossoftexture（temperatureabuse）食品伙伴个性空间Uux`+F+l）u
Lossofflavor（lipoxygenase,peroxidase）食品伙伴个性空间/TgD"
JqYZN
Lossoftissuemoisture（formingpackageice）
G1R7rE?
+G0Discoloration
~;
l'
Z0[{0jt~8kj0FrozenconcentratedjuicesLossofnutrients（vitamins）食品伙伴个性空间N7VB,A%e9vJi
Lossofflavor
+F-kjyU[s5n）W\8k0Lossofcloudiness食品伙伴个性空间4]^BM（F2H.L4Y}!
m"
Discoloration
:
Zz%i5DA`,]0Yeastgrowth（upontemperatureabuse）
dj"
Y/w;
OuMnD0Frozendairyproducts
$HPU;
_!
~a6["
[]0（icecream,yogurt,etc.）
H.k0^}y0Iciness（recrystallizationoficecrystals）
;
T'
L（K&
ofX^+ED0Sandiness（lactosecrystallization）
k6qJBG:
k#l7syIs0Lossofflavor食品伙伴个性空间;
DqxZg;
C6}+p
Disruptionofemulsionsystem
O8X#x7Qk）g+~0FrozenconveniencefoodsRancidityinmeatportions
3i4a0l（cT0Weepingandcurdlingofsauces食品伙伴个性空间'
A3S%~x%gF6b（Q6n
q@1P
pXI0Discoloration食品伙伴个性空间/}B/n@]9~
~l
Packageice
.z:
\coo8C_}0Frozenbakeryproducts（rawdough,食品伙伴个性空间4pk6I（iv|s
bread,croissants）
"
iwk0y,tM0Burstcan（upontemperatureabuse）（dough）食品伙伴个性空间Zb8o9vCLtn
Lossoffermentationcapability（dough）食品伙伴个性空间{!
iN9c*V~}+lC
Staling（becomingleathery）食品伙伴个性空间[-woA,T{`
Lossoffresharoma
!
Uz&
s3F6mO*TE_019.2Modelingofqualitydeterioration食品伙伴个性空间[pHeLK|x-A3y
19.2.1Basicequation食品伙伴个性空间,h;
Z5@
bj2c:
D[9m
Afrozenfoodstartstodegradeonceitisproduced（Figure19.1）.Therateand
R4}BR5R%G?
N0thedegreeofdegradationdependsonboththecompositionandtheenvironmental
u%o&
KF*[0conditionsduringstorageanddistribution.Ingeneral,thelossoffoodqualityorshelf食品伙伴个性空间FK6o'
L
p
lifeisevaluatedbymeasuringacharacteristicqualityindex,"
A"
.Thechangeofquality食品伙伴个性空间/Hpu1^Z
indexAwithtime（dA/dt）canusuallyberepresentedbythefollowingkineticequation:
食品伙伴个性空间/{TM*H%n
-dA/dt=kAn（19.1）
`BV5D!
ep0wherekiscalledarateconstantdependingontemperature,productandpackaging
i1MXJ"
w0P+|0characteristics;
nisapowerfactorcalledreactionorderwhichdefineswhethertherate
N'
p0RN[1f"
x04
%?
2n6Nn/l
\/A0ofchangeisdependentontheamountofApresent.Ifenvironmentalfactorsareheld
.Us+vv8\\0constant,nalsodeterminestheshapeofdeteriorationcurve.
^t+Ad3yz&
jS0Ao食品伙伴个性空间7Mty5CS+Eb+f4y_
Aa食品伙伴个性空间,p9lgm3o;
`0MD'
W
b食品伙伴个性空间9l9MA^U;
X\/a
c
l+?
BqCkqZ+CA0t食品伙伴个性空间j`3_cI/NoT?
jb
d
QFqSTA0e
b!
ngz$]a0Figure19.1Qualitydeteriorationcurves:
a）linear;
b）exponential;
食品伙伴个性空间/WVN%@xKe9drT
c）hyperbolic;
d）quadratic;
e）complex.
~Q%M'
J3a+crq/Ef019.2.2Zeroandfirstorderkinetics
W:
m3P,_Iy\t0Equation19.1canalsobewrittenas:
食品伙伴个性空间'
D+p,`5E"
}WBF7R
f（A）=kt（19.2）
%b2J|2FOQR5\0wheref（A）isthequalityfunction,kandtarethesameasabove.Theformoff（A）食品伙伴个性空间F-J9Z.hvE
dependsonthevalueofn.Whennisequaltozeroitiscalledzeroorderreaction
S`_
phG0kinetics,whichimpliesthattherateoflossofqualityisconstantunderconstant食品伙伴个性空间3N&
g%}_`pX
environmentalconditions（curve（a）inFig.19.1）.Ifnisequaltooneitiscalledfirst
c8Z（Ce'
g9E+cW*Re0orderreactionkinetics,whichresultsinanexponentialdecreaseinrateoflossas
a.{3{/w0nC5[0qualitydecreases（curve（b）inFig.19.1,whichbecomesastraightlineifplottedona食品伙伴个性空间（HW/Eta
semi-logplot）.Thesequalityfunctionscanbeexpressedasfollows:
食品伙伴个性空间-{9S*e#Fh）rbR9S
f（A）=Ao-A=kztzeroorder（19.3a）
$R-fIH*["
pF2L0f（A）=lnAo-lnA=kftfirstorder（19.3b）
x!
b9F-[`:
T8J05
Jm{x;
yv,A+KX"
mtY*W0whereAoistheinitialqualityvalue.IfAecorrespondstothequalityvalueattheendof
Ux7uSw}a（R3n
e0shelflife,theshelflife（q）ofthefoodisinverselyproportionaltotherate食品伙伴个性空间'
F8E/rW-U（M）?
~
constant:
食品伙伴个性空间（uEj,Vi~hZ4x
q=（Ao-Ae）/kzzeroorder（19.4a）
ptwl1HTyH0q=ln（Ao/Ae）/kffirstorder（19.4b）
IJ,ij!
|0Itshouldbenotedthatmostchemicalreactionsleadingtoqualitylossinfrozen食品伙伴个性空间u"
i#k'
iy2f
l[
foodsystemsaremuchmorecomplex.However,thereactionkineticscanbe食品伙伴个性空间F}dl4U
simplifiedintoeitherpseudo-zeroorderorpseudo-firstorderkinetics.Inthecaseof食品伙伴个性空间2J7]%mT!
w
complexreactionkineticswithrespecttoreactants,anintermediateorafinalproduct
BeN8Z
p'
J0KWO0（e.g.peroxidesorhexanalinlipidoxidation）couldbeusedasaqualityindex.There食品伙伴个性空间?
3\J7zj
C1~E$hkW（I
arefewcaseswhereneitherzeronorfirstorderkineticsapply.Curve（c）inFig.19.1
y}$S#p6W0showsthedegradationcurvefora2ndorderreaction（withsinglereactant）,whichalso食品伙伴个性空间wb_3drP"
dU_Z
showsastraightonasemi-logpaper.Afractionalordershouldbeusedtodescribe
gA%^,f（i7VG0thecurve（d）inFig.19.1.食品伙伴个性空间O&
M&
]F,H
Sometimes,thereisaninductionperiodorlagtimebeforethequality食品伙伴个性空间VS&
BX"
ZXA
deteriorationbegins（e.g.browningpigmentformationintheMaillardreactionora
m8_f.a-_vc0{c0microbialgrowthlagphase,asshownincurve（e）inFig.19.1.Thelengthofthelag食品伙伴个性空间pV#fq0yv
dependsonmanyfactors,buttemperatureisapredominantfactor.Giventhis,食品伙伴个性空间/_R*b.hX/z
modelingofboththeinductionorlagperiodanddeteriorationphasearenecessaryfor食品伙伴个性空间\x]
R+mft|
accuratepredictionofqualitylossorshelfliferemaining.Anexampleofsuchworkhas
[）xfGJ"
u+Wiz0beendemonstratedbyFuetal.（1991）forthegrowthofbacteriainmilk.食品伙伴个性空间9e9}x&
GtVI
Incertaincircumstances（e.g.Arepresentsasensoryhedonicscore）,anonkinetic食品伙伴个性空间V`,R0gN,X.q
approach,e.g.astatisticaldatafittingtechniquecanalsobeusedtodescribe
e4U#O`1[/FU
o!
Y0thedeteriorationcurves.VarsanyiandSomogyi（1983）foundthatthechangein食品伙伴个性空间T0m~,e）iX{N4p!
pD;
k
qualitycharacteristicsasafunctionoftimecouldbeapproximatelydescribedwith食品伙伴个性空间n"
h0J*U*A
linear,quadraticandhyperbolicfunctionsandthatstoragetemperatureandpacking
j:
x9x0E
f5yT#tl+V0conditionsaffectedtheshapeofthedeteriorationcurves.However,theparameters食品伙伴个性空间2~$ZX;
[7n&
E
determinedbydatafittingaredifficulttouseforpredictionundervariablestorage食品伙伴个性空间&
Qa）eP1[}A
conditionsexceptforthelinearcurve.
6~,LMgJ9y019.2.3Temperaturedependenceofdeteriorationrate
$i{&
nya4U9S5OKD4g019.2.3.1Arrheniuskinetics
zKV!
sql1^$b2FCfc0Onceafrozenprod
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