第三章-鱼糜及其制品加工

第四章鱼糜

及其制品加工

（SurimiandSurimiProducts）鱼糜制品是我国的传统产品，在中国烹煮饪史上相传已久。福州鱼丸，云梦鱼面，山东鱼肉饺子等传统特产是我国鱼糜制品的代表，后来传到日本，鱼糜加工技术得到迅速发展

生产鱼糜的国家和地区主要有日本、韩国、泰国等。鱼糜制品是日本的传统食品，生产量很大。鱼糜品种有蒸鱼糕、烤鱼糕、炸鱼糕、烤鱼卷、鱼肉火腿、灌肠、鱼肉蟹足等，它的原料大多是鱼糜。目前，鱼糜的主要商品形式是冷冻鱼糜。浙江、福建等沿海地区也生产冷冻鱼糜，但由于海洋渔业资源发生重大变化，主要经济鱼种呈衰减趋势，高档鱼糜制品所需的白肉鱼（如鳕鱼）严重短缺。我国淡水养殖业的发达，除鲜销上市或速冻贮藏外，部分鱼加工成冷冻鱼糜。

湖北省，每年淡水鱼产量约为85万t，其中特别高产的白鲢已生产冷冻鱼糜，作为鱼糜制品的原料。鱼糜：将鱼肉经采肉、漂洗、脱水和加入抗冻剂等工序而制成的肌原纤维蛋白，是半成品。Surimiisstabilizedmyofibrillarproteinsobtainedfrommechanicallydebonedfishfleshthatiswashedwithwaterandblendedwithcryoprotectants.Surimiisanintermediateproduct

Before1960,surimiwasmanufacturedandusedwithinafewdaysasarefrigeratedrawmaterialbecausefreezingcommonlydeterioratedmuscleproteinsinducedproteindenaturation,whichresultedinpoorfunctionality.However,withthediscoveryofcryoprotectants,thesurimiindustrywasdeveloped.第一节鱼糜加工工艺原料鱼处理→清洗→采肉→漂洗→脱水→精滤→加入抗冻剂→冻结

一、原料处理

原料鱼处理基本上采用人工方法。

Heading,Gutting,andDeboning

先将原料鱼洗涤，除去表面附着的粘液和细菌，可使细菌减少80-90%。然后去鳞或皮，去头，去内脏。剖割方法有两种：

1.背割沿背部中部往下剖

2.切腹从腹部中线剖开。再用水清洗净腔内残余内脏、血污和黑膜，这一工序必须将原料鱼清洗干净，否则内脏或血液中存在的蛋白酶会对鱼肉蛋白质进行部分分解，影响鱼糜制品的质量。

清洗一般要重复2-3次，水温控制在10℃以下，以防止蛋白质变性。国外在海船上加工，鱼体的处理已采用切头机、除鳞机、洗涤机和剖片机等综合机器进行自动化加工，国内一些企业也已开始陆续配备这些设备，大大提高了生产效率。二、采肉（Mincing）用采肉机采鱼肉，将鱼体皮、骨除掉，而把鱼肉分离出来的过程。国内使用较多的是滚筒式采肉机。采肉时，鱼肉穿过采肉机滚筒的网孔眼进入滚筒内部，骨刺和鱼皮在滚筒表面，从而使鱼肉与骨刺和鱼皮分离。采肉机滚筒上网眼孔选择范围在3-5mm。aroll-typemeatseparatorThefishmeatispressedthroughtheorificesintotheinteriorofthedrum,whileseparatingskin,bone,hardcartilage,andotherimpuritiesintotheexteriorofthedrum.

鱼糜通常是用第1次采下的鱼肉来进行加工。任何形式的采肉机均不能把鱼肉采取干净，即在皮骨等废料中尚缺留少量鱼肉，为了充分利用这些蛋白质应进行第2次采肉，但第2次采得的鱼肉质量要比第1次差，色泽较深，有时还带一些碎骨屑，一般不作冷冻鱼糜，而是用作炸鱼糜制品的原料。

在工业化连续生产过程中，一般是把两台采肉机组合起来使用，一上一下，上面一台作第1次采肉，下面一台作第2次采肉。这样，上面一台采肉后的废料就可作为下面一台的原料直接投入，可节省劳力并提高效率。三、漂洗（Washing）漂洗可以除去鱼肉中水溶性蛋白质、色素、气味和脂肪，提高鱼糜白度和凝胶强度。它是鱼糜生产的重要工艺技术，对提高鱼糜制品质量及保藏性起到很大的作用。Washingisanessentialstepinremovingwater-solubleproteins,primarilysarcroplasmicproteins,whichisthoughttoimpedethegelpropertiesofsurimi,andreduceproductquality.Sarcroplasmicproteinsexistinthefluidswithinandbetweenmusclefibers,andincludemanymetabolicenzymesthatdiminishthestabilityoffunctionalproteinsduringstorage.Myofibrillarproteins,theprimarycomponentsthatpossesstheabilitytoformathree-dimensionalgelnetwork,constituteapproximately70%ofthetotalproteinsinmincedfishmeat.Areductioninwater-solubleproteinsinturnconcentratesthemyofibrillarproteins,thusenhancingthefunctionalpropertyofsurimi.漂洗方法有清水漂洗和稀碱盐水漂洗，根据肌肉性质选择漂漂洗方法。一般白色肉类直接用清水漂洗红色肉、中上层鱼类鲐鱼、远东拟沙丁鱼等用稀碱盐水漂洗，以有效防止蛋白质冷冻变性，增强鱼糜制品弹性。清水漂洗主要用于白色肉鱼类，如狭鳕、海鳗、带鱼、鲢鱼等，介于白色肉与红色鱼之间的鱼类也可使用此法。按比例将水注入漂洗池与鱼肉混合，鱼:水=1:5-10，慢速搅拌，使水溶性蛋白等充分溶出后静置，使鱼肉充分沉淀，倾去表面漂洗液，再按上述比例加水漂洗重复几次。清水漂洗法会使鱼肉肌球蛋白充分吸水，造成脱水困难，通常最后一次漂洗采用0.15%食盐水进行，便于肌球蛋白脱水。稀碱盐水漂洗主要用于多脂红身鱼类，先用清水漂洗两三次，再以鱼肉:稀碱盐水=1:4-6漂洗五次左右，稀碱盐水由0.1%-0.15%食盐水溶液和0.2%-0.5%碳酸氢钠溶液混合而成。漂洗技术关键一般来讲，漂洗用水量和次数与鱼糜质量成正比，用水量和次数视原料鱼的新鲜度及产品质量要求而定，鲜度好的原料漂洗用水量和次数可降低，甚至可不漂洗，生产质量要求不高的鱼糜制品，可降低漂洗用水量和次数。一般对鲜度极好的大型白色鱼肉可不漂洗。漂洗用水一般为自来水，水温要求控制在10℃以下，避免使用高硬度水及富含铜铁等重金属离子的地下水。

Washingefficiencyisoftenaffectedbyvariousfactors.Inadditiontothewater/meatratioandageoffish,thereistheshapeofthewashingtank(roundvs.square),thespeedoftheagitator,theshapeoftheagitator(verticalvs.horizontal),andwatertemperature.Square-shapedtanksseemtoworkbetter四、精滤（Refining）

用滤精机将鱼糜中的细碎鱼皮、碎骨头等杂质除去。红色肉鱼类所用过滤网孔直径为1.5mm，白色肉鱼类网孔直径为0.5-0.8mm。精滤分级过程中必须经常向冰槽中加冰，使鱼肉温度保持在10℃以下，以防鱼肉蛋白质变性。Beforethefinaldewateringunderascrewpress,impurities(suchasskin,finebones,scales,andconnectivetissues)areremovedbytherefiner.Therefiningprocessisusedtoseparateconnectivetissuesfromwashedmince.五、脱水鱼肉经漂洗后含水量较多，必须进行脱水。脱水方法有两种：一种是用螺旋压榨机（ScrewPress）除去水分，另一种是用离心机离心脱水，少量鱼肉可放在布袋里绞干脱水。温度越高，越容易脱水，脱水速度越快，但蛋白质易变性，从实际生产工艺考虑，温度在10℃左右较理想。

pH值在5.0-6.0时鱼肉脱水性最好，但在此pH范围内鱼糜凝胶形成能力最差，不宜采用。根据经验，白色肉鱼类在pH6.9-7.3，多脂红色肉鱼类在pH6.7脱水效果较好。▲螺旋压榨---ScrewPress

Themoisturecontentofmeatincreasesfrom82to85%to90to92%afterrepeatedwashing.Itisessential,therefore,toremovetheexcesswaterpriortoblendingwithcryoprotectantsandfreezing.Thedesirablemoisturecontentofthemeat,priortoblending,rangesbetween80and82%.

Thelengthandspeedofthescrew,thevolumereductionratio,andtheperforationofthescreensdeterminetheeffectivenessofwaterremoval.

Forexample,ascrewpresswithalargervolumereductionratioandlongerscrewcanachievethesamedewateringeffectathigherspeedomparedtothescrewpresswithasmallvolumereductionoperatedatslowerspeed.Screenswith0.5to1.5-mmperforationsarecommonlyusedinindustry.Inaddition,screenswithsmallerperforationsareusuallyplacedattheendsectiontopreserverecovery.Itisnotuncommontousea0.1to0.3%saltmixtureofNaClandCaCl2tofacilitatetheremovalofwaterfromthescrewpress.

Theuseofsaltoftenresultsinincreasedgelvalues.Addedsaltpositivelycontributestotheunfoldingofproteinstructure,resultinginbettergelstrengthwhentestingisdonewithinafewdaysaftermanufacturing.However,thisaddedsaltenhancesproteindenaturationduringfrozenstorageand,consequently,shortensthefrozenshelflifeofsurimi.Therefore,mechanicaldewateringwithoutsaltisbesttomaintainthefrozenstabilityofsurimi.六、加抗冻剂和斩拌-Cryoprotectantsandchopping

Theadditionofcryoprotectantsisimportanttoensuremaximumfunctionalityoffrozensurimibecausefreezinginducesproteindenaturationandaggregation.Sucroseandsorbitol,aloneormixedatapproximately9%w/wtodewateredfishmeat,serveastheprimarycryoprotectantsinthemanufactureofsurimi.However,6%sucroseistypicallyusedinsurimimanufacturedfromwarm-waterspeciesperhapsduetohigherthermalstability.

Inaddition,amixture(1:1)ofsodiumtripolyphosphateandtetrasodiumpyrophosphateat0.2to0.3%iscommonlyusedasbothachelatingagent,whichmakesmetalionsinsurimiinactive,andasapHadjustingagent.

Cryoprotectantswereoriginallyincorporatedintothedewateredmeatusingakneader.Currently,silentcuttersareoftenusedbecausetheyuniformlydistributecryoprotectantsfasterandthetemperatureincreaseslessduringchopping.

☺

Commercialpracticesformixingcryoprotectants(100kgperbatch)usingakneaderandasilentcutterare6minand2.5min,respectively.Thetemperatureofthemixmustnotexceed10℃

becauseattemperaturesgreaterthan10℃

,proteinfunctionalitycouldbedamaged.☺

Since1991,withthecommercialsurimiprocessing,enzymeinhibitors,suchasbeefplasmaprotein,eggwhites,orpotatoextracts,havebeenusedinconjunctionwithcryoprotectants,gelenhancers,andcolorenhancers.☺Enzymeinhibitorsarecommonlyformulatedwithsucrose,sorbitol,sodiumtripolyphosphate,tetrasodiumpyrophosphate,calciumcarriers(calciumlactate,calciumsulfate,calciumcitrate,orcalciumcaseinate),sodiumbicarbonate,mono-ordiglyceride.☺

Theformulationoftheseingredientsvaries,dependingonthecompany.Therefore,thereareslightdifferencesfromonecompanytoanother.Theadditionofenzymeinhibitorsorcalciumcompounds,however,beforefreezingsurimiisnotnecessary,especiallybecauseaddedcalciumcompoundscanactuallyenhanceproteindenaturationduringfrozenstorage.Instead,thesecalciumcompoundscanbeaddedwhenthesurimipasteispreparedtomakeslow-cookedgels.DuetotherecentoutbreaksofBSE(bovineserumencephalopathy,ormad-cowdisease)intheEU,Japan,Canada,andtheUnitedStates,theuseofbeefplasmaasanenzymeinhibitorhasbeenprohibited.七、包装、冻结Packagingand

Freezing☺

Incommercialapplications,surimiisformedinastandard10-kgblockinaplasticbag,whichisthenplaceonastainlesssteeltray.Thetraysarethenplacedinacontactplatefreezerandheldforapproximately2.5hroruntilthecoretemperaturereaches-25℃.Afterinspectingthefrozensurimiblockswithametaldetector,two10-kgfrozensurimiblocksarepackedintoacardboardbox.

Drumfreezingofsurimiofferstheprospectofrapidfreezing,whichenhancessurimiquality.按规格要求进行定量包装，2、4、6、10kg包装为聚乙烯塑袋，包装后的厚度为4-6cm。为了防止氧化，包装时应尽量排除袋内的空气。鲜鱼糜应尽可能在最短的时间内送去冻结，通常使用平板冻结机。由于平板结机具有冻结速度快的特点，能迅速通过-1～-5℃的最大冰晶生成带，这样能保持冻结产品的细小冰晶，保证冷冻鱼糜的冻结质量。冷冻鱼糜的品温越低，越有利于冷冻鱼糜的长期保藏，所以冷冻鱼糜的冷藏温度要在-25℃以下，并要求冷库温度稳定、少波动。八、MetalDetectionMetaldetectionisacriticalcontrolpointforthesurimiHACCPprogram.FDAhassupportedregulatoryactionagainstproductswithmetalfragmentsof7to25mminlength.Processorsmustmakesurethattheunsafeproductdoesnotreachtheconsumer.Themostcommontypesofmetalliccontaminationinclude

ferrous,copper,aluminum,lead,andvarioustypesofstainlesssteel.Ofthese,ferrousmetalsaretheeasiesttodetect.Insurimimanufacturingequipment,stainlesssteelalloysaremostcommonlyusedandarethemostdifficulttodetect.

Otherfactorsalsoaffectthesensitivityofmetaldetection,includingtheshapeofthemetal,orientationofthemetal,conditionoftheproduct(frozenvs.chilled),operationfrequency.九、BIOLOGICAL(INTRINSIC)FACTORSAFFECTINGSURIMIQUALITY

EffectsofSpeciesThereareanumberofspeciesthatareutilizedasrawmaterialforcommercialsurimiprocessing.Dependingonthespeciesused,however,thefunctionalandcompositionalpropertiesofthesurimivary.Thefunctionalpropertiesofsurimidependoncomposition,butcannotgenerallybepredictedfromcompositionalanalysis.Itis,therefore,importantforprocessorstounderstandtherelationshipsbetweenthephysico-chemicalfunctionsoffishandthefunctionalandcompositionalpropertiesofsurimi.Withthedevelopmentofsurimi,theimportanceofunderstandingtheintrinsicenzymesinthefishhasbeenhighlighted.Anetal.identifiedtheenzymesinPacificwhitingascathepsinsB,H,andL.Theybehavedifferentlywithdifferentenvironmentalconditions,suchaspH,temperature,andionicstrength.

CathepsinBandHareeasilywashedoffduringsurimiprocessing,whilecathepsinLremainsinthemuscletissue.CathepsinLhasanoptimumtemperatureof55°Candcausestexturaldeteriorationwhenthesurimipasteisslowlyheated.Therefore,enzymeinhibitorsarerequired

unlessthesurimiiscookedrapidlyusingeitheranohmicheaterormicrowave,oristhinlyextrudedandcookedrapidly,asincrabstickprocessing.Arrowtoothflounder（比目鱼）

isanotherfishthatrequiresenzymeinhibitorstominimizetexturaldeteriorationduetoaheat-stableenzyme.

Gelweakeningataround55to60°Chasalsobeenreportedinthreadfinbream（马鲅）,Atlanticmenhaden（鲱鱼）,whitecroaker（白姑鱼）,ovalfilefish（豚鱼）,andlizardfish.Alaskapollockhasbeenknownasafishthatgivesnoproteolyticenzymes.However,recentstudiesindicatethatAlaskapollockisinfestedwithmicrosporia（小孢子虫）,whichinducegelsoftening.Theinfestedmusclecontainsaproteasethatdegradesmyofibrillarproteinsataround50to60°C.

Cycteineproteaseinhibitorswereabletoreducetheenzymeactivity,

whereasspecificinhibitorsofserineproteasesandasparticproteaseswereineffective.Tomakesurimifromoily/darkorred-fleshedfish（红肉鱼）,suchasmackerel（鲭）,sardine,andsalmon（大麻哈鱼）,certainstepsmustbetakentonegatetheeffectsoftheoilandhemeproteins.Hemeproteins,suchasmyoglobinandhemoglobin,accountfortheredcolorofdarkmuscle.Inaddition,fatoxidationindarkmuscleispromotedbyhemeproteins,whichcausesanoffensive,rancidodortodevelop.Itisthereforesuggestedthat0.1to0.5%NaHCO3inthefirstwashingsolutionbeusedtoremovetheextraoil.Additionof0.05to0.1%sodiumpyrophosphateandtheuseofavacuumduringwashingarealsorecommendedtoremovehemeproteins.

EffectsofSeasonalityandSexualMaturityCompositionalpropertiesoffishvaryasthefishingseasonchanges.InAlaskapollock,proteincontentwashighest(19.0%)inNov.andlowest(16.5%)inMay,whilemoisturecontentwashighest(82.3%)inJulyandlowest(80.2%)inNov.Thehighestmoisturereading(84.5%)forPacificwhiting（大西洋鳟）

wasrecordedinApril,whilethelowestreading(80to82%)attheendofOct.Proteincontentwasatitslowest(14to15%)inApril,andthenincreasedandheldrelativelysteady(15.5to16.5%)afterJune.Fatheldfairlysteady(0.5to1.5%)untilAugust,andthenstartedtoincrease(1.5to2.5%)inOct.Therefore,forPacificwhitingsurimi,bothyieldandqualityincreaseduringthesummermonths.SeasonalchangesinthefatcontentofsardineharvestedinthemiddlePacificOcean.InAug.,thefatcontentwasashighas33%andwasthelowestinAprilat3%.Consequently,tomanufacturesurimifromsardinesinsummer,duetothehigherfatcontent,specialtechnologiesusingNaHCO3andacentrifugingdecantermustbeapplied.Ingeneral,fishharvestedduringthefeedingperiodproducethehighest-qualitysurimi.Duringthisperiod,fishmusclehasthelowestmoisturecontentandpH,aswellasthehighesttotalprotein.

Therefore,fishharvestedduringandafterthespawning(产卵)seasonproducethelowest-qualitysurimi.IthasbeenestablishedthatspawningfishhavearelativelyhigherpHandtendtoretainmorewater.Consequently,itisdifficulttoremovetheextrawaterfromthewashedmeat.Toeasilyremovetheextrawater,muscletissuecharacteristicsmustbealteredbyeitherloweringthepHorincreasingthesalinityofthefinalwashwater.However,thisalterationcanleadtosignificantlyreducedquality,particularlyafterfrozenstorage.

EffectsofFreshnessorRigorThefreshnessoffishisprimarilytime/temperaturedependent.Duetoendogenousenzymes

activatedbyrisingtemperatures,Pacificwhitingisprocessedwithinashortertimeperiod:within20hrafterharvest.Thebiochemicalandbiophysicalchangesduringthedevelopmentofrigormortisinducesignificantchangesinthefunctionalpropertiesofmuscleproteins.Fishshouldbeprocessedassoonaspossibleaftergoingthroughrigor.

Priortopassingthroughthisstage,about5hrinthecaseofpollocksurimi,itisdifficulttoremovethe“fishy”odor,variousmembranes,andothercontaminantsthataffectproductquality.However,Significantlyhigherproteincontentandyield,reducedcookingloss,andenhancedgel-formingabilityareassociatedwithsurimiprocessedfrommanuallyfilletedpre-rigortilapiafish（罗非鱼）.Thelengthoftimethatfishcanbeheldiniceorrefrigerationbeforeprocessingvaries,dependingonthespecies.Theeffectoftimeisespeciallyprominentinfish,suchasPacificwhiting,thathaveintrinsicenzymeproblems.Time/temperatureeffectsonthecompositionalandfunctionalqualityofPacificwhitingsurimiissignificant.Ifkeptrefrigerated,Pacificwhitingshouldbeprocessedwithinapproximately24hrofcapture.Otherwise,thequalitybeginstodecline.IfPacificwhitingarenotcooledquickly,processingmustoccurwithin8to10hr.Currentpracticeofsurimifromthreadfinbreamorotherwarm-waterspeciesinThailandutilizes40%frozenfishmixedwith60%freshfish.Manufacturingofsurimifromfrozencold-waterspeciesisvirtuallyimpossibleandresultsinnoorextremelypoorgels.Itispossible,however,tomakedecentsurimifrom

frozenwarm-waterspeciessimplybecauseofitshigherthermalstability.However,bettersurimicanbemanufacturedfromwarm-waterspeciesiffreshfishisused.十、PROCESSING(EXTRINSIC)FACTORSAFFECTINGSURIMIQUALITYHarvestingSurimiqualityisaffectedbytheharvestingconditionsandmethodsusedforcapture,aswellastheon-boardhandlingmethodsandvesselstorageconditions.Thegeographiclocationofthefishinggroundsmayalsoaffectqualityanddeterminefactors,suchasthesizeofthefishortheamountoftimerequiredtodeliverthefishtotheprocessingplant.Severalfactorsintheactualcaptureoffishcanalsoaffectfinalproductquality.Theseincludeat-seaweatherconditions,capturemethods,saltuptake,andthetemperatureofthefishpost-capture.

Althoughfreezingofgadoidfish,suchaspollock,severelydecreasesproteinfunctionality,threadfinbreamappeartowithstandproteindenaturationduringfrozenstorageandproduceanacceptableproduct.

On-BoardHandlingTimeandtemperatureofthefishbetweencaptureandprocessingcanbeconsideredtwoofthemostimportantfactorsthataffectfinalsurimiquality.Factorytrawlershavetheadvantageofprocessingatseaandusuallyproduceafinalproductwithin12hrafterharvestingthefish.However,fewfactorytrawlershavesystemsthatallowthemtochillthefishwhilewaitingtobeprocessed.Holdingtemperaturesat4to6°Ccanmakeasignificantdifferenceinsurimiqualitycomparedtofishheldcloseto0°C.

WaterTheimportantqualityfactorsassociatedwithwateraretemperature,hardnessormineralcontent,pH,andsalinity.Thelevelofchlorinationinthewatershouldalsobeconsideredbecauseofitsbleachinganddeodorizingeffects.

Thewatermustberefrigerated

toatemperaturebelowwhichthefishmuscleproteinscanretaintheirmaximumfunctionalproperties.Thetemperatureofthewatercanvary,basedonthethermostabilityofthefishproteins.Warm-waterfishcanthereforetoleratehigherwatertemperaturesthancold-waterfishwithoutreducingproteinfunctionality.Ca-activatedmyofibrillarMg–ATPasewashighestatthehabitattemperature(25.5°C)ofcarp.However,consideringthechangesinairtemperatureduringprocessing,therecommendedwatertemperatureforobtainingmaximumqualityis5°Corless.Theoretically,softwaterwithminimumlevelsofmineralssuchasCa2+,Mg2+,Fe2+,Mn2+isrecommendedforwashing.Hardwatercausesdeteriorationoftextureandcolorqualityduringfrozenstorage.Inaddition,Ca2+andMg2+areresponsibleforthetexturechange,particularlywhensurimiisfrozen,whileFe2+andMn2+areresponsibleforthecolorchange.Furthermore,thepHofthewatermustbemaintainedatapproximatelythatofpre-rigorfishmuscletissue(6.8to7.0)toobtainhigherwaterretentionofthegels.Wellwater,dependingongeographicallocations,oftenshowssignsofhighhardnessandtypicallycontainscations(Ca2+andMg2+).Forlarge-scaleoperations,alime-sodaprocesscanbeusedtosoftenhardwaterbyremovingCa2+andMg2+.Hardwateristreatedwithacombinationofslakelime,Ca(OH)2andsodaash,Na2CO3.CalciumprecipitatesasCaCO3

andmagnesiumprecipitatesasMg(OH)2.Theresidualcontentofsodium(Na+)intheprocessingwaterdoesnotdirectlyaffectthequalityofthesurimi.However,theintakeofsodiumfromsurimicouldnegativelyaffectthenutritionalprofileofthesubsequentsurimiseafood.Therefore,unlessreverseosmosis(RO)isusedtoremovesodiumions,theuseofadifferentsofteningmethodthatemploysamagnettoremoveCa2+andMg2+wouldbeideal.Beforewashing,thesalinityoffishminceisapproximately0.7%.Moistureremovalgraduallyincreaseswhenthepercentsaltconcentrationofthewashwaterisincreased.Itiscommon,therefore,touseamixtureofNaClandCaCl2at0.1to0.3%inthefinalwashwater.However,specialcaremustbegiven.Residualsaltinsurimi(0.2to0.4%)wouldminimizethelossofsolubleproteinsduringwashingandgiveslightlyimprovedgelstrength.However,thisresidualsaltcontentwillacceleratethedenaturationoffishproteinsduringfrozenstorage(beyond2mo),resultinginamuchshorterfrozenshelflife.Processingwaterhasalsobeentreatedwitheitherozone（臭氧）(O3）orUVlighttodisinfectbacteriaandotherpollutants.Becausethesechemicalsaredissipatedeasilyduringprocessing,theyareusedasaprocessingaidwithoutlabeling.Ozoneisapprovedasasanitizerforcontactwithfoodandfoodequipmentbecauseitiseffectiveagainstmanymicrobesandleavesnoresidueafteritreactsanddecomposes.Unlikeanotherstrongoxidizer(i.e.,chlorine),ozonedoesnotreactwithorganicmaterialstoproduceundesirablecompoundsanddoesnotleaveanunpleasanttaste.Accordingtotheindustrialtrialswithozonewaterinsurimimanufacturing,itreducesbacterialcountsaswellasincreaseswhiteness.Afterexposing0.6ppmfor30to60min,reducedbacterialcounts(2to3logs)andextendedshelflife(by1.2to1.6times)wereobserved.Theeffectofozoneonsurimicolorcanbeexplainedbasedonitsbleachingeffect.

Theporphyrinstructureofthehemepigmentisdestroyedduringozonation.

Time/TemperatureofProcessingIncommercialsurimioperations,fishareusuallydeliveredtoprocessingplantswithin6to12hrafterharvest.Duetothelimitedcapacityofprocessingfacilities,thefishareoftenkeptinholdingtankswithicewater(~0°C)foruptoanother6to14hr.Thus,fishareusually6to24hrpost-harvestbeforetheyaresubjectedtosurimiprocessing.

Duringthisholdingperiod,ifthefisharenothandledproperly,thetemperaturecanrise.Prolongedholdingtimeandelevated

temperaturescancausesevereproteolysisofmyofibrillarproteins.Consequently,proteolysisbeforeandduringprocessingcausesmore

myofibrillarproteinstobedissolvedaswater-solublewaste.Theeffectsofvariouspost-harveststoragetemperaturesandtimesontheproteolysisoffishanditsrelationshiptochangesinproteinsolubilitywereevaluated.

DegradationofMHC(myosinheavychain)increasedrapidlyduringthepost-harveststorageperiod.Thisdegradationoccurredevenwhenthetemperaturewasmaintainedat0°C.Incommercialoperations,fishiscommonlykeptinholdingtanks(~0°C)upto14hrbeforefisharesubjectedtoprocessing.

MHCorheavymeromyosinsubfragment-1(HMM-S1)Resultsshowedthat23.5%ofMHCdegradationoccurredforthisstoragetime(0°C,14hr).GreaterdegradationofMHCwasobservedwithprolongedstorage.Morethan70%oftheMHCwasdegradedwhenfishwerestoredat0°Cfor72hr.MHCdegradationwasalsoaffectedbystoragetemperatures.Fishkeptat5°Cshowedhigherdegradationthanthosestoredat0°C,suggestingthaticewaterwasmoreefficientthanrefrigerationincontrollingproteolysis.Whentemperaturesincreasedfurther,degradationoccurredmorerapidly.Withina14-hrstorageperiod,degradationnearlydoubledwhentemperaturesincreasedfrom0to10°C.Afterholdingat20°Cfor2hr,31.6%MHCwasdegraded,whichwasequivalenttothedegradationthatoccurredwhenfishwerestoredat0°Cfor24hr.Thesedata,therefore,indicatedthatbothtimeandtemperaturewerecriticaltoMHCdegradation.Lowtemperaturesalsoslowedproteolysis.Withprolongedstoragetime,however,severedegradationoccurredalthoughthestoragetemperaturewasmaintainedat0°C.Inthetemperaturerangeof0to5°C,theactivityofcathepsinL

wasinsignificant,whilecathepsinBexhibitedhalfitsmaximalactivity,andcathepsinHretainedaboutafifthofitsmaximalactivity.Therefore,cathepsinsBandHmightcontributetothedegradationoccurringatlow-temperaturestorage.Consequently,tominimizeproteolysis,fishshouldbeprocessedpromptlyuponlandingorkeptat0°C.Thetrendofactindegradationwassimilartothatofmyosinheavychain(MHC),buttoalesserextent.

Actindegradationalsoincreasedasstoragetimeandtemperatureincreased.At0°C,degradationofactinwasnotsignificantinthefirst3to6hr.Whenprolongedstoragetimewasallowed,however,degradationincreasedsubstantially.Consequently,actinwasdegradedbyabout20%after12hrat0°C.SimilartoMHCdegradation,actindegradedmorerapidlyat5°Cthanat0°C.Astemperaturesincreasedfurther,thedegradationofactinoccurredmorerapidly.Solubilizationof

MyofibrillarProteins

duringProcessingEfficientwashingisthemostimportantstepinsurimiprocessingtoensuremaximumgellingaswellascolorlessandodorlesssurimi.Mincedfishmeatcontainsapproximatelytwothirds

myofibrillarproteins.Theremainingonethirdconsistsofblood,myoglobin,fat,andsarcoplasmicproteins,whichimpedethefinalqualityofsurimigels.Washingincreasesthequalityofsurimiandextendsthefrozenshelflifebyremovingtheundesirableonethird,thusconcentratingthefunctionalmyofibrillarproteins.Aconsiderableamountofmyofibrillarproteins,myosinandactin,werelostinwastewaterduringwashinganddewatering.Thelossofmyosinwassmallinthefirstwastewater,increasedsubstantiallyinthesecond,andthenremainednearlyconstant

throughouttherestofprocessing.Generally,thewashingofmincedfleshwithwaterremovessarcoplasmicproteins,whichinturnconcentratesthemyofibrillarproteins.However,thehigherlossesofmyofibrillarproteins,particularlywithMHC,duringwashinganddewatering,havebecomeofparticularinterest.lane4–6:the1,2,3rdWSofthe3WC,respectively;lane7–10:the1,2,3,and4thWSofthe4WC,respectively.MHC:myosinheavychain;ATN:actin;β-TPM/TNT:β-tropomyosin/troponin-T;α-TPM:α-tropomyosinElectrophoreticpatt