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1、第四章 鱼糜及其制品加工（Surimi and Surimi Products）,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
2、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。Surimi is stabilized myofibrillar proteins obtained frommechanically deboned fish flesh that is washed with water and blended with cryoprotectants.Surimi is an intermediate product,Before
3、1960,surimi was manufactured and used within a few days as a refrigerated raw material because freezing commonly deteriorated muscle proteins induced protein denaturation,which resulted in poor functionality.However,with the discovery of cryoprotectants,the surimi industry was developed.,第一节 鱼糜加工工艺,
4、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,and Deboning 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
5、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。a roll-type meat separator The fish meat is pressed through the orifices into the interior of the drum,while separating skin,bone,har
6、d cartilage,and other impurities into the exterior of the drum.,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（Wash
7、ing）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。Washing is an essential step in removing water-soluble proteins,primarily sarcroplasmic proteins,which is thought to impede the gel properties of surimi,and reduce product quality.,Sarcroplasmic proteins exist in the fluids
8、within and between muscle fibers,and include many metabolic enzymes that diminish the stability of functional proteins during storage.Myofibrillar proteins,the primary components that possess the ability to form a three-dimensional gel network,constitute approximately 70%of the total proteins in min
9、ced fish meat.A reduction in water-soluble proteins in turn concentrates the myofibrillar proteins,thus enhancing the functional property of surimi.,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
10、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
11、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。,Washing efficiency is often affected by various factors.In addition to the water/meat ratio and age of fish,there is the shape of the washing tank(round vs.square),the speed of the agitator,the shape of the ag
12、itator(vertical vs.horizontal),and water temperature.Square-shaped tanks seem to work better,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。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。Before the final dewatering under a screw press,impurities(such as skin,fine bones,scales,and conn
13、ective tissues)are removed by the refiner.The refining process is used to separate connective tissues from washed mince.,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（Screw Press）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
14、鱼类在，多脂红色肉鱼类在pH6.7脱水效果较好。,螺旋压榨-Screw Press The moisture content of meat increases from 82 to 85%to 90 to 92%after repeated washing.It is essential,therefore,to remove the excess water prior to blending with cryoprotectants and freezing.The desirable moisture content of the meat,prior to blending,rang
15、es between 80 and 82%.The length and speed of the screw,the volume reduction ratio,and the perforation of the screens determine the effectiveness of water removal.,For example,a screw press with a larger volume reduction ratio and longer screw can achieve the same dewatering effect at higher speed o
16、mpared to the screw press with a small volume reduction operated at slower speed.Screens with 0.5 to 1.5-mm perforations are commonly used in industry.In addition,screens with smaller perforations are usually placed at the end section to preserve recovery.It is not uncommon to use a 0.1 to 0.3%salt
17、mixture of NaCl and CaCl2 to facilitate the removal of water from the screw press.,The use of salt often results in increased gel values.Added salt positively contributes to the unfolding of protein structure,resulting in better gel strength when testing is done within a few days after manufacturing
18、.However,this added salt enhances protein denaturation during frozen storage and,consequently,shortens the frozen shelf life of surimi.Therefore,mechanical dewatering without salt is best to maintain the frozen stability of surimi.,六、加抗冻剂和斩拌-Cryoprotectants and chopping The addition of cryoprotectan
19、ts is important to ensure maximum functionality of frozen surimi because freezing induces protein denaturation and aggregation.Sucrose and sorbitol,alone or mixed at approximately 9%w/w to dewatered fish meat,serve as the primary cryoprotectants in the manufacture of surimi.However,6%sucrose is typi
20、cally used in surimi manufactured from warm-water species perhaps due to higher thermal stability.,In addition,a mixture(1:1)of sodium tripolyphosphate and tetrasodium pyrophosphate at 0.2 to 0.3%is commonly used as both a chelating agent,which makes metal ions in surimi inactive,and as a pH adjusti
21、ng agent.Cryoprotectants were originally incorporated into the dewatered meat using a kneader.Currently,silent cutters are often used because they uniformly distribute cryoprotectants faster and the temperature increases less during chopping.,Commercial practices for mixing cryoprotectants(100 kg pe
22、r batch)using a kneader and a silent cutter are 6 min and 2.5 min,respectively.The temperature of the mix must not exceed 10 because at temperatures greater than 10,protein functionality could be damaged.,Since 1991,with the commercial surimi processing,enzyme inhibitors,such as beef plasma protein,
23、egg whites,or potato extracts,have been used in conjunction with cryoprotectants,gel enhancers,and color enhancers.Enzyme inhibitors are commonly formulated with sucrose,sorbitol,sodium tripolyphosphate,tetrasodium pyrophosphate,calcium carriers(calcium lactate,calcium sulfate,calcium citrate,or cal
24、cium caseinate),sodium bicarbonate,mono-or diglyceride.,The formulation of these ingredients varies,depending on the company.Therefore,there are slight differences from one company to another.The addition of enzyme inhibitors or calcium compounds,however,before freezing surimi is not necessary,espec
25、ially because added calcium compounds can actually enhance protein denaturation during frozen storage.Instead,these calcium compounds can be added when the surimi paste is prepared to make slow-cooked gels.,Due to the recent outbreaks of BSE(bovine serum encephalopathy,or mad-cow disease)in the EU,J
26、apan,Canada,and the United States,the use of beef plasma as an enzyme inhibitor has been prohibited.,七、包装、冻结 Packaging and Freezing In commercial applications,surimi is formed in a standard 10-kg block in a plastic bag,which is then place on a stainless steel tray.The trays are then placed in a cont
27、act plate freezer and held for approximately 2.5 hr or until the core temperature reaches-25.After inspecting the frozen surimi blocks with a metal detector,two 10-kg frozen surimi blocks are packed into a cardboard box.Drum freezing of surimi offers the prospect of rapid freezing,which enhances sur
28、imi quality.,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、Metal DetectionMetal detection is a critical control point for the suri
29、mi HACCP program.FDA has supported regulatory action against products with metal fragments of 7 to 25 mm in length.Processors must make sure that the unsafe product does not reach the consumer.The most common types of metallic contamination include ferrous,copper,aluminum,lead,and various types of s
30、tainless steel.Of these,ferrous metals are the easiest to detect.,In surimi manufacturing equipment,stainless steel alloys are most commonly used and are the most difficult to detect.Other factors also affect the sensitivity of metal detection,including the shape of the metal,orientation of the meta
31、l,condition of the product(frozen vs.chilled),operation frequency.,九、BIOLOGICAL(INTRINSIC)FACTORS AFFECTING SURIMI QUALITY Effects of Species There are a number of species that are utilized as raw material for commercial surimi processing.Depending on the species used,however,the functional and comp
32、ositional properties of the surimi vary.The functional properties of surimi depend on composition,but cannot generally be predicted from compositional analysis.It is,therefore,important for processors to understand the relationships between the physico-chemical functions of fish and the functional a
33、nd compositional properties of surimi.,With the development of surimi,the importance of understanding the intrinsic enzymes in the fish has been highlighted.An et al.identified the enzymes in Pacific whiting as cathepsins B,H,and L.They behave differently with different environmental conditions,such
34、 as pH,temperature,and ionic strength.Cathepsin B and H are easily washed off during surimi processing,while cathepsin L remains in the muscle tissue.,Cathepsin L has an optimum temperature of 55C and causes textural deterioration when the surimi paste is slowly heated.Therefore,enzyme inhibitors ar
35、e required unless the surimi is cooked rapidly using either an ohmic heater or microwave,or is thinly extruded and cooked rapidly,as in crabstick processing.,Arrowtooth flounder（比目鱼）is another fish that requires enzyme inhibitors to minimize textural deterioration due to a heat-stable enzyme.Gel wea
36、kening at around 55 to 60C has also been reported in threadfin bream（马鲅）,Atlantic menhaden（鲱鱼）,white croaker（白姑鱼）,oval filefish（豚鱼）,and lizardfish.,Alaska pollock has been known as a fish that gives no proteolytic enzymes.However,recent studies indicate that Alaska pollock is infested with microspor
37、ia（小孢子虫）,which induce gel softening.The infested muscle contains a protease that degrades myofibrillar proteins at around 50 to 60C.Cycteine protease inhibitors were able to reduce the enzyme activity,whereas specific inhibitors of serine proteases and aspartic proteases were ineffective.,To make su
38、rimi from oily/dark or red-fleshed fish（红肉鱼）,such as mackerel（鲭）,sardine,and salmon（大麻哈鱼）,certain steps must be taken to negate the effects of the oil and heme proteins.Heme proteins,such as myoglobin and hemoglobin,account for the red color of dark muscle.In addition,fat oxidation in dark muscle is
39、 promoted by heme proteins,which causes an offensive,rancid odor to develop.,It is therefore suggested that 0.1 to 0.5%NaHCO3 in the first washing solution be used to remove the extra oil.Addition of 0.05 to 0.1%sodium pyrophosphate and the use of a vacuum during washing are also recommended to remo
40、ve heme proteins.,Effects of Seasonality and Sexual MaturityCompositional properties of fish vary as the fishing season changes.In Alaska pollock,protein content was highest(19.0%)in Nov.and lowest(16.5%)in May,while moisture content was highest(82.3%)in July and lowest(80.2%)in Nov.The highest mois
41、ture reading(84.5%)for Pacific whiting（大西洋鳟）was recorded in April,while the lowest reading(80 to 82%)at the end of Oct.,Protein content was at its lowest(14 to 15%)in April,and then increased and held relatively steady(15.5 to 16.5%)after June.Fat held fairly steady(0.5 to 1.5%)until August,and then
42、 started to increase(1.5 to 2.5%)in Oct.Therefore,for Pacific whiting surimi,both yield and quality increase during the summer months.,Seasonal changes in the fat content of sardine harvested in the middle Pacific Ocean.In Aug.,the fat content was as high as 33%and was the lowest in April at 3%.Cons
43、equently,to manufacture surimi from sardines in summer,due to the higher fat content,special technologies using NaHCO3 and a centrifuging decanter must be applied.In general,fish harvested during the feeding periodproduce the highest-quality surimi.During this period,fish muscle has the lowest moist
44、ure content and pH,as well as the highest total protein.,Therefore,fish harvested during and after the spawning(产卵)season produce the lowest-quality surimi.It has been established that spawning fish have a relatively higher pH and tend to retain more water.Consequently,it is difficult to remove the
45、extra water from the washed meat.To easily remove the extra water,muscle tissue characteristics must be altered by either lowering the pH or increasing the salinity of the final wash water.However,this alteration can lead to significantly reduced quality,particularly after frozen storage.,Effects of
46、 Freshness or RigorThe freshness of fish is primarily time/temperature dependent.Due to endogenous enzymes activated by rising temperatures,Pacific whiting is processed within a shorter time period:within 20 hr after harvest.The biochemical and biophysical changes during the development of rigor mor
47、tis induce significant changes in the functional properties of muscle proteins.,Fish should be processed as soon as possible after going through rigor.Prior to passing through this stage,about 5 hr in the case of pollock surimi,it is difficult to remove the“fishy”odor,various membranes,and other con
48、taminants that affect product quality.However,Significantly higher protein content and yield,reduced cooking loss,and enhanced gel-forming ability are associated with surimi processed from manually filleted pre-rigor tilapia fish（罗非鱼）.The length of time that fish can be held in ice or refrigeration
49、before processing varies,depending on the species.,The effect of time is especially prominent in fish,such as Pacific whiting,that have intrinsic enzyme problems.Time/temperature effects on the compositional and functional quality of Pacific whiting surimi is significant.If kept refrigerated,Pacific
50、 whiting should be processed within approximately 24 hr of capture.Otherwise,the quality begins to decline.If Pacific whiting are not cooled quickly,processing must occur within 8 to 10 hr.,Current practice of surimi from threadfin bream or other warm-water species in Thailand utilizes 40%frozen fis
