Influence of plasticizers on the properties of edible films prepared from fish water-soluble proteins

SUMMARY: The effects of type and concentration of plasticizers on the mechanical properties and water vapor permeability (WVP) of edible films from fish water-soluble proteins (FWSP) were investigated. Among plasticizers investigated in the present study, glycerol and polyethylene glycol (PEG) gave the films flexible structure. As the concentration of glycerol increased, tensile strength (TS) decreased with concomitant increase of elongation at break (EAB) and WVP. In contrast, PEG showed more marked influence on TS than on EAB. The FWSP films containing a glycerol : PEG ratio of 2 : 1 exhibited the maximum EAB value, while the increased ratio of glycerol to PEG reduced the water vapor barrier properties of FWSP films. It was revealed that the mechanical properties as well as WVP of edible films prepared from FWSP can be modified by the combination of glycerol and PEG.     

鳀鱼鱼肉与白鲢鱼鱼糜混合热聚集行为分析

斑点叉尾鮰 (Ictalurus punctatus) 刺少肉多,非常适合加工为鱼糜产品。为了评价不同家系斑点叉尾鮰鱼糜的加工特性,选取“江丰1号”鮰鱼的4个家系 (DZ1-1、KB4-1、K2-1、46-1) 鱼背肌肉为研究对象,经漂洗、斩拌、脱水、精滤等工艺制备成鱼糜,再通过二段式加热制成热诱导鱼糜凝胶。通过测定鱼糜蛋白的热稳定性以及鱼糜凝胶的白度、质构特性、持水性和凝胶强度等理化指标,分析不同家系鮰鱼鱼糜热诱导凝胶特性的差异。结果显示,DZ1-1家系鱼糜肌原纤维蛋白与其他家系相比热稳定性较高,β-折叠和β-转角结构相对含量较高,从而影响了热诱导鱼糜凝胶品质。各家系制备的热诱导鱼糜凝胶在白度上无显著性差异,持水性均大于80%。DZ1-1家系的凝胶强度为2.7×10² g∙cm,优于其他家系,而硬度、弹性和胶黏性与KB4-1家系无差异,但显著优于其他2个家系。综上,DZ1-1家系较适合作为鱼糜加工原料。     

Effect of Squid Melanin-Free Ink and Pre-Emulsification on Properties and Stability of Surimi Gel Fortified with Seabass Oil during Refrigerated Storage

ABSTRACT

The effects of melanin-free ink (MFI) and pre-emulsification on gel properties and stability of bigeye snapper surimi gel fortified with seabass oil during refrigerated storage of 10 days were studied. Lipid oxidation as determined by peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) of surimi gel increased as the level of seabass oil increased (P < 0.05). When MFI was incorporated into surimi gel, lower PV was obtained throughout the storage (P < 0.05). Addition of seabass oil pre-emulsified with soy protein isolate (SPI) in the presence of MFI yielded surimi gel with the highest breaking force and could improve oxidative stability during refrigerated storage (P < 0.05). Slight decrease in whiteness was found in surimi gel added with MFI, while those added with MFI along with pre-emulsified seabass oil showed increased whiteness (P < 0.05). Addition of MFI did not affect total viable count and psychrophilic bacterial count in surimi gels. Thus, the incorporation of pre-emulsified seabass oil prepared using SPI in conjunction with MFI could improve quality and oxidative stability of gel from bigeye snapper surimi.     

Effect of Bay (Laurus nobilis L.) Essential Oil on Surimi Gels Nutritionally Enhanced with Salmon and Flaxseed Oils

Bay essential oil (BEO) at 0.5 and 1 g/100 g was added to surimi gels fortified with omega (ω)-3 rich oils. Although the fortification resulted in increased (P < 0.05) susceptibility of surimi to lipid oxidation, 0.5 g/100 g BEO significantly reduced TBARS (P < 0.05). Addition of ω-3 rich oil or BEO improved the texture. Color values of the surimi seafood were improved particularly when BEO was added. Sensory properties, water activity, and pH values were generally within the acceptable range. These results suggest that the incorporation of BEO may allow food manufacturers to nutritionally enhance surimi seafood with beneficial ω-3 rich oils.     

Inhibiting effect of polymerization and degradation of myosin heavy chain during preheating at 30°C and 50°C on the gel-forming ability of walleye pollack surimi

ABSTRACT: To confirm the contribution of polymerization and degradation of myosin heavy chain (MHC) during preheating to the gel-forming ability of fish meat paste, walleye pollack surimi paste was preheated at 30°C and 50°C prior to heating at 80°C in the presence of various inhibitors. At 30°C, ethyleneglycol bis(2-aminoethyl ether) -N,N,N ', N '-tetraacetic acid (EGTA) and ethylenediaminetetraacitic acid (EDTA) inhibited gel formation as well as the polymerization of MHC, whereas dithiothreitol (DTT) and leupeptin promoted gel formation, which was accompanied by the enhancement of MHC polymerization and decreased MHC degradation, respectively. At 50°C, leupeptin inhibited MHC degradation and improved gel strength, whereas EGTA, EDTA and DTT had no effect on MHC polymerization and degradation and did not affect gel formation. The results demonstrate that the gel strength of cooked gel (80°C) is not affected by preheating at 30°C and 50°C and does not inhibit polymerization and degradation. Results suggest that the gel strength of cooked gel is dependent on the polymerization and degradation of MHC during preheating.     

鱼皮明胶蛋白膜的制备及其热稳定性

利用鲨鱼皮明胶制备蛋白可食膜,测定了成膜液蛋白浓度、甘油含量对明胶蛋白膜理化性质的影响,以及环境湿度对膜热稳定性的影响.结果发现,利用鲨鱼皮明胶可以制备成无色透明的蛋白可食膜,成膜液蛋白浓度对明胶蛋白膜的断裂延伸率(EAB)、水蒸气透过率(WVP)以及透明度值有一定的影响,对拉伸强度(TS)没有发生显著影响,但甘油含量从10％增加到70％时蛋白膜的TS逐渐降低.利用DSC对膜的热稳定性进行分析,结果表明当水分活度(Aw) ＜0.33时,明胶蛋白膜在常温下可以处于玻璃态,机械性质能够保持稳定.然而,当Aw超过0.44后,膜的玻璃化转变温度(Tg)起始点低于25℃,膜的EAB上升,TS出现显著下降.当Aw达到0.92时,膜甚至开始溶解变成溶胶.因此,利用鲨鱼皮制备的明胶蛋白膜只适合在Aw小于0.44的干燥环境中应用.     

耗氧率及溶氧胁迫对长蛸体内酶活力的影响

采用Winkler法测定水中溶氧含量,通过比较对照呼吸室与试验呼吸室水中溶解氧含量之差,测定长蛸(Octopus variabilis Sasaki)耗氧率及窒息点,并在不同程度的溶氧胁迫下测定长蛸体内多种酶的活力变化.结果表明,长蛸耗氧率在一个昼夜内呈现"低-高-低-高"的趋势;耗氧率与水温(10～30 ℃)呈正相关,与pH值(6.40～9.20)呈负相关;随着盐度的升高(14～31),长蛸耗氧率表现为两头高、中间平稳, 曲线呈凹状分布;雌性长蛸耗氧率高于雄性.窒息点随长蛸体重的增加而降低,平均体重为(30.50±6.03)g 的长蛸窒息点为0 4179mg/L;平均体重为 (54.50±4.65) g 的长蛸窒息点为0.3902 mg/L;平均体重为(97 00±11 36) g的长蛸窒息点为0.2738mg/L.随着溶氧胁迫程度的增加,LDH活力呈先升后降趋势,脂肪酶活力下降,SOD、POD、CAT、ACP、AKP和蛋白酶活力均呈"降-升-降"的趋势.     

耗氧率及溶氧胁迫对长蛸体内酶活力的影响

采用Winkler法测定水中溶氧含量,通过比较对照呼吸室与试验呼吸室水中溶解氧含量之差,测定长蛸(Octopus variabilisSasaki)耗氧率及窒息点,并在不同程度的溶氧胁迫下测定长蛸体内多种酶的活力变化。结果表明,长蛸耗氧率在一个昼夜内呈现低-高-低-高的趋势;耗氧率与水温(10~30℃)呈正相关,与pH值(6.40~9.20)呈负相关;随着盐度的升高(14~31),长蛸耗氧率表现为两头高、中间平稳,曲线呈凹状分布;雌性长蛸耗氧率高于雄性。窒息点随长蛸体重的增加而降低,平均体重为(30.50±6.03)g的长蛸窒息点为0.4179mg/L;平均体重为(54.50±4.65)g的长蛸窒息点为0.3902mg/L;平均体重为(97.00±11.36)g的长蛸窒息点为0.2738mg/L。随着溶氧胁迫程度的增加,LDH活力呈先升后降趋势,脂肪酶活力下降,SOD、POD、CAT、ACP、AKP和蛋白酶活力均呈降-升-降的趋势。