Deterioration of Fresh-Water Whitefish Muscle During Frozen Storage at −10°C

SUMMARY— Organoleptic and chemical deterioration of freshwater whitefish muscle frozen at −10°C for periods up to 16 weeks was assessed. As frozen storage of muscle progressed, the toughness and rancidity of baked muscle increased. The solubility of the myofibrillar protein fraction, "actomyosin," dropped from about 72 to 22% over the 16 week storage period of whitefish muscle. No change in the solubility of sarcoplasmic protein in frozen stored muscle was observed. However, with polyacrylamide disc electrophoresis, two new sarcoplasmic protein bands were detected after 16 weeks of storage. With storage of frozen muscle, water-binding capacity diminished. Although the total lipid and cholesterol contents of muscle remained constant throughout frozen storage, the phospholipid content decreased as the free fatty acid content increased. Oxidative deterioration of lipid in frozen muscle was estimated.     

Effect of Mixing and Moisture Modification on Toughening and Dimethylamine Formation in Alaska Pollock Mince during Frozen Storage at −10°C

Alaska pollock minces having reduced, normal and elevated levels of moisture were stored at - 10°C for 2 and 4 wk to determine how toughening was influenced by different amounts of ice in the frozen tissue. Minces containing reduced or elevated amounts of ice exhibited greater toughening than that observed in control minces. Also, some minces received an extra mixing step prior to freezing and this resulted in less toughening during storage, perhaps due to oxygen incorporated and partial inhibition of the enzyme system that converts trimethylamine oxide to dimethylamine and formaldehyde. However, among moisture-modified minces that received the same mixing treatment, development of toughening did not relate in any consistent manner with the development of dimethylamine.     

不同多糖对冻藏过程中草鱼肌原纤维蛋白流变性的影响

以草鱼肌原纤维蛋白作为研究对象,添加魔芋葡甘聚糖降解产物及葡聚糖（7 000 D,T7）,测定草鱼肌原纤维蛋白质量浓度、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gelelectrophoresis,SDS-PAGE）和流变性质的变化,比较不同多糖对冻藏过程中肌原纤维蛋白的冷冻保护效果,探讨不同多糖对草鱼肌原纤维蛋白结构的冷冻保护机制。研究发现,随冻藏时间的延长,空白、酶解魔芋葡甘聚糖、辐解魔芋葡甘聚糖、T7及商业抗冻剂各组对应草鱼肌原纤维蛋白质量浓度和流变储能模量（G’）均下降,与冻藏过程草鱼肌原纤维蛋白SDS-PAGE的变化基本吻合。同时,添加上述不同多糖各组草鱼肌原纤维蛋白质量浓度和G’均高于空白组。研究结果表明：T7、酶解魔芋葡甘聚糖及辐解魔芋葡甘聚糖通过保护副肌球蛋白和肌球蛋白轻链,延缓草鱼肌原纤维蛋白的变性,其中,辐解魔芋葡甘聚糖效果最强,T7次之,酶解魔芋葡甘聚糖最弱,但都具有明显的冷冻保护作用。     

Chemical Deterioration of Frozen Bovine Muscle at −4° C

SUMMARY— During an 8-week storage period of bovine muscle at −4°C, the total extractable protein content dropped from 91 to 51%. This decline, accompanied by a decrease in water-binding capacity of muscle, was primarily caused by the insolubilization of both sarcoplasmic proteins and actomyosin. The increase in the free fatty acid content from about 1.6 to 9.1% over the 8-week period may be attributed to phospholipid hydrolysis. The TBA number rose progressively throughout the entire storage period while the peroxide value increased to a maximum in 2 weeks of storage and then decreased to a constant value of 7.     

3 种鱿鱼冻藏过程中肌原纤维蛋白功能特性变化

为探讨阿根廷鱿鱼、北太平洋鱿鱼（以下简称北太鱿鱼）和秘鲁鱿鱼冻藏过程中肌原纤维蛋白功能特性的变化情况。将3 种鱿鱼于－18 ℃冰箱中冻藏,分别于0、15、30、45、60、75、90、105 d和120 d进行取样,分析测定鱿鱼肌肉中肌原纤维蛋白质量浓度、溶解性、浊度、乳化能力、Ca2＋-ATPase活力、起泡性及泡沫稳定性、羰基含量和总巯基含量等。结果表明,与未冻藏（0 d）相比,经冻藏120 d后,阿根廷鱿鱼、北太鱿鱼、秘鲁鱿鱼肌原纤维蛋白浊度、羰基含量明显增加;其中,肌原纤维蛋白浊度分别增加至1.303、0.608和1.177,羰基含量分别增加了8.74、13.95 nmol/mg和4.79 nmol/mg。肌原纤维蛋白质量浓度、溶解性、起泡性、泡沫稳定性、乳化活性指数（emulsification activity index,EAI）、乳化稳定性指数（emulsification stability index,ESI）、Ca2＋-ATPase活力和总巯基含量则明显下降,其中阿根廷鱿鱼肌原纤维蛋白质量浓度、溶解度、Ca2＋-ATPase活力和总巯基含量冻藏120 d后依次下降72.22%、69.68%、93.07%和76.66%。冻藏120 d后,阿根廷鱿鱼、北太鱿鱼和秘鲁鱿鱼肌原纤维蛋白的EAI分别下降了10.09、15.48 m2/g和11.63 m2/g,其ESI下降趋势与EAI下降趋势基本一致。北太鱿鱼肌原纤维蛋白起泡性和泡沫稳定性下降较为明显,冻藏120 d后,分别下降了60.00%和8.89%,下降速率明显高于阿根廷鱿鱼和秘鲁鱿鱼。综上,在低温冻藏过程中,3 种鱿鱼肌肉中肌原纤维蛋白理化特性表现出类似的变化趋势,但不同理化特性下降幅度及速率有所不同。     

Chilled (5°C) and Frozen (−18°C) Storage Stability of the Purple-Hinge Rock Scallop, Hinnites multirugosus Gale

Purple-hinge rock scallops (Hinnites multirugosus), native to northeast Pacific Coast waters and under evaluation for commercial aquaculture, were harvested wild and analyzed for storage stability. Over 2 wk of chilled storage at 5°C or 5 months of frozen storage at ?18°C, scallops showed no appreciable lipid oxidation, proteolytic change, and ammonia development. Hypoxanthine fluctuated throughout fresh storage. Bacterial numbers were unchanged at ?18°C but sharply increased during the second week at 5°C. Odor of raw scallops deteriorated somewhat at week 2 of chilled storage and month 4 of frozen storage. However, when cooked, scallops showed no significant differences for most sensory characteristics or for acceptability. Cooking losses were variable. Textural shear parameters changed with weight and frozen storage.     

冷冻贮藏引起的鱼肉蛋白变性及物理化学特性的变化

冷冻贮藏是鱼类重要的贮藏方法,但不适当的冻藏和缓化会引起鱼肉肌原纤维蛋白的变性,造成鱼肉质量降低。鱼肉蛋白质变性主要和蛋白质的结构变化有关,包括空间结构的变化、溶解性的变化、Ca2+-ATPase活性变化、巯基和二硫键含量变化、表面疏水性变化及海水鱼中甲醛含量的变化,而结构的变化进一步影响蛋白质的功能特性。本文主要论述鱼肉蛋白质的冷冻变性机理,并对鱼肉蛋白质在冷冻贮藏期间引起的蛋白质物理化学特性的变化进行论述。     

不同冻结温度下牛肉的肌原纤维蛋白变性与肌肉持水性

为明确冷冻温度对牛肉肌原纤维蛋白变性和肌肉持水性（water-holding capacity,WHC）的影响、探讨肌 原纤维蛋白变性与WHC的相关性。以牛背最长肌作实验材料,探究－9、－18、－23、－38 ℃下冻结后肌原纤维 蛋白理化特性和牛肉WHC。通过测定巯基含量、蛋白质溶解度、Ca2＋-三磷酸腺苷酶（adenosine triphosphatase, ATPase）活力及蛋白质热稳定性考察牛肉冻结后肌原纤维蛋白变性情况,利用解冻汁液流失与加压失水率指标衡 量牛肉WHC,采用低场核磁共振（low field-nuclear magnetic resonance,LF-NMR）波谱和磁共振成像（magnetic resonance imaging,MRI）技术对比分析了肌肉水分分布情况,并于4 ℃解冻后测定了色差与剪切力。结果表明： －23 ℃与－38 ℃下冻结试样较－9 ℃与－18 ℃肌原纤维蛋白变性程度小：－23 ℃与－38 ℃下冻结试样蛋白质溶解 度、Ca2＋-ATPase活力、巯基含量和总变性焓相比－9 ℃与－18 ℃实验组较高（P＜0.05）。－23 ℃与－38 ℃下冻 结牛肉解冻后L*值、b*值、剪切力、解冻汁液流失和加压失水率显著低于－9 ℃与－18 ℃（P＜0.05）。LF-NMR 及MRI结果相互佐证了肉样在－23 ℃与－38 ℃冻结下肌肉WHC高于－9 ℃与－18 ℃的实验结果。肌原纤维蛋白理 化特性（蛋白质溶解度、Ca2＋-ATPase活力、巯基含量、总变性焓）与WHC（解冻汁液流失率、加压失水率）均呈 极显著相关（P＜0.01）,L*、b*值及剪切力亦与WHC存在极显著相关（P＜0.01）。相关性分析结果验证了牛肉冻结 过程中肌原纤维蛋白变性对肌肉持水性存在显著影响,进而导致牛肉解冻后出现肉色劣变、嫩度下降及汁液流失。     

不同漂洗处理后冻藏对鲤鱼蛋白功能特性的影响

蛋白质氧化是引起食品加工及贮藏过程中品质发生劣变的一个主要原因。本文以鲤鱼肉为研究对象,主要研究鱼糜加工过程中经不同漂洗处理后冻藏对鲤鱼肌原纤维蛋白功能特性的影响。把鱼肉经不同方式漂洗[未漂洗;传统漂洗;添加抗坏血酸钠漂洗;添加没食子酸丙酯(PG)漂洗]后置于-25℃,经不同时间(0、30、60、90、120 d)冷冻贮藏后,利用质构仪、电子显微镜、流变仪等设备对鲤鱼肌原纤维蛋白乳化性、凝胶性以及流变性等指标进行测定,结果表明冻藏过程中发生的蛋白质氧化会引起鲤鱼肌原纤维蛋白各项功能特性降低,在漂洗过程中加入PG处理的鱼肉功能特性改变最小,说明添加PG漂洗可以有效地抑制蛋白质氧化的发生,从而减少鲤鱼肌原纤维蛋白功能特性的改变。     

Effect of previous gutting on rancidity development in horse mackerel (Trachurus trachurus) during frozen storage at −20 °C

Gutting was applied to fresh horse mackerel (Trachurus trachurus) to study its effect on rancidity development during a prolonged frozen storage (up to 12 months at −20°C). To do so, chemical (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescence ratio, FR) and sensory (odour and taste) analyses were carried out. The results showed that the gutting of horse mackerel led to a higher degree of oxidation in the frozen product, according to the chemical (PV, TBA-i and FR) and sensory (odour and taste) analyses. However, a lower extent of lipid hydrolysis (FFA formation) was detected at the end of the storage (twelfth month) as a result of gutting. It is concluded that the gutting of a medium-fat fish species such as horse mackerel is not recommended as previous treatment to frozen storage.     

冻藏对肌原纤维蛋白结构特性与功能特性的影响

冷冻贮藏是肉类食品重要的贮藏方法,但在冻藏会引起肉类食品中的主要蛋白一肌原纤维蛋结构发生变化,引起蛋白质发生变性,从而影响其功能特性,降低肉类制品的品质。论述了肌原纤维蛋白的冷冻变性机理,并对冷冻贮藏期间肌原纤维蛋白结构与功能特性的变化进行论述。     

刺云实胶对草鱼肌原纤维蛋白的冷冻保护作用

为探究刺云实胶对肌原纤维蛋白的冷冻保护作用,以商业抗冻剂(4%蔗糖+4%山梨醇)为对照,研究刺云实胶对草鱼肌原纤维蛋白溶液冻结曲线的影响,并通过测定0～28 d冻藏过程(-20±1℃)中肌原纤维蛋白Ca²⁺-ATPase活性、巯基含量、表面疏水性、内源性荧光光谱及解冻后水分流动性的变化来研究刺云实胶对草鱼肌原纤维蛋白冻藏稳定性的影响。结果表明,添加1.0%刺云实胶和商业抗冻剂的草鱼肌原纤维蛋白溶液的冻结点分别为-8.3℃和-7.3℃,低于空白样品的-5.5℃。与新鲜肌原纤维蛋白相比,冻藏28 d后,添加1%刺云实胶和商业抗冻剂的肌原纤维蛋白的Ca²⁺-ATPase活性、总巯基含量、活性巯基含量分别下降了45.69%和45.17%、24.49%和42.28%、25.13%和39.79%,而表面疏水性分别增加了176.00%和122.23%,变化幅度显著低于空白对照组。低场核磁共振分析研究结果表明添加1%刺云实胶和商业抗冻剂可以显著抑制肌原纤维蛋白溶液解冻后水分流动性增加。因此,1%刺云实胶可以增强冻藏过程中草鱼肌原纤维蛋白的稳定性。     

菊粉对冻藏鲢鱼鱼糜肌原纤维蛋白抗冻性的影响

研究菊粉对冻藏鲢鱼鱼糜肌原纤维蛋白抗冻性的影响,对鲢鱼鱼糜盐溶性蛋白含量、肌原纤维蛋白的Ca2＋-ATPase活性、总巯基含量、活性巯基含量、表面疏水性进行分析。结果表明,在－18 ℃条件下冻藏5 周后,菊粉可以抑制鲢鱼糜肌原纤维蛋白的冷冻变性,盐溶性蛋白含量、肌原纤维蛋白的Ca2＋-ATPase活性、总巯基含量、活性巯基含量的下降趋势和表面疏水性的增加趋势均得到抑制,其中1.5%菊粉的抗冻效果优于其他实验组且与商业抗冻剂接近。研究结果为开发热量和甜度较低的抗冻剂提供一定的理论依据。     

Quality changes in frozen whole and gutted anchovies during storage at −18°C

Fresh samples of whole and gutted anchovies were blast frozen at −35°C and stored at −18°C. The quality of the samples was examined as organoleptic, microbiological and chemical changes during the storage period. Gutting had no significant effect on the quality of the final product. Sensory quality was good for up to 90 days of storage. No increase in microbial activity was detected, but some oxidative and hydrolytic deterioration of fats were observed. The final product was still edible after 180 days.     

Behaviour of the mechanically separated flesh of some common fish species of the Mexican shrimp by-catch during storage at −20°C

Deboned minces prepared from fish species predominant in the Mexican shrimp by-catch were examined with respect to their stability during storage for 10 months at –20°C. Reductions in the extractability of salt-soluble proteins occurred to varying levels in all samples, particularly in the initial storage phase. These changes were shown to influence the textural characteristics of the minces, albeit to a minimal extent. Considerable variability in the colour of minces from different species was observed and a washing procedure which effectively removes dark pigments is described. In general, the acceptability of the products was maintained throughout the storage period. It is thus concluded that deboning and the freezing of the resultant minces could offer a potential means of processing currently wasted by-catch fish into human food.     

Characterization of aroma changes in human milk during storage at −19 °C

Breastfeeding is believed to impart major beneficial effects on babies, due to various human-specific components. Compatibility of family and profession, however, often necessitates the pumping of breast milk and its storage under diverse conditions, either in a refrigerator, freezer or for brief periods at room temperature. The present study investigates the formation of a characteristic fish-like and metallic off-odour during the conventional storage of human milk that does not develop during cow milk storage, and elucidates the molecular factors for these specific aroma changes. Odorants in fresh and stored human milk containing the specific fishy-metallic off-odour were characterized by means of gas chromatography–olfactometry and identified based on their mass spectrometric data and specific chromatographic and sensory characteristics.     

Moisture Sorption Isotherms of Dried Apricot, Fig and Raisin at 20 °C and 36°C

Isotherms were found to be of type I, typical of high sugar foods. Study on temperature dependence of isotherms showed that above water activities of 0.6, moisture content was higher at higher temperature. This was explained by endothermic dissolution of sugar at high water activities. Iglesias and Chirife, Halsey, BET and GAB equations were tested to fit the data. Monolayer moisture contents for the three foods were determined from BET and GAB equations. In both models, monolayer moisture was found to decrease with increasing temperature. Isosteric heat of sorption data from the isotherms at two temperatures, revealed that strength of interactions between water vapor and adsorbent increased with moisture content.     

Microbial, Compositional, and Other Quality Characteristics of Pecan Kernels Stored at −20°C for Twenty-five Years

Sensory, microbial, and compositional characteristics of pecans hermetically sealed in cans and stored at ?20°C for 25 yr were compared to those of pecans harvested in 1986 and stored at ?20°C for 10 mo. Total aerobic and yeast/mold populations were 10²?10³ CFU/g in stored and 1986 crop nuts. Peroxides were not detected, and no difference in iodine values and free fatty acid contents were observed between 25-yr-old and 1986 crop nuts. Although subjective analyses revealed that texture changed during storage, other sensory quality characteristics (color, flavor, appearance) were not different from pecans harvested in 1986. It is concluded that low temperature (?20°C) storage will maintain quality of pecans packaged in hermetically sealed under ambient air in containers for up to 25 yr.     

Development of flavour defects in pasteurized double cream during storage at 6°C and at 10°C

A total viable count in excess of 1× 10⁷ cfu/ml is required before organoleptic defects can be detected in pasteurized double cream, although defects were shown to be the results of non-bacterial sources in creams from one creamery in the survey. Proteolysis was associated mainly with the presence of Bacillus spp. and resulted in the detection of a bitter flavour in the creams.