摘要
为了研究不冻液冻结对乌鳢块冻藏过程中冰晶及品质的影响,采用不同冻结温度(-20、-30、-40℃)的不冻液和空气冻结乌鳢块,以冰晶大小、盐溶性蛋白含量、pH值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)含量、硫代巴比妥酸(thiobarbituricacid,TBA)值和持水性等为指标,考察了乌鳢块冻藏(-18℃)过程中的品质变化。结果表明:采用-20、-30、-40℃不冻液冻结的乌鳢块通过最大冰晶生成带的时间分别为310、226 s和125 s,生成冰晶的面积分别为308.8、142.4μm~2和86.5μm~2,分别显著短于和小于空气冻结方式下乌鳢块通过最大冰晶生成带的时间(3 412 s)和生成冰晶的面积(939.6μm~2)(P<0.05)。另外,在-18℃冻藏过程中,经不冻液冻结的乌鳢块的盐溶性蛋白含量均明显高于空气冻结组,而形成冰晶大小、pH值、TBA值、TVB-N含量、汁液流失率和蒸煮损失率均明显低于空气冻结组,其中-40℃不冻液冻结后的乌鳢块在冻藏过程中品质变化最小。综合以上结果,不冻液冻结比空气冻结能够更好地保持冻藏过程中乌鳢块的品质,且不冻液的冻结温度越低,冻结速率越高,形成冰晶越小,越有利于鱼肉品质的保持。
The objective of this study was to investigate the effect of immersion freezing(IF) on ice crystal formation and quality changes in snakehead blocks under different freezing temperatures(-20,-30 and-40 ℃) in comparison with air freezing(AF). Quality indices including salt-soluble protein content, pH, total volatile basic nitrogen(TVB-N) content, thiobarbituric acid(TBA) value and water-holding capacity(WHC) were determined in all samples. The results showed that the time needed to pass through the zone of maximum ice crystal formation was 310, 226 and 125 s for IF at-20,-30 and-40 ℃, respectively, and the areas of ice crystals generated were 308.8, 142.4 and 86.5 μm~2, respectively. However, AF took a significant longer time(3 412 s) to pass through the zone of maximum ice crystal formation and resulted in a significantly larger area(939.6 μm~2) of ice crystals(P < 0.05). In addition, during storage at-18 ℃, a significantly higher concentration of salt-soluble protein was noted in the IF frozen sample as compared to the AF frozen sample, accompanied by a significant decrease in ice crystal size, pH, TBA value, TVB-N value, drip loss and cooking loss. Moreover,-40 ℃ IF treatment caused minimal quality changes in snakehead blocks. Collectively, it was suggested that IF could better maintain snakehead quality during frozen storage than AF, and lower freezing temperature could lead to higher freezing rate and formation of smaller ice crystals, thus being more favorable for quality maintenance.
引文
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