对鱼肉品质变化指标和鱼腥味变化的测定分析,探究了冻藏期间罗非鱼腥味的主要形成机理。实验结果显示:共轭二烯(CD)值随着储藏时间的延长而不断增加,说明脂肪氧化发生于整个冻藏期间;挥发性盐基氮(TVBN)在贮藏9d后迅速上升,表明在鱼肉中已开始出现明显的微生物腐败;表征脂肪氧化程度的硫代巴比妥酸值(TBARS)值在12d的冻藏期中不断上升,并且在9d后急剧上升。对冻藏期间罗非鱼肉腥味进行感官评价,在新鲜鱼肉中青草味占主体,其强度随着贮藏时间延长而降低,然而鱼腥味、哈喇味、腐败味随之加剧,6d后样品中鱼腥味和哈喇味强度增加,9d后鱼肉中开始出现腐臭味。将品质变化指标与鱼腥味感官评价结果进行相关性分析发现,罗非鱼肉中鱼腥味等异味的产生主要是由于贮藏过程中鱼肉发生脂肪氧化,在后期也伴随着明显的微生物腐败。

Quality change and fishy odor development in tilapia during freezing storage were studied. Conjugated diene( CD) contents increased with lipid oxidation occurring in fish muscle. Significant increase of total volatile basic nitrogen( TVBN) values at the storage of 9d indicated that microbial spoilage was started in the muscle. Degree of lipid oxidation could be represented by the value of thiobarbituric acid reactive substances( TBARS),which increased continuously through the whole storage,It sharply increased after 9 days. Results of sensory evaluation showed that grassy odor was detected in fresh tilapia muscle and the intensity decreased during storage,while intensity of offodours including fishy,rancid and putrid odors increased as storage time extended. Fishy and rancid odors of sample increased significantly after day 6. Within the storage,no putrid odor was found in tilapia muscle until day 9. Correlations between chemical indexes and sensory evaluation scores showed that the off-odour in fish muscle was mostly due to lipid oxidation. In the late period of frozen storage,microbiological spoilage was more severe.