液氮/液氨速冻鮰鱼片理化性质与组织结构变化

研究分析液氮与液氨速冻对斑点叉尾鮰鱼肉品质的影响。新鲜斑点叉尾鮰分割鱼片后分别进行工业隧道式液氮喷淋速冻（－90 ℃、35 min）、隧道式液氨速冻（－35 ℃、90 min），速冻样品置于－18 ℃下贮藏90 d。分析比较新鲜鱼肉以及速冻鱼肉在不同冻藏时间解冻损失率、蒸煮损失率、加压失水率、剪切力、pH值、K值、挥发性盐基氮（total volatile basic nitrogen，TVB-N）含量、三甲胺（trimethylamine，TMA）含量与硫代巴比妥酸反应物（thiobarbituric acid reactive substance，TBARs）值，应用荧光显微镜观察鱼肉组织微观结构变化。结果表明：与新鲜鱼肉相比，速冻鱼肉蒸煮损失率增加，加压失水率、剪切力、pH值降低，K值、TVB-N含量、TMA含量、TBARs值均呈上升趋势；随着冻藏时间延长，速冻鱼肉理化性质发生劣变；鱼肉速冻后肌肉细胞面积减小，细胞间隙增大；相比液氨速冻，液氮速冻更有利于保持鱼肉持水性、新鲜度以及组织结构完整性，可有效抑制鱼肉冻藏期间的品质劣变。综上，液氮速冻可以有效保持冷冻鱼肉品质，冻藏30 d内，液氮速冻鱼肉品质特性更接近于新鲜鱼肉。

Changes in Physicochemical Properties and Microstructure of Channel Catfish (Ietalurus punetaus) Fillets Quick Frozen with Liquid Nitrogen or Liquid Ammonia

The effect of liquid nitrogen versus liquid ammonia quick freezing on the quality of channel catfish was investigated. Fresh fillets were frozen by tunnel liquid nitrogen spraying freezing (?90 ℃/35 min) or tunnel liquid ammonia freezing (?35 ℃/90 min), and then stored at ?18 ℃ for up to 90 days. The thawing loss, cooking loss, pressurized water loss, shear force, pH value, K value, volatile base nitrogen (TVB-N) content, trimethylamine (TMA) content and thiobarbituric acid reactive substance (TBARs) value of fresh and freeze-stored fish were analyzed. The microstructure of fish tissue was observed by fluorescence microscope. Results showed that compared with fresh fish, the cooking loss of frozen fillets increased, the pressurized water loss, shear force and pH value decreased, and the K value, TVB-N, TMA content and TBARs value showed an increasing trend. The physicochemical properties of frozen fish deteriorated during frozen storage. It was observed that the area of muscle cells decreased and the intercellular space increased after quick freezing. Compared to liquid ammonia quick freezing, liquid nitrogen quick freezing was more beneficial to maintain the water-holding capacity, freshness and structural integrity of fish meat, thereby effectively restraining quality deterioration during frozen storage. It was conducted that the quality of fish fillets treated by liquid nitrogen quick freezing was close to fresh fish during frozen storage for 30 days.