Effects of Different Freezing Temperatures on the Quality Changes of Larimichthys polyactis during Storage
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Abstract:
Toassessthe quality changes of Larimichthys polyactis under ultra-low temperatures, the effects of -18, -25, and -45 ℃ on the quality changes of Larimichthys polyactis were investigated. In particular, the freezing curve, total volatile basic nitrogen (TVB-N) content, water holding capacity (WHC), Ca2+-ATPase activity content, carbonyl group, total sulfhydryl group, and ice crystal morphology were examined. The time taken for samples frozen at -18, -25, and -45 ℃ to cross the maximum ice crystal formation zonewas 230, 95, and 60 min, respectively, with the ultra-low temperature (-45 ℃) group taking the shortest time. The area and diameter of the ice crystals in Larimichthys polyactis frozen at -45 ℃ were smaller than those in Larimichthys polyactis frozen at the other temperatures, and displayed a more uniform distribution. At 150 days, the gaps in the muscle tissue increased; however, the gap in the -18 and -25 ℃ groups was markedly larger than that in the -45 ℃ group. The samples frozen at -45 ℃ had the lowest content of total volatile basic nitrogen (TVB-N) (7.96 mg/100 g) and carbonyl groups (30.60 nmol/mg prot), the highest values for water holding capcity (74.62%), total sulfhydryl content (0.36 mmol/g prot), and Ca2+-ATPase activity content (4.78 μmol/mg); these values were significantly better than those of samples frozen at -18 and -25 ℃ (P<0.05). Furthermore, as the duration of storage extended, the quality of Larimichthys polyactis at all temperatures changed; however, the samples frozenat the ultra-low temperature (-45 ℃) changed the least compared with those frozen at the other two temperatures. This result indicates that ultra-low temperatures can delay the deterioration of the quality of Larimichthys polyactis and more effectively maintain its edible value.
