Effects of Multiple Freeze-Thaw Cycles on Biochemical and Physical Quality Changes of White Shrimp (Penaeus vannamei) Treated with Lysine and Sodium Bicarbonate

摘要

AbstractFreezing and thawing occur during storage, transportation, and retail display, leading to deterioration of frozen shrimp. The objective of this research was to investigate the change in quality of frozen white shrimp treated by lysine and NaHCO3 after multiple freezethaw cycles. Shrimp were soaked in lysine and lysine/NaHCO3 each at 1% (w/v) frozen in an airblast freezer at 30 °C, and kept in a chest freezer (18 ± 2 °C) for a week before they were thawed using tap water before the analysis (freezethaw cycle 1). The samples were subjected to five freezethaw cycles, which were repeated every week. Qualities of the samples were determined for thawing loss, cutting force, and total volatile basic nitrogen (TVBN), as well as oxidation stability by using Rancimat. The use of lysine/NaHCO3 could significantly reduce thawing loss at all freezethaw cycles compared to the control and lysine treatment (P < 0.05). Similar results were found with TVBN and the oxidation stability of the samples. A difference in cutting forces of the shrimp between lysine and lysine/NaHCO3 treatment was found when the frequency of freezethawing was increased to three cycles; it was lower than that in the control at all cycles. Histological study showed that the treatment with lysine/NaHCO3 led to the swelling of muscle fibers and fewer fragments at five freezethaw cycles. The results showed that lysine/NaHCO3 could effectively retard the quality loss from repeated freezethawing during frozen storage.Practical ApplicationRepeated freezing and thawing usually occur during storage, transportation, retail display or in restaurants, and in consumers kitchens. The temperature at the manufacturing site and during transportation in a tropical country like Thailand is relatively high, and frozen food producers come across quality deterioration resulting from multiple freezethaw cycles occurring during transportation and storage. Frozen shrimp producers require research to improve product quality by adding nonphosphate food additives or, if possible, by using natural food ingredients instead of polyphosphate or sodium bicarbonate.