Microestrutura e qualidade do filé de tilápia (Oreochromis niloticus) submetidos a diferentes métodos de congelamento

Abstract

The objective of the study was to evaluate the effects of different freezing methods (slow freezing, static air (AE) at -20 °C; fast, forced air (AF) at -25 °C; mixed freezing, cryo-mechanical (CM) by associating freezing with liquid nitrogen with air-forced freezing to -25 °C; and ultra-fast freezing with liquid nitrogen (NL) in times of frozen storage (0, 30, 60 and 90 days to -18) on the quality of Nile tilapia fillets (Oreochromis niloticus) and get the freezing curves of each process. The results showed that the freezing time for NL, AF, CM and AE was 5, 32, 127, 146 and 268 minutes, respectively. Among the freezing methods evaluated, NL freezing took less time to pass through the maximum zone of ice crystal formation. The samples of the treatment (NL) were more yellowish during storage and had higher levels of N-BVT, which may be due to the high freezing rate, causing fractures and interfering with the quality of the fillets, due to the ultra-low freezing temperature. The samples of freezing AE had the worst quality indexes and the microstructure was visibly affected, with larger spaces between the fibers left by the ice crystals. The results showed that the freezing methods AF and CM have fast freezing speed and presented better quality of tilapia fillets during the 90 days of storage, compared to the others evaluated, promising potential for the conservation of fish during long-term storage.