Abstract
Abstract The aim of this investigation was to evaluate the impact of multiple freezing and thawing cycles on the physicochemical properties of Nile tilapia fillets. For this purpose, 72 fresh Nile tilapia fillets were packed and stored in a freezer at -18 °C. The frozen samples were submitted to five freeze-thaw cycles; in each cycle, the freezer was switched off during 14 hours. The consecutive freeze-thaw cycles resulted in a fillet’s total weight loss of 9.48%, with a quadratic regression (P < 0.0001) for thaw loss, with a greater loss percentage in cycle 3 (2.68%). pH values differed between the cycles (P < 0.0001), being observed an increment in this parameter only from cycle 4. The lipid oxidation remained constant in cycles 1, 2, 4 and 5, however in cycle 3 the lowest value (P < 0.0002) was observed. The luminosity, and intensity of the red and yellow colours increased linearly (P < 0.0001) as the cycles increased. Thereby, the tilapia fillets’ quality were adversely affected by the freezing cycles. The unfavourable alterations included weight loss, lipid oxidation and elevated pH, as well as the increasingly augmentation of brightness and red and yellow colorations of fillets as the progressive cycles occurred.
Highlights
Meat freezing has been employed as conservation strategy for thousands of years, and even today, this process plays a key role in ensuring the safety of products that are marketed worldwide (Leygonie et al, 2012).Through the freezing process, it is possible to extend fish’s shelf life, aggregate commercial value to the product and reach distant markets (Ninan, 2018)
The five freeze-thaw cycles resulted in a total weight loss of 9.48% of the fillets
It was observed a quadratic regression (P < 0.0001) for the thaw loss (Figure 1), with weight loss increasing until cycle 3, for which the highest loss percentage (2.68%) was registered
Summary
Meat freezing has been employed as conservation strategy for thousands of years, and even today, this process plays a key role in ensuring the safety of products that are marketed worldwide (Leygonie et al, 2012). It is possible to extend fish’s shelf life, aggregate commercial value to the product and reach distant markets (Ninan, 2018). Freezing slows down the rate of bacterial growth and the chemical changes responsible for quality deterioration (Ordóñez et al, 2005). The loss of frozen meat quality depends on many factors, such as storage temperature, freeze-thaw rate and temperature fluctuations (Srinivasan et al, 1997). Temperature fluctuations or temperature rise usually occur during transportation, distribution, storage and display in retail (Benjakul & Bauer, 2000; Hansen et al, 2004)
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