The Effect of Multiple Freeze–Thaw Cycles on the Microstructure and Quality of Trachurus murphyi

Abstract

Temperature fluctuation in frozen food storage and distribution is the perpetual and core issue faced by the frozen food industry. Ice recrystallisation induced by temperature fluctuations under cold storage causes microstructural changes in fish products and irreversible damages to cells and tissues, which lower the frozen fish quality in the food chain. This study is intended to explore how repeated freezing–thawing affected the microstructure and quality of Trachurus murphyi during its frozen storage. The results showed the consistency between the increase in ice crystal diameter, volume, and porosity in frozen fish and the increase in centrifugal loss (from 22.4% to 25.69%), cooking loss (from 22.32% to 25.19%), conductivity (from 15.28 Ms/cm to 15.70 Ms/cm), TVB-N (from 16.32 mg N/100 g to 19.94 mg N/100 g), K-value (from 3.73% to 7.07%), and amino acid composition. The muscle structure change observed by Fourier-Transform Infrared spectroscopy (FT-IR) showed that the content of α-helix reduced from 59.05% to 51.83%, while the β-sheet fraction grew from 15.44% to 17.11%, β-turns increased from 5.45% to 7.58%, and random coil from 20.06% to 23.49%. Moreover, muscular structure exhibited varying degrees of deterioration with increasing cycles of freezing and thawing as shown by scanning electron microscopy (SEM). We studied the muscular morphology, which included the measurement of porosities (%) of pore that increased (from 1.4% to 4.3%) and pore distribution, by X-ray computed tomography (uCT). The cycles of the freeze–thaw resulted in structural changes, which seemed to be closely associated with ultimate quality of frozen fish products.

Recent advances in emerging techniques for freezing and thawing on aquatic products' quality

“…According to Hu and Xie (2021b), the K-value following the second F-T cycle reached 3.73%, which increased with increasing F-T cycles (7.07% following the eighth F-T cycle). With more cycles of freezing and thawing, the freshness of the sample decreased.…”

“…Generally, before further processing, frozen aquatic products need to be thawed and repeated F-T cycles often happen during transportation, retail stores, and by consumers (Boonsumrej et al, 2007). Ice recrystallization induced by temperature fluctuations during frozen storage causes microstructural changes in aquatic products and irreversible damage to cells and tissues, which lower the frozen aquatic products quality (Hu & Xie, 2021b). F-T cycles can have a prominent negative effect on the fish quality, such as color, freshness, and tenderness.…”

“…Generally speaking, high WHC reduces expressible water and shear strength of muscle tissue (Lee et al, 2016). Hu and Xie (2021b) reported that cooking loss ranged from 22.32% after the second F-T cycle to 25.19% after the eighth F-T cycle. With more F-T cycles, the gap between cell structures became larger and the water retention became worse.…”

“…The edible value may be reduced by protein denaturation due to oxidation of the protein, for example, discoloration, decreased juiciness and deterioration of flavor Shi, Lei, et al, 2019). Some oxidative changes usually involve the production of carbonyls and hydroperoxides in shrimp proteins, which can enhance the hydrophobicity of the protein surface (Hu & Xie, 2021a;.…”

Effects of Freeze–Thaw Cycles on Water Migration, Microstructure and Protein Oxidation in Cuttlefish

“…In recent years, much headway has been made in the assessment of fish freshness and safety, but little research has been undertaken on cephalopods, much of it on squid [2,10]. The effects of multiple F-T cycles on muscle protein and quality have been receiving attention from several scholars both at home and abroad [11,12]. At present, few studies on the effect of multiple F-T cycles on the quality of cuttlefish have been reported.…”