Protein Degradation and Instrumental Textural Changes in Fresh Nile Tilapia (Oreochromis niloticus) during Frozen Storage

Abstract

Textural changes as well as protein degradation during frozen storage of Nile tilapia (Oreochromis niloticus) at −18C for 150 days were studied. Salt-soluble protein and protein solubility decreased significantly during the frozen storage period. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was performed, and no visible changes in myosin heavy chain were observed up to 90th day of frozen storage period; however, the thickness of band was found to decrease thereafter. A new lighter band with molecular weight of 29 kDa was found on 120th and 150th day of sampling period. Actin was found more resistant to proteolysis. Texture profile analysis revealed that hardness 1, hardness 2, gumminess and chewiness gradually decreased up to 120th day, but showed an increase thereafter. Although sensory attributes decreased with the progress of frozen storage period, the fish was in acceptable condition on 150th day. Gradual toughening of muscle was recorded by the sensory panelists. PRACTICAL APPLICATIONThe popularity of tilapia is gaining importance for the development of different value-added fish products as well as for canning purposes. Therefore, it is important from the part of fish processor to know the changes of protein and texture profile during frozen storage. Although there was protein degradation and changes in texture profile during the study period of 150 days, the fish was in acceptable condition. , etc.) are significantly different (P < 0.05) with respect to period of storage.STUDY OF TILAPIA DURING FROZEN STORAGE K. SUBBAIAH ET AL.

Freshness and Shelf Life of Air Packaged and Modified Atmosphere Packaged Fresh Tilapia Fillets during Freezing-point Storage

“…Naturally, the initial reduction of pH in this study may be attributed to the decomposition of glycogen, ATP, and creatine phosphate and the dissolution of CO 2 in the fish muscle [14]. While the later increase in the pH value may relate to the production of volatile basic components, such as ammonia, by the decomposition of proteins and amino acids Subbaiah et al [9]. Our results had similar trends with their theories.…”

“…The pH values decrease upon storage time and then increase. In the present study, the initial pH is 6.85, which is higher than those detected by Liu et al [8], and Subbaiah et al [9], Khalafalla et al [12] for tilapia. According to the findings of Khalafalla et al [12], differences in initial pH values may be due to the species, diet, season, and level of stress during the catch, as well as the type of muscle.…”

“…The SSP was extracted from the tilapia as described by Subbaiah et al [9], with some modifications. Five grams of minced fish were placed in 50 mL of extraction buffer A (50 mM phosphate buffer, pH 7.4) and homogenized.…”

“…Cyprian et al [1] indicated that minor changes in the pH drastically affect the properties of the connective tissue, which directly affect the WHC of the fish muscle. Subbaiah et al [9] proposed that the denaturation and aggregation of the main contractile proteins responsible for the functional properties of the organism are typically caused by ice crystal growth and increasing ionic strength. A weak water bonding capacity would significantly affect the sensory quality of a specimen.…”

“…Excepting cohesiveness, the other texture parameters show smaller extents of decline in MAP than in AP, indicating that damage of myofibrillar proteins in AP is much more serious than that in MAP fillets. Subbaiah et al [9] found that the softening of fish muscle during frozen storage was caused by the breakdown of the three-dimensional structures of proteins and their aggregation following the activity of proteases. Huff-Lonergan and Lonergan [20] suggested that the deterioration of fish flesh texture may relate to various intrinsic and extrinsic factors, such as the loss of water from the muscle and the destruction of muscle tissues.…”