Establishment of quality evaluation method for frozen tilapia ( Oreochromis niloticus ) fillets stored at different temperatures based on fractal dimension

Abstract

To explore an effective quality evaluation system based on microstructure changes, tilapia samples were preserved at the temperature of −20, −40, and −80°C up to a storage period of 270 days. The porous structure of fish muscle was quantified using the cross‐section area (CA) and fractal dimension (FD) of ice crystals, and the effectiveness of the two was compared. The relationships between microstructure changes and traditional quality parameters, including water‐holding capacity, texture properties, K value, and total volatile basic nitrogen (TVB‐N), were also explored. The results showed that FD dropped by 8.79, 4.53, and 3.03% of fillets at −20, −40, and −80°C after 270 days of storage, respectively. The better fitting on the basis of FD for evaluating quality of tilapia compared with CA. Traditional quality indicators were correlated well with the FD (R2 > 0.94), except for relaxation time (T2). The first‐order kinetic equation FD = exp (0.0895 t exp[−7240.26/RT])/1.8903 was developed, and FD relative errors between predicted and observed values were all less than 3%, which demonstrated that the feasibleness and accuracy of quality evaluation based on FD during frozen storage. Practical applications Frozen storage inevitably has a negative impact on the tissue, water‐holding capacity, and protein properties of fish. Thus, it is of great urgency to put forward an effective quality evaluation system of frozen fish. Here, tilapia samples were studied over a period of 270 days by measuring their microstructure of muscle fibers and traditional quality parameters. Correlation analysis of each index was also conducted and kinetic model based on FD was established and validated finally. In addition to establishing an effective quality evaluation system based on microstructure changes for tilapia, these results will provide new insights into the quality evaluation and laid a foundation for the application of fractal dimension in tilapia processing and transportation.

Quality and Safety Concerns of Farmed Tilapia Fish during Freezing and Frozen Storage: Review

“…Lowering the storage temperature reduces the rate of deterioration in fish. Equally [94,79,93] both observed that a shelf life of 23 weeks was achieved by freezing fish fillets at 20°C, but the thawing process was not investigated in this study. The stiffness of frozen carp fillets decreased due to the freezing process [14], but not due to the storage time.…”

“…Additionally, [94] and found that temperature changes can also affect rigour contractions in rested and partially exercised Tilapia fillets stored at different temperatures, with higher temperatures leading to faster rigour stages in the muscle. Therefore, it is important to maintain lower temperatures [34].…”

“…Despite the development of advanced technologies for fish processing and preservation, fish chilling and freezing remain the most commonly used preservation methods for farmed fish, such as Tilapia [35]. These techniques are used to preserve fish quality at low temperatures, [94] including refrigerated storage at 0°C to 4°C and frozen storage at 18°C to 40°C [38]. At the farm level, fish chilling is commonly achieved using ice, which may involve the use of super chilling technology.…”

“…However, the type of fish that is freeze-frozen and stored can significantly affect the rate of deterioration during storage. [3,94] Studies have shown that low storage temperatures can increase the rate of deterioration in fish, so it is important to maintain very low temperatures that can deter micro-bacterial growth to improve the quality of farmed Nile Tilapia fish during freezefrozen storage. The recommended temperature for frozen storage is -18°C [37], for Tuna.…”

“…They suggested an approach for evaluating frozen fillets and frozen mince based on soluble and total proteins. [94] developed a topological dimensional quality evaluation approach for frozen tilapia fillets kept at various temperatures, which established composite qualities by distinguishing their units and relevance to assessing the unit's level of acceptance and tilapia fillet quality.…”