High-pressure processing before freezing and frozen storage of European hake (Merluccius merluccius): effect on mechanical properties and visual appearance

High-pressure processing of fish and shellfish products: Safety, quality, and research prospects

Seafood products have been one of the main drivers behind the popularity of high-pressure processing (HPP) in the food industry owing to a high demand for fresh ready-to-eat seafood products and food safety. This review provides an overview of the advanced knowledge available on the use of HPP for production of wholesome and highly nutritive clean label fish and shellfish products. Out of 653 explored items, 65 articles published during 2016-2021 were used. Analysis of the literature showed that most of the earlier work evaluated the HPP effect on physicochemical and sensorial properties, and limited information is available on nutritional aspects. HPP has several applications in the seafood industry. Application of HPP (400-600 MPa) eliminates common seafood pathogens, such as Vibrio and Listeria spp., and slows the growth of spoilage microorganisms. Use of cold water as a pressure medium induces minimal changes in sensory and nutritional properties and helps in the development of clean label seafood products. This technology (200-350 MPa) is also useful to shuck oysters, lobsters, crabs, mussels, clams, and scallops to increase recovery of the edible meat. High-pressure helps to preserve organoleptic and functional properties for an extended time during refrigerated storage. Overall, HPP helps seafood manufacturers to maintain a balance between safety, quality, processing efficiency, and regulatory compliance. Further research is required to understand the mechanisms of pressure-induced modifications and clean label strategies to minimize these modifications.

Comparative effect of a previous 150-MPa treatment on the quality loss of frozen hake stored at different temperatures

BACKGROUND

This study addresses the quality loss of European hake (Merluccius merluccius) during frozen storage. Its objective was to comparatively analyse the effect of a previous high-pressure processing (HPP) (150 MPa for 2 min) when different storage temperatures (-10, -18 and -30 °C) were employed.

RESULTS

Most chemical quality indices (trimethylamine, TMA; dimethylamine, DMA, formaldehyde, FA; free fatty acids, FFAs) provided a marked content increase with freezing and frozen storage time, values being higher by increasing the storage temperature. Previous HPP led to an inhibitory (P < 0.05) effect on the TMA, DMA, FA and FFA formation in frozen fish kept at -10 and -18 °C, the preservative effect being higher at the highest temperature tested; however, in agreement to the low damage development, no effect could be proved on samples stored at -30 °C. Concerning lipid oxidation, peroxides formation was found low, although a slight increasing effect (P < 0.05) was implied in fish corresponding to all temperatures as a result of the previous HPP; furthermore, an inhibitory effect (P < 0.05) on fluorescent compounds formation (tertiary lipid oxidation) was evident after freezing and at month 9 for -10 °C samples.

CONCLUSION

It is concluded that a 150-MPa high-pressure treatment may inhibit the formation of degradative molecules such as DMA, FA, TMA and FFAs during the frozen storage at -18 °C (maximum recommended) and -10 °C. However, results have indicated that lowering the storage temperature showed to be more effective than the current HPP (150 MPa for 2 min). © 2020 Society of Chemical Industry.

Effects of ultrasound-assisted freezing at different power levels on the structure and thermal stability of common carp (Cyprinus carpio) proteins

This study investigated the effect of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power levels on the myofibrillar protein primary, secondary and tertiary structures of common carp (Cyprinus carpio). Furthermore, protein thermal stability, electrophoresis pattern, and microstructure of the muscle tissue were also studied. Compared with a control, an ultrasonic power of less than 175 W had no significant negative effect on protein primary structure (P > 0.05), including total sulfhydryl, reactive sulfhydryl, carbonyl groups, free amino groups, dityrosine content, and surface hydrophobicity. UIF at 175 W (UIF-175) minimized the changes in protein secondary and tertiary structures. There were no obvious changes in the SDS-PAGE patterns of the control and frozen sample proteins. Microstructure analysis showed that an appropriate ultrasonic power (UIF-175) promoted the formation of smaller and more uniform ice crystals, reduced the damage of muscle tissue by ice crystals, and maintained the sarcomere integrity. In addition, UIF-175 samples had higher protein thermal stability. Overall, ultrasound treatment at a proper power (UIF-175) effectively minimized the changes in protein structure and protected the protein thermal stability during freezing process.

Effects of High-Pressure Treatment on the Muscle Proteome of Hake by Bottom-Up Proteomics

A bottom-up proteomics approach was applied for the study of the effects of high-pressure (HP) treatment on the muscle proteome of fish. The performance of the approach was established for a previous HP treatment (150-450 MPa for 2 min) on frozen (up to 5 months at -10 °C) European hake ( Merluccius merluccius). Concerning possible protein biomarkers of quality changes, a significant degradation after applying a pressure ≥430 MPa could be observed for phosphoglycerate mutase-1, enolase, creatine kinase, fructose bisphosphate aldolase, triosephosphate isomerase, and nucleoside diphosphate kinase; contrary, electrophoretic bands assigned to tropomyosin, glyceraldehyde-3-phosphate dehydrogenase, and beta parvalbumin increased their intensity after applying a pressure ≥430 MPa. This repository of potential protein biomarkers may be very useful for further HP investigations related to fish quality.