RESUMEN
Protein oxidation during chilling and frozen storage has recently attracted great attention due to its consequences on protein solubility and functionality. In this study, the effects of kappa-carrageenan oligosaccharides on myofibrillar protein oxidation in peeled shrimp (Litopenaeus vannamei) during frozen storage were investigated by assessing the content of the carbonyls, total sulfhydryl, dityrosine, and surface hydrophobicity. We also examined the means of antioxidant activity in vitro, degradation of muscle proteins, and integrity of tissue structure. Our data revealed that in vitro carrageenan oligosaccharides exhibited good capacities of OH, O2-, and DPPH· scavenging and Fe2+-chelating activity. Chemical analyses showed that frozen storage increased susceptibility of myofibrillar proteins to frozen oxidation. We found that the incorporation of carrageenan oligosaccharides during the treatment of the shrimp prior to frozen storage significantly decreased the formation of protein carbonyl and dityrosine, lowered the changes in myofibrillar surface hydrophobicity, and maintained a higher total sulfhydryl content when compared with the water-treated samples (control). Additionally, the results of protein degradation and tissue structure confirmed that these antioxidant oligosaccharides exhibited marked effects on stability of muscle proteins and effectively inhibited the degradation/oxidation of muscle proteins during frozen storage. Overall, the contribution of the antioxidant activities played an important role in cryoprotective effects of carrageenan oligosaccharides on frozen shrimp. Further application of these findings might maintain better quality and extend the commercialization of refrigerated products.
Asunto(s)
Carragenina/química , Almacenamiento de Alimentos , Congelación , Proteínas Musculares/metabolismo , Oligosacáridos/química , Oligosacáridos/farmacología , Penaeidae/metabolismo , Animales , Crioprotectores/química , Crioprotectores/farmacología , Depuradores de Radicales Libres/química , Depuradores de Radicales Libres/farmacología , Oxidación-Reducción/efectos de los fármacos , Penaeidae/efectos de los fármacos , Proteolisis/efectos de los fármacos , Factores de TiempoRESUMEN
Metallothionein (MT) plays a major role in the detoxification of toxic metal ions in mussel. This study served to investigate the effects of prepared protein hydrolysate-Fe2+ (PH-Fe2+ ) on depuration of cadmium salt (Cd2+ ) from blue mussel (Mytilus edulis). The results indicated that Cd2+ concentrations in control ranged from 46.1 to 47.1 µg/g during 15 d of depuration. While, 40 mg/L PH-Fe2+ feed mussels exhibited obvious changes in Cd2+ concentration variables, which decreased by 22.8 µg/g after 15 d of depuration, making them significantly lower than the values of the control. Our assumption was that Cd2+ could be dissociated effectively from the complex of MT-Cd2+ in mussels affected by the incorporation of PH-Fe2+ during the feeding period. Further results of homology modeling and molecular dynamics (MD) confirmed that the combined power between MT and Cd2+ weakened significantly by PH-Fe2+ . This condition affected the charge density and/or the loop flexibility of MT and decreased the interaction energy within MT-Cd2+ complex and resulted in the release of Cd2+ from the complex, thereby exhibiting excretion detoxification. Finally, by comparing the experimental results to MD results, significant positive correlations were observed between PH-Fe2+ and the depuration of Cd2+ from MT-Cd2+ complex. Overall, the findings of this study may help better understand the depuration mechanisms of Cd2+ combined with MT, and the PH-Fe2+ can be recommended as a depuration agent to decrease Cd2+ concentrations in mussels. PRACTICAL APPLICATION: Metallothionein (MT) is a low-molecular-weight protein with high metal-ion affinity. If the intracellular concentrations of metals are too high or if toxic metals are present within the cell, then the synthesis of MTs is induced and generated. In our previous work, it was found that the prepared hydrolysate-metal element complex showed obvious depuration activity of heavy metals (Cd2+ ) from blue mussel (Mytilus edulis). This study provided further the depuration mechanisms of Cd2+ from mussel (M. edulis), in particular to the role of MT and its chelate during the depuration process.