Hydrolysates from rainbow trout (Oncorhynchus mykiss) processing by-products: Properties when added to fish mince with different freeze-thaw cycles

Rainbow trout (Oncorhynchus mykiss) mixed processing by-product homogenates were subjected to 8 mM CaCl2-5 mM citric acid (1:5 w/v) pretreatments followed by hydrolysis with Alcalase (W-CaCi-RTBH). These hydrolysates decreased the loss of total sulfhydryl groups, protein solubility and protein carbonyl formation in a fish mince after 6 freeze-thaw cycles (P <= 0.05). The thermal properties of myosin heavy chains and actin were maintained as shown using differential scanning calorimetry (DSC) (P <= 0.05). Based on low field NMR T-2 relaxation, the fastest relaxation component (T-21) showed no changes with addition of W-CaCi-RTBH into a fish mince after 6 freeze-thaw cycles, indicating no changes for the major pool of water molecules within the myofibrillar protein structure (P >= 0.05). After 6 freeze-thaw cycles, W-CaCi-RTBH had better antifreeze activity when combined with sucrose - sorbitol (4%) (P <= 0.05). Therefore, W-CaCi-RTBH could potentially be an additive in frozen fish mince.