Effects of different phosphorus‐free water‐retaining agents on the quality of frozen tilapia fillets

Tilapia is an economically important fish worldwide, but its quality is affected by storage practices. To improve the quality of tilapia fillets during frozen storage, we examined the effect of pretreatment with various combinations of different concentrations of trehalose, potassium bicarbonate, and chitosan. Following pretreatment, we analyzed the tilapia fillets using quality indicators, including soaking weight gain, coating weight gain, water-holding capacity, thawing loss, pH, Ca2+-ATPase activity, and texture characteristics. Water distribution was analyzed using low-field nuclear magnetic resonance and the optimal combination of water-retaining agents was obtained using an L8(27) orthogonal experiment. The results showed that trehalose, potassium bicarbonate, and chitosan improved fillet quality at pretreatment concentrations of 5%-8%, 1.0%, and 0.5%, respectively. The optimal combination was 4% trehalose plus 1.2% potassium bicarbonate plus 0.2% chitosan. The Ca2+-ATPase activity and mastication property of the frozen fillets that were pretreated with the optimized formulation were 1.39 μmol Pi/mg protein·h and 8.55 mJ, respectively, which were 43.3% and 80.0% greater, respectively, than that of the control group. Using a suitable concentration and combination of water-retaining agents cannot only lock-in the internal water content of frozen tilapia fillets but also improve their quality during frozen storage. These results can inform practical storage practices of similar aquatic products.