Effect of Water Activity-Lowering Agents on the Quality of Semi-Dried Blunt Snout Bream

The effect of different water activity (a_w)-lowering agents on the water state and quality of semi-dried blunt snout bream was studied by measuring its a_w, water state, total viable counts (TVC), yeast count, total volatile basic nitrogen (TVB-N) content, thiobarbituric acid reactive substances (TBARS) value, and sensory scores. The results showed that the type and amount of a_w-lowering agents had a significant impact on the a_w, water state and physicochemical indicators of semi-dried blunt snout bream, the latter effect being more pronounced than the former one. Trehalose, sorbitol and glycerol reduced the a_w, glycerol being the most effective among the a_w-lowering agents. When 6% glycerol was added, the a_w was reduced from 0.917 to 0.873. With increasing amounts of added trehalose, sorbitol and glycerol, the T₂₂ significantly decreased (P < 0.05), but the T₂₃ did not significantly change. The proportion of immobilized water increased significantly (P < 0.05), whereas the proportion of free water decreased significantly (P < 0.05). Relative to the control group, the TVC, yeast count, TVB-N content, and TBARS value were significantly reduced (P < 0.05) with increasing addition of a_w-lowering agents, and the optimal values of these parameters were obtained with the addition of 6% glycerol. To sum up, the addition of a_w-lowering agents could effectively reduce water freedom and fluidity and slowed down the quality deterioration of semidried blunt snout bream.