Effects of Rewilding Aquaculture Time on Nutritional Quality and Flavor Characteristics of Grass Carp (Ctenopharyngodon idellus)

Wild fish are preferred by consumers primarily for their superior sensorial qualities, including taste and texture. However, their limited availability often results in higher prices. Considering this, we explored the possibility of enhancing the quality of earthen pond aquaculture fish by transferring them to a near wild environment. This study investigated how rewilding time affects the physical properties, nutritional composition, and volatile profile of grass carp muscle. The results showed that compared to the 0M group, the crude protein content in grass carp muscle did not change significantly (p > 0.05) as the rewilding time increased to 6 months. Meanwhile, the significant increase in hardness and springiness (p < 0.05) indicated that the textural characteristics of muscle, which were key sensory and physical indices of muscle quality, were improved. Although the 6M group showed a 58.93% reduction in crude fat content compared to the 0M group, it retained the highest docosahexaenoic acid (DHA) content. Sensory evaluation demonstrated that as the rewilding time increased, the fishy and grassy odors of the rewilding grass carp diminished. Furthermore, cluster heatmaps and partial least squares discriminant analysis (PLS-DA) revealed that cultured grass carp and rewilding grass carp at three time points exhibited differences in various indicators. The variable importance in projection (VIP) showed that volatile flavor compounds (acetone, propionaldehyde-D, 1-penten-3-ol) and hardness were key factors in distinguishing between them. Therefore, extending the rewilding time can potentially enhance the acceptability of cultured grass carp by improving the physical properties, nutritional quality, and volatile profile of the muscle. This approach may provide a new pathway for fish aquaculture.