Effects of dietary replacement of fishmeal by defatted Tenebrio molitor meal, Clostridium autoethanogenum protein meal and Chlorella vulgaris meal on the freshness of turbot ( Scophthalmus maximus) ) during chilled storage

The present work evaluated the effects of dietary fishmeal replacement with three non-food protein sources, including defatted Tenebrio molitor meal (TM), Clostridium autoethanogenum protein meal (CAP) and Chlorella vulgaris meal (CV), on the freshness traits of turbot Scophthalmus maximus. . TM, CAP, or CV were used to respectively replace 0%, 15%, 30%. 45%, 60% and 75% of dietary fishmeal protein. Turbot (180.5 +/- 2.5 g) were fed with eighteen experimental diets for 70 days, and were stored at 4 degree celsius for 3 days. TM and CAP linearly increased QIM scores, but no obvious trend between QIM scores and CV dietary level. The TM15 diet decreased the QIM score, indicating better overall freshness compared to the other TM-groups. Chromameter indicated that consumers could not distinguish the color differences among groups (Delta E < 3). The muscle hardness of all groups was significantly reduced after storage (P<0.05), P <0.05), except the fish fed TM15 diet. Moreover, the TM15 group showed lower pH, TVB-N, and TBA levels after storage, whereas higher TM replacement levels (>30 %) resulted in increased pH, TVB-N, and TBA levels compared with the fish fed TM0 diet. But cathepsin B and L activities showed no significant differences across all TM-groups. Among the CAP-groups, no significant differences were noted in pH and TBA levels; however, CAP linearly increased TVB-N levels after storage. CV did not significantly influence the post-storage pH, TVB-N, and TBA levels. The muscle glycogen content showed no significant variance among the groups. In conclusion, a 15 % dietary replacement of fishmeal with TM optimized the freshness of turbot by decelerating muscle softening, lipid oxidation, and the production of volatile nitrogen compounds, whereas higher levels of TM accelerated these processes. CAP replacement level exceeding 15 % enhanced the production of volatile nitrogen compounds. Dietary inclusion of CV did not impact the freshness of turbot during storage.