Dietary tuna hydrolysate modulates growth performance, immune response, intestinal morphology and resistance to Streptococcus iniae in juvenile barramundi, Lates calcarifer

This study investigated the effects of tuna hydrolysate (TH) inclusion in fishmeal (FM) based diets on the growth performance, innate immune response, intestinal health and resistance to Streptococcus iniae infection in juvenile barramundi, Lates calcarifer. Five isonitrogenous and isoenergetic experimental diets were prepared with TH, replacing FM at levels of 0% (control) 5%, 10%, 15% and 20%, and fed fish to apparent satiation three times daily for 8 weeks. The results showed that fish fed diets containing 5% and 10% TH had significantly higher final body weight and specific growth rate than the control. A significant reduction in blood glucose was found in fish fed 10%, 15% and 20% TH compared to those in the control whereas none of the other measured blood and serum indices were influenced by TH inclusion. Histological observation revealed a significant enhancement in goblet cell numbers in distal intestine of fish fed 5 to 10% TH in the diet. Moreover, fish fed 10% TH exhibited the highest resistance against Streptococcus iniae infection during a bacterial challenge trial. These findings therefore demonstrate that the replacement of 5 to 10% FM with TH improves growth, immune response, intestinal health and disease resistance in juvenile barramundi

Evaluation of functional properties in protein hydrolysates from bluewing searobin (prionotus punctatus) obtained with different microbial enzymes

Enzymatic hydrolysis of proteins from low commercial value fish could be produced for uses like functional ingredients in a wide and always increasing zone of application in different food products. The objective of this work was to evaluate the functional properties and the amino acid profile of enzymatic hydrolysates from Bluewing searobin (Prionotus punctatus), using two microbial enzymes, Alcalase and Flavourzyme. The enzymatic hydrolysate obtained through the addition of the enzyme Alcalase reached the maximum solubility (42%) at pH 9, water holding capacity (WHC) of 2.4 gwater gprotein−1, 4.5 goil gprotein−1 of oil holding capacity (OHC) and an emulsifying activity index (EAI) of 54 m2 gsolids−1 at pH 3. On the other hand, the hydrolysate obtained from Flavourzyme attained 38% of solubility at pH 9, 3.7 gwater gprotein−1 and 5.5 goil gprotein−1 for the holding capacities, and an EAI of 71 m2 gsolids−1 at pH 11. The hydrolysate with Flavourzyme produced best results for WHC, OHC, and EAI because it had solubility lower than the hydrolysate of Alcalase. The hydrolysate produced by Alcalase had a higher amino acid content compared with Flavourzyme’s hydrolysate. However, both showed a good essential amino acid amounts. In general, these results indicate the potential utilization of the hydrolysate from Bluewing searobin in food formulations for the direct human consumption