Effects of postharvest processes on quality of Australian sardines (Sardinops sagax) and redbait (Emmelichthys nitidus nitidus) for feeding aquacultured southern bluefin tuna (Thunnus maccoyii)

Abstract

Feed nutritional quality impacts on the performance of aquacultured species. This study was undertaken to assess the consequences of existing postharvest handling practices on nutritional quality of local baitfish (Australian sardines, Sardinops sagax and redbait, Emmelichthys nitidus nitidus) used to feed farmed southern bluefin tuna (Thunnus maccoyii). Controlled experiments were then undertaken to determine the most appropriate postharvest treatments to maintain baitfish nutritional quality, assessed through measurement of vitamins C and E, histamine, K value and TBARS. During frozen storage (−18 °C) vitamins and fish freshness decreased significantly and rancidity increased; after approximately 3 months baitfish were of questionable utility, particularly as a source of antioxidants. On‐land freezing method [i.e. block or individually quick frozen (IQF)] affected vitamin E loss with IQF sardines losing vitamin E faster than block‐frozen baitfish. Block‐frozen baitfish, particularly sardines, should be thawed in seawater, not air or freshwater, to minimize vitamin losses. Thawing time should be no more than 2 days, and baitfish storage less than 3 months. Thiobarbituric acid reactive substances (TBARS) correlated well with remaining vitamin E, indicating its usefulness as an indicator of antioxidant status. TBARS analysis is methodologically simpler, faster and cheaper than that for vitamins, and is therefore recommended for determination of baitfish nutritional quality.

Effects of dietary enrichment with alpha-tocopherol acetate and post-harvest filleting on lipid oxidation and flesh quality of tropical farmed barramundi (Lates calcarifer)

“…Lipid oxidation was measured by a distillation-colorimetric technique, the 2-thiobarbituric acid method (TBARS) modified from Wong et al (1991) as used in previous studies to measure lipid oxidation in teleosts (Frigg et al, 1990;Jittinandana et al, 2006;Musgrove et al, 2011;Ruff et al, 2002). Analyses were performed at the Lincoln Marine Science Centre (Port Lincoln, School of Biological Sciences, Flinders University).…”