Waste salt from the manufacturing process of mullet bottarga as source of oil with nutritional and nutraceutical properties

BACKGROUND The Sardinian food delicacy 'bottarga' is the final product of a number of treatments (salting and drying) on the ovaries of mullet (Mugilspp) and represents an important natural source of n-3 polyunsaturated fatty acids (n-3 PUFA) with nutraceutical properties. During the salting process of mullet roes to obtain bottarga, huge amounts of waste salt are generated, rich in residual ovary material. RESULTS We evaluated the lipid composition (main lipid components and fatty acids) and bioactivity of oil obtained from the ovary material separated from waste salt (waste salt oil). Oil was obtained by supercritical fluid extraction with carbon dioxide (SFE-CO2), an environmentally friendly separation technique. The lipid composition of waste salt oil was determined by carbon-13 nuclear magnetic resonance (C-13-NMR) spectroscopy and reversed-phase high-performance liquid chromatography with diode array detector and an evaporative light scattering detector (HPLC-DAD/ELSD) chromatography. The oil was characterized by a relatively high level of n-3 PUFA (122 +/- 7 g kg(-1)of oil), and these beneficial health compounds were mainly present in the form of wax esters. Waste salt oil showed a marked cytotoxic effect [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay] in cancer B16F10 melanoma cells, with a slight cytotoxic effect in normal cells (3T3 fibroblasts). Waste salt and its derivatives (salt oil and residual material after oil extraction) were also tested for the attractant effect and acceptability to insects (Ceratitis capitata) to gain preliminary information about their potential application for animal supplementation. CONCLUSION The results qualify waste salt as a potential resource for veterinary dietary supplements, nutraceuticals, and pharmaceutical applications. (c) 2020 Society of Chemical Industry