Physical, chemical composition and umami compound of dried immature and mature roes of skipjack tuna (Katsuwonus pelamis)

In this study we investigate physical and chemical characteristics of immature and mature skipjack tuna ( Katsuwonus pelamis ) roes in fresh and dried forms. Fresh roes were studied for histological structure and also dried by three methods: hot air drying (HD), vacuum drying (VD) and freeze drying (FD). The obtained roe powders were analysed for proximate composition, color value, fatty acid composition, amino acid profile, equivalent umami concentration (EUC) and protein pattern. Unyolked oocytes were more common in immature roes, while fully yolked oocytes were more common in mature roes. All dried tuna roes contained high content of protein and lipid (69.31%–70.55% and 11.14%–16.02%, respectively). The powders obtained by FD provided the highest lightness value (L*). The main fatty acid found in all roe powders was docosahexaenoic acid (DHA) (23.49%–27.02%). Glutamic acid, leucine, and aspartic acid were the three most abundant amino acids found in the powders (13.58–14.61, 8.06–8.42, and 7.81–8.39 g/100 g of protein, respectively). The mature roe powder obtained from HD provided the highest EUC value (73.09 g monosodium glutamate/100 g of samples). The protein band at molecular weight of 97 kDa (vitelline) represented the major protein. Therefore, dried tuna roe could be a functional ingredient source of protein and lipid rich in DHA and it also has potential to be used as taste enhancer with umami compound.