Carob seed peel as natural antioxidant in minced and refrigerated (4 °C) Atlantic horse mackerel (Trachurus trachurus)

•Carob seed peel is rich in fibre and polyphenols (tannins and flavonoids).•The addition of carob seed peel to minced fish was effective in retarding oxidation.•Carob seed peel could be used as antioxidant ingredient in food formulations.

A novel processing method allows obtaining peel of carob seed (CSP) as a by-product during carob bean gum extraction. The aims of the present study were to characterise CSP and to evaluate its potential application as natural antioxidant in ground Atlantic horse mackerel (Trachurus trachurus).Proximate composition, phenolic content, phenolic profile and antioxidant capacity of CSP were determined. Atlantic horse mackerel mince was formulated at three different CSP concentrations (0%, 1%, 2% and 5% w/w) and stored at 4 °C over 4 days.CSP was effective in preventing lipid and protein oxidation of minced horse mackerel. CSP reduced the peroxide value, conjugated dienes and trienes, thiobarbituric acid reactive substances, protein carbonyls and protected against α-tocopherol oxidation of fish mince, showing a concentration-dependent antioxidant effect. Fish samples with CSP showed better physicochemical parameters (pH, aw, Total Volatile Basic Nitrogen) and lower perceived off-odours (fishy and rancid) over storage than control.In conclusion, carob seed peel could be used as natural antioxidant additive as it showed antioxidant properties and prevented protein and lipid oxidation when applied in a food product (minced fish).