Mechanistic insights to the strong antioxidative capacity of lingonberry press cake during recovery of fish protein ingredients

• Lingonberry press cake (LPC) was lost 23.73 % TPC at alkaline during pH shift. • LPC fractions from pH shift had the strong antioxidation ability on lipid oxidation. • 50 % aqueous ethanol improved antioxidation abilities of LPC fractions. • LPC fractions had different binding abilities affecting them inhibit lipid oxidation. • Proanthocyanidin A1 and Cy3Gal were two most abundant antioxidants in LPC fractions. Lingonberry press cake (LPC) has been shown to limit lipid oxidation in fish filleting co-products during pH-shift processing. To explore the underlying mechanism, this study subjected LPC to pH-shift processing (native pH → pH 12 → pH 5), and analyzed the resultant fractions for phenolic content and antioxidant capacity. It was observed that LPC experienced a 23.73 % reduction in total phenolic content (TPC) when the initial homogenate was adjusted to pH 12; however, no significant further losses were noted during centrifugation or subsequent adjustment to pH 5. Both LPC and the soluble fraction at pH 5 (“S2”) demonstrated effective inhibition of hemoglobin (Hb)-mediated lipid oxidation in washed cod mince (WCM) model system. Additionally, the insoluble fraction at pH 5 (“P2”) exhibited the strongest binding to WCM. Proanthocyanidin A1 and cyanidin 3-O-galactoside were identified as the most effective antioxidants in LPC. Overall, this study affirms LPC's value as an effective natural antioxidant ingredient in muscle foods and proposes an innovative strategy for valorizing multiple food side streams together to support sustainable development.