Ethanolic cashew leaf extract: Antioxidant potential and impact on quality changes of dried fermented catfish during storage

Ethanolic cashew (Anacardium occidentale, L.) leaf extract (ECLE) rich in phenolic compounds was prepared with the aid of ultrasonication. Impacts of light, heat, and pH on stability of antioxidant activity of ECLE were investigated. Exposure to light at an intensity of 1000 lx for 24 h showed no effect on activity of ECLE (p > 0.05). When being exposed to light for an extended periods (48 h), total phenolic content (TPC) became lower (p < 0.05). Light intensities at 2400-4000 lx for 24 h significantly decreased TPC and reduced antioxidant activities (p < 0.05). Thermal treatment at 60-100 ̊C for 1 h plausibly induced decomposition at simultaneously and released low-molecular-weight phenolic compounds, leading to an increase in activity (p < 0.05). ECLE showed the augmented antioxidant activity in pH range of 3-5. When ECLE was added to dried fermented catfish (DFC) at 200-600mg/kg and stored for 21 days at 30 ̊C, ECLE at 600 mg/kg effectively retarded lipid oxidation and inhibited the growth of microorganisms of DFC during storages, thereby extending the shelf life of DFC. ECLE could therefore be utilized as natural food additive or preservative in DFC.