Exploring the extraction, antioxidant activities and its stabilities of peanut skins crude proanthocyanidins extract

Peanut skin is a low-value by-product in the peanut oil and peanut product industry, with only a small amount utilized as animal feed while the majority discarded as waste. However, peanut skin contains high-value proanthocyanidins (PCs). Therefore, the objective of this paper is to optimize the extraction conditions for PCs, thereby increasing the added value of peanut skins. The results demonstrated that under the optimal conditions-liquid-solid ratio 1 (50:1 mL/g), temperature 1 (50 °C), ethanol concentration 2 (65%), and time 2 (16 min) - the yield of lyophilized crude PCs extract reached 129.14 ± 2.45 mg/g, with a PCs purity of 50.61 ± 2.27%. The crude PCs extract exhibits significant antioxidant activities. Under conditions including temperatures below 65 °C, pH values less than 7, and the presence of Na⁺, K⁺, Ca²⁺, Cu²⁺, Mg²⁺, Zn²⁺, glucose, sucrose, ascorbic acid, sodium bisulfite, as well as microwave sterilization, boiling water sterilization, pasteurization, and UV sterilization, crude PCs extract demonstrates favorable antioxidant stability. The process optimization and antioxidant activity investigation of crude PCs extract provide novel insights for the comprehensive processing and utilization of peanut skins.