Optimization of Antioxidant Extraction from Avocado Peel and its Antibacterial Properties and Potentials in Food Products

Avocado peel, with a high proportion of bioactive compounds, is usually discarded as waste. Preliminary study was carried out to determine the most suitable solvent (out of acetones, water, ethanol and methanol) for extraction of antioxidants from avocado peel. Free radical scavenging activity (DPPH), Ferric reducing antioxidant (FRAP) and total phenolic content (TPC) were evaluated as responses. The oxidative stability of cooked ground beef, fish, oil samples (soybean, palm, groundnut) treated with optimum concentration of avocado peel ethanol extract (APE) was evaluated over time using standard procedures. Although methanol had a significantly higher (p<0.05) TPC and FRAP, it was not significantly different (p>0.05) in DPPH from ethanol; hence ethanol was selected based on its known low-toxicity. Results indicated that process variables with. Optimum solvent concentration, extraction time and extraction temperature with the highest desirability index of 0.868 was 80 %, 90 min and 60 օC respectively. Cooked ground beef and fish treated with > 0.3 % APE resulted in a more significant reduction (p<0.05) in pH values than the positive control (0.1 % BHT). However, there was no significant difference (p>0.05) in TBARS in both ground beef and fish samples treated with 0.5% APE and the positive control. Similarly, treatment with APE significantly reduced peroxide value (PV) in order groundnut oil>soybean oil> and palm oil and acid value (AV) in the order soybean oil> groundnut oil > palm oil used in this study. The minimum inhibitory concentration of APE was 20 mg/ml for S. aureus, 10 mg/mL for S. typhi and E. coli. The preservative effect of APE increased with increase in concentration of APE. Thus, its potentials in preservation of food products.