Optimization of extraction parameters and stabilization of anthocyanin from onion peel.

A large amount of onion waste is produced by the food industries. This onion waste contains high-value functional ingredients, since several compounds and nutrients are present in onion peel. The objective of this work is to extract and stabilize the anthocyanin from onion peel waste in various forms. The major component present in onion peel is anthocyanin. The anthocyanin was extracted from onion peel by the microwave-assisted extraction process. A fractional factorial experiment was used to carry out 16 possible extractions instead of 64 possible extractions. The highest yield of total anthocyanin content such as 21.99 attains when using 2 g of onion peel with the extraction time 5 minutes, power as 700 W, ethanol concentration as 75 mL, and solvent feed ratio as 20 g/mL. The anthocyanin was stabilized in three ways such as co-pigmentation, a combination of buffer and hardpan coating. The most stable and colorless anthocyanin was observed by the co-pigmentation method. Stable and red color anthocyanin is obtained using a combination of buffer and dark brown color stable anthocyanin is perceived using hard pan coating. The antioxidant activity of each sample was studied during 3 weeks of storage. Sample A (co-pigmented sample) showed 75% of antioxidant activity, sample B (hardpan coating) exhibited 60% of antioxidant activity and sample C (buffer combination) confirmed 81% of antioxidant activity. This anthocyanin study can be used in future studies for various applications such as the preservation of meat and natural colorant.