The enhanced yield of polyphenols and antioxidant activity from onion peel (Allium cepa L.) and its incorporation into low-density polyethylene films

This study aimed to forecast the optimum condition for polyphenols extraction from onion peel using conventional maceration extraction (CME) and ultrasound-assisted extraction (UAE) methods and incorporated these compounds in plasma-treated low-density polyethylene (LDPE) film. Response surface methodology (RSM) was employed to determine the effect of three independent variables, including the type of solvent (water, ethanol, methanol, and acetic acid), solvent concentration (0-100%), and extraction time (10-1440 min) on responses. The responses included extraction yield, phenolic content, flavonoids, and antioxidant activity. Finally, the model was optimized to predict the optimum condition that would yield maximum responses. In the next stage, the surface of LDPE was activated by normal air cold plasma treatment. The onion peel extract's 10 and 20% solutions were prepared and incorporated into the treated-LDPE films. The optimum conditions included the mixture of 83.57 ml ethanol, 1.01 ml methanol, 15.41 ml water, 30 min extraction time with a desirability value of 0.95 in the UAE method. The combination of 79.58 ml ethanol and 20.42 ml water at 1398 min extraction time with a desirability value of 0.94 for the CME method. The finding of this investigation achieving the highest yield, phenolic, flavonoid content, and antioxidant activity 0.75, 428.14, 390.41, and 550.19 mg/g, respectively, in UAE and 0.60, 388.75, 413.37, and 395.94 mg/g, respectively, in CME. The results indicated the highest yield, phenolic, flavonoid content, and antioxidant activity 0.75, 428.14, 390.41, and 550.19 mg/g, respectively, in UAE and 0.60, 388.75, 413.37, and 395.94 mg/g, respectively, in CME. Results of the present study showed a good agreement between predicted and experimental values at optimum conditions. Suitable attachment of phenyl compounds at the region 580-1740 cm(-1) in ATR-FTIR results was observed.

Automated summary

This study optimized the best conditions for extracting polyphenols from onion peel using RSM, including UAE and CME methods, achieving the highest yield and antioxidant activity under the optimum conditions.