Optimization of Natural Anthocyanin Extraction from Onion Peels

Abstract

Anthocyanins are natural pigments with valuable functional properties, widely utilized as colorants in the food and pharmaceutical industries. Red onion (Allium cepa L.) peels,

often treated as agricultural waste, are increasingly recognized for their richness in cyanidin- based anthocyanins and their potential as a sustainable source of natural dyes.

This study aimed to optimize anthocyanin extraction from red onion peels by investigating the effects of solvent acidity and extraction time. Two acidified ethanol solutions (70% v/v) were prepared using 0.01 M and 0.04 M HCl, and applied to dried peel powder (5 g) following a 20-minute maceration step at room temperature and incubation in a water bath at 30°C for 15 and 40 minutes. Extracts were filtered and analyzed spectrophotometrically using the pH differential method, with absorbance recorded at 520 nm and corrected at 700 nm. The results showed that both acidity and extraction time had a significant positive effect on anthocyanin yield. The highest content, 581.57 mg/100g dry matter, was obtained with the solvent containing 0.04 M HCl after 40 minutes of incubation. Regression analysis confirmed the statistical significance of both factors and their interaction (p < 0.001), with an excellent model fit (R2 = 0.9984), supporting the reliability of the findings. These results demonstrate the efficiency of using acidified ethanol under mild thermal

conditions for the extraction of anthocyanins from onion peels, offering a simple and eco- friendly alternative for natural pigment recovery.