Optimizing the extraction of phenolic compounds from edible flowers of Onion (Allium cepa) using response surface methodology

Allium cepa (onion) flowers have been documented as a rich source of phenolic compounds with an ability to combat oxidative stress. Thus, effective extraction of phenolic compounds from these flowers is important in utilize them in food-based applications. The present study aims to make use of central composite design to investigate the effects of four extraction variables (solid:liquid ratio, ethanol concentration, temperature and time) on three different response variables viz., total phenolic content, total anthocyanin content and antioxidant activity. The results showed that the polynomial models for all responses were significant (p<0.05) and did not show lack of fit and presented determination of coefficients above 95%, indicating the predictive capacity of the models. The optimum process parameters generated were temperature 31.5°C, 48.46% ethanol, 1:36 solid:liquid ratio and extraction time of 57 minutes. The experimental values obtained for the response under the recommended optimum conditions confirmed the validity of the proposed second-order polynomial model.