Influence of controlled curing process on physico-chemical, nutritional, and bio-active composition of brown Spanish onion

Abstract

Fundamental aim of this study was to mimic the traditional curing conditions for Brown Spanish variety of onions that is highly perishable variety and least explored for its scope The central composite rotatable design experiment using the response surface methodology approach was adopted to evaluate the relationship of curing parameters viz, Relative humidity (RH), time and temperature with physical, chemical, and biochemical properties of Allium cepa L. Var. Brown Spanish. The lightness (L*) value and water activity (aw) have a positive relationship with the curing time and RH respectively, However, hue value(h°) indicated negative relationship with the RH. Tannic acid increased considerably with RH, however, showed a reduction with an increase in curing temperature and curing time. Quercetin increased with RH, however it decreased with curing time and temperature. Considering the desirability (0.83 %), the curing process for 5 days at 65 % RH and 28 °C was found to be optimum. Furthermore, a comparative evaluation of uncured and the cured onions revealed that the optimized curing process resulted in an increase in hardness (N) and Quercetin by 8.37 % and 2.3 %, respectively, while as curing reduced water activity, h° and tannic acid by 3.6,17 % and 29 %, respectively.