OPTIMIZATION OF EXTRACTION CONDITIONS FOR ANTIOXIDANT PHENOLIC COMPOUNDS FROM MALT ROOTLETS USING RESPONSE SURFACE METHODOLOGY

Abstract

ABSTRACT Significant levels of antioxidant phenolic compounds were detected in malt rootlets, indicating that malt rootlets may serve as an excellent source of natural antioxidants for disease prevention and health promotion. To improve this by-product value, response surface methodology (RSM) was used for the optimization of extraction conditions for obtaining the maximum amount of antioxidant phenolic compounds from malt rootlets in the malting industry. The Box-Behnken experimental design was used to investigate the effects of three independent invariables on total antioxidant activity (TAA). These three independent variables were solvent composition (% v/v), extraction temperature (C) and time (min), respectively. By RSM and canonical analysis, the optimal conditions for higher TAA were: 50%, 84C, 22 min. Under optimal conditions, the predicted response value for TAA reached 9.49 µmol Trolox equivalent (TE). Verification of the optimization showed that 9.79 µmol TE was observed under the optimal condition, which was a 3.13-fold increase of TAA at the lowest level. PRACTICAL APPLICATIONS Antioxidant phenolic compounds have gradually been used in the medicine industry with the ability of reducing risks of cardiovascular diseases and certain cancers. On the one hand, they are beneficial to grains, fruits and vegetables through several possible mechanisms, such as directly quenching free radicals, chelating transition metals, reducing peroxides and stimulating the antioxidative defense enzyme activities. On the other hand, many of the biological functions, such as antimutagenity, anticarcinogenity and antiaging, originate from this property of antioxidant phenolic compounds. Generally, a great deal of malt rootlets are produced in the malting industry and treated as by-products for animal feed. However, significant levels of antioxidant phenolic compounds were detected in malt rootlets, indicating that malt rootlets may serve as an excellent source of natural antioxidants for disease prevention and health promotion. While the optimization of extraction conditions for antioxidant phenolic compounds from malt rootlets would not only add value to this by-product, but also offer a new source of natural antioxidant.