Optimization of Extraction of Vitamin E and γ – Oryzanol from Thai Rice Germs Using Response Surface Methodology

Abstract

The lipophilic antioxidants including vitamin E and γ–oryzanol contained in rice germs from three cultivars, namely Hommali Numnom (white rice), Tubtim Chumphae (red–brown rice) and Riceberry (purple rice) were evaluated. The objective of this research was to optimize the extraction conditions using Box–Behnken design (BBD) with response surface methodology (RSM) for achieving high efficiency extracts. The extraction process was conducted using ultrasonic–assisted extraction (UAE) with soybean oil as a green solvent. The effects of extraction temperature (30–50 °C), extraction time (30–50 min), and liquid–solid ratio (3–7, v/w) on vitamin E and γ–oryzanol contents were studied. The contents of vitamin E and γ–oryzanol from all rice germ cultivars using UV–vis spectrophotometer ranged from 2.510 to 63.605 μg/g extract and 0.230 to 8.482 μg/g extract, respectively. The antioxidant activity of extracts was determined by the ferric reducing antioxidant power (FRAP). FRAP varied from 17.76 to 305.35 μmol Trolox/g extract. Optimal extraction conditions for maximum vitamin E and γ–oryzanol contents were analyzed as 40 °C, 40 min, and liquid–solid ratio of 5 v/w. The results suggested that the RSM can be an appropriate approach for optimizing the extraction of vitamin E and γ–oryzanol from Thai rice germs. Furthermore, it is a green technology and has also great potential to be applied in functional food ingredients.