Ultrasound bleaching and quality evaluation of rice bran oil

Abstract

Rice bran oil (RBO) contains rich nutrients that are beneficial to the human body, but RBO suffers from severe nutrient loss due to bleaching difficulties. This article investigates low‐power ultrasound‐assisted bleaching as a new method for RBO during the bleaching process, which could potentially reduce nutrient loss and lipid oxidation. First, florisil (FL), magnesium trisilicate (MAT), and activated blending earth (ABE) were selected to use a mixture design for formula optimization from six adsorbent types, and then, central composite design was employed to optimize the parameters of the bleaching process for the ultrasound‐assisted adsorbent formula. The results showed that the optimal formula was 66% FL, 10% MAT, and 24% ABE, the highest L* value and the lowest a* value is obtained at ultrasound power of 50 W for 9 min. The various parameters of RBO were subjected to comparison before and after ultrasound‐assisted bleaching. Following this bleaching procedure, the color and quality of RBO experienced notable enhancements, all the while maintaining micronutrient and fatty acid compositions within acceptable ranges. The characterization analysis of the adsorbent by FT‐IR spectroscopy and atomic force microscopy confirmed its adsorption of pigments and other substances. The results indicate that the low‐power ultrasound‐assisted bleaching is effective for RBO bleaching and may provide a promising alternative to the adsorption‐based bleaching method.Practical ApplicationsRBO is made from pressed rice bran and has high nutritional value, such as fatty acids, vitamin E, sterols, and oryzanol, with over 90% absorption by the body. The dark color of RBO makes it difficult to produce clear, transparent, and light‐colored rice bran oil, and even if bleaching is achieved, it results in significant nutrient losses. Conventional bleaching methods are commonly inefficient while emerging technologies cannot be applied industrially. Three adsorbents were selected for formulation optimization based on the fact that the bleaching effect of a single adsorbent is not obvious. Low‐power ultrasound‐assisted bleaching was performed to reduce nutrient loss and lipid oxidation. The aim is to find new bleaching methods that achieve bleaching results with acceptable nutrient losses.