Fractionation of the rice bran layer and quantification of vitamin E, oryzanol, protein, and rice bran saccharide

Rebecca Schramm,Marybeth Lima,Na Hua,Alicia Abadie,Zhimin Xu

doi:10.1186/1754-1611-1-9

Abstract

Value-added processing with respect to rice milling has traditionally treated the rice bran layer as a homogenous material that contains significant concentrations of high-value components of interest for pharmaceutical and nutraceutical applications. Investigators have shown that high-value components in the rice bran layer vary from differences in kernel-thickness, bran fraction, rice variety, and environmental conditions during the growing season. The objectives of this study were to quantify the amount of rice bran removed at pre-selected milling times and to correlate the amount of rice bran removed at each milling time with the concentration of vitamin E, gamma-oryzanol, rice bran saccharide, and protein obtained. The ultimate goal of this research is to show that rice bran fractionation is a useful method to obtain targeted, nutrient-rich bran samples for value-added processing. Two long grain rice cultivars, Cheniere and Cypress, were milled at discrete times between 3 and 40 seconds using a McGill mill to obtain bran samples for analysis. Results showed that the highest oryzanol and protein concentrations were found in the outer portion of the rice bran layer, while the highest rice bran saccharide concentration was found in the inner portion of the bran layer. Vitamin E concentration showed no significant difference across the bran layer within a variety, though the highest magnitude of concentration occurs within the first 10 seconds of milling for both varieties. To extract the higher concentration of oryzanol and protein only the outer portion of the bran layer requires processing, while to extract the higher concentration of rice bran saccharide, only the inner portion of the bran layer requires processing. Rice bran fractionation allows for the selective use of portions of the bran layer and is advantageous for two reasons: (1) bran fractions contain higher concentrations of components of interest with respect to the overall bran layer average, and (2) less bran needs to be processed to obtain components of interest.

Highlights

The importance of rice to the world population's dietary requirement is evident from its presence in the diet of a quarter of the world's people [1]
The objectives of this study were: (1) to quantify the amount of rice bran removed at selected process time settings, and (2) to correlate the amount of rice bran removed at a given process time setting with the concentration of Rice bran saccharide (RBS), protein, vitamin E, and γ-oryzanol present
There is no significant difference in vitamin E concentration among milling times within a variety

Summary

Introduction

The importance of rice to the world population's dietary requirement is evident from its presence in the diet of a quarter of the world's people [1]. Rice processing or milling produces several streams of material, including husks, milled rice, and bran. In the United States, rice bran material is considered a by-product of the milling process and is most commonly used in animal feed or as a food ingredient due to its high nutritional content [2]. As interest in value-added processing research grows, attempts are being made to increase the value of agricultural crop by-products, including rice bran, by increasing their pharmaceutical or nutraceutical potential. While rice bran has traditionally been utilized for pet food products [3], there is growing interest in the wide array of potentially human-health enhancing compounds found in rice bran. Value-added processing to obtain these phytochemicals has the potential to be an important way of improving human health while increasing economic rates of return

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Conclusion