Abstract
β-glucan is a dietary fiber that is beneficial to human health, and its content varies according to its different parts, type of cereal grain, and growing environment. In this study, the β-glucan of milled rice, rice husk, and rice bran fractions, as well as the amylose content of milled rice fraction, from 38 selected rice-paddy grains from six regions of Thailand were quantitatively determined. The milled rice of the Sakon Nakhon (SN) cultivar grown in the northeast contained the highest β-glucan content (0.88 ± 0.03%), followed by the milled rice of the Jow Khao Chiangmai (JKC) cultivar (0.71 ± 0.03%) and rice bran of the Sew Mae Jan (SMJ) cultivar (0.67 ± 0.03%) grown in the north. The results reveal that the rice cultivars from each region showing variation in the β-glucan level in each fraction, which is mainly found in milled rice and rice bran, are similar to those found in other cereal grains, although low amounts are found in the husk. The amylose and β-glucan contents in the milled rice fraction showed a strong negative correlation (r = −0.805; p < 0.0001). This new information about the β-glucan content of Thai rice cultivars could be used for the development of cereal-based functional food.
Highlights
A slight difference was found in milled rice and rice bran fractions, but both clearly differed from rice husk, which had a low level of β-glucan
The milled rice of the Sakon Nakhon (SN) cultivar, lowland rice grown in the northeastern region, contained the highest β-glucan content, followed by the milled rice of the Jow Khao Chiangmai (JKC) cultivar and rice bran of the Sew Mae Jan (SMJ) cultivar, which are upland rice grown in the northern region
The environmental classification, based on riceland ecosystem and photoperiod sensitivity, showed some patterns with the level of β-glucan content for each paddy-rice fraction, while the cooked texture of glutinous and non-glutinous rice, which is strongly influenced by amylose, was obviously related to the β-glucan content in the milled rice fraction
Summary
Milled rice is mainly consumed by humans for nutrition and is valuable for use in functional foods. The waste fractions from rice milling comprise bran and husk that are of low economic value but have high nutritional content. Rice bran is commonly a mixture of bran and germ (embryo) that contains high levels of several phytochemicals that have antioxidant properties; they are extensively utilized in functional food and as food additives [3,5,7]. The bran is generally not fully reused, and the utilization of the husks is limited. They are usually discarded as waste or eliminated by burning [8]
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