Grain Morphology and Thiamine Content in Thai Rice (Oryza sativa L.) Grains

Abstract

Rice is a nutritious cereal which contains several vitamins especially vitamin B1 or thiamine. There were reports of thiamine present in parts of rice grain particularly in bran, but samples analyzed were usually contaminated by starch from endosperm which caused thiamine estimation to be lower than its real value. This research reports the investigations of morphology and thiamine contents in grain parts of 6 rice cultivars; RD11, RD29, RD41, RD43, Suphunburi 1 and Phitsanulok 2. Grain size and weight were measured and the results showed statistically significant difference (P<0.05). Width, length, and weight were between 1.82-2.05 mm, 6.89-7.46 mm, and 17.66-20.74 g/1,000 grains, respectively. The volume of endosperm, embryo and bran were 10.70-14.55, 0.58-1.08 and 1.19-1.73 mm3, respectively. Thiamine in endosperm, embryo and bran were extracted by deionized water and analyzed by HPLC. Thiamine contents were 0.4-0.8, 13.8-21.2, 30.4-54.8 ng/mm3, respectively. The results showed the highest thiamine concentration in bran of each variety and demonstrated the importance of bran as a site of thiamine storage. Thiamine concentration in bran per volume varied among varieties up to 1.5 times suggested that other factors might be involved in thiamine accumulation in addition to bran volume. Varieties RD11 and Suphunburi 1 had the highest thiamine content in brown rice. They might be used as genetic resources to develop high-thiamine rice cultivars in the future.