‘Great potential’ of immature rice grains for nutraceuticals: Study

By Nathan Gray

- Last updated on GMT

Related tags: Rice

Immature rice grains may contain ‘a remarkable amount of bioactive compounds’, giving them great potential for applications in nutraceutical foods, according to new research.

New findings, published in Food Chemistry​, indicated that developing rice grain contains higher bioactive compounds than its mature grain.

Dr His-Mei Lai, Professor in the department of agricultural chemistry at the National Taiwan University, and her co-workers report that immature rice grains would be attractive for use as a novel ingredient in food products as they contain “high contents of total free phenolics and total free flavonoids.”

They added that immature rice grains would be attractive for use as a novel ingredient, to enhance the nutraceutical properties of foods.

Rice bioactives

Rice bran is a by-product of the rice milling process that has potential as a rich source of valuable health-promoting compounds. It accounts for approximately 10 percent of brown rice by weight.

Recent evidence has suggested that many bioactive compounds are not found in the rice cereal grain but instead in the husk and bran layer. The health-promoting compounds found in the bran layer include sterols, gamma-oryzanols, tocopherols, tocotrienols and phenolic compounds

Previous research has suggested that red and purple rice bran extracts may be a rich natural source of phytochemicals​ for nutraceutical and functional food developments; whilst other data has suggested that the anthocyanin content of black rice may rival that of blueberries and blackberries​, but be available for a fraction of the cost.

“Although some immature rice grain products have been consumed in some areas because of their nutritional values, little is known about variations in the bioactive compounds and antioxidative activities at different stages of rice grain development,”​ wrote Prof. Lai and her colleagues.

The new study examined the levels of phenolic compounds, and antioxidant properties, of two domestic rice cultivars during grain development in order to correlate the nutraceutical value of mature and immature rice grains.

Study details

Two rice cultivars, Kuang-fu-shiang-waxy (KFSW, a waxy indica rice with red coloured bran) and Taikeng 16 (TK16, a non-waxy japonicarice), were cultivated at the National Taiwan University.

The authors found the total phenolics and total flavonoids of the developing rice grains were significantly higher than those in mature seeds, with the authors reporting a high amount of free and soluble ferulic acids in developing rice grain.

“The tocols as hydrophobic antioxidants were plentiful in developing rice grain and mainly composed of alpha-tocopherol, gamma-tocotrienol and alpha-tocotrienol,”​ they said.

In addition, Lai her co-workers reported a high content of soluble dietary fibre in immature rice grains, which they suggested may have benefits for gastrointestinal health.

Based on the concentrations of bioactive compounds at different rice grain development, the authors reported that immature grains between the 15th and 18th day after anthesis (full flowering) would be suitable for food applications.

Market potential

Data from Leatherhead Food International (LFI) shows that the world functional antioxidants market is increasing year on year by around 3 per cent, and was valued at US$ 400 million in 2004, and US$ 438 million in 2007. Europe, the US, and Japan account for 90 per cent of this market.

With flavonoids and polyphenols reported to be 45 per cent of this functional antioxidant market, equivalent to almost US$ 200 million,

Source: Food Chemistry
Volume 127, Issue 1​, Pages 86-93, doi: 10.1016/j.foodchem.2010.12.092
“Bioactive compounds in rice during grain development”
Authors: Pei-Yin Lin, Hsi-Mei Lai

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