This technology is a method for processing aged rice by immersing rice (paddy, brown, or white) stored for over a year in a gum solution—prepared by dispersing 0.3–0.6% (w/w) of gum relative to the weight of the aged rice—followed by hydrothermal treatment at 50–70°C for 30 minutes to 24 hours without gelatinizing the rice, and then drying. During hydrothermal treatment, water-soluble substances released from the rice bind with the gum to form a complex that coats the rice surface during drying.
While rice consumption has declined due to Westernized diets, leading to stockpiles of government-held rice, long-term storage causes rice to become hard and lose stickiness due to the degradation and recombination of starch, proteins, and lipids, as well as the formation of fatty acid-amylose complexes and disulfide bonds in sulfur-containing amino acids. The oxidation of free fatty acids also produces off-odors like hexanal, causing it to be shunned in the domestic market, which prefers sticky, soft rice. Existing grain improvement methods, such as high-pressure treatment or chemical modification, have seen little research regarding aged rice or raise concerns about chemical byproducts.
This technology utilizes one or more food-grade gums, such as guar gum, xanthan gum, carrageenan, pectin, or chitosan, with the aged rice immersed in the gum solution at a ratio of 1–60% (w/w). Drying can be performed via natural, hot air, freeze, vacuum, or hydrothermal methods. Specifically, hydrothermal drying at 45–70°C and 30–80% relative humidity for 1–24 hours stabilizes the surface complex. Since it relies solely on physical processing without chemicals, there are no concerns regarding byproducts. It can be applied to instant rice, HMR products, and rice flour products, revitalizing surplus government-held rice into ingredients with texture and aroma comparable to new rice, thereby boosting consumption.
This invention was developed with support from the Ministry of Agriculture, Food and Rural Affairs for the development of physically modified starch for clean-label foods.
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