Using moisture transport properties of rice seed components for identifying fissure resistance

Abstract

Fissure resistance was related to the moisture transport properties of Cypress, Lemont, LaGrue, and Teqing rice varieties. The moisture transport properties, moisture diffusivity and resistance, were calculated using a three-dimensional moisture diffusion model. Fissure resistance was determined based on the relative fissure response of the four rice varieties. Fissure responses of the four rice varieties were compared to identify fissure resistance by exposing 50 kernels of paddy and brown rice to air conditions of 10, 25, and 40°C and 90% and 100% relative humidity. Conditions at 25°C and 90% relative humidity showed significant differences in fissure responses of the four varieties. Fissure resistance increased in the following order: Teqing, LaGrue, Lemont, and Cypress. Equilibrium moisture content (EMC) tests exposed 200 grams of brown rice to identify how the four varieties compare in their ability to hold moisture at a specific condition. Cypress, Lemont, and LaGrue tended to hold less moisture than Teqing at the four exposure air conditions (22°C at 98% RH and 80% RH and 35°C at 75% RH and 88% RH). This would suggest that the moisture Teqing holds might induce more stresses within its endosperm and thus create fissures. Moisture transport properties were determined by developing desorption and adsorption curves, using the same air conditions as in the EMC tests, for 50 grams each of white, brown, and paddy rice to determine the moisture diffusivity and of the endosperm and bran and the moisture resistance of the bran and hull. These properties were compared to identify any trends and relationships between fissure resistance and moisture transport properties. It was determined that the ideal rice kernel that would resist fissuring would have a lower EMC, an endosperm with high moisture diffusivity, a bran with either low moisture diffusivity, a thick bran, or a combination of both, and a hull with high moisture resistance. Cypress, the variety most resistant to fissuring, appears to have these desirable moisture transport properties to prevent fissuring and this may aid breeders in identifying traits to improve fissure susceptible varieties.