Relating Rice Milling Quality Changes During Adsorption to Individual Kernel Moisture Content Distribution

Abstract

Cereal Chem. 75(1):129-136Several varieties of rough rice that were either stored for an extended period of time or freshly harvested were conditioned to initial moisture contents ranging from 10 to 17%. After the individual kernel moisture content distributions were measured, the samples were soaked in water at temperatures ranging from 10 to 40°C. The samples were then dried and milled. The bulk critical moisture content, at which head rice yield began to decline due to moisture adsorption, ranged from 12.5 to 14.9%, depending on the variety, harvest moisture content, and storage conditions. The kernel critical moisture content, determined from each sample from the cumulative kernel moisture content frequency distribution, increased with increasing sample initial moisture content.

Effects of Nitrogen Rate and Harvest Moisture Content on Physicochemical Properties and Milling Yields of Rice

“…3A), although significant differences were observed only with the Wells cultivar. Increased fissured-kernel percentages in response to HMCs below optimal levels agree with the findings of Siebenmorgen et al (1998Siebenmorgen et al ( , 2007. In contrast, the impact of HMC level on brown rice fissured-kernel percentages was significant for all cultivars (Fig.…”

“…Differences in fissured-kernel percentages were minimal between the 19 and 23% HMC levels, with statistical difference observed only for the Cheniere cultivar. Increased fissured-kernel percentages in response to HMCs below optimal levels agree with the findings of Siebenmorgen et al (1998Siebenmorgen et al ( , 2007.…”

Effect of Weather and Rice Moisture at Harvest on Milling Quality of California Medium-Grain Rice

“…The PHRY was based on the assumption that all kernels that dry below 15% moisture and are rehydrated will fissure and result in broken kernels when milled. The 15% threshold moisture was based on laboratory tests (not reported) and is at the upper range of critical moistures reported by Siebenmorgen et al (1998). PHRY was calculated using equation 1:…”

“…A great deal of research beginning the 1930s showed that paddy rice kernels fissure when dried below a critical moisture content and then rehydrate because of exposure to free moisture or high humidity, (Kunze, 1993;Siebenmorgen et al, 1998;Lan et al, 1999). The fissured kernels break during milling, causing low HRY in lots with high amounts of fissured kernels.…”

“…While maximum HRY was obtained at HMCs above 20%, lots below 18% HMC had nearly the same quality, and lots above 22% moisture had HRY values of less than 50%. The data show that in commercial practice HMC was not a good predictor of HRY, and apparently there must be other variables influencing rice quality.A great deal of research beginning the 1930s showed that paddy rice kernels fissure when dried below a critical moisture content and then rehydrate because of exposure to free moisture or high humidity, (Kunze, 1993;Siebenmorgen et al, 1998;Lan et al, 1999). The fissured kernels break during milling, causing low HRY in lots with high amounts of fissured kernels.…”