Effects of Moisture Adsorption on the Head Rice Yields of Long-Grain Rough Rice

Abstract

T HE head rice (whole kernel) yield oflong-grain rough rice ranging from 7.6 to 19.2% initial moisture content was determined after subjecting the rice to moisture adsorption conditions. The conditions ranged from those representing severe moisture adsorption environments-soaking in water, misting with water. equilibrating to a 95% relative humidity environment-to less severe methods created by mixing low and high moisture contcnt rice in proportions of 3: 1. I :1. and I :3. All methods showed significant reduction in head rice yield whcn the moisture content at which remoistening was initiated was lower than 13%,. Remoistening of rice at a moisture content above 16°)(, had no discernable effect on head rice yields. Head rice yields lower than 2% were prodnced by severe moisture adsorption treatments when rice at 7.6%, moisture content was remoistened. The effects of the moisturc adsorption treatments on head rice yields were accurately described by a two-parameter. sigmoid equation commonly 1I sed to prcsent adsorption and desorption isotherms in cereal grains.

Optimal Harvest Moisture Content for Maximizing Mid‐South Rice Milling Yields and Returns

“…Conversely, harvesting with a low HMC can save in drying costs but can also decrease HRY due to fissuring. Moreover, the literature is rich (Kunze and Prasad, 1978;Siebenmorgen and Jindal, 1986;Siebenmorgen et al, 2007) on the effects of HMC on HRY, but our research on the impact of high nighttime temperatures shows that neglecting heat stress can lead to omitted variable bias when estimating HRY (Asaoka et al, 1984; Counce Cooper et al, 2008;Fitzgerald and Resurreccion, 2009). Thus, this study combines two determinants of HRY-HMC and high nighttime temperatures-to estimate how HMC is related to these variables.…”

“…Head rice yields are adversely affected by harvesting rice at MCs that are either too high or too low (Siebenmorgen et al, 1992;Jodari and Linscombe, 1996). Previous research (Siebenmorgen and Jindal, 1986;Juliano and Perez, 1993) highlights the existence of an optimal HMC at which milling yield peaks in a convex fashion with regard to HRY. Siebenmorgen et al (2007) found that the optimal HMCs for maximizing HRY varied from 18.7 to 23.5% across rice cultivars and types.…”

“…Broken rice (also called "brokens"), which is typically either ground into fl our or used in pet food, is currently valued at 68.5% of unbroken kernels, or head rice yield (HRY) (USDA-FAS, 2014). Studies have shown that although kernels of some rice cultivars are genetically more susceptible to breakage during milling, the rice moisture content (MC) at the time of harvest (HMC) and exposure to high nighttime air temperatures during critical stages of production can directly aff ect the ratio of unbroken rice (i.e., HRY) to broken rice on milling.Other studies indicate that fi ssures in the kernel will develop when rice at low MC (£15%) is exposed to conditions that cause the dry rice kernels to rapidly absorb moisture (Kunze and Prasad, 1978;Siebenmorgen and Jindal, 1986). Subsequently, fi ssures form within the rice kernel when internal stressors exceed the material tensile strength of the kernel.…”

“…Other studies indicate that fi ssures in the kernel will develop when rice at low MC (£15%) is exposed to conditions that cause the dry rice kernels to rapidly absorb moisture (Kunze and Prasad, 1978;Siebenmorgen and Jindal, 1986). Subsequently, fi ssures form within the rice kernel when internal stressors exceed the material tensile strength of the kernel.…”

Use of gross income as a measure of productivity in rice breeding

“…Cultural factors include seeding date (Gravois and Helms 1998), time of draining the field (McCauley and Way 2002), and harvest grain moisture (Jodari and Linscombe 1996;McCauley and Way 2002), whereas moisture adsorption of rough rice (Siebenmorgen and Jindal 1986;Siebenmorgen et al 1992), and degree of milling (Reid et al 1998) are examples of post-harvest handling factors. Cultivar parameters that affect milled rice percentages include grain length and susceptibility to grain fissuring (Jodari and Linscombe 1996), panicle density, filled grain per panicle, and grain weight .…”