Chapter 9: Rough-Rice Drying—moisture Adsorption and Desorption

Kunze, O. R.; Calderwood, D. L.

doi:10.1094/1891127349.009

Cited by 19 publications

(14 citation statements)

References 21 publications

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“…Rice grains of a same panicle can differ up to 10 pp in MC. MC of rice grains on the same plant and/or on the same field can vary even more (Kunze and Calderwood, 2004;Li et al, 2003;Siebenmorgen et al, 1990Siebenmorgen et al, , 1992. During harvest, kernels with both high and low MC are mixed.…”

Section: Fissuresmentioning

confidence: 99%

“…When the MC gradients exceed the rice kernel mechanical strength, fissures can develop (Jia et al, 2002;Kunze, 2001;Kunze and Choudhury, 1972;Sarker et al, 1996;Yang et al, 2002). Such fissures are large internal fractures, usually perpendicular to the longitudinal axis of the rice grain (Hwang et al, 2009;Jia et al, 2002;Kunze, 1979;Kunze and Calderwood, 2004;Sharma and Kunze, 1982). Rice grain kernels primarily break during dehulling and milling because of weakness caused by these fissures (Bhattacharya, 1969;Matthews et al, 1970;Nguyen and Kunze, 1984;Qin and Siebenmorgen, 2005;Rhind, 1962;Sarker et al, 1996;Siebenmorgen et al, 1998b;Swamy and Bhattacharya, 1979;Velupillai and Pandey, 1990;Zhang et al, 2005).…”

Section: Fissuresmentioning

confidence: 99%

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The breakage susceptibility of raw and parboiled rice: A review

Buggenhout

Brijs

Celus

et al. 2013

Journal of Food Engineering

148

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Rice (Oryza sativa L.) is one of the most important cereals in the world. Before it is consumed, it is common to remove the hull, bran and germ from the rough rice kernel which is either parboiled or not. During such processing, rice kernels are subjected to mechanical stresses which cause some rice grains to break. A main challenge of the rice industry is to minimize the quantities of broken rice. We here review the factors impacting the breakage susceptibility of rice kernels. Their tendency to break is primarily determined by fissures, chalkiness, immaturity and rice kernel dimensions, properties which are both cultivar and rice grain history dependent. The intensity of processing of any given rice feedstock determines the actual level of broken rice kernels. If performed properly, parboiling, a three-step hydrothermal treatment consisting of soaking, heating and drying of rough rice, substantially reduces the level of broken kernels.

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Section: Fissuresmentioning

confidence: 99%

Section: Fissuresmentioning

confidence: 99%

The breakage susceptibility of raw and parboiled rice: A review

Buggenhout

Brijs

Celus

et al. 2013

Journal of Food Engineering

148

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“…When these sorption processes are very rapid, they produce large moisture gradients within the rice kernel, which are believed to cause fissures (or cracks) in rice. [1] Some of these fissures cause the rice kernel to break on milling. Since the full-length grain is the preferred form of rice, such broken rice has typically lower market value.…”

Section: Introductionmentioning

confidence: 99%

Moisture Diffusivity in Rice Components During Absorption and Desorption

2011

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Moisture diffusivity values of different rice kernel components, namely endosperm, bran and husk, are required to solve mathematical models describing absorption and desorption processes. In addition to the rice variety and temperature, the moisture diffusivity also depends on its instantaneous moisture content or water activity (a w ) and whether rice is absorbing or desorbing moisture. This research was undertaken to determine moisture diffusivity values of rough rice components in different a w ranges during absorption and desorption. Experiments were performed to measure sorption rates of different rice forms, including white rice, brown rice, and rough rice kernels. Mathematical models were developed to predict their moisture distribution during moisture sorption processes. These models were solved by finite element method using Comsol Multiphysics 1 simulation program. Moisture diffusivity values of different rice components were calculated and found to be different during absorption and desorption. Diffusivity of rice endosperm was higher during desorption than absorption at a w higher than 0.20 and increased with an increase in a w in 0.20-0.80 a w range. Diffusivity of bran remained almost the same with a w while diffusivity of husk decreased with an increase in a w . Results obtained in this research demonstrated that the moisture diffusivity of different rice components varies significantly with the change in water activity or moisture and should be accounted in the mathematical models.

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“…For example, the drying rates of rice samples with IMC of 20.5% were 1.3, 0.9, and 0.7 percentage points per min during heating for single-layer, 5 mm, and 10 mm drying bed thicknesses and heating time of 60 s. Similarly, when the IMC was increased to 23.8%, the drying rates of rice samples were 1.5, 1.1, and 0.8 percentage points per min. Therefore, it is important to note that a high drying rate was achieved by using IR heating alone, even without counting the moisture removal during tempering and cooling, compared to conventional heated-air drying of 0.1 to 0.2 percentage points per min due to the low air temperature used (Kunze and Calderwood, 2004).…”

Section: Moisture Removal Under Different Drying Treatmentsmentioning

confidence: 99%

“…Therefore, to minimize the moisture gradient generated during conventional rice drying, multiple drying passes are typically used. The multiple drying normally removes a relatively small amount of moisture (2% to 3%) in each drying pass by exposing the rough rice to relatively low heated air temperature (Kunze and Calderwood, 2004).…”

mentioning

confidence: 99%

Drying Characteristics and Quality of Rough Rice under Infrared Radiation Heating

Pan¹,

Khir²,

Bett‐Garber³

et al. 2011

Transactions of the ASABE

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Infrared (IR) radiation heating could provide a high heating rate and rapid moisture removal for rough rice drying. The objective of this research was to investigate the effect of the drying bed thickness on drying characteristics and quality of rough rice subjected to IR heating. Samples of freshly harvested medium grain rice (M202 variety) with 20.5% and 23.8% (w.b.) moisture contents were used for this study. They were dried with two different radiation intensities (4685 and 5348 W m-2) and exposure times of 15, 30, 40, 60, 90, and 120 s for each drying bed thickness. The three tested drying bed thicknesses were single layer, 5 mm, and 10 mm. After IR drying, the samples were tempered for 4 h followed by natural cooling. The drying rate, moisture removal, and temperature of the rice were determined. The rice temperatures after the IR heating were in the range of 35.9°C to 71.4°C. The heating and drying rates decreased with the increase of bed thickness. Up to 2.2% of moisture was removed during natural cooling after tempering, without additional energy input. IR heating under tested conditions did not have adverse effects on rice sensory and milling quality, including total rice yield, head rice yield, and degree of milling of the dried rice. We concluded that a high heating rate, fast drying, and good rice quality can be achieved by IR heating of rough rice to about 60°C followed by tempering and natural cooling with a tested bed thickness up to 10 mm.

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Chapter 9: Rough-Rice Drying—moisture Adsorption and Desorption

Cited by 19 publications

References 21 publications

The breakage susceptibility of raw and parboiled rice: A review

The breakage susceptibility of raw and parboiled rice: A review

Moisture Diffusivity in Rice Components During Absorption and Desorption

Drying Characteristics and Quality of Rough Rice under Infrared Radiation Heating

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