Multipass drying of paddy (rice) in the humid tropics

Beeny, J.M.; Basil, Chin Shin Ngin

doi:10.1016/0021-8634(70)90096-x

Cited by 14 publications

(6 citation statements)

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“…The emphasis in most of the studies was on the effect of tempering duration on drying performance (i.e., drying rate and energy utilization). Few researchers (Beeny and Chin, 1970;Cnossen et al, 1998;Steffe et al, 1979;Wasserman et al, 1964), however, have studied the effect of tempering on kernel quality.…”

Section: Tempering Researchmentioning

confidence: 99%

“…High tempering temperatures have been shown to be effective in maintaining high HRYs and decreasing tempering duration. Beeny and Chin (1970) dried rice with an initial MC of 24% using 54. 4°C air and found an THE GLASS TRANSITION TEMPERATURE CONCEPT IN RICE DRYING AND TEMPERING: EFFECT ON MILLING QUALITY increasing HRY with increasing tempering duration up to 5 h. Cnossen et al (1998) showed increasing HRYs for tempering durations up to 150 min when drying mediumgrain rice with 60°C air and tempering at this drying temperature.…”

Section: Tempering Researchmentioning

confidence: 99%

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The Glass Transition Temperature Concept in Rice Drying and Tempering: Effect on Milling Quality

Cnossen¹,

Siebenmorgen²

2000

Transactions of the ASAE

160

131

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A true understanding of rice kernel fissuring and breakage, as a result of drying and tempering, must include both engineering and cereal science principles. Particular emphasis must be placed on the change of states of starch occurring at the glass transition temperature (T g). This transition from a glassy to rubbery state, or vice versa, has been identified to play an important role in rice fissuring and breakage. A hypothesis has been developed explaining rice kernel fissuring during drying and tempering. The objectives of this research were to determine the effect of the T g during rice drying and tempering on milling quality. Additionally, the minimum tempering time required for various drying conditions, to optimize milling quality, was determined. Rice was dried under three conditions, two with a drying air temperature above T g and one below T g , for four durations and then tempered for 0 to 240 min. The experimental procedure was designed to directly test the T g hypothesis by cooling rice to a temperature below the T g after each tempering duration. Results for both medium-grain rice and long-grain rice at 19.6 to 23.7% harvest moisture content (MC) * show that 5 to 6 percentage points MC can be removed per drying pass without damaging the rice kernel, as long as sufficient tempering is allowed. Required tempering durations were shorter for long-grain rice as compared to medium-grain.

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Section: Tempering Researchmentioning

confidence: 99%

Section: Tempering Researchmentioning

confidence: 99%

The Glass Transition Temperature Concept in Rice Drying and Tempering: Effect on Milling Quality

Cnossen¹,

Siebenmorgen²

2000

Transactions of the ASAE

160

131

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“…Drying air temperature of 70-150 o C, air velocity of 0.5-2 m/s and grain bed depth 5-20 cm was used in this study Maximum head yield, minimum specific energy and minimum drying time were found with grain bed depth 7-10 cm. Benny et al did an experimental study of multi-pass drying of wet paddy and achieved an moisture content reduction of about 45 with drying air temperature of 50-55 o C in a drying period of 61.57 mins (Beeny and Basil, 1970). Tohidi et al studied the energy and quality attributes for deep bed drying of paddy at various temperature velocity and relative humidity (Tohidi et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Design, development and performance evaluation of a fluidized bed paddy dryer

Kalita¹,

Deka²,

Das³

et al. 2018

JEES

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In this study a fluidized bed paddy dryer has been developed and its performance was investigated. The fuel used for generation of heat required for drying is wood rejects. In order to investigate the performance of the dryer, the experiments were performed at four different inventories and at three different air velocities. The locally available paddy variety "Ranjit" was used for experiments. The drying air temperature was maintained within 58-62 °C to retain all the nutrients content. The change in nutritional values was also determined at different drying times viz. at 0, 5 and 10 minutes from the start of the experiment and found to decrease with drying time as compared to the fresh sample. From the experiment it is evident that the drying rate increases with increase of air velocity and found to be optimum at an air velocity of 23.60 m/s.

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“…To reduce these moisture gradients, rice is usually held between passes in a multipass drying process. Tempering temperatures of 35-60°C have been employed so far (Wasserman et al 1964;Beeny and Chin 1970;Steffe and Singh 1980;Cnossen et al 1998;Li et al 1999). Tempering temperatures of 35-60°C have been employed so far (Wasserman et al 1964;Beeny and Chin 1970;Steffe and Singh 1980;Cnossen et al 1998;Li et al 1999).…”

mentioning

confidence: 99%

“…This practice is known as tempering, which refers to the equilibration of moisture content inside a kernel and serves to equalize the moisture content throughout the mass (Steffe and Singh 1980). Tempering temperatures of 35-60°C have been employed so far (Wasserman et al 1964;Beeny and Chin 1970;Steffe and Singh 1980;Cnossen et al 1998;Li et al 1999). High tempering temperatures have proved to be effective in preserving head rice yield (HRY) and reducing tempering durations.…”

mentioning

confidence: 99%

Preservation of Head Rice Yield Under High‐Temperature Tempering as Explained by the Glass Transition of Rice Kernels

2003

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Cereal Chem. 80(6):684-688Tempering has been shown in literature to preserve head rice yield after heated air drying. Most reported tempering work was done adiabatically at a temperature below that for rice drying. In this study, the effect of a tempering temperature above that for rice drying on the whole kernel percentage was investigated. High-temperature tempering is an effective way to preserve the whole kernel percentage for rice dried at a raised temperature (e.g., 60°C) at which head rice yield would otherwise incur a pronounced reduction without tempering. Tempering helped relax the strains inside a rice kernel induced by internal stresses developed during the drying process. The strains had two components (elastic component and viscous component) due to the viscoelasticity of rice kernels. The reduction of moisture content gradients inside a rice kernel during tempering helped eliminate the elastic component of the strains due to the elasticity of the rice kernel. Results showed that to effectively eliminate the viscous component of the strains due to the viscosity of the rice kernel, tempering temperatures must be kept well above the glass transition temperature of the rice kernel. A tempering temperature below the glass transition temperature failed to preserve the whole kernel percentage. For example, with a tempering temperature of 80°C and a tempering duration of 80 min, the whole kernel percentage for the rice with an initial moisture content of 20.4% wb dried at 60°C and 17% rh for 120 min down to 10.2% wb (10.2 percentage points of moisture content removal in one drying pass) was preserved to a level close to that of the control sample.

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Multipass drying of paddy (rice) in the humid tropics

Cited by 14 publications

References 0 publications

The Glass Transition Temperature Concept in Rice Drying and Tempering: Effect on Milling Quality

The Glass Transition Temperature Concept in Rice Drying and Tempering: Effect on Milling Quality

Design, development and performance evaluation of a fluidized bed paddy dryer

Preservation of Head Rice Yield Under High‐Temperature Tempering as Explained by the Glass Transition of Rice Kernels

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