George Ondier

Drying Characteristics and Milling Quality of Rough Rice Dried in a Single Pass Incorporating Glass Transition Principles

The objective was to study the drying characteristics and milling quality of rough rice subjected to single-pass drying while controlling kernel material states. Drying experiments were conducted at 60, 70, and 80°C and relative humidities ranging from 13 to 83%. For all drying air temperatures and tempering conditions, milling quality was not significantly different from the controls when the relative humidity of the drying air was maintained above 63% (kernel core and surface maintained in a rubbery state) and rice was tempered immediately after drying, in sealed plastic bags and at the drying air temperature, for at least 60 min.

Equilibrium Moisture Contents of Pureline, Hybrid, and Parboiled Rice Kernel Fractions

The effects of temperature and relative humidity on the equilibrium moisture contents of rough rice, brown rice, and head rice from non-parboiled pureline cultivars Wells (long-grain) and Jupiter (medium-grain), hybrid cultivar CL XL730 (long-grain), and a parboiled rice (long-grain) of unknown cultivar, were investigated. In addition, equilibrium moisture contents of broken kernels, rice bran, and rice hulls of Wells cultivar were also investigated. Air conditions were maintained at temperatures of 10°C to 60°C, and relative humidities of 10% to 70% to measure kernel-fraction moisture contents. For each air condition, rough rice and constituent fractions were allowed to equilibrate, after which the equilibrium moisture content of each fraction was measured. Rice hulls attained the lowest equilibrium moisture content followed by rice bran, brown rice, broken kernels, and head rice; this held for both parboiled and non-parboiled samples. Five, three-parameter equations, namely, the Modified Henderson, Modified Chung-Pfost, Modified Halsey, Modified Oswin, and Modified Guggenheim-Anderson-DeBoer were evaluated for their ability to describe the sorption data of each kernel fraction. The Modified Chung-Pfost and Modified Guggenheim-Anderson-DeBoer equations were the most suitable for describing equilibrium data of rough rice, brown rice, broken kernels, and head rice of both parboiled and non-parboiled samples, followed by the Modified Oswin and Modified Henderson equations. The Modified Oswin equation was the most suitable for rice bran and hulls. The measured equilibrium moisture content of rough rice was closely predicted by the weighted average equilibrium moisture content of the kernel fractions.

EQUILIBRIUM MOISTURE CONTENTS OF ROUGH RICE DRIED USING HIGH-TEMPERATURE, FLUIDIZED-BED CONDITIONS

Desorption isotherms of long-grain rough rice with initial moisture content of 20.6% (wet basis) and dried in a fluidized-bed system at temperatures ranging from 60°C to 90°C and relative humidities from 7% to 75% were measured. Rice sample mass and drying air conditions were recorded throughout the drying duration for each test until a steady-state mass was attained. The Page equation, with experimentally determined drying parameters, was used to describe the drying data. Equilibrium moisture contents were used to estimate empirical constants of the modified Chung-Pfost equation. The resulting modified Chung-Pfost equation described the experimental data with a root mean square error (RMSE) of 0.73 and a coefficient of determination (R2) of 0.94.

Equilibrium Moisture Contents of Pureline, Hybrid, and Parboiled Rice

Equilibrium moisture contents of long- and medium-grain rough rice of both pureline and hybrid cultivars, and a parboiled rough rice of unknown cultivar, were measured in a near-static air environment at five temperatures (10°C, 20°C, 30°C, 45°C, and 60°C) and relative humidities in the range of 10% to 70% using a gravimetric method. Results showed that there were no consistent significant differences between the equilibrium moisture contents of pureline and hybrid or medium- and long-grain rice cultivars. However, the equilibrium moisture content of parboiled rice was significantly less than that of non-parboiled rice for almost all air conditions. Nonlinear regression analysis was used to estimate empirical constants of five models used for describing grain sorption isotherms. The appropriateness of each model in describing the equilibrium data was evaluated using root mean square errors and residual patterns. The modified Chung-Pfost equation best described equilibrium data of non-parboiled samples, followed by the modified GAB, modified Oswin, modified Halsey, and modified Henderson equations. The modified Chung-Pfost and modified GAB equations were equally effective when describing equilibrium data of individual cultivars.

Research-Scale DRYING OF Rough Rice Using Silica Gel

After harvest, most rough rice research samples are dried using ambient air, the temperature and relative humidity of which oscillates. Fluctuations in environmental conditions produce variation in the final moisture contents (MCs) of samples, yielding inconsistent functional properties. The goal of this study was to develop an alternative method for drying small rough rice samples using silica gel that would be capable of yielding accurate and precise final MCs while maintaining grain quality. Drying experiments incorporated a combination of 1- and 5-g moisture-permeable packets of silica gel, mixed with rough rice samples in plastic bags. The average adsorptive capacity of the packets in closed rough rice samples was established as 25% to 27% (i.e., 0.25-0.27 g water / 1 g silica gel). A desired final MC (12.5%) was achieved for silica-gel-dried rice samples within four to five days, and the milling quality of samples dried to 12.5% MC, expressed as head rice yield, was not significantly different from that of control-dried samples.

Physicochemical Properties of Rice Dried in a Single Pass Using High Temperatures

ABSTRACT This study evaluated the physicochemical properties of high-temperature, single-pass dried rough rice. Pureline cultivars Wells (long grain) and Jupiter (medium grain) and hybrid cultivar CL XL729 (long grain), at initial moisture contents of 17.9–18.1% were dried in a single pass to approximately 12.5% moisture content with drying air temperatures of 60, 70, and 80°C and relative humidities of 13–83%. Immediately after drying, the samples were tempered for 1 h at the drying air temperatures in sealed plastic bags. Color, degree of milling, pasting viscosity, and thermal properties of the milled rice were evaluated. Results showed that color, degree of milling, and thermal properties were not affected by drying treatments. However, peak and final viscosities increased with increasing drying air temperatures in all three cultivars.

Predicting farinograph parameters by rapid visco analyser pasting profile using partial least square regression

Farinograph parameters are widely used to predict flour and dough functionality. Accurate prediction of farinograph parameters using other instruments would provide key information in determining cereal products quality and functional properties. This study was undertaken to provide calibration models using rapid visco analyser (RVA) to predict farinograph flour parameters and dough end-use functionality. A total of 267 samples consisted of wheat flour substituted with various ratios of disrupted chickpea (Cicer arietinum) and lentil (Lens culinaris) flours were used in this study. Samples (n=237) were randomly selected and used to develop calibration models of farinograph parameters using RVA profile. Another sample set consisting of 30 flour samples were used to validate the developed models. The partial least squares regression method using the RVA profile was used to develop prediction models for farinograph parameters treatments. Farinograph parameters (water absorption, peak time, mixing tolerance i...

Sequential Acid, Alkaline, and Enzymatic Modifications of Chickpea and Lentil Flours Impacted Batter Physical Properties

The effect of sequential acid, alkaline, and enzymatic treatment of chickpea and lentil flours on batter rheological properties was investigated. Substitution of wheat with disrupted chickpea and lentil flours significantly (P < 0.05) increased water-holding capacity from 66.8% in wheat flour to more than 70.0% based on the disruption treatment, indicating an improved adhesion of coated batter. Flow behavior index of batter treatments of partially replaced wheat flour with various ratios of disrupted chickpea and lentil flours ranged from 0.88 to 1.36 and was significantly (P < 0.05) lower than the flour (i.e., 2.15) and nondisrupted control (i.e., 1.28–1.38 for chickpea and 1.22–1.28 for lentil) flours. Consistency coefficients of disrupted chickpea and lentil flours were significantly (P < 0.05) greater when replacing wheat control, indicating a best fit for the shear-thickening model. Flour disruption decreased the treatment’s pasting properties, except the setback, providing support for the significan...