Mathematical Modelling and Optimisation of Low-Temperature Drying on Quality Aspects of Rough Rice

Abstract

Rice when harvested normally has a high moisture content of 20–25% which requires immediate drying, reducing its mass loss and preventing it to spoil. This situation is more crucial with the areas under humid tropical conditions, where moisture and temperature mainly play an important role in deteriorating the quality of rough rice. Keeping the importance of quality attributes of rough rice, the study was carried out to assess the effects of low-temperature drying and suggest an optimum condition. Response surface methodology (RSM) with a central composite design was employed to study the effects of variables, i.e., temperature (X1), time (X2), and air velocity (X3) on responses, i.e., head rice yield (HRY), hardness, lightness, and cooking time. The experimental data were fitted to the quadratic model, studying the relationship between independent and dependent variables. The results revealed that the HRY, hardness, lightness, and cooking time increased with increasing variables, whereas for HRY, it particularly increased and then decreased. It was observed that temperature had more influence on the quality of rough rice followed by time and velocity. Results for analysis of variance revealed that the quality aspects of rough rice were significantly (p<0.05) affected by temperature and time, whereas for velocity, it only significantly affected hardness. The optimal drying conditions predicted by RSM for variables were 25°C, 600 min, and 1 m·s−1, and the optimal predicted HRY, hardness, lightness, and cooking time were 73.93%, 38.28 N, 71.40, and 27.58 min respectively. Acceptable values of R2, Adj R2, and nonsignificance of lack of fit demonstrated that the model applied was adequate and can be used for optimization. The study concluded that the RSM with a central composite design was successfully used to study the dependence of quality aspects of rough rice at low temperature and can be utilized by the rice processing industries.

Influences of moisture content and compressive loading speed on the mechanical properties of maize grain orientations

“…Further results revealed that the highest vertical hardness was obtained for 17.5%. The results are in agreement with those reported by Soomro et al [40] for rough rice.…”

Optimisation of oven-drying of baobab leaves using a central composite design

“…The dry leaf powder was duller (Minolta, 2003) than the fresh baobab leaves, based on the chroma values; and their hue values and lightness ranged from yellow to green colour, and in greyish zone, respectively ( Table 2). The lower the dry matter of the analysed baobab leaf, the lower is the associated lightness.This observed variation of the lightness (Table 2) was consistent with the findings of Soomro et al (2020), who reported that the lightness of paddy was low at low dry matter. Moreover, the correlation coefficient between dry matter and the lightness was 0.614, indicating that dry matter could be used as a proxy for the variability of the lightness.…”

Performance and Prospects of Mobile Rice Mill Unit

“…An undesirable relationship between milled rice yields and broken grains is reported as 18-20% moisture content during harvest time [44]. Therefore, after harvesting, rice grains have to be dried to a certain level of water content before milling into consumable white rice [41], especially in humid tropical conditions like Indonesia, where humidity and temperature rapidly deteriorate the quality of grains [45]. Our observation showed that water content variation was quite evenly distributed in the three sub-districts, with the lowest value of 10.16% and the highest of 16.54% wet basis (wb).…”