Physical and cooking qualities of milled rice parboiled at optimal conditions for three selected Rice varieties in Nigeria
Ogunbiyi MO, Adejumo BA, Gbabo A, Chinma CE
The physical and cooking characteristics of parboiled milled rice of three commonly grown rice varieties in Nigeria (FARO 44, FARO 52 and FARO 60) were investigated in this study. Rough rice samples of the three varieties were parboiled, dried and milled separately in a Central Composite Design (CCD) experiment with three factors at five levels using MINITAB 16 statistical software to provide for the optimisation of the paddy parboiling process. The physical and cooking qualities were thereafter evaluated using standard procedures. Results showed that the optimum Initial soaking temperature (IST), Soaking time (ST) and Final moisture content (FMC) for desirable physical qualities of FARO 44 rice variety are 70.3°C; 10 hours, 24 minutes and 15%. For FARO 52, the optimum values are 67.7°C; 13 hours, 18 minutes and 12.7% while for FARO 60, the optimum conditions are 76°C, 6 hours, 54 minutes and 15.2%. Parboiling at these optimum conditions resulted in high head rice yield in the three varieties with FARO 44 having the highest head rice yield and lowest percentage broken rice. However, FARO 52 has the highest grain hardness value of 74.7N while FARO 60 variety gave the highest lightness value of 27.71. For desirable cooking quality, the optimum IST, ST and FMC are 73.3°C; 16 hours, 18 minutes and 15.7% (wet basis) respectively for FARO 44 rice variety, 63.5°C, 7 hours and 12.9% (wet basis) for FARO 52 and 65.2°C, 13 hours 36 minutes and 11% for FARO 60 rice variety. The minimum cooking time for the three rice varieties is 15 minutes. The cooking time and elongation ratio of the milled rice of the three varieties however showed no significant difference though elongation ratio was lower in FARO 60 rice variety. The water uptake ratio of FARO 60 was 2.45, FARO 52, 2.19 and FARO 44, 1.77. For improved physical and cooking qualities, increased productivity and profitable paddy processing, it is recommended that rice processors should parboil the selected rice varieties at the optimised conditions obtained from this study.