Comparative studies of the effect of processing conditions on cooking and sensory properties of selected rice varieties

Cooking and sensory properties of rice varieties are important quality indices that influence market value and consumer acceptability. The objective of this study was to evaluate the effect of processing conditions on cooking and sensory properties of five rice varieties grown in Nigeria. The rice varieties; FARO 44, FARO 52, FARO 60, FARO 61 and NERICA 8, were processed using four processing parameters at varying conditions [soaking temperature (65-75°C), soaking time (10-16 h), steaming time (20 – 30 min) and paddy moisture content (12-16%)] using response surface methodology. The effect of processing conditions on cooking properties (cooking time, water uptake ratio and elongation ratio) was analyzed using standard procedures. Quantitative descriptive analysis and principal component analysis were used to describe eleven sensory characteristics (uniform appearance, black specks, whitish appearance, yellow colour, brown colour, creamy flavour, typical rice odour, sweet taste, sticky texture, grainy texture and hard texture) of the rice varieties. The cooking time, elongation ratio and water uptake ratio ranged from 12.75 to 51.58 min, 0.91 to 1.94 and 2.21 to 4.95, respectively. The cooking properties differed with respect to rice varieties and processing conditions. The shortest cooking time, longest elongation ratio and highest water uptake ratio varied from one variety to another. It was observed that NERICA 8 had the shortest cooking time (12.75 min) at 65ºC soaking temperature, 16 h soaking time, 20 min steaming time and 16% paddy moisture content while FARO 52 had the highest water uptake ratio (4.95) at 65ºC soaking temperature, 16 h soaking time, 20 min steaming time and 16% paddy moisture content. The maximum elongation ratio (1.94) was observed at 65ºC soaking temperature, 16 h soaking time, 30 min steaming time and 12% paddy moisture content in FARO 60. The sensory properties of the rice varieties were generally characterised as having uniform appearance, whitish appearance, sweet taste, creamy flavour and rice odour. The information on the cooking and sensory properties of the rice varieties would assist rice processors and consumers in selecting rice variety of choice. Key words: Cooking properties, Rice varieties, Processing conditions, Sensory properties