Effect of Drying Conditions on the Texture and Taste Characteristics of Rough Rice

Abstract

The effects of drying conditions, viz. drying temperature, surface velocity, and initial moisture content, on the quality characteristics of cooked rice, including both texture and taste attributes, were investigated. A response surface methodology was employed to analyze the effects of drying conditions on the cooked rice quality and to optimize the drying parameters. The results show that moisture content is the most important positive factor, followed by drying temperature with a negative effect, and surface velocity is the least important, with a negative effect on taste. The drying conditions exert the significant effects on the texture and taste attributes of cooked rice. Drying temperature has a positive effect on the cohesiveness value of cooked rice and negative effects on the partial quality attributes, including hardness, gumminess, chewiness, stickiness, color, and flavor. The increase of surface velocity may cause an increase in cohesiveness and color and a decline in hardness, gumminess, smell, palatability, and flavor. Higher moisture content of rough rice contributes to improved color and palatability attributes and reduce the hardness and gumminess indexes. The overall taste value of cooked rice for the dried rough rice has a positive correlation with the hardness, gumminess, and stickiness (p < 0.05). Results suggested that the highest taste value for the rough rice was obtained under optimal conditions of drying temperature of 35.13°C and surface velocity of 0.41 m/s for rough rice with an initial moisture content of 19.69%. The result was verified by validation experiments.

Keywords:

• Heated air drying
• Response surface methodology
• Rough rice
• Taste
• Texture

ACKNOWLEDGMENTS

The authors of this article acknowledge financial support from the Doctorate Unit Foundation of the Ministry of Education of China (No. 20070224003) and overseas researcher project of Heilongjiang Province Education Agency, China (No. 1151hz013).

Notes

Notes: A, drying temperature (T); B, surface velocity (V); C, initial moisture content (IMC); Sum of squares, the sum of the squared deviations; df, degrees of freedom; MS, mean square; F-value, ratio of variance estimate; p-value, probability of obtaining a test statistic at least as extreme as the one; R ², defined as the ratio of the explained variation to the total variation; CV, ratio of the standard deviation to the mean value; Adeq Precision, measurement of the signal-to-noise ratio.

Notes: ns, not significant; A, drying temperature; B, surface velocity; C, initial moisture content; F-value, ratio of variance estimate; p-value, probability of obtaining a test statistic at least as extreme as the one; R ², amount of variation in new data explained by the model.

Note: *Significant at p < 0.05, **extremely significant at p < 0.01.