Starch viscosity properties: New criteria for assessment of cooking quality of rice (Oryza sativa L.) cultivars

Development and release of high quality rice cultivars is one of the major objectives in rice breeding programs in Iran. Amylose content (AC), gelatinization temperature (GT) and gel consistency (GC) are very important characteristics determining end-use and cooking quality in rice. However, there are rice cultivars with similar AC, GT and GC, but are different in cooking quality. It seems that starch viscosity properties are also effective in rice cooking quality. Six local rice cultivars including: Hashemi, Binam, Salari, Domsiah, Gharib and Hassansaraei, and six improved cultivars including: Khazar, Sepidroud, Bahar-1 hybrid rice, Dorfak, Saleh and Kadous were considered for study of grain starch viscosity characteristics. All cultivars had similar AC, GT, GC and protein content (PC), but were different in cooking quality. 30 samples were taken from each cultivar and evaluated for viscosity parameters using rapid visco analyzer in completely randomized design with three repetitions. Analysis of variance showed that differences between local and improved cultivars were significant for viscosity characteristics, however, viscosity characteristics were inter-mediate in the local cultivars. 95% confidence intervals for viscosity characteristic of local cultivar including peak viscosity (PV), minimum viscosity (MV), breakdown (BD), final viscosity (FV), setback (SB) and pasting temperature (PT) were 258.07-297.61, 170.72-214.98, 78.06-105.28, 278.15-333.57, 106.20-138.84 and 94.61-99.07, respectively. However, minimum and maximum values of most viscosity characteristics were extended in the improved cultivars as compared to local cultivars. Therefore, starch viscosity characteristics are suggested as efficient criteria for assessment of cooking quality in rice cultivars..