Effects of storage period on physicochemical properties of selected improved and traditional rice (Oryza sativa L.) varieties in Sri Lanka

Abstract

Rice (Oryza sativa L.) is the dietary staple food in Sri Lanka and the major livelihood of farmers since ancient times. After harvesting rice, storage is done as a postharvest operation to prolong the shelf life and commercial value. Gelatinization temperature and amylose content are the most important physicochemical properties that influence the cooking and eating characteristics of rice. Knowing those properties is important in the processing, handling, and storage of rice. This study was carried out to evaluate the several physicochemical properties of rice grains of selected improved and traditional rice varieties harvested in three seasons (2021 Yala, 2021/22 Maha, and 2022 Yala). Twelve rice varieties, including traditional (Pachchaperumal, Herathbanda, Madathawalu, Suduheenati) and improved (Bg 352, Bg 360, Bg 366, Bg 374, Bg 450, At 362, At 311, Ld 253) were cultivated and harvested at the Rice Research and Development Institute, Bathalagoda, Sri Lanka. The gelatinization temperature was determined based on the alkali spreading score, and the amylose content was determined according to the iodine binding procedure. All the tested parameters had significant (p<0.05) variations among rice varieties within and among seasons. The most rice varieties harvested in all three seasons, except for suduheenati in 2021 Yala and 2021/22 Maha showed an intermediate gelatinization temperature (70–74 ℃). At 362, rice variety in all three seasons showed low gelatinization temperature of 55-69 ℃. No variety was found with a high gelatinization temperature (>74 ℃). High amylose content was observed in most varieties except for At 311 in the 2021/22 Maha and 2022 Yala seasons. The traditional rice variety Herathbanda showed high amylose content within the 31-35% range for three seasons. Grain elongation varied significantly (p<0.05) in the 2021/22 Maha season, and there was no significant (p>0.05) difference between the 2021 and 2022 Yala seasons. Bg 450 rice variety showed a higher grain elongation ratio (71.25%) in the 2021/22 Maha season compared to the 2021 Yala and 2022 Yala seasons. The lowest grain elongation ratio was observed in Bg 374 in 2021 Yala and 2021/22 Maha (31.27% and 30.54% respectively). Herathbanda showed a lower grain elongation ratio (21.79%) in 2022 Yala. The resulting information can be utilized in planning postharvest practices and selecting suitable rice varieties for commercial cultivation in Sri Lanka