Effects of variable steaming on chemical composition, starch characteristics, and glycemic index of basmati (Pusa Basmati 1121) rice

Abstract

AbstractEffects of variable steaming on important quality characteristics of Pusa Basamti 1121 rice were evaluated in the study. Pre‐soaked (at 65°C for 345 min) paddy was steamed at variable steaming consisted of 4 pressure levels (0–1.5 kg/cm2) and 5 steaming times (5–25 min). Steaming affected rice quality characteristics significantly (α = 0.05). It increased head rice yield by 12%. Starch, amylose, Am/Ap ratio, crude protein, crude fats, crude fibers, and ash contents of steamed rice varied from 63.34 to 68.24%, 22.83 to 24.40%, 0.53 to 0.58, 8.11 to 8.39%, 2.47 to 2.58%, 1.59 to 1.63%, and 0.75 to 0.77%, respectively. Peak, final, breakdown, and setback viscosities of raw rice were 1,305, 3,995, −4, and 2,693 cP, respectively; however, their values reduced to 114, 216, −1 and 102 cP, respectively, after steaming. Starch crystallinity of raw rice was 28.49% which reduced to 5.72% after steaming. Scanning electron microscopic images indicated that complete gelatinization of starch was observed after steaming at 1.5 kg/cm2 for ≥10 min. Glycemic index of raw PB1121 rice was 58.41 whereas that of rice steamed at 1.5 kg/cm2 for 20 min was 47.04. Based on results, steaming at 1.5 kg/cm2 for 20 min was found more appropriate to achieve higher HRY (54.16%) and to reduce GI considerably (47).Practical applicationsEffects of variable steaming on chemical composition, starch characteristics and GI of PB1121 rice were evaluated in present study. Study demonstrated that steaming step alone brings considerable alterations in the overall quality of PB1121 rice. In present times, millers and traders strongly look for rice with higher milling yield, lower pasting viscosities (indicator of better cooking quality) and low GI. Therefore, results of present study would be useful to the millers to produce rice with higher HRY, improved cooking quality and lower GI. Severity of steaming parameters (i.e., steaming pressure and steaming time), during parboiling, would be decided if one knows the qualitative changes occurring in the parboiled grains.