Optimization of Malting Conditions for Two Black Rice Varieties, Black Non-Waxy Rice and Black Waxy Rice (Oryza sativa L. Indica)

Abstract

Two black rice varieties, "black non-waxy" and "black waxy", were investigated as possible raw materials for the production of malt. The malting conditions were optimised using response surface methodology. The three process parameters were steeping, germination time and temperature. Each parameter was tested at three levels: adjustment degrees of steeping were 38, 41, and 44%, germination times were 6, 7, and 8 days, and the temperatures were 20, 25 and 30°C. At the end of the germination process, all samples were kilned at 50°C for 24 h, and shoot/rootlets were removed before a detailed quality assessment was performed. Data analysis was performed using the Design Expert Statistic Program. The optimal conditions found for both rice varieties were as follows: germination time of 8 days at 30°C and 44% grain moisture. Although the extract yield, and α-amylase and β-amylase activities of both rice malts were lower than barley malt, the higher activity of limit-dextrinase enzyme and apparent attenuation limit (AAL), which was higher than 80%, suggests that rice malt has potential for use in brewing.

Effect of Germination Conditions and Mashing Temperature on the Amylolytic Enzyme Activity and Degree of Starch Saccharification of Brown Rice Cultivars During Syrup Production

“…In general, the long-grain rice displayed greater activities, while the waxy rice exhibited lower activities for all three enzymes. Usansa et al (2011) reported higher α-amylase and β-amylase activities but lower α-glucosidase activity in waxy rice than in long-grain rice when steeped for 5 hr and germinated for 8 days, which could be due to a shorter steeping duration and a longer germination period compared with the present study. The activities of both α-amylase and β-amylase increased up to the third day and then decreased in aerobic condition, but continuously increased in anaerobic condition, presumably because of the insufficient metabolism in the absence of oxygen.…”

Development of Low Phytate Rice by RNAi Mediated Seed-Specific Silencing of Inositol 1,3,4,5,6-Pentakisphosphate 2-Kinase Gene (IPK1)

“…The activity of α-amylase [37], β-amylase [37], [38], and α-glucosidase [39] were analyzed at different time periods after germination in non-transgenic and transgenic seeds.…”

“…The determination of the α-glucosidase activity was performed as per a modified protocol [39], [41]. One gram of finely ground seeds collected at 0, 12, 24, 36, 48, 60, 72, 84, and 96 hours after germination was extracted for crude α-glucosidase by adding 10 mL of 10 mM acetate buffer (pH 5.0, containing 5 mM DTT and 90 mM NaCl).…”

Indian black rice: A brewing raw material with novel functionality

“…For rice, the minimum temperature is 10-12°C, the optimal temperature is 30-37°C and the maximum temperature is 40-42°C (12). Additionally, optimum temperature conditions for malting black rice were reported to be 30°C (13,14) which is close to room temperature in Asian countries. Ceppi and Brenna reported development of a gluten-free beer (3.5-4.5% ABV) using Italian rice variety Loto and a mashing-in liquor-to-grist ratio of 1:3.5 (15).…”