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

• Published in: Journal of the Institute of Brewing Vol. 117; no. 1; pp. 39 - 46
• Main Authors: Usansa, Ulaiwan, Burberg, Felix, Geiger, Eberhard, Back, Werner, Wanapu, Chokchai, Arendt, Elke K, Kreisz, Stefan, Boonkerd, Nantakorn, Teaumroong, Neung, Zarnkow, Martin
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 2011; Institute of Brewing
• Subjects: alpha-amylase; Beers; beta-amylase; Biological and medical sciences; black rice; Brewing; Enzymes; Fermented food industries; Food industries; Fundamental and applied biological sciences. Psychology; Germination; glutinous rice; limit dextrinase; Malt; malting; malting barley; Optimization; Oryza sativa; raw materials; response surface methodology; response surface methodology (RSM); Rice; shoots; soaking; Statistical methods; Steeping; temperature; Methodology; Malting; Brewing; Variety; Optimization; black rice; response surface methodology (RSM)
• ISSN: 0046-9750; 2050-0416
• DOI: 10.1002/j.2050-0416.2011.tb00441.x

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 degrees C. At the end of the germination process, all samples were kilned at 50 degrees 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 degrees C and 44% grain moisture. Although the extract yield, and alpha-amylase and beta-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.