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Optimizing red sorghum malt quality when Bacillus subtilis is used during steeping to control mould growth
Author(s) -
Tawaba JeanClaude Bwanganga,
Béra François,
Thonart Philippe
Publication year - 2012
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/jib.36
Subject(s) - steeping , bacillus subtilis , brewing , food science , aeration , chemistry , sorghum , fermentation , amylase , agronomy , biology , biochemistry , enzyme , bacteria , organic chemistry , genetics
Previous work has shown that Bacillus subtilis ‐S499‐based biocontrol treatments applied without aeration at the steeping stage of red sorghum malting offer good mould reduction, but yield malts with low levels of key hydrolytic enzymes. Thus we attempted to raise these levels by aerating the steeping liquor, varying the steeping time (from 8 to 40 h) and temperature (from 25 to 35 °C), and combining a biocontrol treatment with prior steeping in 0.2% NaOH. Aeration proved particularly important whenever B . subtilis cells were present in the steep liquor. The optimal temperatures for α ‐ and β ‐amylase were 30 and 25 °C, respectively. By increasing the steeping time, it was possible to improve the α ‐amylase activity, but the β ‐amylase activity peaked sharply between 16 and 20 h, depending on the steeping medium. A good compromise was steeping in a biocontrol medium for 14–16 h at 30 °C. Combination steeping treatments (0.2% NaOH for 8 h followed by biocontrol for 8 h) yielded malts of a quality approaching that afforded by dilute alkaline treatment. Copyright © 2012 The Institute of Brewing & Distilling