Malt and Grains Session
Mekonnen M Gebremariam, Institute of Brewing and Beverage Technology, Center of life and Food Sciences, TUM, Weihenstephan-Freising, Germany
Co-author(s): Martin Zarnkow and Thomas Becker, Institute of Brewing
and Beverage Technology, Center of Life and Food Sciences, TUM,
Weihenstephan-Freising, Germany
ABSTRACT: Variations in cereal, growing region, year of
cultivation, cultivation practices, and malting conditions have
considerable influence on the enzyme activities and DMS level of malt.
This research was aimed at studying the influence of using different
teff (Eragrostis tef) varieties on the DMS content and enzyme
activities of the final malt. Five teff varieties (Kuncho [DZ-Cr-387],
Ivory, Brown, Dessie, and Sirgaynia) obtained from Ethiopia and North
America were investigated as possible raw materials for the production
of gluten free malt. Portions of the samples were used for analysis of
thousand corn weight, gelatinization temperature, and germination
energy. The remaining portions were steeped for 5 hr on the first day
and 4 hr on the second day at 24°C, and germinated for 4 days at 24°C in
a temperature controlled chamber with 95% relative humidity. Kilning
was for 18 hr at 30°C, 1 hr at 60°C followed by 3 hr at 65°C. Thousand
corn weight, germination energy, gelatinization temperature, and malting
losses due to rootlets ranged between 0.27 and 0.28 g, 96 and 100%, 69
and 73°C, and 1.95 and 5.49%, respectively. Teff variety Kuncho had the
highest malting loss (5.49%), while Brown had the lowest (1.95%). There
was a significant increase in amylolytic enzyme activities throughout
the germination process, but some of the amylolytic enzyme activities
decreased during the kilning process. The moisture contents, DMS levels,
and alpha-amylase, beta-amylase, and limit dextrinase activities of the
malts ranged from 3.04 to 3.8%, 2.2 to 4.1 mg/kg, 14 to 68 U/g, 10 to
440 U/g, and 375 to 1,072 U/kg, respectively. The enzyme activities were
markedly (P < 0.05) influenced by the type of teff cultivar.
The alpha-amylase activities of all teff varieties increased in the
first few hours of kilning but started to decrease in the later stages.
However, the limit dextrinase and beta-amylase activities of all samples
decreased throughout the kilning process. At the end of kilning, there
was 7–50% higher alpha-amylase activity in the final malts than in the
green malts, whereas the more temperature sensitive beta-amylase and
limit dextrinase activities were about 8–53% and 5–17%, respectively,
less than in the green malts. The highest increase in alpha-amylase
activity (50%) during the kilning process was recorded for teff variety
Sirgaynia, whereas the lowest increase (7%) was for Ivory. The highest
loss in beta-amylase (53%) and limit dextrinase (17%) activities were
for teff varieties Dessie and Kuncho, respectively, and the lowest were
for Ivory and Brown, respectively. In this study, teff variety Dz-Cr-387
had the highest enzyme activities compared with the other cultivars
studied. This variety had the best malting characteristics and brewing
potential, with alpha-amylase, beta-amylase, and limit dextrinase
activities of 68 U/g, 440 U/g, and 1,072 U/kg, respectively. In general,
it can be concluded that the use of different teff varieties yields
malts with significantly different malt quality attributes.
Mekonnen
Melaku Gebremariam received his B.S. degree in chemistry from Debub
University, Ethiopia. He began employment with the Ethiopian Ministry of
Education in July 2000 as a chemistry teacher in the South Nations and
Nationality People Region. He terminated his contract agreement with the
Ministry of Education after four years. He next was employed as a
chemist in the Federal Micro and Small Enterprises Development
Authority. After 18 months with this company, he terminated the contract
agreement and joined Addis Ababa University for further studies. He
graduated from Addis Ababa University, Ethiopia, in 2007 with an M.S.
degree (with great distinction) in food engineering. Immediately after
graduation he was employed as a lecturer and researcher by Hawassa
University, Ethiopia. After about two-and-a-half years of work at
Hawassa University, he went to Germany for his Ph.D. studies with the
support of his employer, Hawassa University. Currently he is pursuing
his doctoral studies at the Technical University of Munich, Germany.
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