Isolation, identification and changes in the composition of lactic acid bacteria during the malting of two different barley cultivars
Malt has a complex microbial population, which changes as the malting process commences. Little is known about the proliferation of lactic acid bacteria (LAB) in each of the malting phases. In this study, we determined the number of LAB present in the different phases of malting with Clipper and Prisma barley cultivars. The strains were identified to species level by using numerical analysis of total soluble cell protein patterns, RAPD-PCR banding patterns and 16S rRNA sequencing. The number of viable LAB in the barley before steep was higher in Prisma than Clipper (7.6×104 and 1.2×103 cfu/g, respectively). Despite this, the number of viable cells recorded in the first steep water was slightly higher for Clipper (9.0×105 cfu/g) than Prisma (5.5×105 cfu/g). More or less, the same cell numbers were recorded for the two barley cultivars after the first and second dry stands. Both cultivars displayed more or less the same cell numbers (3.7×107 for Clipper and 3.2×107 cfu/g for Prisma) after the third day of germination. However, a higher number of LAB were detected in the kilned Prisma malt (6.9×104 cfu/g) than the Clipper malt (1.5×104 cfu/g). Leuconostoc argentinum, Le. lactis and Weissella confusa were the most predominant in both cultivars. A few strains were identified as W. paramesenteroides (four strains), Lactobacillus casei (five strains), Lactococcus lactis (five strains) and Lb. rhamnosus (two strains). Lb. casei and Lb. rhamnosus were not isolated from the Prisma cultivar, while W. paramesenteroides and Lc. lactis were absent in the Clipper cultivar. Kilned malt of the Clipper cultivar contained predominantly Le. argentinum, whereas the Prisma cultivar contained mainly Lc. lactis. To our knowledge, this is the first report of LAB in Clipper and Prisma barley and the various malting phases. The influence of the various groups of lactic acid bacteria on the fermenting ability of brewers' yeast is currently being determined. Copyright © 2002 Elsevier Science B.V.