Metabolic products of the microorganisms naturally present on barley before and during the malting process can have significant effects on the quality of the malt and of the wort and beer produced from it. In particular, certain mould fungi produce a compound or compounds responsible for many cases of beer gushing, as well as mycotoxins which can constitute a health hazard. It has already been found that when starter cultures of appropriate beneficial microorganisms are added to malting barley, they can compete with harmful microorganisms and prevent their populations from reaching numbers detrimental to malt quality. Industrial scale trials of such a treatment, using selected strains of Geotrichum candidum (a yeast which in its wild state is often naturally present on barley and has also been cultured for use in certain branches of the food industry, e.g. the manufacture of soft cheeses) already successfully used for this purpose in laboratory and pilot malting trials, are described. The addition of Geotrichum to the first steep completely inhibited contamination by mould fungi of the genus Fusarium throughout the malting process, producing a malt free from Fusarium mycotoxins, whereas control malts showed significant levels of contamination. Treatment with Geotrichum also resulted in a higher and more homogeneous degree of malt modification, with consequent improvements in brewhouse performance. While industrial brewing trials had not yet been completed at the time of writing, beers produced in a 20 hl pilot brewery using treated malts proved to be very similar to control beers and at least equal to them in flavour quality. The treatment is very easy (a starter culture suspension is either sprayed over the barley before steeping or mixed into the water when commencing the first steep) and is expected to be cheap (probably costing less than 1% of the purchase price of the barley to be treated).
Keywords : barley contamination fungi inhibition inoculum malt malting microorganism quality steeping yeast