The Effect of Barley Adjuncts on Free Amino Nitrogen Contents in Wort

Abstract

Free amino nitrogen (FAN) and other low-molecular-weight nitrogen compounds (LNC) are highly important as nutrients for yeast. Many different types of low-malt beer exist around the world, some of which are produced with barley as an adjunct. In these cases, inhibitors contained in barley are known to influence the amount of LNC in wort. Accordingly, it is important to investigate which proteinase class is key in producing these compounds. By investigating the relationship between the FAN contained in wort produced from malt and barley (barley adjunct wort) and malt proteinase activity, it was found that cysteine proteinase and 1,10-orthophenanthroline (O-Phen)-inhibitable metallo proteinases had a significant correlation to the barley adjunct wort FAN levels. In addition, the relationship between malting conditions and these proteinase activities was investigated and the conditions defined for maximal production of proteinases as follows: steeping degree, 50%; germination temperature, 12°C; germination days, 6 days; water spray, 3 times and concentration of gibberellic acid, 10 mg/kg (barley).