CHELATORS AND METAL BUFFERING IN FERMENTATION

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Abstract
Trace elements are important components of brewer's wort. The effect of these metals is dependent upon the metal binders, (chelators) present. These chelators are wort components with reactive groups such as carboxyl, sulphydryl, o-diphenol or amine. The properties of different types of complex are briefly reviewed together with the general equations for their stability. The stability of some of the complexes formed in wort is comparable with the stability of EDTA complexes. The distribution of metals can be calculated by means of the equation for complex formation. This is the distribution between free ionized form and chelated forms. The ratio between free and bound forms or between assimilable and not assimilable complexes can be regulated by addition of EDTA. The calculated levels of free metals are compared with the formation of isobutanol in experimental fermentations. The same low free metal levels obtained with EDTA in a synthetic medium may be present in an all malt wort.