An investigation of zinc concentrations in brewhouse worts.
Three series of brews were carried out using a similar brewing process with three different grists: 1. malt A, 2. malt B and 3. a mixture of 78% malt A and 22% malt B. The contents of zinc in the mashes and worts were measured by atomic absorption spectroscopy. After mashing in malt A gave a zinc content of 1.20 ppm which fell to 0.42 at the end of mashing and to 0.37 at mashing off, continued to fall during lautering and was 0.07 ppm in the unhopped wort. After wort boiling the content of zinc in the hopped wort was 0.04 ppm. With malt B the zinc content fell from 1.48 ppm at mashing in to 0.10 in the hopped wort. This trend of zinc concentration was typical for mashes including that of malt C which gave a zinc content in its hopped wort of less than 0.1 ppm. Addition of 0.02 ppm zinc to the sparging liquor did not greatly alter the level in the wort. Addition of zinc as sulphate to the boiling wort at a level of 0.52 ppm revealed that 60% of the added zinc remained in the wort and was available for uptake by yeast. High concentrations of zinc were found in the floc after wort boiling and in the trub.
Keywords : fermentation mashing metal wort yeast zinc