| Premature yeast flocculation (PYF) is a sporadic phenomenon, which can have serious economic and production implications for both the brewer and maltster. PYF is characterized by the occurrence of poor or incomplete attenuation, early or premature flocculation and results in poor flavour development and aberrant fermentation profiles. Malt constituents are believed to cause PYF. Fermentations of wort, from control & PYF malts, were fermented and analyzed for wort constituents, yeast growth, attenuation and cell surface physical properties (hydrophobicity, zeta potential, Helm's flocculation, orthokinetic capture coefficient, zymolectin and mannose receptor densities). Differences were found in carbohydrate and FAN composition of the worts produced from both classes of malted barley. The PYF wort exhibited aberrant fermentation profiles after 60 h when modeled by a logistic equation.; Yeast was inoculated into two fermentations, prepared from two grades of malted barley, a high quality and a poor quality, suggested to induce the premature flocculation phenomenon. Wort composition was determined utilizing FPLC, GC and HPLC. Fermentations were examined to determine the effect of malt quality on cell surface physical properties, yeast growth, and attenuation during fermentation progression.; Differences in peptide and carbohydrate composition of worts produced from both classes of malted barley are discussed. In addition, the occurrence of premature yeast flocculation is characterized in terms of effect on fermentation progression and cell surface physical properties. Results suggest that while PYF malt impaired the metabolic activity of the yeast cells and there was little effect on cell surface physical properties. |
