Correct Method To Measure Premature Yeast Flocculation Activity In Malt And Its Mechanism Research

Premature yeast flocculation （PYF） is qualitatively described as the early flocculation ofyeast during fermentation. The effect of PYF can be devastating to brewers. Moreover, thefrequency of PYF occurrence is unknown but has been suggested that traditionally believed.Since the1950s it has been suggested that certain compounds found in wort induce earlyflocculation in yeast. However, there is still much debate as to the nature and mechanisms ofPYF-inducing factors found in wort, mat, and barley.The ability of PYF factors which contained in malt induced early flocculation of yeastduring fermentation should be described correctly. In this paper, small-scale fermentationtested the PYF ability of different malt and discussed the new test-method. LC analysisshowed that there is a small amount of glucose and maltose if only purify the malt by ethanol.CRB2yeasts are NewFlo1and the flocculation was inhibited by glucose and maltose.With10000Da MWCO hollow fiber ultrafiltration membranes to remove small molecules ofsugar on the impact of test result.After optimization, we chose112hours cultured yeast as the test yeast, pH4.5, and crudeextract need purification, with this we can successfully find the PYF malt, but the result wasnot very accurate if the PYF factor lost part of activity. This article tried a new method to testthe PYF malt, and the result is accurate.Five different kinds of yeast was chose to test their ability of anti-ahead premature yeastflocculation, and the result showed that different yeasts may get different anti-aheadpremature yeast flocculation. CRB-R1Y07yeast show it has perfect ability of anti-ahead PYF,but CRB-P05is very sensitive to PYF factor. So for the beer fermentation we should choseyeast like CRB-R1Y01, if we want to find PYF malt we can chose yeast like CRB-P05as thetest yeast.1mol/L H₂SO₄can make PYF factor lost it activity, the factors could be gotten bywashing concentrating and purifying the water which washed the brewing yeast. And theresults showed that it has the similar character with the malt factors. Also, this article discussed whether or not it has some relations between PYF factors yeast and Ca²⁺. But theresult showed they have no direct connection.PYF malt fermentation could lead to high levels of diacetyl and acetaldehyde, low levelsof higher alcohols and esters.