Yeast flocculation effect of external factors and control measures
1. Flocculation of yeast on Beer Production and quality
Yeast flocculation on the beer Wine Production and quality are manifold, including yeast recycling; beer fermentation rate and fermentation degree; beer clarifying and filtration; beer flavor, etc..
2. Affect yeast flocculation of external factors
2.1 malt Recent study showed that malt contains a premature flocculation (PYF) factors, on the flocculation of yeast have a major impact factor value is too low PYF malt easily lead to yeast flocculation. PYF value by barley varieties and quality of malting process and microbial contamination and other factors, because these conditions affect the finished malt quality, thereby affecting wort component, and by extension to the impact on the yeast. Dissolved malt poor amino acid content and composition of poor and low-malt quality indicators saccharification defects cause saccharification of wort composition is not conducive to the growth and reproduction of yeast and fermentation, thus will cause premature yeast flocculation or sedimentation.
2.2 of sugar composition and concentration
Wort is the material basis of yeast fermentation, wort lack of nutrients or nutrient limited conditions, to enhance the surface hydrophobicity of yeast cells, induced yeast flocculation. However, the higher the concentration of wort, the concentration of yeast cells more difficult, especially with the high volume of high concentration of glucose wort yeast cohesion on the more difficult. Because the fermentation of sugar molecules in the free yeast flocculation associated with a specific surface protein binding, inhibition of yeast cells by adjacent mannan-binding, that is, some of wort sugars to inhibit the yeast flocculation, but different glucose Yeast flocculation of inhibition is different. Such as glucose, maltose, sucrose can inhibit the New-FLO yeast flocculation, and the inhibition of various sugars are different. With the continuous fermentation, glucose, maltose and other nutrients will be depleted yeast metabolism of sugar and the CO2 impact of inhibition are weakened, their production late in the primary fermentation in yeast flocculation and sedimentation on the bevel on the end of the fermentation tank, settlement will grow.
2.3 amino acid composition and concentration of wort
Wort amino acids and various enzymes of the yeast flocculation induced very important. Yeast when the wort lack of adequate reproductive assimilable nitrogen so that the yeast propagation slower, less new cells, affecting the flocculation of yeast. At present, many domestic beer enterprises to constantly raise Rice The proportion of auxiliary materials such as, making the level of amino nitrogen decreased, there has been varying degrees of difficulty in the yeast flocculation phenomenon, seeking to resolve the high amount of nitrogen is beer yeast flocculation auxiliary one of the key difficulties.
2.4 volume of wort oxygenation
The right amount of oxygenated help to improve the flocculation of yeast. Oxygenation excessive fermentation increased, short period, after fermentation is still a lot of beer yeast suspended in the tender, is difficult to settlement, resulting in significantly reduced yeast flocculation. However, lack of wort oxygenation, will affect the vitality of yeast cells to multiply and eventually cause premature flocculation, leading to sluggish fermentation, fermentation degrees below standard, slightly sweet tasting broth. Some studies show that the wort can lead to poor ventilation, but not entirely premature yeast flocculation, and normal ventilation in order to achieve oxygen saturation would be delayed and beneficial yeast flocculation.
2.5 wort solids content and turbidity
Wort high turbidity, suspended coagulum more significant effect on yeast activity and cohesion. Separation of these particles, if bad, easily adsorbed on the yeast surface, affecting the permeability of cell membrane, hinders yeast material exchange with the outside world and breathing, resulting in autolysis of the yeast early settlement and even death.
2.6 metal ions
First of all, calcium is the most effective yeast flocculation is also essential to promoting factor, calcium ion concentration effect on yeast flocculation. Calcium not only involved in yeast cell wall, the composition, but also the role of cell surface carboxyl groups form a "bridge effect of calcium" to promote flocculation and aggregation of cells, the role of the other alkaline earth metals ions can not be replaced. However, other components of the wort in the synergistic effect of calcium ions such as strontium ion, barium ion has a strong deterrent flocculation, but competitive inhibition of calcium ion.
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