Yeast hulls
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Yeast hulls are byproducts of the commercial manufacture of yeast extract. Consisting of cell walls and membranes, hulls are added to enhance fermentation rates and to restart stuck fermentations. Their mode of action has been described as lowering the concentration of inhibitory C8-10 fatty acids. Ingledew (3) reported that yeast hulls stimulate yeast populations by providing a source of C16 and C18 unsaturated fatty acids which act as oxygen substitutes under long-term fermentative conditions. Additionally, hulls may provide a source for some amino acids as well as surface area to facilitate release of potentially inhibitory levels of saturated CO2.[1]
Yeast cell wall material produced as a by-product of yeast extract preparation can be added to fermentations to overcome the phenomenon of stuck and sluggish fermentation. This effect was attributed to the incorporation of longer chain fatty acids into the yeast membranes and a greater degree of unsaturation and consequent increase in ethanol tolerance.[2]
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References[edit]
- ↑ Gump BH, Zoecklein BW, Fugelsang KC. Prediction of prefermentation nutritional status of grape juice: The formol method. Food microbiology protocols. 2001:283-96.
- ↑ Gibson BR. 125th anniversary review: improvement of higher gravity brewery fermentation via wort enrichment and supplementation. J Inst Brew. 2011;117(3):268–284.