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Caro_98992100_2022.pdf
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- Abstract
- At Hoegaarden, more than half of the yeast pitchings were overpitched and the cropped yeast mortality was too inconsistent and high. Lab experiments have shown higher precision for yeast consistency measurement than yeast cell count measurement. The first part of the study has demonstrated an improvement in the yeast pitching rate precision using the yeast consistency instead of yeast cell count. The second part showed that purge during fermentation improved the quality of the cropped yeast. For this purpose, first, pitching was performed using the yeast mass obtained from the consistency formula and the yeast cell count formula. Pitching rate precision was estimated by cell counting after the pitching. Then, precision between pitching rates using yeast consistency and the yeast cell count were compared. Secondly, ten croppings under different conditions (with or without purge during the fermentation and time of cone cooling activation) were followed by yeast sampling. Yeast cell count, consistency mortality, pH, extract, and ethanol content were checked out to describe the differences in cone heterogeneity between yeast layers with and without a purge. Pitching rates with consistency formula enable to achieve of an average accurate pitching rate of 4,94×106 cells/mL and against 6,14×106 cells/mL with the population formula for a target pitching rate of 5.0×106 cells/mL. Pitching with the consistency formula has improved the pitching rate precision and will reduce the problem of overpitching. Croppings with purge enable to reduce the mortality of the cropped yeast by two: 17,7% without purge and 8,1% with a purge. Nearly all the trub was successfully discarded and so the main part of the dead yeast is removed too. Cone cooling also shows its utility to keep good viability. New cropping practices will include purge and efficient cone cooling.