New techniques for control of fermentation in breweries

Moll, M. and others

Abstract
Monitoring systems to permit better control of fermentation are presented. Controls before fermentation are suggested for (a) dissolved O2; (b) wort carbohydrates; (c) yeast performance; and (d) quantity of pitching yeast. For (a), a de-bubbling device, located in a by-pass wort pipe, has been developed to permit continuous measurement. By high pressure liquid chromatography, wort carbohydrate profiles are measurable in 10 min. Yeast performance can be measured by estimating glucose assimilated and ethanol formed by the yeast during the first hours of fermentation. In (d), difficulties of homogenizing the large amounts of yeast required to pitch large fermentations were overcome by a system of preparing a yeast cream, using a low rate of agitation for 5-10 min (French Patent 76.30999). For control during fermentation in vessles of 10,000 barrels capacity, a system of sequential sampling at 3 levels was adopted (French Patent 77.04025). The system gives foam-free, representative beer samples fed to sensors for measurements of pH, dissolved O2, cell counts, temperature and conductivity and for gas chromatographic analyses. Changes of extract during fermentation may be made by such methods as refractometry, differential pressure and density. The latter may be continuously determined by an apparatus applying the principle of resonance, or indirectly by determining the CO₂produced and relating it to loss of extract. A measuring device for CO₂in a 10 barrel fermenter is illustrated. To measure continuously the number of yeast cells in suspension, an automatic system of supply, linked to the Coulter Counter, was developed.
Keywords: air brewing control cylindroconical tank equipment pitching sampling