The walls of two strains of Saccharomyces uvarum (flocculent and non-flocculent) were isolated from exponential and stationary phase cells after growth in media of different Ca2+ and K+ composition. Flocculation of the walls was identical to that of intact cells. The transition from the non-flocculent to the flocculent state involved alterations of the polysaccharide, protein and mineral (Ca2+ and K+) composition of the walls. The walls of flocculent cells had a higher mannose/glucose molar ratio, a lower percentage of protein, a lower percentage of Ca2+ and a higher percentage of K+.

The use of the enzyme alpha-acetolactate decarboxylase allows the acceleration of beer fermentation/maturation because it shunts diacetyl formation, whose elimination is the rate-limiting step of the process. To obtain a cost reduction by using this exogenous enzyme, we propose a new process involving recoverable encapsulated alpha-acetolactate decarboxylase. The performance of traditional and new processes was investigated by a modeling approach. A simple model, focused on alpha-acetolactate and diacetyl profiles during beer fermentation, was set up. The simulated profiles are consistent with literature data. This study shows also that encapsulated alpha-acetolactate decarboxylase allows the acceleration of beer fermentation as efficiently as free alpha-acetolactate decarboxylase. The advantage of immobilized alpha-acetolactate decarboxylase versus free enzyme is that it is recoverable and reusable, which means a process cost reduction.

Kinetics of malt starch hydrolysis by endogeneous alpha- and beta-amylases has been experimentally investigated in laboratory-, pilot- and industrial-scale reactors. The production rates of glucose, maltose, maltotriose and total extract, and the separate alpha- and beta-amylases deactivation rates are measured at varying mashing temperature and different initial starch concentrations and qualities. Based on the experimental results, a model is proposed that takes into account the initial carbohydrates and enzymes dissolution, the starch gelatinization, the separate hydrolytic action of alpha-and beta-amylases on insoluble and soluble starch and dextrins, and the influence of temperature both on enzyme activities and thermal denaturation rate. The model can predict, at the three scales, the final sugars concentrations in the wort for given initial malt concentrations and enzymatic contents, and for a fixed temperature profile during the mashing process.

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Methods of assessing the brewing qualities of new varieties are reviewed. A new method for making this assessment is proposed. This is ideally a three-step process but it would be possible to eliminate the third, costly, step without severe loss of effectiveness. The use of the new method is illustrated by reference to trials using 251 samples from recent trials in France.

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