Horace Brown Memorial Lecture a Realistic View on the Role of Research in the Brewing Industry Today

Abstract

Present-day economic pressures stimulate technological innovations toward more rapid processing and to minimise both capital and production costs.Fermentation and maturation practices in most production plants are essentially unchanged from the low productivity batch processes. In terms of process economics two alternatives exist-moving to greater volume accelerated-batch processing and applying fully continuous high rate fermentation systems. Central to these issues are the growth controlling aspects of yeast performance in brewery fermentations. The importance of dissolved oxygen on lipid metabolism, yeast growth and beer flavour, the precise role of storage carbohydrates and the critical nature of the glycolytic/ gluconeogenic junction in controlling fermentation performance are reviewed. The objectives of process optimisation are to build up sufficient yeast concentrations to gain optimal rate and extent of attenuation and desired flavour development whilst balancing but not over-expending wort nutrients for growth and maintenance. In this regard great promise may lie with new technologies including yeast oxygenation and immobilised cell systems. Particular emphasis is placed upon the ways in which this may be technically achieved and attention is drawn to the complexity of innovation management.Practical implications of factors benefiting and adversely affecting fermentation efficiency and beer flavour in both traditional and continuous immobilised cell systems are discussed.

Continuous immobilized yeast reactor system for complete beer fermentation using spent grains and corncobs as carrier materials

“…It is known that the excess of aeration inhibits the cytosolic alcohol acetyltransferase, responsible for ester formation in yeast [21]. Consequently, the sudden decrease in ester production (Table 1) and a higher than optimum fusel alcohol to esters (A/E) ratio in continuous beers can be explained by the excess oxygen supply through direct aeration of R1 (Table 1).…”

Continuous Beer Fermentation Using Immobilized Yeast Cell Bioreactor Systems

“…Insufficient aeration leads to decreased yeast viability, low amino acid uptake due to suppressed cell growth, and suboptimal lipid synthesis giving rise to altered membrane composition and thus to fermentation problems and unbalanced flavor profile (72). On the other hand, excess oxygen leads to production of unnecessary yeast biomass, low ester production, but excessive acetaldehyde, diacetyl, and fusel alcohol formation (29,73).…”

A Review of Flavour Formation in Continuous Beer Fermentations*

“…Although ethanol production is an anaerobic process, some oxygen is essential for yeast growth and for unsaturated fatty acid and sterol synthesis 54 . In order to supply optimum oxygen into bioreactors, the knowledge of volumetric oxygen mass transfer coefficients (k L a) under real fermentation conditions is indispensable.…”