The Horace Brown Medal Lecture: Forty Years of Brewing Research

Abstract

Horace Brown spent fifty years conducting brewing research in Burton-on-Trent, Dublin and London. His contributions were remarkable and his focus was to solve practical brewing problems by employing and developing fundamental scientific principles. He studied all aspects of the brewing process including raw materials, wort preparation, fermentation, yeast and beer stability. As a number of previous presenters of the Horace Brown Lecture have discussed Brown's achievements in detail, the focus of this paper is a review of the brewing research that has been conducted by the author and his colleagues during the past forty years. Similar to Horace Brown, fundamental research has been employed to solve brewing problems. Research studies that are discussed in this review paper include reasons for premature flocculation of ale strains resulting in wort underattenuation including mechanisms of co-flocculation and pure strain flocculation, storage procedures for yeast cultures prior to propagation, studies on the genetic manipulation of brewer's yeast strains with an emphasis on the FLO1 gene, spheroplast fusion and the respiratory deficient (petite) mutation, the uptake and metabolism of wort sugars and amino acids, the influence of wort density on fermentation characteristics and beer flavour and stability, and finally, the contribution that high gravity brewing has on brewing capacity, fermentation efficiency and beer quality and stability.

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

“…However, co-flocculation of S. pombe and S. cerevisiae strains has been reported and attributed to the presence of 3-OH oxylipins on the cell surfaces of both yeasts 89 . Conceivably, 3-OH oxylipins might be involved in the co-flocculation of non-flocculent ale strains described by Stewart 79 , but we know of no relevant experimental evidence.…”

Flocculation in ale brewing strains of Saccharomyces cerevisiae: re-evaluation of the role of cell surface charge and hydrophobicity

“…Flocculation can be defined as a nonsexual, reversible and multivalent process of aggregation of yeast cells into multicellular masses, called flocs, with the subsequent rapid sedimentation from the medium in which they are suspended (Stewart 2009). At industrial level, the autoaggregation property of flocculent yeasts facilitates enormously the cell separation process.…”

Morphophysiological and molecular characterization of wild yeast isolates from industrial ethanol process

“…This mechanism is activated by cell-surface adhesions; the flocculin (Flo) proteins are activated in response to stressing conditions (El-Kirat-Chatel et al, 2015). This response is mainly regulated by environmental conditions such as changes in pH and ethanol concentration or nitrogen and glucose depletion (Braus et al, 2003;Rossouw et al, 2015;Reis et al, 2016;Stewart, 2009). On the other hand, some S. cerevisiae strains can show sexual aggregation patterns, described as co-flocculation and cell chain formation, derived from the failure of the bud to separate itself from its mother cell, resulting in an aggregation of approximately 30 to 50 cells, unable to regroup after being mechanically dispersed (Soares, 2010).…”