The role of nitrogenous components in malt and wort during the production of beer has long been recognized. The concentration and range of wort amino acids impact on ethanolic fermentation by yeast and on the production of a range of flavour and aroma compounds in the final beer. This review summarizes research on Free Amino Nitrogen (FAN) within brewing, including various methods of analysis.

Progress during the past 25 years regarding our knowledge of brewer's yeast strains is considered. This is not a comprehensive review but rather focuses on some specific areas. These areas include a brief description of genomics, proteomics and metabolomics as applied to brewer's yeast strains. This review subsequently considers differences between ale and lager yeast strains, the uptake and metabolism of wort sugars and amino acids, yeast flocculation, yeast management between fermentations and yeast strain genetic stability. The question of process intensification, with particular attention to high-gravity brewing, is also addressed. Fermentation systems and processes are considered with an emphasis on novel procedures for stirred fermentations. Copyright © 2013 The Institute of Brewing & Distilling

The Free Amino Nitrogen (FAN) content of wort prescribes efficient yeast cell growth and fermentation performance. FAN consists of the individual amino acids, small peptides and ammonia ions formed during malting, the relative amounts of which vary. In this paper, the individual constituents of FAN were dissected and their effect on both ale and lager fermentations determined. The patterns of amino acid and small peptide uptake and the changes in extracellular protease activity revealed the dynamic environment that develops during fermentation. Lysine and methionine, previously identified as key amino acids in wort fermentation, were investigated further.

The utilisation of small peptides by brewing yeast is poorly understood despite a wealth of information on peptide transport by other microorganisms. A novel method for detection, isolation and measurement of small peptides during brewery wort fermentations was used to monitor utilisation by ale and lager yeast strains. Oligopeptide levels in wort were found to fluctuate throughout the fermentations. Measurement of extracellular protease activity provided evidence that yeast are able to continually regulate protease production in order to break down wort polypeptides into utilisable nitrogeneous materials.

Whisk(e)y is a major global distilled spirit beverage. Whiskies are produced from cereal starches that are saccharified, fermented and distilled prior to spirit maturation. The strain of Saccharomyces cerevisiae employed in whisky fermentations is crucially important not only in terms of ethanol yields, but also for production of minor yeast metabolites which collectively contribute to development of spirit flavour and aroma characteristics. Distillers must therefore pay very careful attention to the strain of yeast exploited to ensure consistency of fermentation performance and spirit congener profiles. In the Scotch whisky industry, initiatives to address sustainability issues facing the industry (for example, reduced energy and water usage) have resulted in a growing awareness regarding criteria for selecting new distilling yeasts with improved efficiency. For example, there is now a desire for Scotch whisky distilling yeasts to perform under more challenging conditions such as high gravity wort fermentations. This article highlights the important roles of S. cerevisiae strains in whisky production (with particular emphasis on Scotch) and describes key fermentation performance attributes sought in distiller’s yeast, such as high alcohol yields, stress tolerance and desirable congener profiles. We hope that the information herein will be useful for whisky producers and yeast suppliers in selecting new distilling strains of S. cerevisiae, and for the scientific community to stimulate further research in this area.

Wort FAN (free amino nitrogen) is the sum of the individual amino acids and small peptides (mainly di-, tripeptides). A further source of assimilable nitrogen is ammonium ions. This study has substantiated previous reports that both lager and ale yeast strains can simultaneously use wort amino acids and small peptides followed by ammonium ions. It is confirmed that amino acids are taken up in a distinct order. However, it is proposed that methionine, isoleucine and leucine be reclassified from group B to group A. Further studies are necessary to confirm that wort with enhanced L-methionine levels reduced fermentation rate and extent and lower beer VDK levels. Also the reason why fermenting wort containing supplemented lysine levels produced elevated VDK concentrations is unclear, but it is probably due to the enhanced biomass formation compared to the unsupplimented wort. Proteolytic enzymes secreted/excreted by viable yeast cells during fermentation are responsible for degrading larger wort peptides into smaller molecules and provides the yeast with an additional source of assimilable nitrogen and this hydrolysis has a negative effect on beer foam stability.