Wort fermentation

Sroka, P. and Tuszynski, T. (2007). Changes in organic add contents during mead wort fermentation. Food Chem. 104,1250-1257. 

Ratkova J., Smogrovicova D., Domeny Z. and Bafrncova R. Very high gravity wort fermentation by immobilized yeast. Biotechnology letters 22 (14) (2000) 1173-1177. 

The new edition appears as two volumes because a single one would be inconveniently bulky. The first volume outlines the entire process and leads from barley, malting and water to the production of sweet wort. In the second volume there are chapters on hops and hop products, production of hopped wort, fermentation, yeast biology and all aspects of beer qualities and treatment. 

ANAEROBIC CARBOHYDRATE METABOLISM Yeasts growing in media containing high concentrations of fermentable carbohydrate invariably metabolize it fermentatively to produce ethanol and CO2. If air is present, and when the sugar concentration has been lowered, the ethanol is respired using the metabolic routes described above. Under the anaerobic conditions of a brewery fermentation the hexoses derived from wort fermentable carbohydrates are catabolized by the EMP pathway (Fig. 17.2) to pyruvic acid. The pyruvate produced is decarboxylated by the enzyme pyruvate decarboxylase, with the formation of acetaldehyde and CO2. The enzyme requires the cofactor thiamine pyrophosphate (TPP) for activity and the reaction is shown in Fig. 17.10. The acetaldehyde formed acts (in the absence of the respiratory chain) as an electron acceptor and is used to oxidize NADH with the formation of ethanol ... 

High-gravity and very-high-gravity wort fermentation... 

The strategy of wort supplementation with metal ions, lipids and yeast foods , with the aim to improve fermentation performance, is reviewed in detail by Gibson (2011). Among metal ions, zinc and magnesium were identified as elements with a crucial role in wort fermentation, the supplementation of which led to reduced attenuation time (Zn, Mg), increased uptake of trisaccharides (Zn) and increased ethanol production (Zn) and tolerance (Mg). It was also found that zinc has an indirect effect on the synthesis of higher alcohols and esters as well as on foam properties. Calcium supplementation of wort may only be beneficial when Ca concentration is limited in the local water supply (Gibson, 2011). 

Oevelen, D., Spaepen, M., Timmermans, R, VerachterL H. (1977). Microbiological aspects of spontaneous wort fermentation in the production of lambic and gueuze. Journal of the Institute of Brewing, 83(A), 356-360. 

It is important to emphasize that although considerable information is available about brewer s yeast fermentation per se (e.g. Boulton Quain, 2(X)1 Sofie et al., 2010 Stewart Russell, 2009), by comparison, basic detailed information on yeast management processes between wort fermentations has been lacking. Indeed, although the overall fermentation procedures and control have become very sophisticated, yeast management was, until recently, the poor relation of the process. 

The number of times that a yeast crop (generations or cycles) is used for wort fermentations is usually standard practice in a particular brewery. Typically today, a lager yeast culture is currently used 6-10 times before reverting to a fresh culture of the same strain... 

Cooper, D. J., Stewart, G. G., Bryce, J. H. (2(XX)). Yeast proteolytic activity during high and low gravity wort fermentations and its effect on lead retention. Journal of the Institute of Brewing, 106,197-201. 

Five chapters are devoted to brewer s yeast and they consider, in appropriate detail, their taxonomy and related areas such as identification and characterization. Wort fermentation and metabolism are discussed and, in particular, the metabolic engineering of these organisms. The fact that brewer s yeast cultures are normally recycled through a number of wort fermentations is emphasized and details of yeast management between fermentations are discussed. 

Fig. 75.8 Follow-up of the degradation of trani-resveratrol and trani-piceid (a) in an aqueous model medium previously flushed by nitrogen-mimicking wort ebullition (b) through wort fermentation [112, 114]...

Jerkovic V, Nguyen F, Timmermans A, Collin S (2008) Comparison of procedures for resveratrol analysis in beer. Assessment of stilbene stability through wort fermentation and beer aging. J Inst Brew 114 143-149... 

A. Bonastre, R. Ors, M. Peris, Monitoring of a wort fermentation process by means of a distributed expert system, Chemom. Intell. Lab. Syst. 50 (2000) 235—242. 

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