A study of the causes and control of diacetyl in Nile special and club pilsner beer brands

Abstract

This is a final year project report that covers research undertaken on one of the off flavors hindering the quality of beer, specifically Nile Special and Club Pilsner beer brands which hold the flagship of Nile Breweries Limited. The off flavour researched about was diacetyl, its causes, control and minimization during fermentation and maturation of which fermentation is the process by which organic substrates (wort) are converted to products like ethanol (beer) while exploiting action of microorganisms. Presence of diacetyl above the threshold value is considered a defect in the suggested beer brands. The report is therefore titled “A study of the causes and control of diacetyl in Nile Special and Club Pilsner beer brands during fermentation”

The report covers theoretical information and experimental work done while at Nile Breweries Limited (NBL) and contains five chapters arranged in a manner that will give any reader knowledge of the ways diacetyl can be minimized in beer brands expected at any kind Brewery.

The first chapter is the introduction which contains the background, problem statement, general and specific objectives, justification, significance and scope of the study

Chapter two contains the literature review, in which off flavors are described as the result of undesirable flavor active compounds which drive a beer’s taste away from that expected by consumers, many of these compounds being normally present in beer in concentrations below or just above the taste threshold, the point where they can be tasted or smelled by the human tongue or olfactory sense. For this case diacetyl, also known as 2,3-butanedione, organically classified as a vicinal di ketone, VDK, responsible for beer VDK content and happening to be one of the most popular and at the same time controversial flavoring agents, detected by its pronounced buttery or butterscotch taste/tone was studied. The third chapter is the experimental design which shows details of the methods, apparatus and materials adopted while carrying out the research. Documented data for values of diacetyl was used, obtained by carrying out analysis using a gas chromatography machine. These values represented selected Unitanks (UTs) containing the Nile Special and Club Pilsner beer brands under study and from the recorded diacetyl values, UTs were tracked in cellars to see how they were aerated, how yeasts were managed and as well the microbial analysis data from the Microbiology Laboratory. The results were interpreted, discussed followed by recommendations for diacetyl reduction

The fourth chapter contains tables and graphs of the results obtained as well as discussion of the results. Chapter five of this report conclusions and recommendations in line with the results obtained.