Article reviews by David Sohigian
Republished from BrewingTechniques' March/April 1998 issue.

A collection of abstracts from leading brewing journals selected for their relevance to the brewing processes and business of craft brewing.

The Link between Diacetyl and FAN Levels
  T.A. Pugh, J.M. Maureer, and A.T. Pringle, "The Impact of Wort Nitrogen Limitation on Yeast Fermentation Performance and Diacetyl," MBAA Technical Quarterly 34 (3), p. 185 (1997).

Much research has been done on the removal of diacetyl during beer maturation, but this article takes another tack by focusing on factors affecting the actual production of diacetyl during fermentation. The authors link the production of diacetyl to the levels of free amino nitrogen (FAN) in the wort (which in turn is linked to the protein and modification levels in the malt and to the proportion of adjuncts used). One of the more interesting points made in the article is that diacetyl levels can increase in beers made from worts with too high or too low a concentration of FAN. Small-scale brewers should keep in mind that the most effective method of diacetyl control is to remove it during maturation; controlling its formation by monitoring FAN levels is difficult at best.

The Advantages of a Rapid Fermentation
  Gerolf Annemüller and Dr. Hans-Jürgen Manger, "Pitching and Starting Phase in a Cylindroconical Fermenter - the Black Box of the Fermentation and Maturation Process?" Brauwelt International 15 (4/97), pp. 338-341 (October 1997).

This article focuses on large-scale brewery operations; however, much of the information it contains applies to any small-scale brewers using cylindroconical fermentors who are interested in evidence of the economic value of a rapid fermentation. The article discusses strategies for increasing the vigor of the first stage of fermentation to improve beer stability and shorten process times. Particularly valuable is a chart showing how individual fermentation factors such as pitching rate, oxygen dosage, and temperature control affect the yeast's performance. A separate section describes analytical procedures for measuring the initial performance of yeast in a brewery (these are of general interest, though the procedures are likely to be well out of the reach of small-scale brewers).

Summary of Malting Chemistry
  Bruce Sebree, "Biochemistry of Malting," MBAA Technical Quarterly 34 (3), p. 148 (1997).

This brief transcript of a talk given by Dr. Sebree (the time or nature of the talk weren't disclosed in the article) gives a good overview of what occurs in a single kernel during the malting process. Sebree focuses primarily on germination (which is when most of the biochemical changes occur) and avoids many of the complex reactions that occur during kilning. The material is well presented and should serve as a good primer for brewers who want to gain some understanding of what processes their grain undergoes before it arrives at their brewery.

Effect of Wort Gravity and Fermentation Temperatures on Yeast
  S. Takahashi, K. Yoshioka, N. Hashimoto, and Y. Kimura, "Effect of Wort Plato and Fermentation Temperature on Sugar and Nitrogen Compound Uptake and Volatile Compound Formation," MBAA Technical Quarterly 34 (3), p. 156 (1997).

Although the material presented in this paper is very specific to large-scale brewery applications, it brings up points likely to be of interest to small-scale brewers. The conclusion discusses and summarizes the effect of original gravity and fermentation temperature on various volatile compounds (esters and higher alcohols, for instance). Both factors are well within the control of most microbrewers, and understanding their effects on yeast metabolism (and resulting flavor production) is key to producing quality products. Several valuable graphs show how the proportion of esters increases in relation to increased wort Plato, while the proportion of higher alcohols (not to be confused with total esters or total higher alcohols) decreases. The article also does a good job of showing how nitrogen and sugar uptake are linked to the production of these volatile compounds (for example, the uptake of nitrogen compounds seems to be directly proportional to the amount of higher alcohols formed).

Cooling Rates in Jacketed Cylindroconical Tanks
  T. Ishiguro, S. Mizutani, and K. Kuwahara, "Numerical Analysis of Cooling Mechanisms in Cylindroconical Lager Tanks," MBAA Technical Quarterly 34 (3), p. 164 (1997).

The authors used supercomputer modeling to compare the efficacy of various cooling jacket configurations on cylindroconical tanks. The excellent computer-simulated graphics show how stratification affects the overall cooling rate in most cylindroconical fermentors. The authors found that baffles reduced the stratification, but did not affect the overall cooling rate. The greatest effect on cooling rate was obtained by using internal cooling systems positioned at the bottom half of the tank. The authors also printed valuable information on how the density of beer changes as it cools (beer is at its maximum density at 86 °F [30 °C], meaning that its density decreases both above and below this temperature). Small-scale brewers may not change the design of their tanks after reading these results, but they may rethink their willingness to rely on a single temperature probe in their cylindroconical fermentors.

Beer and Health
  Anton Piendl, "Physiological Effects of Alcohol Consumption," Brauwelt International 15 (4/97), pp. 310-319 (October 1997).

Brewers fighting the socially irresponsible image beer has as an intoxicant would do well to take notes from this comprehensive and balanced survey of both the positive and negative health effects of alcohol consumption. Weihenstephan professor Anton Piendl cites multiple studies in current research that conclude that although overindulgence can lead to numerous health problems, moderate consumption of alcohol can have many positive physiological effects. Some of the findings link moderate alcohol intake to a reduced risk of heart disease, cancer, and gastrointestinal inflammations. In addition, many of the studies show a U-shaped relationship between abstention, moderate consumption, and excessive consumption, which indicates that oftentimes drinking moderately (defined differently in different studies) is healthier than abstaining. Beer also has particular health advantages, including a calming effect, diuretic qualities, and appetite enhancement.

How to Contact the Publishers

MBAA Technical Quarterly
Master Brewers Association of the Americas
Wauwatosa, Wisconsin
Tel. 414/774-8558
fax 414/774-8558
e-mail: channer@mbaa.com
URL: www.mbaa.com
(Back issues available on-line)

Brauwelt International
Verlag Hans Carl
Nürnberg, Germany
Tel. (49) 911 / 9 52 85 34
fax (49) 911 / 9 52 85 47
(English edition home page)

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