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
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
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
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
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Verlag Hans Carl
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