Article reviews by David Sohigian
from BrewingTechniques' May/June 1998 issue.
|A collection of abstracts from leading brewing
journals selected for their relevance to the brewing processes and business
of craft brewing.
Determining Yeast Viability
||Dr. Erin O'Connor-Cox, "Improving Yeast Handling in the Brewery, Part 1:
Yeast Cropping," Brewers' Guardian, pp. 26-34 (December 1997).
Written from the viewpoint of a major brewery (located in South Africa),
this well-composed article manages to convey key points of interest to all
brewers. Part one of three parts discusses various methods of measuring
yeast viability, noting the weaknesses of methylene blue staining, and
proposes measuring yeast slurry pH to help determine yeast viability. If
the pH of the yeast slurry is >0.5 pH units higher than that of the beer,
the yeast has probably undergone considerable autolysis and is of poor
viability. Dealing with non- flocculent yeast is also discussed, but most
of the options for cropping (for example, centrifugation) are well outside
small brewers' budgets. The article also mentions the importance of
measuring the quantity of the crop when harvesting; crop size provides an
indication of the fermentation performance (poor yeast growth can indicate
problems with yeast health).
Yeast Storage Tips
||Dr. Erin O'Connor-Cox, "Improving Yeast Handling in the Brewery, Part 2:
Yeast Collection," Brewers Guardian, pp. 22-34 (February 1998).
The second article
in this three-part series has some extremely practical tips for yeast
storage, although much of it will be of use only to larger micros
and regional breweries. Using case studies drawn from her own brewery,
Dr. O'Connor-Cox demonstrates that the key to avoiding yeast degeneration
is to keep the slurry cool and oxygen-free during both harvesting
and storage. She also proposes that CO2 is detrimental to yeast not
only during the growth phase (as is commonly accepted) but also during
the stationary phase. She supports this theory by showing that yeast
exposed to CO2 in nongrowth conditions show an increased level of
trehalose, which indicates that the yeast is stressed.
Methods of deaerating
the yeast slurry are included, along with the acid wash method of
decontamination. O'Connor-Cox also points out that a much milder form
of acid washing, called acid conditioning, is used at her brewery
to deflocculate the yeast before pitching to shorten the lag phase.
She also makes the somewhat controversial point that yeast should
not be aerated before pitching, arguing that it will result in yeast
degradation (she suggests aerating the wort instead, a practice that
many small-scale brewers use by necessity). The many other insights
contained in this article make it a valuable resource for any brewery
storing their yeast outside of the cone of the fermentor.
Optimizing Yeast Pitching
||Dr. Erin O'Connor-Cox, "Improving Yeast Handling in the Brewery, Part 3:
Yeast Pitching and Measurement of Yeast Quality," Brewers Guardian, pp.
20-26 (March 1998).
In the final installment on yeast handling, Dr. O'Connor-Cox covers the
optimum conditions for pitching yeast and summarizes the various methods of
analyzing yeast quality. O'Connor-Cox stresses the importance of a
consistent pitch rate for good cell health and refers often to how the
advent of high-gravity brewing led to poor yeast performance before
corrections were made to the pitching rate.
This material applies well to small-scale brewers, because much of our
brewing would be considered "high gravity." The author notes that adjusting
the pitching rate too high can have negative results because the poor yeast
growth will lead to older and older cell populations in subsequent
fermentations. She also mentions that cone-to-cone pitching can be an
advantageous procedure as long as the yeast is not left under the beer for
The Effect of Water Quality on Cleaning Chemicals
||A. Ahrens and G. Schumann, "Water Treatment, Cleaning and Disinfection
Specifications," Brauwelt International 15 (4/97), pp. 408-412 (November
The quality of the water used to dilute chemicals for cleaning and
disinfecting will affect the efficiency and usage rate of those chemicals.
This article examines the types of water suitable for use with many of the
chemicals used inU.S. microbreweries. In general, drinking water quality is
required (particularly for disinfectants), and soft water is preferred for
many cleaning agents. Iron seems to have a particularly negative effect on
many disinfecting agents (including chlorine dioxide, chlorine, and
peracetic acid). One of the most interesting conclusions of the article is
that brewers should use soft water for the initial dilution of quaternary
ammoniums and hard water for more efficient rinsing.
Efficient Brewhouse Configuration
John Mallet, "Brewery Configuration for Craft Brewing Optimization," MBAA
Technical Quarterly 34 (4), pp. 252-256 (1997).
This article takes a practical look at designing and improving microbrewery
operations. Mallet focuses on brewhouse capacity and efficiency and looks
at alternative configurations to increase brewhouse throughput. He
discusses hot-side aeration, and although the effects of hot-side aeration
are a matter of opinion Mallet offers some inexpensive and effective
methods for controlling oxidation that are certainly worth considering (for
example, Mallet recommends eliminating an open grant and replacing it with
a variable speed pump and check valve for lauter run-off). Wort cooling and
liquor requirements are well addressed and the article concludes with some
valuable safety tips centered on brewpub operations.
R.V. Leather, "From Field to Firkin: An Integrated Approach to Beer
Clarification and Quality," Journal of the Institute of Brewing 104 (1),
pp. 9-18 (January/February 1998).
This excellent article covers all the factors in brewing destined to
affect beer clarification, with a focus on isinglass finings. It discusses
the role of kettle finings, auxiliary finings, and process variables in
isinglass fining performance. The strength of the article is that it
discusses the relationship between initial raw materials and processing
before fining and their final effect on the fining's performance. It also
discusses contaminant levels in fining agents (they are found to be
significantly lower than the levels found in beer) and the relative effect
finings have on filtration performance and foam stability (many beers fined
with isinglass demonstrate improved foam stability). If you are currently
using isinglass or copper finings in your brewery, or plan to in the
future, this article is an excellent reference that covers most of what you
need to know.