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“Before taking up your duties in a new microbrewery capable of producing up to 50 hl of cask-conditioned beer per week, you have been asked to organize a small laboratory. Bearing in mind the limited funds available and the simple analyses required of the new laboratory, what equipment would you order and what analyses would you suggest? Explain your decisions.”
2.Introduction to Cask-Conditioned Beer
Cask-Conditioned beer is beer that remains in contact with viable yeast throughout the fermentation, stillage, and serving cycles. d02 respiration, flavor maturation, and natural carbonation (“condition”) are all achieved via secondary fermentation in a serving vessel, most commonly a cask. Clarification is usually achieved through the use of finings, added either at the brewery or pub. When the beer is judged to be “ready,”1 the cask is vented of excess CO2 and the beer is served – via gravity, or through a beer “engine” or pump.
(a) Methods of Secondary Fermentation
There are three methods of secondary fermentation:
Spunding. When the fermenting beer has reached a pre-determined level of attenuation, and a given amount of residual sugar and viable, suspended yeast is determined to remain, the fermentation vessel (FV) is “capped.” As the fermentation progresses to its final stages, the CO2 which evolves is unable to escape the FV, and condition is thus achieved. Typically, the FV is capped with 1 – 1.5% residual extract, and 1-4 million viable yeast cells/ml in suspension.
Krausening. A pre-determined volume of high-krausen, vigorously fermenting beer is introduced into fully attenuated beer. The FV is capped and secondary fermentation proceeds. Krausen volumes range from 5-10% of total beer volume.
Priming. The above two methods are more common among lager breweries. Priming is more common among ale breweries. It involves the introduction of a pre-determined amount of fermentable extract (typically dextrose or glucose, less commonly maltose or wort) to fully fermented beer, with residual or added suspended yeast populations in the range of 2.5 x 105 to 3.0 x 106 cells/ml.2
For the purposes of this assignment, it will be presumed that primary fermentation is carried out in a cylindrical-conical fermentor (CCV), despite its arguable drawback in terms of possible over-carbonation and flavor effects.3 For each brand, it will also be presumed that key primary fermentation benchmarks (such as brand final gravity) are well known by empirical observation and history. Secondary fermentation is achieved by priming with glucose.
3.Concerns of the Laboratory
Given the economic constraint imposed by 50 hl/week of beer production, the range of equipment and analyses to be employed is fairly limited. Broadly, there exist six areas of concern for the laboratory of this cask-condition, small brewery:
(a) Microbiological Control
Due to the relatively inhospitable environment which exists in finished beer for most micro-organisms, the range of possible brewery contaminants is fairly limited. 4 Nevertheless, at numerous key points throughout the production process, various classes of contaminating micro-organisms may flourish or, if they eventually die off, they may contribute substantial off-characteristics to the beer prior to their death.
The heart of the laboratory microbiological control regimen is the routine sampling program. Under “normal” conditions, when no product faults are detected, sterile samples would be routinely taken at key points throughout the production process. At this level, the goal is merely to detect early changes within the brewery yeast culture, and to rule out the growth of contaminant, spoilage species. Here, the widest possible “net” is cast to recover the broadest possible spectra of potential spoilers.
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