Fermentation rooms

The outcome of fermentation is crucial to the success of the entire brewing process. Since wort is an ideal growth medium for a multitude of micro-organisms apart from brewing yeast, it is essential that every precaution is taken to prevent infection and to ensure that controlled conditions are maintained within fermentation vessels. In this respect, the fermenting vessels and the room in which they are located should be viewed as an integrated whole. Thus, the vessel represents the primary barrier between the fermenting wort and the immediate environment whereas the fermentation room (hall or cellar) is the secondary barrier between the vessels and the external environment. It follows that the design of fermentation room and fermenting vessels should be complementary.

The principal functions of the room may be summarised as follows:

(1) to enclose the fermenters and ancillary plant within a contained and hygienic environment which minimises the risk of microbiological (or other) contamination of the contents of the fermenter;

(2) to assist in attemperation of fermenting vessels;

(3) to provide a safe working environment with respect to concentrations of atmospheric C02.

In many respects, the degree of sophistication required for the fermenting room is inversely related to the level of containment and control achievable in the fermenting vessel. Vessels of very simple design with rudimentary control facilities rely on the room to compensate for their deficiencies. Conversely, large closed vessels are self-contained and in many cases are constructed entirely outdoors with no dedicated fermentation room. Commonly, tall cylindrical fermenters are arranged in 'tank farms' with their lower parts contained within a fermentation room and the upper two-thirds projecting through the roof and exposed to the elements.

There are advantages and disadvantages to each type of installation. Open vessels, by their very nature, must be enclosed within a room. However, the cost of the room can be defrayed to some extent in that it is not necessary to weatherproof the individual vessels. Further cost savings may be made if the room is the sole source of attemperation since it is less expensive to refrigerate the room as opposed to supplying coolant to several vessels. On the other hand room refrigeration as a means of attemperating vessels is inefficient, very low temperatures cannot be achieved and it lacks flexibility.

Vessels with separate facilities for attemperation offer maximum flexibility. Individual vessels may be used simultaneously to produce several beer qualities, each requiring a different attemperation regime. Similarly, fermentation and cold conditioning may be performed concurrently. However, each vessel must be supplied with services for monitoring and control. Outdoor installations save costs because no building is required but this is partially offset by the need to insulate and weatherproof each vessel. However, there is no restriction on the size of vessels and groups of tall cylindrical tanks make very effective use of available floor space.

Tank farms that are totally outdoors can only be operated safely in areas with a mild and dry climate. In less temperate geographical locations it is necessary to enclose the base of vessels within a building. The building provides a physical support for the vessels and a contained, hygienic and weatherproofed area, which protects the mains, pumps, and other services.

5.2.1 Hygienic design of fermenting rooms

It is essential that fermenting rooms are constructed and operated with an appropriate regard to standards of hygiene. Frequently this important aspect of fermentation system design is neglected. Where new installations are made, it is common for budgets to not extend to the finish of the new fermentation room. Furthermore, rooms may be constructed to good standards but subsequent poor maintenance can entirely negate the initial economic investment. In fact, it might be argued that the only occasion where hygienic design of the room is not relevant is where the fer mentation is spontaneous, as in the case of Belgian Iambic beers (see Section 8.1.4.2). The rigour of the hygienic precautions extended to the room depends upon the microbiological susceptibility of the fermentation system and the scale of the potential economic loss due to contamination.

Historically in United Kingdom breweries, using open vessels to produce ales, it was considered uneconomic to brew during the summer months because of losses due to contamination (Anderson, 1989). Improved hygiene, in all respects, coupled with the introduction of effective attemperation has removed this bar to brewing! Nevertheless, open vessels can be prone to infection and they afford the possibility of cross-contamination where several yeast strains are used in the same fermentation room. Closed vessels are by design more microbiologically robust, and consequently the design of the fermenting room is less critical. The trend towards the increasing use of closed vessels perhaps explains why the finer nuances of room design are sometimes neglected. Fermentation systems that use immobilised yeast are now becoming more common and continuous fermentation, although rare, is a commercial reality. In these cases, the consequences of contamination are very severe because of the prolonged unproductive down-time. Although such systems are designed to present a microbiological barrier to the external environment, it is still important to minimise risks by locating them in hygienic surroundings.

The internal surfaces of the fermenting room should be covered with a material which is cleanable, crevice-free and impervious. Preferably the surface should be seamless and particular care should be taken to ensure that corners are sealed. The most suitable materials are synthetic resins, which provide a continuous membrane. Glazed tiles are satisfactory but it is essential to keep the grouting in good repair. Table 5.4 summarises the hygienic properties of commonly used materials, together with details of resistance to chemicals and wear.

Table 5.4 Hygienic and durability properties of materials used for internal surfaces of fermenting rooms (Institute of Brewing, 1988).

Material

Hygiene

Resistance to

Resistance to strong

Resistance to strong

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