Boundary conditions and implications of yeast propagation in brewer’s wort

Aerobic propagation of yeast is a preferred option in modern yeast management. It is important that brewers strike a balance between the performance capabilities of the yeast and the associated yeast metabolism. Drawing on experience and knowledge gained with baker’s yeast strains, boundary conditions for yeast propagation in the context of brewer’s yeast composition can be established.

Modern yeast management involves, inter alia, process control and process equipment required for yeast harvest, yeast treatment, yeast storage, pitching of wort and above all pure yeast culture and yeast propagation. A survey of this is contained in 1. This leads to vigorous foam formation. One of the main objectives is to remove carbon dioxide from the yeast crop as completely as possible.g.
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Dispersion mashing - A new process for optimising mechanical starch hydrolysisQuality parameters of mashes, worts and beers, Part II

The dispersion mashing process developed by A. Ziemann GmbH and described in Brauwelt No. 45/1998 (Brauwelt interntional No. I/2000) was tested on a semi-industrial scale (360 kg throw) in the Pilot and Testing Brewery of Cervecería Polar C.A. in Caracas. This operational run was carried out in the presence of staff from TUM-Weihenstephan (Faculty for Machinery and Equipment Science) working on a thesis.

The state-of-the-art testing brewery is equipped with a lauter tun as well as a mash filter with the pertinent mechanical size reduction equipment comprising a 6-roller mill and a hammer mill.

A test procedure geared to the standard process of the testing brewery was selected.A. Ziemann GmbH (80 - 110 kg throw).A. carried out sensory analysis of the beers.
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Process combination in the brewhouse - a new wort boiling system and external wort heating

In breweries, unit operations of wort heating and wort boiling as a rule account for the major portion of total energy consumption. Using a combination of a novel wort boiling system with external heating of wort, it has become possible to recover the whole of the waste heat arising in the “wort boiling” unit operation and to supply this to the subsequent brew for "wort heating", with the result that no excess heat arises in the form of warm water. In many instances, there is no requirement for this.

In this paper, achievable improvements in terms of energy requirements and the resulting emission situation will be detailed on the basis of an actual design case.g. coagulation of protein, hop isomerisation, driving off unwanted substances).7 – 0.
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A new wort boiling systemPart I: First results from pilot tests

At first glance, wort boiling seems to be a very simple process. In the classical manner, the wort is boiled for about 75 - 90 minutes at atmospheric pressure. After hot break separation, the wort is cooled, aerated and yeast is added.

Past experience has shown that every change in boiling conditions, equipment or technology, e.g. vessel shape, type of heating, heating medium, boiling time or boiling temperature, leads to changes in beer quality, frequently these turn out to be negative (1).

Heat requirements in beer production amount overall to about 145 - 285 MJ/hl of sales beer. Wort preparation, requiring 81 - 128 MJ/hl of sales beer, accounts for the largest energy input (2). Of this, wort boiling requires 24 - 54 MJ/hl (3).g.
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Investigations on use of bacteriocin-producing lactic acid bacteria for biological acidification of brewers’ worts

Bacteriocins are biologically active peptides produced by some bacteria, among others by species of lactic acid bacteria. These can inhibit certain other bacteria, including beer-spoilage bacteria. The objective of these investigations was to study selected lactic acid bacteria strains used for biological acidification of mashes and worts in breweries and to establish their ability to produce bacteriocins and to examine the behaviour of bacteriocins in brewing.

Two bacteriocin producers were isolated from plant cultures of acidified matter. The B 2/5 strain as well as the bacteriocin produced by this strain proved to be stable and potentially suitable at pH, temperature and media conditions arising in brewing. They are therefore regarded as completely harmless for humans.
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Aeration in fresh yeast propagation - too much of a good thing!

Issues relating to yeast oxygen requirement under conditions of fresh yeast and brewing yeast propagation in breweries are discussed, and realistic consumption levels derived.

In modern yeast management, economical sterile yeast propagation in pure culture yeast propagation plants is accorded high priority so that, if possible, every single brew can be pitched with fresh propagated yeast. Processes and equipment are offered which are primarily geared towards a maximum aeration rate and thus getting maximum oxygen transfer to the yeast [1 - 4]. But this is not the case!

Based on the evaluation of values quoted in the literature and on in-house model investigations, an estimate of oxygen and air required for optimal yeast propagation under brewery conditions is given below.

Zinc problem solved ?

Zinc deficiency in pitched wort is a well-known and accepted problem in breweries. Zinc is an essential trace element for yeast and, in the normal course of events, assures an adequate yeast propagation.

In parallel to the increase in biomass, the activity of enzymes required for fermentation is influenced by zinc, and it affects also the spectrum of fermentation by-products.

Many technological attempts to provide sufficient zinc to the yeast have failed or have had very modest success up to now. Especially when operating within the framework of the Purity Law, this problem is very difficult to solve when remaining within legal limits. The addition of mineral zinc in the form of zinc sulphate or zinc chloride has become established in other countries.
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