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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