Laboratory yeast storage and supply

The storage and assured supply of brewing yeast strains is an important step in the propagation cycle. Although arguably obvious, it is perhaps not generally appreciated that storage and supply are critical to the ongoing success and consistency of yeast management in the brewery. Indeed as noted by Guldfeldt and Piper (1999), 'despite the fundamental importance of a reliable supply of pure and stable cultures, culture maintenance is often afforded low priority'. This attitude is unfortunate...

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Wort contains various nucleic acids and their degradation products. MacWilliam (1968) reported that 5.7-6.4 of the total wort nitrogen consisted of purines and of this 33 was free adenine and guanine, the remainder being adenosine and guano-sine. During mashing nucleases are active, liberating ribosides and phosphate. Higher temperature mashes are associated with reduced concentrations of free purines. This author concluded that there were no reports of pyrimidines occurring in worts. However,...

General properties of fermentation vessels

Several fermentation systems are used in brewing. These reflect the type of beer which is being made, the traditions of the country of production and possibly the volume throughput and modernity of the brewery. Within these systems many different types of fermenting vessel may be used. These differ in terms of capacity, materials of construction, geometry and mode of operation. The plethora of types of fermenting vessel mirrors the diversity of brewing operations that are encountered throughout...

Fermentation management

Beer quality, yeast type, fermenter design and operation are all intimately related. In particular, the design of many traditional fermenters arose because they were suited to the quality of beer produced and the properties of the yeast used (see Chapter 5). Modern vessels tend to be used for any beer quality and yeast type although perhaps with some compromises being made. All fermentations proceed through a number of stages. Several variations are possible and the terminology can be somewhat...

Cell wall and flocculation

4.4.1 The cell wall - an introduction The brewing yeast cell wall is a hugely important and frequently underestimated organelle. Primarily it is made up of an array of carbohydrates (80-90 of the wall) with proteins embedded within it. As memorably described by Stratford (1994) it is not an 'inorganic egg shell' but a living organelle whose properties and functions change during the cell's lifetime. As if to emphasise its importance the wall accounts for 15-25 of cell dry weight. The yeast cell...

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Possible to arrange to pitch the culture at a lower than maximum count but during the exponential phase when the yeast is still very active. This ensures that the onset of fermentation is rapid. High-yield propagators allow larger step-up ratios. Assuming a terminal count from propagator of 250 x 106 cells ml 1 and a target pitching rate in the first fermentation of 15 x 106 cells ml this would allow a scale-up ratio of 1 16. Thus, a typical cylindroconical fermenter of 1500 hi capacity could...

Yeast propagation

Maintenance of stocks of pure yeast strains in the laboratory is discussed in Section 7.1. Here are described the methods in which these stocks are used to introduce new yeast cultures into the brewery. All fermentations generate yeast sufficient to re-pitch two or more further fermentations. In some breweries, particularly traditional ale top-cropping types, this cycle proceeds ad infinitum and single yeast cultures have been in use for many years. Frequently, these may be mixed cultures...

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Continuous Distillation Lab

Where y concentration of cells in the effluent x concentration of cells in the fermenter i specific growth rate D dilution rate. A further division of systems is possible based on the extent of mixing within the fermenter. Where mixing is assumed to be perfect, as in the simple chemostat, the system is described as homogeneous. Conversely, where a gradient of conditions exists between the point of entry and exit, the system is defined as heterogeneous. As with the partially-closed category...

Assessing yeast condition

Before any batch of pitching yeast is used it is necessary to confirm that it is fit for the purpose. Three types of quality test may be applied. First, the yeast must be free from microbial contamination. Testing the microbiological integrity of yeast is described in Chapter 8. Second, it is usual to determine the viability of the yeast. Most breweries operate a quality reject system in which yeast is discarded if the viability falls below a pre-set value. In addition, viability measurements...

Product spoilage

In his excellent review on beer spoilage micro-organisms, Rainbow 1981 noted that 'beer is resistant to microbial spoilage because of its relatively low nutritional status, its content of products of yeast metabolism, its adverse values of pH and redox potential and its content of hop bitter substances'. This, in a nutshell, explains the relative robustness of beer to microbial spoilage. Although the 'low nutritional status' is self-evident, it is worth reiterating that yeast removes the vast...

Recovery of carbon dioxide

Carbon Dioxide Recovery

All breweries require a supply of carbon dioxide for use as a motor gas for transporting liquids from one location to another, for de-aerating water, other process liquids and empty tanks and for adjusting carbonation levels in beers. This requirement may be satisfied by recovering the carbon dioxide evolved during fermentation. Whether or not this is actually done is dependent on economic considerations. Thus, the cost of purchase of carbon dioxide from an external source must be weighed...

Largecapacity fermenters

Burton Union Fermentation System

In modern breweries, there has been a trend towards batch sizes larger than those achievable with traditional vessel designs. To meet this demand several fermenter Fig. 5.7 a Schematic, b detail and c side elevation of a 44 cask double Burton Union set. Fig. 5.7 a Schematic, b detail and c side elevation of a 44 cask double Burton Union set. types have been developed. These are all of the closed design and now are invariably fabricated from stainless steel. Earlier forms were constructed from...

Normal Cell

No H gradient so food cannot be transported and the cell starves Fig. 8.9 Effect of iso-a-acids on the physiology of sensitive bacterial cells after Simpson, 1993 . yeasts is diffuse and, for convenience, is traditionally divided into i Saccharomyces and ii non-Saccharomyces. Irrespective of classification, wild yeast contamination of process and product can be a major cause for concern. This reflects their diversity, difficulty of detection and, for Saccharomyces wild yeast, similarity to...

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Fermentation Vessel Brewery Diagram

Fig. 5.34 Cascade continuous fermentation system. cylindroconical design, and the top-cropping deck was omitted. The fourth vessel was essentially a conditioning tank in which the green beer was cooled and provision was made for adjustment of levels of carbonation. In 1956, Mr Morton Coutts, Technical Director of the Dominion Breweries Company of New Zealand, patented a method for wort stabilisation and continuous brewing process, the contents of which are described in Coutts 1966 . This was...

Formation of flavour compounds

Formation Sulphur Flavour Compounds

A multitude of compounds contribute to beer flavour. Many of these are derived directly from the raw materials used to produce the wort. In this respect the blend of malt and hops are influential. However, fermentation has the most significant impact on flavour development. Both ethanol and carbon dioxide contribute to beer flavour, imparting 'warming' and 'mouth tingle' characters, respectively. The essential character of any beer is determined by the plethora of other yeast metabolites, that...

Structure Of Fermenter

Cylindoconical Fermenter

T2 Warm conditioning time h . height restriction. The majority of services are supplied to the base of vertical vessels in a simpler arrangement, which uses fewer valves. With very tall vertical vessels, the large hydrostatic head requires heavy-duty pumps to fill from the base. In this regard, horizontal vessels present less of a problem however, even this advantage is lost where the vessels are stacked. On balance, vertical cylindrical vessels are more...

Continuous fermentation

The use of very large combined fermentation and conditioning vessels in a uni-tank process is in essence a strategy which seeks to increase productivity by a combination of shortening process times and reducing capital costs. Thus, the uni-tank process is more rapid than the traditional separate fermentation and conditioning tank approach and with very large vessels there is an opportunity to minimise the ratio of surface area to volume. An alternative approach is continuous fermentation in...

Laboratory fermentation systems

Yeast Fermentation Using Syringe

It is necessary to have appropriate laboratory scale fermentation systems in order to study the biochemistry that underpins brewery fermentation, to assess the properties of individual yeast strains, to screen and select new yeast stains and to develop novel processes. Much of this work may be carried out using conventional laboratory apparatus. This may range from the simple Erlenmeyer shake flask to the highly sophisticated fermenter fitted with a plethora of sensors and control devices...

Mass balance

The gross changes which occur during the course of a typical high-gravity lager fermentation are illustrated in Fig. 3.1. In this case the initial temperature was 11 C. This was allowed to increase to 12 C and held at this value throughout primary fermentation. There was an initial lag phase, which lasted for 12-24 hours. During this period there was little or no observable change in specific gravity, yeast count and ethanol concentration. However, the oxygen concentration rapidly decreased,...

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Fig. 2.5 Structures of hop alpha acids kindly provided by Richard Webster, Bass Brewers . between 2 and 15 of the weight of the hop cone. During the copper boil the alpha acids undergo isomerisation to form the cis and trans forms of the humulones. It is these iso-alpha acids that impart the bitter character to beer. In addition, iso-alpha acids have antiseptic properties and bittered beers have much better keeping properties than the earlier unbittered ales. The hop oil fraction accounts for...

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For example, strains of S. cerevisiae used in baking or winemaking may produce splendid bread or wine but quite unacceptable beers. Similarly, there are many environmental 'wild' yeasts, which, although taxonomically S. cerevisiae, result in the 'spoilage' of beer through the formation of unpleasant flavours or aromas. An excellent example of this is those strains of S. cerevisiae able to ferment non-fermentable oligosaccharides or starch formally described by...

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Direction of convection current flow Fig. 5.18 Relationship between temperature and beer density adapted from Wilkinson, 1991 . Temperature distribution and fluid flow patterns in large cylindroconical vessels during crash cooling have been studied by Brandon Larson amp Brandon, 1988 Reuther et al., 1995 . The studies used a combination of experimental observation in production-scale and model vessels. The ineluctable conclusion was that the mixing patterns are far more complex than is usually...

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With respect to brewing processes using such yeast, some of these alterations have beneficial effects and some are disadvantageous. The precise causes of the changes are obscure and many factors appear to be influential. A proper elucidation of cause and effect is difficult because of the heterogeneous nature of immobilised systems. In addition, it is difficult to unravel those effects due solely to immobilisation of cells and those which relate to restricted mass transfer. It is...

Assimilation of wort nutrients

Brewing yeast strains are heterotrophic organisms capable of utilising a wide variety of nutrients to support growth and generate energy. A property of such organisms is that they must be capable of selective uptake. Thus, assimilation of individual nutrients from wort is made complex by the response of yeast to the mixture of components present. As with all cells, specific systems exist in brewing yeast strains to accommodate the uptake of individual or related classes of nutrients. Of...

Traditional fermentation systems

Figures 5.4 a , b and c show stages in the evolution of traditional fermentation vessels, which are principally associated with top-fermenting yeasts. Figure 5.5 shows a photograph of square fermenting vessels. The most primitive vessel Fig. 5.4 a is a shallow open coopered wooden cask which receives no attemperation other than that provided by the room in which it is housed. The vessel is mounted on legs to allow air circulation and promote cooling. Cooling is further assisted by the shallow...

Wort collection

Wort collection describes that part of the brewing process in which wort is delivered from the brewhouse to the fermenting vessels. This must be done in such a way that after the process is complete appropriate initial conditions are established within the filled fermenting vessels. At first sight this may appear a relatively straightforward operation however, it involves several distinct steps which if performed incorrectly will have adverse effects on both fermentation performance and the...

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A-Acetohydfoxybutyrate 2,3-Pentanedione NADH Fig. 3.17 Pathways leading to the formation and dissimilation of the vicinal diketones, diacetyl and 2,3-pentanedione. An alternative synthetic route has been suggested Chuang amp Collins, 1968, 1972 . As a result of studies with radiolabeled substrates these authors concluded that in S. cerevisiae, acetoin and diacetyl arose from condensation reactions between hydro-xyethylamine pyrophosphate and acetaldehyde and hydroxyethylamine pyrophosphate and...

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...

Highgravity brewing

High-gravity brewing is the practice of producing concentrated wort followed, at some stage, by dilution to produce finished beer of a desired alcohol content. In essence, therefore, it is a strategy that involves brewing using a concentrate, which thereby reduces the requirement for handling water, the major component of wort and beer. In terms of plant efficiency, it follows that it is prudent to delay the dilution step until the last possible process stage. Usually this will be in bright...

The brewing process

Obesumbacterium Proteus

The major stages that together comprise the brewing process for a European-style beer made by a traditional batch process are shown in Fig. 2.2. The process consists of three phases wort manufacture, fermentation and post-fermentation processing. Each of these phases contains several distinct steps. The precise detail of each step depends, to some extent, on the nature of the beer being made and the plant used. However, there are common themes and these are described in this section. The raw...

Overview

The biochemistry of brewery fermentation is complex and many of its aspects remain to be fully elucidated. The reactions - which underpin the growth of yeast during fermentation and the concomitant conversion of wort to beer - touch on almost every facet of cellular metabolism. Many of the pathways involved are those which may be found described in any standard biochemistry text and to duplicate this information here is both needless and beyond the scope of this book. Instead the intention is...

Wort composition

The nature of the materials and procedures used to make wort make it inevitable that its composition is complex and, in fact, not well characterised. Thus, Hudson 1973 described the single condition that wort composition must meet as that which pro duces a beer of desired character by intention rather than by chance. It is perhaps implicit in this definition that it is not necessary to know the precise composition as long as the materials and methods used in its preparation are themselves...

Morphology cytology and cellular function

Yeast Cell Lipid Granule

It has been said that yeast is known more for what it can do than what it is Robinow amp Johnson, 1991 . Until comparatively recently this was certainly the case and, thus, early brewers had by and large to be content with gauging yeast condition on the basis of observed relationships between behaviour and macro-morphological appearance. For example, assessing fermentation progress based on the appearance of the yeast head in an open square fermenter. In this sense yeast was and perhaps still...

Requirement for oxygen

Failure to provide oxygen at the start of fermentation results in slow fermentation rate, incomplete attenuation and poor yeast growth. Oxygen is required in brewery fermentation to allow yeast to synthesise sterols and unsaturated fatty acids. These lipids are essential components of membranes Parks, 1978 Brenner, 1984 Weete, 1989 Nes et al., 1993 . Thus, S. cerevisiae is capable of growth under strictly anaerobic conditions only when there is an exogenous supply of sterols and unsaturated...