Back / Gastl / Krottenthaler Brewing Techniques in Practice

An In-depth Review of Beer Production with Problem Solving Strategies
1. Auflage 2020
ISBN: 978-3-418-00925-4
Verlag: CARL, HANS, FACHVERLAG
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Deutsch, 394 Seiten

This handbook addresses both students of brewing technology and technological practitioners. It provides a comprehensive overview of raw materials, modern plant and process engineering, quality characteristics, stability values, sensorics, microbiology, speciality beers and health aspects. Biochemical fundamentals and technological interrelationships are impressively depicted in well-arraned tables and illustrations.

Autoren/Hrsg.

Back, Werner

Gastl, Martina

Krottenthaler, Martin

Narziß, Ludwig

Zarnkow, Martin

Leseproben

MALT
1INTRODUCTION
Malt quality is of great consequence in beer production and thus has a substantial impact on the quality of the finished beer. Individual production steps, e.g. lautering, fermentation and filtration, as well as attributes central to the character of beer, e.g. flavor, color, foam and stability, are heavily influenced by malt quality. The malt utilized in beer production is mainly produced from malting barley; however, for some specialty beers, e.g. Southern German-style wheat beer, malt is also produced from wheat or even other cereals, e.g. rye or oats (cf. Cereals and Pseudocereals). Barley is a natural product, making it subject to regional and seasonal fluctuations. The task of compensating for this variation, at least to the extent physically possible, falls to the maltster whose vocation it is to make homogeneous malt of a consistent quality available to breweries. However, biological and economic constraints limit the degree to which quality can be rectified in the malthouse. Maintaining high standards of quality for German malting barley and, in turn, for the malt created from the barley for the purpose of brewing beer, is the responsibility of the entire production chain, from the farmer to the brewer. Advancements in barley breeding and cultivation have resulted in malting barley of an extremely high quality, particularly spring barley varieties. Specifications define the quality of malt required for effortless processing and thus have become the standards used by malt producers and other processing companies. Through selection of the barley variety and the level of malt quality and hence the standard values and thresholds for the quantifiable attributes described in the malt analysis, a brewer ultimately determines the quality of the raw materials required for a particular beer style. When deciding which attributes should receive the highest priority, the accuracy of the analyses as well as how these various attributes interact with one another should be taken into account. Meticulous attention must be exercised in obtaining analysis results. The procedures for conducting the brewing analyses established throughout Europe have been published in collections of brewing analysis methods by the Mitteleuropäische Brautechnische Analysenkommission (Central European Brewing Technology Commission or MEBAK) and by the European Brewery Convention (EBC) [1, 5]. The laboratory mashing method for the evaluation of malting barley varieties was changed prior to the 2012 harvest. The Congress mash method was replaced with an isothermal 65 °C mash (similar to hot water extract), allowing a more practically oriented assessment of new barley varieties to be carried out while also providing insights into processability [2]. However, when evaluating malt quality, the results obtained with the Congress mash method are not equivalent to those found with the isothermal 65 °C mash method. In this situation, comparative analysis is needed to find a common basis. Direct conversion factors will certainly never be generated for adapting the pool of data collected for the Congress mash method to the data for the isothermal 65 °C mash method [3]. Due to the considerably advanced proteolytic and cytolytic modification of grain accomplished in the malthouse, brewers can concentrate their efforts on degrading the starch in the mash vessel (cf. Mashing). Before discussing the individual attributes measured in malt analysis, one should understand that the quality of the assessment itself, as well as the quality of a particular lot of malt, largely depends on representative sampling. The importance of collections, along with the rules governing collection and the preparation of samples, have been described in numerous publications [1, 6, 4]. 2THE QUALITY ATTRIBUTES OF BARLEY MALT AND WHEAT MALT
2.1QUALITY ATTRIBUTES OF BARLEY MALT
First and foremost, a barley malt analysis describes the three primary modification processes that have occurred in the kernel: cytolysis, proteolysis and amylolysis. The single most important task of the maltster, given the fact that modern brewhouse procedures often entail mashing in at temperatures above 60 °C, is to effect a homogenous and complete degradation of the cell walls and to attain a suitable level of protein modification. Thus, malt quality plays a key role in ensuring that the production process runs smoothly. In large breweries, where up to twelve batches of wort are brewed per day, modifying the temperatures and rests in the mash program to accommodate individual fluctuations in malt quality is not practicable if brewing operations are to remain on schedule. Thus, mashing is largely limited to amylolysis, that is, the degradation of amylose and amylopectin required for brewing (cf. Mashing). 2.1.1CYTOLYSIS Cytolysis describes the degradation of the substances providing structure and support to the cells that surround the starch in the endosperm. Structural proteins and polysaccharides in the cell wall, especially ß-glucans, are subject to these degradation processes. If the processes are allowed to continue during malting until the support structures of the cells are largely broken down, the enzymatic degradation of the endosperm during mashing is much less arduous, resulting in higher brewhouse yields. Likewise, insufficient modification of these support structures not only brings about shortfalls in brewhouse yield but also causes large quantities of high molecular weight ß-glucans to become soluble and enter the process of wort production. Older sources attest to the favorable influence of high molecular weight ß-glucans on foam and mouthfeel. As long as the ß-glucans are not in gel form, quantities of up to approximately 350 mg/l do not pose a problem from a brewing standpoint (isothermal 65 °C mashing procedure)[7, 8, 9]. ß-Glucan gel can lead to filtration issues even at concentrations as minute as 10–15 mg/l, a level only slightly above the reliable detection threshold (cf. Filterability – Issues with Turbidity). Wort produced using mash programs with mash-in temperatures above 60 °C are particularly susceptible to gel formation. At mash temperatures in the range from 60 to 65 °C, a substantial amount of ß-glucans still bound to the cell walls is liberated by the enzyme ß-glucan solubilase. However, degradation of this high molecular weight fraction can no longer take place, since the endo-ß-glucanases – the enzymes responsible for breaking down these large ß-glucans – are inactivated at temperatures as low as 52 °C. Thus, given a consistent malt quality, brewhouse procedures incorporating high mash-in temperatures will always lead to higher total ß-glucan concentrations in wort and beer. For this reason, high mash-in temperatures require more extensive modification of the cell wall (cf. Mashing). Various key metrics are used to describe the level of cytolytic modification. The value for friability has proven useful in this regard. The procedure is simple, and the value can also be ascertained rapidly. Cell wall modification is evaluated with a friabilimeter to determine the overall friability of a specific lot of malted grain and the percentage of kernels that are classified as completely glassy. This information is then used to draw a conclusion regarding how uniform the process of malting the barley has been. High values for friability are not necessarily an indication of over-modification, as long as they only apply to cell wall modification and not to protein modification. Therefore, breeders involved in developing malting barley varieties face the challenge of striking the right balance among the individual traits used to define modification, especially with respect to proteolytic and cytolytic processes. Other attributes providing information about the degree of cytolytic modification include the viscosity and the ß-glucan content of both the Congress wort and of the 65 °C mash as well as the homogeneity and modification of the malt. The values obtained for the 65 °C mash are a better gauge of cytolytic modification than the values obtained with the Congress mash. Owing to the 45 °C rest, the Congress mash method promotes more ß-glucan degradation. However, with this method, once the temperature of the mash reaches 45 °C, it is immediately heated to 70 °C, which does not allow enough time for an adequate ß-glucan solubilase rest. Thus, variation in cytolytic modification among different lots of malt cannot be sufficiently characterized by means of the Congress mash method. The isothermal 65 °C mash, on the other hand, more clearly distinguishes this variation with its high mash-in temperature and intensive ß-glucan solubilase rest. From time to time, the difference in the results between the Congress mash and the isothermal 65 °C mash is also employed as an assessment criterion. One should be mindful of the fact that both MEBAK and the EBC no longer include the method for determining the difference in extract between fine and coarse grist in their analysis collections. Based on statistical evaluation in combination with practical tests, the following analysis results...