A Multi-Parameter, Predictive Model of Starch Hydrolysis in Barley Beer Mashes

Abstract

A key first step in the production of beer is the mashing process, which enables the solubilization and subsequent enzymatic conversion of starch to fermentable sugars. Mashing performance depends primarily on temperature, but also on a variety of other process parameters, including pH and mash thickness (known as the “liquor-to-grist” ratio). This process has been studied for well over 100 years, and yet essentially all predictive modeling efforts are alike in that only the impact of temperature is considered, while the impacts of all other process parameters are largely ignored. A set of statistical and mathematical methods collectively known as Response Surface Methodology (RSM) is commonly applied to develop predictive models of complex processes such as mashing, where performance depends on multiple parameters. For this study, RSM was used to design and test a set of experimental mash conditions to quantify the impact of four process parameters—temperature (isothermal), pH, aeration, and the liquor-to-grist ratio—on extract yield (total and fermentable) and extract composition in order to create a robust, yet simple, predictive model. In contrast to previous models of starch hydrolysis in a mash, a unique aspect of the model developed here was the quantification of significant parameter interaction effects, the most notable of which was the interaction between temperature and mash thickness (i.e., the liquor-to-grist ratio). This interaction had a sizeable impact on important mash performance metrics, such as the total extract yield and the fermentability of the resultant wort. The development of this model is of great future utility to brewery processing, as it permits the multi-parameter optimization of the mashing process.

Analysis of Physicochemical Parameters of Congress Worts Prepared from Special Legume Seed Malts, Acquired with and without Use of Enzyme Preparations

“…Brewhouse efficiency is a parameter that takes into consideration both wort volume as the extract content [ 19 ]. The goal of the typical mashing process is to transfer most of the substances present in the mash to the filtered wort [ 42 ]. Brewhouse efficiency shows that legume malts, created by the malting features used typically for barley, are poorly modified.…”

Brewing with Starchy Adjuncts: Its Influence on the Sensory and Nutritional Properties of Beer

“…The two critical objectives of these steps are to maximise gelatinisation and the subsequent hydrolysis of starch into fermentable sugars. Both processes are complex and rely on a great number of mashing variables [36].…”

“…However, this rise in temperature will also speed up the denaturation of all enzymes, and the rise in dissolution rate may lead to the extraction of undesirable substances (e.g., tannins) in the malt. Hence, the temperature of a mash must be high enough to achieve fully gelatinisation, but also low enough to not degrade the different amylolytic enzymes very quickly [36].…”

“…This gap in knowledge is magnified by the fact that acid dissociation rises with temperature, thereby the measured pH value of a sample is dependent on the temperature of the sample during measurement [10]. In general, the pH of wort is in the 4.6-5.8 range [36].…”

Effective strategies to maximise dextrin formation in brewing

“…Moreover, kinetic parameters can characterise thermal inactivation, including the rate of thermal inactivation and decimal reduction time (De Schepper et al 2022a). Conceptually, the balance established at each temperature-time point during mashing between starch gelatinisation and the enzymes acting on gelatinised starch may affect the content of dextrin and fermentable sugars together with the structure of dextrins in wort (MacGregor et al 2002;De Rouck et al 2013;Fox et al 2019;Saarni et al 2020).…”