Brewing is possibly the oldest fermentation process. Around 12,000 years ago, people fermented a mix of grains and other plants to produce a sweet liquid that they found made them happy and relaxed, and helped build communities. The controlled process of germination and drying grain (malting) followed a short time later, allowing these early brewers to have more control over the process. Over the subsequent millennia, the malting and brewing processes have become more precise with the use of predominantly barley as a source of color, fermentable sugars, and flavor; hops for bitterness and aroma and yeast to produce alcohol, CO2, and some additional flavors. Also, over the many centuries, different beer styles have evolved based on different grains or plants, alternative processing, and diverse yeasts. Today, the global brewing industry is worth over $500B and contributes to 1 in every 110 jobs. Maltsters and brewers have in-depth knowledge of the hundreds of biochemical reactions that occur in malting, brewing, and fermentation. This chapter will cover the historical foundations of malting and brewing and discuss key factors that influence processing, flavor, aroma, and other aspects of quality.

Abstract The production of beer is a highly complex process, but this chapter offers a description of the conversion of barley into beer that is readily intelligible to the layperson. The grain from the barley is hard and unpleasant in flavor. Malting converts the grain into a softer, tastier form that can be efficiently extracted in the brewhouse. The successive stages are as follows: milling of malt into extractable particles; mashing, in which milled malt is mixed with hot water, primarily to allow the enzymic breakdown of starch into fermentable sugars; lautering, in which the extracted sugars are separated from spent grains; boiling with hops to extract bitterness; clarification and cooling prior to fermentation, in which yeast converts the sugars into alcohol, carbon dioxide, and certain flavor compounds; followed by clarification and packaging.

Abstract Beer has been a feature of society for some 8,000 years. It has been argued that brewing was a fundamental driving force for the shift from a nomadic to a static, agriculture-based society. Beer has been successively a societal norm in cultures from the Sumerians, through the Egyptians, to the monasteries of medieval Europe and on to today’s craft-driven businesses. There is an intertwining of beer and religion! The British and German brewing histories serve to illustrate well the driving forces that dictate the shape of brewing to this day. And both nations influenced the direction taken by the brewing industry in the United States, which has featured the growth of enormous brewing companies despite the ravages of prohibition. Scientists working within the brewing industry over the past 1.5 centuries have made major contributions not only to improvements in brewing operations, but also in ways applicable far more widely in society (e.g., the concept of pH).

Approaches to brewing are suffused with dogmatic insistence that certain techniques are unequivocally linked to the delivery of quality products. Amongst these belief sets is the perseverance with prolonged maturation (or ‘conditioning’) times post-fermentation. Historically the justification for these lagering techniques was to allow settling of solids, carbonation, flavour maturation and removal of chill haze entities. As science and technology have advanced it is unequivocally the case that solids and chill haze precursors can be dealt with in short order and without the need for lengthy treatments. Equally it is perfectly possible to deliver specified levels of carbonation without the need for all the carbon dioxide to be introduced via yeast action. However, there remain many who feel that the nature of carbonation differs depending on which approach is taken. Herein lies one of the research areas that the author proposes. The perception of carbonation is not primarily due to bubble release on the palate, but rather is through the detection of carbonic acid. Is there a difference in the availability of this form of the gas depending on the mode of carbonation and to what extent does the adsorption of the carbonic acid on polypeptides in the beer have a role to play? In terms of flavour, the advocates for lagering insist that there needs to be a handling of vicinal diketones, acetaldehyde, and hydrogen sulphide. However, all of these can be controlled through attention to primary fermentation. Then, the proponents for maturation insist that there is a desirable release of non-volatile materials into beer, which substances supposedly benefit the balance and mouthfeel of the lager. These include amino acids and nucleotides. It seems to this author however that the likeliest explanation for the greatly increased levels of these materials and of pH is autolysis of yeast. This, together with the disadvantageous impact of increased free amino nitrogen and higher pH on aspects such as biological stability, flavour stability and foam, should convince any brewer that there is a sound argument for avoiding the prolonged contact of beer with yeast. Indeed, a metabolomic approach to studying changes in non-volatile substances under conditions where there is little or no autolysis, revealed no detectable changes in any entity. The author is open to being convinced that there are yet unidentified materials that are developed (whether through the action of viable yeast or by yeast autolysis) as beer is stored, substances which can be proven through sound organoleptic investigation to benefit the flavour of beer. Perhaps the Japanese term kokumi is what we are looking for here: ‘rich taste’. This is believed to be afforded by γ-glutamyl peptides and, inter alia, these are to be found in yeast extracts. Herein lies the second experimental approach that the author recommends for pursuit.

The assurance of a stable and appealing foam on beer requires an understanding and application of several physical and chemical principles and these are reviewed in this paper. In terms of physics, it is essential that the foam is produced efficiently, the presence of nucleation sites being important, with major determining factors being temperature and carbonation level. The principle driving force for foam instability is disproportionation, wherein bubble collapse is caused by the passage of carbon dioxide from smaller to larger bubbles. As nitrogen does not readily make this passage, this gas allows for much more stable foams. The stability of foam depends on the balance of foam-positive foaming components (polypeptides, hop bitter acids, metal ions, melanoidins) over foam-negative entities (ethanol, lipids, detergents). The principal foam-stabilizing proteins contributed by malted barley are Protein Z4 and Lipid Transfer Protein (LTP1), but the fragments of hordein produced by proteolysis in malting and perhaps mashing have a greater ability to enter into the foam but display less ability to stabilize the bubbles. They compete with Protein Z and LTP1 which display less foamability but greater foam stability. Carbohydrate complexed with protein may have a significant role to play, and this is potentially the reason for the benefits to foam afforded by wheat. Kinetic models analogous to those employed in the study of enzyme kinetics are useful in terms of interpreting foaming systems, as are model systems.

The paper reviews a career of more than forty years researching topics in malting and brewing science. Some themes attracted particularly close attention, namely the endosperm cell walls of barley, dimethyl sulphide, flavour stability, foam and the impact of beer on health. However, the scope has been far broader than that. The underlying imperative was to pursue research that was close to application and always focussed on a specific need in the processes involved in the production of beer. (C) 2020 The Institute of Brewing & Distilling