What Makes Beers Different From Each Other?

Abstract

W hat makes beers different from each other ? B S J Jared Rosen One might imagine that since beer has been around for thousands of years, all of its secrets and intricacies would have been unlocked by now and that there is little research left to be done. In fact, very much the opposite is true. One major overarching theme in much of this article is what causes us to perceive different varieties of beer as distinct and why we might enjoy some but not others. Before diving into the cutting edge research on one of man’s oldest beverages, let us take a moment to review how beer is actually made. Beer is more or less made from a solution of water, hops, and grain extract that has been boiled and allowed to ferment with yeast that converts the sugars from grain extract into alcohol and carbon dioxide. The hop plant is a distant relative of modern conifers and has been used in the brewing process since the middle ages. The oils (also known as hop acids) present in its cones are extracted in the boiling process and lend flavoring and a desirable level of bitterness. The grains favored by brewers are malted barley or wheat for their high content of maltose (a type of sugar). Maltose is broken down to glucose by the enzyme amylase during the boiling process. Brewer’s yeast is added in after the boiled solution of sugar and hops, known as wort, is cooled, and is then allowed to work its magic, turning glucose and other sugars into alcohol and carbon dioxide, which carbonates the beer. Over the course of thousands of years, a countless number of varieties based on this simple recipe have been created by making incremental tweaks. Different beers vary because their recipes are different, but from the consumer end all that matters is the perception of one beer versus another; thus, much research has been devoted to this end. Everything from fermentation temperature, byproducts of fermentation, and addition “About 8,000 years, probably. I like to say it’s the basis of civilization, and when people first realized they could make beer, they stopped wandering” of hops, to container type and conditions of storage, temperature of tasting, and interactions of chemical compounds that modulate taste, are parameters that brewers and researchers alike consider when trying to understand and improve this already amazing beverage. Beer has a fairly high caloric content (mainly due to alcohol and carbohydrates) so one target researchers Figure 1. Beer is one of the oldest beverages created by man. have is to and reduce the number of calories (Wang, et al., 2010). When carbohydrates are converted into alcohol, some of the complex sugars cannot be easily broken down by yeast (notably maltotriose) and remain in the beer, adding to the caloric content and leading to potentially unwanted flavors (Wang, et al., 2010). Other compounds such as acetaldehydes, diacetyls, and pentanedione can contribute undesirable flavors at high enough concentrations (Wang, et al., 2010). As a result, researchers in China have worked to genetically engineer a strain of yeast to help lower both the caloric content and some of these undesirable compounds. The yeast strain used in this study was endowed with the gene for the enzyme amylase, which helps break down some of these more complex sugars, thereby lowering the sugar content (Wang, et al., 2010). The production of acetaldehyde, which lends an unpleasant flavor, was decreased by about half by disabling one copy of the gene that codes for alcohol dehyrogenase (Wang, et al., 2010). This disrupts the metabolic pathway that results in acetaldehyde. Similar results were seen when other 1 • B erkeley S cientific J ournal • S cience of F ood • V olume 16 • I ssue 1