The Beer Yeast Effect

Beer yeast effect

When you enjoy a beer it is the result of the work of many different yeast strains. These yeast cells reproduce at a high rate producing ethanol and other by-products which have an impact on flavour and aroma. These include higher alcohols, esters, sulfur compounds and vicinal diketones. These are all created in the course of fermentation and their concentrations can be controlled by a number of factors such as temperature, pitching rate, aeration and pressure.

Different brewing cultures and traditions have made use of different yeast strains. Ales typically rely on top fermenting strains which produce a slightly fruity flavour, and lagers are brewed with bottom fermenting strains to give the beer a clean, crisp finish. Different yeast strains also have different levels of tolerance to diacetyl, a volatile compound that can impart an unpleasant grassy/green apple flavour if its level is too high. Yeasts can produce an enzyme called diacetyl reductase to break down acetaldehyde into more benign by-products such as acetoacetate and butanoate. However, if the wort is cooled too much during fermentation or if the yeast is pitched too quickly the reduction in diacetyl will be limited, leaving high levels of acetate to form and impart an unpleasant grassy/green apple flavour in the finished beer.

Two to three teaspoons of brewer’s yeast a day was once recommended for diabetes patients, but this was never proved in a clinical trial. However, a brewer’s yeast supplement containing beta-glucan has been shown to reduce the blood sugars of diabetic mice. And a recent study showed that the nicotinamide riboside, a form of vitamin B3, found in brewer’s yeast prevented noise-induced hearing loss in mice.

Other research has suggested that brewer’s yeast may be beneficial for pregnant women. It is known that the mother needs folate for a healthy pregnancy, and it was found that S. cerevisiae reduced oxidative stress in maternal cord red blood cells of unborn mice.

Laboratory studies also suggest that using leftover brewer’s yeast as a feed additive can help lower greenhouse gas emissions. It can cause ruminant animals such as cows to belch less methane, which is a significant contributor to global climate change. Using this waste to make feed for farm animals could help reduce the amount of methane released into the atmosphere by these animals, which account for 11 percent of the total U.S. greenhouse gas emissions (5,981 million metric tons CO2 equivalent). See the video below and at 0:33 in Flashback Friday: Benefits of Brewer’s Yeast for Diabetes.