By-products of the beer brewing process

Among the processes involved in brewing beer, these processes generate a large number of by-products. The main brewing industry wastes include brewer’s spent grains, hot residue and carbon dioxide. Proper disposal of these wastes brings economic benefits and helps protect the environment from pollution caused by their excessive accumulation.

Although studies have shown that beer contains various functional compounds, the amount of these functional compounds in beer is diluted due to the high water content, while the large calorie value and alcohol content also limit the health effects of beer. In contrast, brewing by-products may contain more functional components during isolation. They can be used as a low-cost and nutritious source of feed and food additives. They also have the potential to be an inexpensive material for extracting compounds that are valuable to the food industry.

Distillers Grains

Distillers grains are the most abundant by-product of beer brewing, accounting for about 85% of the total beer by-product production. Distiller’s grains consist of barley husks, remaining endosperm starch granules, and other grain additives (such as wheat, rice, and corn) that give beer its distinctive flavor. Distiller grains are rich in protein, cellulose, and minerals, so they are often used to feed ruminants. Research has investigated adding distiller grains to bread and snacks to increase their fiber content.

Hops

The main component of dry hops is fiber, followed by hop bitters and protein. Dried hops also contain ash, salt, polyphenols, tannins, and oils. The fiber in hops consists of xylose, mannose, galactose, and glucose. Of the added hops, only 15% remains in the final beer product. The other 85% is residue from spent hops. Although hops are rich in nitrogen, carbon, and protein, their bitter taste limits their application in food. The bitterness of spent hops can be fermented with Candida parapsilosis. After removal, the spent hops can be made into animal feed supplements. Because hops are rich in nitrogen, they can be used as soil conditioners and fertilizers.

Surplus Yeast

Residual yeast is the second most abundant by-product in beer brewing, accounting for approximately 10% of total by-products. The predominant element in yeast is carbon, accounting for 50% of the dry weight, followed by oxygen (30–35%), nitrogen (5%), helium (5%) and phosphorus (1%). The protein composition of leftover yeast, distillers grains and hops is similar, as they all contain many essential amino acids, vitamins and minerals, and are thus more used in animal feed and nutritional supplements. But, since yeast contains ribonucleic acid (RNA), which is produced by uric acid metabolism, excessive consumption of excess yeast can cause gout.

Brewery waste is used in various branches of the food industry, as feed additives and food ingredients. They can also be used as raw materials for the extraction of compounds used in the food industry or can be applied in biotechnological processes to get additives for the food industry.