Physicochemical composition, fermentable sugars, free amino acids, phenolics, and minerals in brewers' spent grains obtained from craft brewing operations

Authors: JIN, ZHAO - North Dakota State University; LAN, YANG - North Dakota State University; GILLESPIE, JAMES - North Dakota State University; Ohm, Jae-Bom; CHEN, BINGCAN - North Dakota State University; SCHWARTZ, PAUL - North Dakota State University

Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2022
Publication Date: 1/11/2022
Citation: Jin, Z., Lan, Y., Gillespie, J., Ohm, J., Chen, B., Schwartz, P. 2022. Physicochemical composition, fermentable sugars, free amino acids, phenolics, and minerals in brewers' spent grains obtained from craft brewing operations. Journal of Cereal Science. 104. Article 103413. https://doi.org/10.1016/j.jcs.2022.103413.
DOI: https://doi.org/10.1016/j.jcs.2022.103413

Interpretive Summary: Craft breweries are a rapidly growing industry and craft beer is in high demand. The industry, however, produces large quantities of brewers’ spent grain, grain that is a byproduct of the brewing process and accounts for 85% of brewing by-products. Generally thought of as waste, this work set out to determine whether nutritive value was still present in the grain. The research in this report found that samples obtained from North Dakota and Minnesota craft breweries were high in fiber, proteins, lipids, phenolics, and essential amino acids. The brewing process did not consume all of the sugars as the samples still contained high levels of starch and other fermentable sugars. Significant levels of nutritional minerals were also found in the grain. This research has shown that spent grain has the potential of being a nutrition source and a secondary income stream as a value-added product.

Technical Abstract: The unconventional processing of grain ingredients in the craft brewing industry changes the production of brewers' spent grains (BSG) byproducts. This study aimed to investigate the nutritional composition of representative BSG samples obtained from craft breweries in the local region of North Dakota and Minnesota in the United States. Whole grain or malt kernels and large fragments were observed in all the craft BSG samples which consisted of 38.2% fiber, 33.1% starch, 18.7% protein, 6.3% lipid, and 3.2% ash (dry basis) on average. The limited sparging in the craft industrial processing resulted in fermentable sugars remained at the level of 8.2±5.8% on average in BSG, including maltose, maltotriose, glucose, and fructose. Craft BSG samples contained 2571.7±940.6 mg/kg free amino acids on average, with 40% being essential amino acids. Hydroxycinnamic acids, accounting for 99% of the total phenolic compounds, primarily existed in the insoluble bound form at the mean level of 2289.8±344.0 mg/kg. The total content of nutritional minerals was 1.0±0.2% of craft BSG. The results demonstrated that BSG yielded from the craft brewing industry is nutritive grain ingredients, rich in starch, protein, lipid, dietary fibers, phenolic acids, minerals, fermentable sugars, and free amino acids.