Brewers' Spent Grain Flour: Antioxidant Properties and Applications

Beer is a widely consumed carbonated beverage produced using natural ingredients such as malted cereals, hops, yeast, and water.¹ During the brewing process, large quantities of Brewers' Spent Grain (BSG), derived from barley malt, represent the residue left after wort extraction and before fermentation. Traditionally regarded as waste, BSG has primarily been used for applications such as animal feed, organic fertiliser, or brick production².

This study aims to evaluate the development of flour from BSG and assess its antioxidant properties to determine its functional benefits as a strategy to valorise this by-product, with potential applications in the food and nutraceutical industries. BSG samples were collected from the brewery Crafters (Sintra, Portugal) after the brewing process. The collected BSG was refrigerated and then dried in an oven with forced air circulation at 50°C, milled into flour, and sieved through a 400 µm mesh. The flour was subsequently packed, sealed in polyethylene bags to prevent exposure to oxygen, and stored at -20°C, away from light, until analysis. The antioxidant activity of the resulting BSG flour was evaluated using the DPPH radical scavenging assay and the ferric reducing antioxidant power (FRAP) method. The flour was analysed for total flavonoid and phenolic contents using the Folin–Ciocalteu method. The results showed that BSG flour has an antioxidant activity of 2.12 ± 0.37 µmol TE/g flour for the FRAP assay and 1.69 ± 0.16 µmol TE/g flour for the DPPH assay, with significant levels of total phenolics (1.27 ± 0.03 mg GAE/g flour) and flavonoids (3.05 ± 0.54 mg QE/g flour). These results highlight the potential of BSG as a valuable source of natural polyphenolic compounds. The developed flour could be used as an eco-friendly antioxidant ingredient with applications in the food and nutraceutical industries, improving product preservation and functional properties.

1. Senna Costa, F. et al. (2021). DOI: 10.1007/s12649-020-01163-6

2. Chetrariu, A., Dabija, A. (2023). DOI: 10.3390/foods12071533