Investigating Antimicrobial Factors for the Stabilization of Beyond Beer Products

Traditional beer presents a hostile environment to the growth of most microorganisms. However, brewers have begun expanding their product offerings, producing “Beyond Beer” products that have one or more traditional beer elements removed, such as alcohol, carbonation, or hops. When these attributes begin to be removed, the assumed safety and stability of these new beverages may be compromised, requiring investigation into how the remaining intrinsic and extrinsic factors act as hurdles to prevent microbial growth. A brief review of current food safety literature will identify gaps in knowledge created by product innovation, before exploring the results of one completed study and discussing ongoing research. A study was conducted to determine the minimum inhibitory concentration (MIC) of both traditional and advanced hop products against human pathogens Bacillus cereus and Salmonella Typhimurium, as well as beer spoilage organisms Pediococcus acidilactici and Pediococcus damnosus. Hop products tested included T-90 pellets, lupulin enhanced pellets, CO2 extracts, iso-α-acid extracts, β-acid extracts, and aroma extract products. Hop products were dosed both into tryptic soy broth (TSB) and diluted dry malt extract (DME), serially diluted into well plates, then inoculated with 1.67 X 10^5 CFU/ml of bacteria and incubated at 37°C for 24 hours. Well plates were scanned at 600nm to determine optical density as a measure of microbial growth and compared to positive and negative control samples. TSB and DME samples were run on both HPLC-UV and HPLC-MS to quantify the presence of hop acids including α-acid, iso-α-acid, tetra/rho/hexa iso acids, and β-acid. Results showed that no hop products were effective in inhibiting gram-negative bacteria Salmonella Typhimurium. Products containing hop acids did show efficacy against both Bacillus cereus and the two Pediococcus spp. β-acids showed efficacy at the lowest concentration but were not readily soluble in the beer-like DME matrix. Pure oil products and terpene blends did not show antimicrobial activity, but other aroma products containing botanical extracts, carrier compounds, and hop acids did show antimicrobial efficacy, giving insight into how advanced hop products may be designed to deliver both desirable flavor and anti-microbial protection for novel products. Iso-α-acids appear to provide the most relevant anti-microbial activity due to both their solubility and abundance, with a level below 10ppm providing control of Bacillus cereus in this matrix. These insights aim to provide brewers with further tools to create stabilized beverages while also optimizing for desirable flavor traits.