The microbiological quality of draught no- and low-alcohol beers

Abstract

Why was the work done: To determine the microbiological quality of draught no- and low-alcohol beers in the on-trade and to provide insight into the factors that may influence susceptibility to spoilage.

How was the work done: 53 samples comprising of 17 brands, seven different beer styles (lager, India pale ale, pale ale, wheat, radler, pilsner and amber ale), were sampled at least twice in 12 different public houses in Nottingham, UK. Spoilage potential was determined using a forcing test with beers incubated statically at 30°C for 96 hours. Quality was assessed – using four categories - based on the relative increase in absorbance at 660 nm, reflecting the growth of beer spoilage microorganisms present in the beer at dispense. The physiochemical properties of each beer (ethanol, present gravity, pH) were evaluated pre- and post-forcing.

What are the main findings: 54.7% of the draught beers sampled were of ‘unacceptable’ quality due to microbial growth. Additionally, the concentration of ethanol was elevated, with some samples exceeding the limit for no- and low-alcohol beers in the UK. Principal Component Analysis showed that samples ranked as ‘unacceptable’ were positively correlated with a high present gravity and high pH. However, the susceptibility of no- and low-alcohol beers to spoilage is also determined by interacting intrinsic factors (lack of ethanol and carbohydrate profile) and extrinsic influences (hygiene of dispense equipment together with the rate of beer throughput).

Why is the work important: The reduction or elimination of ethanol (an antimicrobial hurdle) in the production of no- and low-alcohol beers results in a product that is more susceptible to spoilage by microorganisms. To ensure product quality and food safety, it is recommended that no- and low-alcohol beers should have a pH < 4.0, contain minimal residual sugar content, and undergo appropriate stabilisation procedures prior to packaging. The production of ethanol by dispense microorganisms presents an additional risk to the no- and low-alcohol category. This should be considered by brewers to ensure that this does not become a compliance issue. Further, particular care should be taken in the hygienic handling of no and low products, with implementation of robust and regular cleaning regimes for conventional long line dispense systems.