By Chris Rice - 19 September 2016

Contamination of beer by spoilage micro-organisms remains a considerable challenge for the brewing industry. Traditional beers are susceptible to contamination by several types of spoilage microorganism. According to the scientific literature, approximately 70% of beer spoilage cases result from contamination by lactic-acid bacteria, which produce flavours considered to be undesirable in most beer styles. The remaining spoilage cases are caused by a range of wild yeasts, as well as aerobic and anaerobic bacteria, that are present in the brewery environment and can carry-over to the beer if rigorous hygiene is not maintained. Happily for beer drinkers, harmful pathogens are not able to grow in beer due to several microbiological ‘hurdles’ such as alcohol, low pH, low nutrient content and the presence of growth inhibitors such as hop acids.

However, in recent years there has been an emergence and growth in popularity of novel alcoholic beverages that may contain added sugar, flavourings and colourings. The brewing industry has seen the emergence of beers mixed with fruit juices, sodas and extracts to produce novel low alcohol, sweetened beverages appealing to non-traditional beer drinkers. These new drinks tend to have far fewer microbiological hurdles for spoilage organisms and, more worryingly, may act as a fertile environment for the germination of spores, and the growth of pathogens and other spoilers not routinely encountered in the brewing industry.

To combat this threat, we have seen the brewing industry turn to methods such as pasteurisation to stabilise their novel products. Unfortunately, the published guidelines for pasteurisation of even traditional beers are very broad and were certainly never designed to advise a pasteurisation regime for novel beverages. In response, brewers tend to over-pasteurise their products, ensuring microbiological stability – but at a cost. Increasing the level of pasteurisation means a higher energy input, and more water loss and risks impacting final product quality by de-stabilising the beverage and introducing ‘cooked’ or ‘aged’ flavours into the drink.

We have developed a lab-based method to accurately model the rate of microbial death during pasteurisation. The approach allows us to see how increasing the level of pasteurisation impacts the survival of even thermo-tolerant microorganisms so that we can advise on an optimal pasteurisation regime for a specific product. We can verify the new pasteurisation regime using our on-site pilot scale tunnel pasteuriser to ensure that the product is microorganism-free, and our panel of trained sensory experts can evaluate the newly-pasteurised product to assess its quality in terms of aroma and taste.

Together, these services help the brewing industry to reduce costs, and save energy and water, while maintaining the highest product quality.