Health & Gastronomy 14/09/2014

Synthetic particles as contaminants in German beers

A total of 24 German beer brands was analysed for the contents of microplastic fibres, fragments and granular material. In all cases contamination was found

If you’re going to Oktoberfest next month to enjoy the delights of German beer, you might get more than you bargained for. New research has revealed the extent to which German beers may be contaminated by foreign substances, most notably, microplastics.

The research, published this month in Food Additives and Contaminants: Part A, analysed 24 beer samples from local supermarkets and included both alcoholic and non-alcoholic beer. Contamination was found in all cases. Defining microplastics as ‘fibres, films, fragments or granular particles smaller than 5 mm in size and made of synthetic polymers’, the authors found that regular tap water may also be subject to this contamination.

Though contamination was found in all instances, it was not possible to establish any one microplastic as being more dominant than the others. Indeed, the contributions ranged from 5% to 71% for granular material, from 14% to 87% for fragments and from 3% to 57% for fibres and varied depending on the brand of the beer.

The study also indicated that the contamination wasn’t just caused by microplastics, indeed one beer sample even contained an almost complete insect belonging to the Order Thysanoptera. Moreover, three samples revealed glass shards of up to about 600 μm size.

The authors of the article, Gerd Liebezeit & Elisabeth Liebezeit conclude their research by suggesting possible causes for the contamination, citing the materials used in the production process and the clothes and skin of brewery workers as likely sources.

Workers in breweries loose, as any other people, the outer part of their epidermis. Healthy skin typically sheds one cell layer per day, with the complete outer skin layer being shed within 1–2 days. This process can result in the release of several million skin scales per minute. A significant fraction can penetrate clothing and become airborne. Exfoliated skin cells are typically shed as individual hexagonal plates, 25 μm on a side and 0.1–0.5 μm thick.

Clothing when worn may be an active source of both natural and synthetic fibres. Furthermore, washed clothing put out to dry in the open will also release large quantities of fibres. Synthetic mineral (e.g. rockwool or glass wool) fibres used in insulation may also become airborne. These are not stained by Rose Bengal but give characteristic microscopic images. These fibres were not encountered in the beers analysed.

The second potential source of particle input to beer can be sought in the materials used in the production process. A total of 66 accessory agents are permitted to be used in beer brewing in Germany (Metzger 2010), nine of these being used in the filtration step (activated charcoal, asbestos, bentonite, cellulose, cotton, isinglass, kieselgur, perlite and wood chippings). Filters used apparently allow particles larger than their nominal pore size to penetrate. Filter breakthroughs, cracking of filter media or separation from the container walls may also lead to an unwanted presence of particles in the finished product.

On the other hand, the bottles used may also become contaminated as unwanted impurities are not removed during cleaning or the cleaning process itself may introduce foreign particles.

To what extent particles already present in the basic components used such as barley or hop are carried through the whole process is unknown. A large number of fragments and fibres that could not be stained with Rose Bengal were found in wheat and rye grain samples.

The small numbers of microplastic items in beer in themselves may not be alarming, but their occurrence in a beverage as common as beer indicates that the human environment is contaminated by micro-sized synthetic polymers to a far-reaching extent. This may be, at least in part, overcome by applying principles of hygienic industrial design

di T N