Researchers find that berries inhibit growth of harmful intestinal bacteria

A research project carried out by VTT Biotechnology and the University of Helsinki has found that cloudberries and raspberries contain a phenol, ellagic tannin, that inhibits the growth of intestinal bacteria.

The study concerned commercially grown Finnish berries, particularly cloudberry and raspberry. One of the substances inhibiting growth of harmful intestinal bacteria and pathogens is a complex phenolic polymer, ellagic tannin, found in the berries. Other berries and fruit contain only small quantities of ellagic tannin.

"We were especially surprised and excited by the observation that probiotics that are beneficial for digestion are not sensitive to the berries, but harmful bacteria are. Consequently, the berries may inhibit the activity of harmful bacteria. The antimicrobial qualities of the berries are also well preserved with e.g. freezing," says the project director, Riitta Puupponen-Pimiä of VTT Biotechnology.

Thus, possible examples of derivatives from the berries might be berry powder to help traveller's tummy, or berry extract as an added preservative for marinades.

During the first three years, the research project collaborated with the food industry. Pharmaceutical and health food industries have joined later. Around ten businesses in all have participated in the project.

The project studied about ten bacteria that cause infections of the alimentary canal and food poisoning, and how they reacted to the phenols in berries. Salmonella and listeria were some of the bacteria under study. The phenols present in the berries were found to inhibit growth of salmonella, staphylococcus and camphylobacter. The phenols in the berries had no significant effect on the functioning of listeria.

"Understanding the interaction of phenolic compounds and bacteria of the alimentary canal is important, for example for developing functional foods. As antimicrobial compounds, phenols may have a previously unforeseen effect on intestinal microbes," says Ms Puupponen-Pimiä.

The study has aroused a great deal of interest, as it has a wide range of possible applications. The results may be utilised e.g. in developing functional foods, new types of safe food packaging, and in pharmaceutical applications.

The project is currently focusing on developing a method of isolating the phenolic compounds, to enable them to be used in industrial applications. Another objective is development of treatments to increase the concentration of beneficial substances contained in the berries.

The project is part of the National Technology Agency of Finland (Tekes) technology programme Innovation in Foods.