Berry phenolics and their antimicrobian properties

Berries are traditionally an important part of the Nordic diet. About 50 different berries are grown in the northern region, and about half of them are edible. The most well-known and important wild berries are lingonberry, bilberry, raspberry, cloudberry, cranberry, buckthorn berry and crowberry. The annual crop of lingonberry and bilberry in Finland has been estimated to be as large as 500 million kg and 250 million kg, respectively. However, only a small part of this is harvested. Thus wild berries in the Nordic region form an enormous natural source, only a fractional part of which has been advantaged so far. In North America cranberry along with blueberry are two important native fruits which are commercially grown. Around 500 million tons are produced every year. Only 5% of the annual crop is harvested for fresh fruit and most of it is used for processing. Interest in the composition of berries has been intensified because of the increased awareness of their possible health effects. Berry fruits are rich sources of bioactive compounds, such as phenolics and organic acids, which have antimicrobial activities against harmful bacteria and human pathogens. Among different berries and berry phenolics, especially cranberry, cloudberry, raspberry, strawberry and bilberry possess clear antimicrobial effects against e.g. salmonella and staphylococcus. These antimicrobial effects on different bacteria may also be species or strain dependent in character. Complex phenolic polymers, like ellagitannins, are strong antibacterial agents present in cloudberry and raspberry. Several mechanisms of action in the growth inhibition of bacteria are involved, such as destabilization of cytoplasmic membrane, permeabilization of plasma membrane, inhibition of extracellular microbial enzymes, direct actions on microbial metabolism and deprivation of the substrates required for microbial growth. Antimicrobial activity of berries may also be related to antiadherence of bacteria to epithelial cells, which is a prerequisite for colonization and infection of many pathogens. The antiadherence properties have so far been reported to cranberry phenolics. Berry juices are often very acidic due to high content of organic acids, and this may have an impact on the antimicrobial properties of the phenolics. Thus pH is a very important parameter when evaluating the antimicrobial activity of the berry compounds either in various food matrices or in the human body. Antimicrobial berry compounds may have important applications in the future in food industry as well as in medicine.