| Summary: | Berries are good sources of phenolic compounds, which often act as defence compounds in plants. In humans plant phenolics besides their other health-inducing effects have been found to possess antimicrobial activities. Our previous studies showed that phenolic berry extracts especially inhibited the growth of Gram-negative but not Gram-positive bacteria such as Lactobacillus. Especially cloudberry, raspberry and strawberry extracts proved to be strong inhibitors of the avirulent Salmonella (1). Materials and Methods Bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), cranberry (Vaccinium oxycoccus), raspberry (Rubus idaeus, var. Ottawa), cloudberry (Rubus chamaemorus), strawberry (Fragaria ananassa Senga Sengana), blackcurrant (Ribes nigrum, var. Öjeby) and sea buckthorn berry (Hippophae rhamnoides), were used in the study. For antimicrobial studies berries were freeze-dried and ground to fine powder. Phenolics were extracted from the berries by aqueous 70% acetone (2). Antimicrobial activity of freeze-dried grounded berries (2 or 10 mg/ml) and phenolic berry extracts (1 or 5 mg/ml) was analysed by determining the bacterial growth curves in liquid cultures (1). The bacterial strains used were Listeria monocytogenes VTT E-991205, L. innocua VTT E-981011, Salmonella enterica ser. Typhimurium VTT E-981151, S. enterica ser. Infantis VTT E-97738, Staphylococcus aureus VTT E-70045 and Lactobacillus rhamnosus VTT E-96666 (ATCC 53103). Results Salmonella strains were inhibited by all the berries. Cloudberry, raspberry, strawberry and bilberry extracts inhibited the growth during the first 12 h incubation. However, during the next 12 h the number of viable cells started to increase. Cloudberry extract was the best inhibitor showing strong antimicrobial effects. Staphylococcus strains were strongly inhibited by all the berries and berry extracts. The number of viable cells did not increase at the end of cultivation. The tested Listeria or Lactobacillus strains were not sensitive to berries or berry ...
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