Possibility of increasing natural folate content in fermented milk products by fermentation and fruit component addition

The possibility of the increase of the natural folate content in fermented milk products by the fermentation process and by the addition of fruit component was evaluated. 5-methyltetrahydrofolate (5-MTHF) content was followed after the inoculation of pasteurised milk with the butter starter and the selected strains of Streptococcus thermophilus in combination with Bifidobacterium longum or Propionibacterium freudenreichii subsp. shermanii followed by fermentation at 30°C and 37°C for 12 and 18 h. 5-MTHF was determined by HPLC method after deconjugation with hog kidney conjugase and SPE SAX purification. The highest 5-MTHF content increase of 4.03 ± 0.44 µg/100 g was found at cofermentation with Streptococcus thermophilus No. 144 and Propionibacterium freudenreichii subsp. shermanii No. 160 at 37°C after 12 h of fermentation. 9 commercial fruit components used in dairy industry contained between 0.17-9.11 µg 5-MTHF/100 g. The components produced with pineapple, sour cherry, apricot, and apple contained low amounts of 5-MTHF - less than 1 µg/100 g. Among the rest of the components tested, the strawberry component proved to be the best source of folate with the content of 9.11 µg 5-MTHF/100 g. The values in 7 varieties of fresh fully ripe strawberries fluctuated between 25.5 and 54.0 µg/100 g fresh sample, i.e. 272 and 554 µg/100 g dry matter with the highest content found in the varieties Elsanta and Honeyoe. Fully ripe berries of the variety Senga Sengana contained by 63% more 5-MTHF in comparison with unripe berries. In order to reach maximum folate content in the fruit component, fully ripe strawberries of the cultivars Elsanta and Honeyoe are recommended for the processing. The folate content in the fermented milk product may be increased in this way by 4.8 µg/100 g, with 69% originating from the fermentation and 31% from the fruit component addition.