Strawberry tree fruit fermentation using the probiotic Saccharomyces boulardii

Strawberry tree (Arbutus unedo) fruits are traditionally used in herbal/folk medicine or in the preparation of jams and alcoholic beverages . Fermentation is a microbial process that transforms the substrate, but also it may increase the nutrient bioavailability and alter the antioxidant properties of the fermented product.

Ripe fruits from a strawberry tree were freeze-dried, reconstituted in water (1:4), pasteurized, inoculated with the probiotic strain Saccharomyces cerevisiae boulardii, and incubated at 20 °C for 8 days. Samples collected before and after fermentation were centrifuged for further analysis.

Yeast growth reached 6.8*10⁷ cfu/mL and the carbohydrate content reduced from 17.5 to 12.5⁰ Brix after the fermentation. The antioxidant activity increased (from 83 to 86 %DA_515nm), but the total amount of phenolics decreased in the supernatant, while no changes were observed in the precipitate. HPLC analysis identified 32 phenolic compounds in the precipitate with no significant differences after fermentation. Color measurements (L*, a*, b*) revealed a slight change, likely due to phenolic oxidation.

The above results indicate the potential utilization of strawberry tree fruits for the growth of the probiotic strain S. boulardii, which ferments the fruits while preserving their antioxidant properties. This S. boulardii–fermented matrix offers a promising platform for crafting new functional food products.