Improving Osmoporation: the impact of processing steps on the stability of phenolic compounds during encapsulation into Saccharomyces boulardii Cells

Fruit-derived phenolics are well-known for their antioxidant properties and potential health benefits, yet their labile nature and sensitivity to oxidation during processing jeopardize their stability and potential application into food products. Osmoporation is a versatile technique that promotes the internalization of target molecules into yeast cells based on the cell’s osmoregulatory responses to osmotic perturbations. Encapsulation techniques, such as osmoporation, can improve the stability of total phenolics (TP) by creating physical protection for these molecules, however it is crucial to understand the impact of the encapsulation process itself on the TP. The primary aim of this study is to evaluate the effects of key processing steps (ultrasound treatment, microfiltration and freezing) on the preservation of acerola pomace-derived TP during osmoporation into Saccharomyces boulardii cells. TP-rich extract was prepared from acerola pomace and used for osmoporation on S. boulardii. To assess the impact of ultrasound, acerola extract was subjected to ultrasound treatment (40 kHz) for 10 min or 20 min, followed by microfiltration (0.45 µm). Freezing tests (-18°C/16h) were carried right after osmoporation protocol. After each process, TP was assessed by the Folin-Ciocalteu method. Ultrasonic treatments and microfiltration did not significantly affect the TP content of the acerola extract, indicating that these processes preserve the integrity of encapsulated phenolic compounds. On the other hand, results showed that freezing (-18°C/16h) after osmoporation led to a substantial loss of phenolic compounds, ranging from 9.5% to 27.3%. This finding suggests that the destabilization resulting from the osmoporation process may facilitate degradation during freezing/thawing, prompting the recommendation to avoid freezing post-osmoporation. In conclusion, while post-osmoporation freezing is detrimental to TP stability, ultrasound and microfiltration showed high TP recovery. Further research is required to explore the mechanisms underlying phenolic compound degradation during post-osmoporation freezing and identify potential optimizations to enhance TP stability.