Exploitation of yeast fermentation to convert citrus by-products into a functional ingredient for beverages

Citrus processing residues account for over 70% of the total fruit weight. To valorise these by-products, microbial fermentation offers a promising strategy to induce chemical and physical modifications that enhance the bioavailability of residual nutritional and nutraceutical compounds, thus enabling their reuse in food sector. This study focuses on the development of an orange-carrot-lemon beverage enriched with a fermented clementine peel as an innovative functional ingredient, obtained using a selected strain of Saccharomyces cerevisiae. Yeast selection involved 27 strains of Saccharomyces and non-Saccharomyces species and was based on their ability to ferment the residue in terms of cell viability, growth rate, modification of the volatile sensory profile, and increase in phenolic content. A S. cerevisiae strain was ultimately selected for its greater performances. The functional ingredient was produced by fermenting clementine peel for two days, followed by freeze-drying. It was then added to the beverage at different concentrations (1, 1.5, 2, and 3% w/v). The effects of ingredient addition were assessed in terms of changes in colour, volatile profile, phenolic and β-carotene content, antioxidant activity, and sensory attributes. Results showed a significant increase (p < 0.05) in total phenolics and β-carotene contents following the ingredient addition. Furthermore, the aroma profile was enhanced due to high levels of terpenes such as 3- carene and bergamotene, resulting from the metabolic activity of the selected yeast strain. Sensory panel evaluations highlighted improved pleasantness and aromatic complexity in the ingredient-added beverages compared to the control one. In conclusion, this research significantly contributes to the circular bioeconomy by offering an effective strategy for valorising agro-food by-products. The findings pave the way for innovative, healthy, and distinctive food products, supporting industry demands and global sustainability goals.