Impact of saline treatment on the biosorption and bioaccessibility of bioactive compounds from fruit juice residues using brewer's yeast

The growing consumer demand for health-promoting food products has driven the industry to identify novel sources of bioactive compounds. In this regard, by-products derived from juice processing, as well as brewer’s spent yeast, a residual biomass originating from the beer brewing process, constitute promising materials for valorization and bioactive compound recovery. In this context, this study aimed to evaluate the biosorption of bioactive compounds from red fruit juice residues into modified and unmodified Saccharomyces cerevisiae . The ethanolic extracts from grape, strawberry, and blackberry juice residues (EGJR, ESJR, and EBJR, respectively) showed higher concentrations of phenolic compounds, anthocyanins, and flavonoids in their composition. In comparison to unmodified yeasts (UY), salt-treated yeasts (STY) retained a higher concentration of phenolic compounds after biosorption and, in general, also reached the sorption equilibrium faster. The pseudo-second-order model best described the kinetic data. The biosorption data of STY with the evaluated compounds were best fitted by the Langmuir isotherm model. The SEM, XRD, and MIR-ATR analyses showed significant changes in STY and UY after the biosorption of phenolic compounds, indicating their incorporation into the biomass. During in vitro gastrointestinal digestion, the extracts had a bioaccessibility of less than 8%. On the other hand, the phenolic compounds from EGJR, ESJR, and EBJR biosorbed onto unmodified and salt-treated yeasts (UY and STY, respectively) showed bioaccessibility values ranging from 24.73% to 68.79%. These results indicate that the interaction between the bioactive compounds and yeast biomass can enhance the protection and subsequent release of phenolics during digestion, thereby improving their potential bioavailability in the human body. Besides biosorbing a higher concentration of phenolic compounds, STY was also able to protect these compounds during gastrointestinal digestion, thereby achieving higher bioaccessibility. Thus, the treatment of yeast with a concentrated saline solution can be considered promising, as it is a cheap, simple, and non-toxic technique that adds value to agro-industrial residues. • Agro-industrial residues were reused as sources of bioactive compounds. • Salt-treated yeast improved phenolic compound biosorption and kinetics. • Bioaccessibility increased after adsorption onto yeast. • Salt treatment is a simple, low-cost method to enhance bioactive retention.