Unlocking the potential of oil by-products: Investigating the influence of co-culture fermentation on phenolic acid degradation in side stream blends from oil and dairy industry

According to the newest trends in food waste management, the priority for valorisation of oil and dairy industry by-products was recognised. New approach of blending side streams of plant and animal origin has been pro- posed for obtaining future foods with improved nutritional value. Major obstacle in valorising sunflower seed cake (SSC) and whey (W) is their perishability and a relatively high content of phenolics contributing to, among others, protein indigestibility. In the study, a new approach of microwave pre-treatment applied for SSC and W blends was used. Its influence on phenolic acids and antioxidant properties after fermentation with co-culture of lactic acid bacteria and yeast was examined. Microwave drying of blends was longer than that of SSC affecting phenolic acids content. Fermentation by L. lactis and K. lactis caused pH decrease and increase in total acidity in 48 h effectively limiting the growth of bacterial contaminants. Fermentation decreased the content of phenolic acids, especially in blend composed of SSC and W (8.75:1; w/w) with the highest content of these constituents (from 1611.3 down to 838.8 mg/100 g dry matter). The study showed the synergistic effect of pre-treatment method and fermentation in terms of reduction in phenolic acids in new food matrices.