Osmoporation of fisetin into probiotic bacteria cells (Lactobacillus acidophilus): process parameters, bioaccessibility and incorporation into dairy beverage.
dairy fermented products; microencapsulation; biotechnology; functional foods.
This study investigates the encapsulation of hydrophobic fisetin into probiotic Lactobacillus acidophilus bacteria cells. Initially, the influence of selected process parameters (fisetin concentration and osmotic pressure) on the encapsulation efficiency was evaluated. Furthermore, the structural characterization (determined by FT-IR and DSC techniques), bioaccessibility of the biocapsules, as well as the acidifying activity performance of L. acidophilus in a dairy beverage (model food) were investigated. Results show that the highest encapsulation efficiency (28%) was achieved at fisetin concentration of 2 mg.ml-1 and osmotic pressure 15 MPa. Additionally, differential exploratory calorimetry curves (DSC) demonstrated an effective fisetin internalization into cell cytoplasm and its adsorption onto cell surface. The in vitro gastrointestinal simulation showed that the bioaccessibility of encapsulated fisetin was 45.9%, while free fisetin reached only 0.7%. When fisetin biocapsules were added to milk, the fisetin content released during milk fermentation substantially increased the antioxidant activity of the final fermented beverage (95.3%) for 14 days and the encapsulated fisetin content remained high (85%) for 28 days. Overall, the results prove that fisetin osmoporation into L. acidophilus cells is a simple and efficient technique that enables phytoactive protection for food industry applications