Caseinates loaded with Brazilian red propolis extract: preparation, protein-flavonoids interaction, antioxidant and antibacterial activities

This study aimed to evaluate the physical–chemical properties (particle size, zeta potential, encapsulation, and thermal stability), antioxidant properties, antibacterial properties and casein-flavonoid interaction studies of soluble complexes, called caseinates of red propolis. The caseinates of red propolis were successfully prepared using the spray-dryer technique, which presented two populations of nanometre and micrometre particles, and were able to encapsulate flavonoids and isoflavonoids from the red propolis extract as a soluble complex. SEM analysis demonstrated casein nanoparticles and fat globules combined with lipophilic compounds (terpenes) from red propolis extract. FTIR analysis proved the encapsulation of flavonoids into caseinates. The thermogravimetric assays demonstrated thermal stability of red propolis caseinates and DTA analysis observed the denaturation during the coagulation temperature. The fluorescence, antioxidant, Folin–Ciocalteu method and chromatographic assays have shown that flavonoids bind to the amino acid residues present in the casein protein matrix, demonstrating a reversible interaction between flavonoids and casein amino acids. Dissolution studies prove the formation of a casein-flavonoids soluble complex and can bring benefits and increase the process of absorption of flavonoids by biological membranes. Despite the interaction of flavonoids with casein amino acids, caseinates of red propolis demonstrated antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. The caseinates of red propolis can be easily incorporated in foods such as cakes, pies, dairy and cocoa such as foods bio-preservatives. The caseinates of red propolis can be manufactured by the pharmaceutical and nutraceuticals industries as intermediary bioproduct in the powder form for supplements, capsules and oral emulsion systems for beverages as yogurts.