Production and characterization of propolis loaded polivinil alcohol nanoparticles with electrospraying method

Propolis is a natural substance which is produced from gums of various plants by honeybees, possesses various phytochemicals such as flavonoids, cinnamic acid and derivatives, steroids and amino acids as well as volatile aldehydes and ketones and is characterized by several bioactive properties such as antioxidative, antimicrobial and antitumor. Due insolubility of propolis in water, its use in foods as a functional additive is limited. Encapsulation is one of the techniques commonly used for making water-insoluble bioactive substances soluble in water. In this study, propolis extract was encapsulated in polyvinyl alcohol (PVA), a water-soluble polymer, at nano scale at different concentrations (0%, 0.4%, 0.8%; 1%, 1.2%) by using electrospraying method. Electrospraying conditions were optimized with preliminary studies conducted. Size and zetapotential values, encapsulation efficiency, SEM, DSC and FTIR characteristics, antioxidant and antimicrobial activities of the propolis loaded nanocapsules obtained under optimal conditions were analyzed. The zetapotential values and particle sizes of the nanocapsules ranged from -5 to +5 mV and 104 nm to 258 nm, respectively. The polydispersity index values of the samples below 0.357 showed that the size distribution of the nanoparticles was homogeneous. Encapsulation efficiency of the nanoparticles was found below 23 %. As a result of thermal characterization with DSC, it was observed that the PVA nanoparticles increased the thermal stability of propolis. It was determined that the PVA nanoparticles loaded with propolis showed DPPH radical scavenging activity in the range of 80% and 89%. As a result of the antimicrobial activity tests, it was determined that S. aureus, a gram-positive bacterium, was highly inhibited against propolis-containing nanocapsules even at low concentration ratios while the activity against gram-negative Escherichia coli O157: H7 was limited. As conclusion of this study, it is revealed that propolis could be used as a water soluble functional additive in the food industry by encapsulating in nano scale by electrospraying method.