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Keywords:

  • antimicrobial activity;
  • antioxidant activity;
  • black pepper oleoresin;
  • hydroxypropyl beta-cyclodextrin inclusion complex;
  • nano-encapsulation

Abstract

Previous studies have reported antimicrobial and antioxidant activity of black pepper oleoresin which is associated to its phenolic compounds and piperine. The ability of cyclodextrins to form an inclusion complex with a guest molecule could improve black pepper oleoresin application, bioavailability, and stability in foods. Hydroxypropyl beta-cyclodextrin (HPBCD) inclusion complex with black pepper olereosin were synthesized using the kneading method and characterized for its physico-chemical properties and its antioxidant and antimicrobial activities. Inclusion complex size was 103.9 ± 7.6 nm and indicated to be a polydisperse system. The entrapment efficiency was 78.3 ± 3.6%, which suggests that other constituents in black pepper oleoresin have higher affinities for HPBCD than piperine (major compound in black pepper oleoresin). Thermograms showed the disappearance of oxidation peaks of black pepper oleoresin, proving complex formation with HPBCD. Phase solubility results indicated 1:1 stoichiometric inclusion complex formation and an increase of black pepper oleoresin aqueous solubility with HPBCD concentration. Nano-encapsulation with HPBCD did not affect (P > 0.05) total phenolic content; however, it enhanced (P < 0.05) black pepper oleoresin antioxidant activity. Black pepper oleoresin and its inclusion complex were analyzed for their antimicrobial activity against Escherichia coli K12 and Salmonella enterica serovar Typhimurium LT2. Both free and encapsulated black pepper oleoresin effectively inhibited bacterial growth within the concentration range tested. Black pepper oleoresin encapsulated in HPBCD was able to inhibit Salmonella at lower (P < 0.05) concentrations than its corresponding free extract. Therefore, black pepper oleoresin-HPBCD nanocapsules could have important applications in the food industry as antimicrobial and antioxidant system.

Practical Application

Nano-encapsulation of plant extracts has great potential for improving their effectiveness as antioxidants and antimicrobials in food systems. Furthermore, it can protect plant extract against degradation and convert them into a free-flowing powder. This study evaluated nano-encapsulation of black pepper oleoresin using HPBCD. Nano-encapsulation improved black pepper oleoresin water solubility and its antioxidant activity. Nano-encapsulated black pepper oleoresin was able to inhibit Salmonella spp. at a lower concentration than free black pepper oleoresin, enhancing its inhibition effect. Results indicate that black pepper oleoresin nano-encapsulation with HPBCD could be a useful antioxidant and antimicrobial delivery system with a broad spectrum of applications.