SYNERGISTIC EFFECT OF BIOACTIVE COMPONENTS IN INCLUSION COMPLEXES FOR ANTIMICROBIAL APPLICATIONS

Presentation: Oral(x) Poster (x)
E-mail: [email protected]

Essential oils have been constantly studied and applied in food products nowadays. Their flavoring capabilities along with their antimicrobial and antioxidant properties make them an interesting and powerful option as natural preservatives. However, the direct application of essential oils in food products frequently presents some technological limitations, mainly regarding to their low solubility, heat sensitivity, and instability. In order to overcome these limitations, the microencapsulation through production of inclusion complexes guarantees the increase of essential oil’s stability and provides novel application possibilities. In this context, the aim of the present work was to produce hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complexes containing cinnamaldehyde and citral, as bioactive components, and to evaluate their synergistic effect on the antimicrobial activity against Listeria monocytogenes and Salmonella Choleraesuis. The inclusion complexes containing cinnamaldehyde, citral, and the mixture of them, in the equimolar ratio of 1: 1, in HPβCD, were prepared by the freeze-drying method. The formation of the inclusion complexes containing the bioactive components was evaluated using the UV-VIS spectrophotometer and Fourier-transform infrared spectroscopy (FTIR). The minimum inhibitory concentration capable of inhibiting 50% of microbial samples (MIC50) and minimum bactericidal concentration (MBC) of Listeria monocytogenes (ATCC 15313) and Salmonella Choleraesuis (ATCC 10708) was determined using the macrodilution in broth method with the subsequent total bacterial count. The formation of the inclusion complexes containing the bioactive components was confirmed using the bathochromic shift and the hyperchromic effect of the HPβCD maximum absorbance peaks. This effect suggests the formation of new interactions between the encapsulating material and the guest molecule, increasing the absorbance intensity and shifting the HPβCD peak with maximum absorbance to a higher energy wavelength. Using medium infrared spectra, it was possible to prove the formation of inclusion complexes after changing the specific peak intensity of hydroxypropyl-β-cyclodextrin and identifying the characteristic peaks of the bioactive compounds in the inclusion complexes formed. In the antimicrobial activity, the free bioactive components showed lower MIC50 and MBC compared to the inclusion complexes containing the cinnamaldehyde and citral mixture. This result was associated to the limited release of the bioactive components into the culture media, due to the strong interactions with the polymer matrix. Also, the mixture of the bioactive components, in both free and complexed forms, did not present a synergistic effect for the antimicrobial activity against Listeria monocytogenes and Salmonella Choleraesuis. Hence, it was concluded that the inclusion complexes containing the bioactive components present potential to be used in food processing due to the effective formation of inclusion complexes and antimicrobial activity against the two microorganisms evaluated.

The authors would like to acknowledge CAPES, CNPq, FAPEMIG and Finep for financial support.