Revestimentos comestíveis à base de quitosana e extratos de Curcuma longa L. em uvas tipo Vitória : preparação, caracterização e aplicação

Abstract

Several fruit preservation techniques have been used to reduce waste. The use of edible coatings has attracted the attention of producers, traders and researchers, as it is an innovative technology to extend the commercial life of both fruits and vegetables. The properties of these coatings can be optimized with the addition of bioactive compounds such as Curcuma longa L. extracts, in order to provide the chitosan film with antioxidant and antimicrobial action, thus improving the quality and shelf life of the Vitória grape used as a test, originating from Petrolina-PE. Turmeric extracts using different solvents (ethanol ExEt, vinegar ExV and the mixture between both in the proportion 1:1 v/v ExEtV) were prepared and added to a chitosan solution at 2% m/v to obtain formulations in concentrations of 16, 28 and 37% v/v of extracts. In the extraction process, ethanol proved to be very efficient in releasing curcuminoid pigments, followed by the solvent mixture (ethanol:vinegar). The extracts and chitosan:extracts formulations were characterized by Fourier transform infrared spectroscopy (FTIR) and molecular absorption spectroscopy in the ultraviolet-visible (UV-Vis) region. Through these spectra, it was possible to identify curcumin as the main bioactive present in the largest quantity in the turmeric under study. Zeta potential analysis showed that all formulations containing chitosan solution, except Q37ExV, presented values greater than +30mV, demonstrating the importance of chitosan in the balance and stability of the nanoparticles; also giving the formulations the viscosity necessary for coating the fruit. Regarding antimicrobial activity, the Q37ExEtV formulation showed relevant results, since in addition to promoting biocidal action against Escherichia coli ATCC 25922 and Candida albicans ATCC 76645, it showed activity with a high percentage of reduction above 93% against Staphylococcus aureus ATCC 13150 and Pseudomonas aeruginosa ATCC 25783. The other formulations (Q37ExEt and Q37ExV) also showed positive results, conferring bactericidal and fungicidal properties. QBase did not show antioxidant activity (AA), but the chitosan formulations containing ExEt showed good results, presenting increasing values as the amount of extracts in the sample increased (Q37ExEt, 75%). Satisfactory values were also achieved for the Q37ExEtV formulations. Finally, the Vitória grapes after coating were analyzed for their physicochemical properties over 21 days. Through this study, it was possible to demonstrate that the ExEt extract, as well as the Q37ExEt formulation, promoted greater stability to the physical-chemical parameters of the fruit, as a consequence of the promising results related to the efficiency of ethanol in the curcuminoid extraction process, as proven through the antioxidant response of the formulations. This effect is also due to the formation of coatings with protective characteristics that favor the maintenance of quality, tending to extend the shelf life of the grape, which was not observed with the Q37ExEtV coating, despite the excellent results of antioxidant and antimicrobial activity.