Aplicação de filmes com nanopartículas de prata na conservação de morangos

Abstract

The consumption of fruits and vegetables has been growing due to the efforts for a healthier diet. In this context, strawberry can be highlighted for its nutritional value and for being a tasty and attractive fruit. However, on Brazil conditions, for being harvested near its physiological maturity, losses in post-harvest quality are high. Polymeric films containing metal nanoparticles (NPs) have been used in food packaging, once they present properties that contribute in maintaining the quality of fruits and vegetables. For instance, silver nanoparticles (AgNPs) stands out for its antimicrobial action. The goal of this work was to evaluate the post-harvest quality of strawberries packed in polymeric films containing AgNPs and conventional net polymeric films (without NPs). For this purpose, commercial low-density polyethylene films (LDPE) containing AgNPs were characterized by scanning electron microscopy (SEM), Infrared Spectroscopy Fourier Transform (FTIR), thermogravimetry (TGA), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD), antimicrobial activity tests. For evaluating the films influence on the physical-chemical and microbiological quality of strawberry, the following experiments were performed: (I) strawberry packaged in LDPE and LDPE+AgNP films were stored in cold chamber at 5 and 25 °C for nine days, where physical-chemical and microbiological analyzes were carried out at every three days; (II) Strawberry packaged by LDPE and LDPE+AgNP films were stored in cold chamber at 5 and 25 °C for nine days, and were submitted to the same physicalchemical analysis. To investigate in more details the antimicrobial effects of packaging, two experiments were carried out with strawberry inoculated by E. coli: (III) firstly, strawberry inoculated with E. coli with an initial concentration of 108 CFU mL-1 were stored at 5°C for ten days; subsequently, the physical-chemistry and microbiological analyses were carried out; and (IV) strawberry inoculated with E. coli with an initial concentration at 105 CFU mL-1 were stored at 10°C for ten days; subsequently, the microbiological analyses were carried out at every two days. Adding AgNPs on LDPE matrix did not influence the thermal and physical-chemical properties of films. Films containing AgNPs showed antimicrobial activity against Gram-positive and Gramnegative microrganims. Physical-chemical quality of strawberry was affected mainly by temperature and storage period. AgNPs contained in LDPE packaging was efficient on controlling microbial population growth. Antimicrobial activity and post-harvest quality attained by polyetilene films containing AgNPs may be an indicative for using such Aplicação de filmes com nanopartículas de prata na conservação de morangos type of active packing for other fruits and vegetables, which can help decreasing post harvest losses, and may contribute to improve food safety.