Obtenção de extratos de folhas de oliveira para aplicação como agente antimicrobiano em embalagens biodegradáveis ativas

Abstract

This work had as objective to obtain extracts of olive leaves (OLE) through the technique of extraction assisted by microwaves for later application of the extracts obtained in the elaboration of active biodegradable films. The extraction process, as well as the influence of the process parameters on the content of bioactive compounds present in the aqueous extract, were studied using design of experiments. The content of total phenolic compounds (PC), the antioxidant activity (AA), the antimicrobial activity of OLE against Escherichia coli (E. coli) and the content of oleuropein obtained under optimal conditions of extraction were the responses evaluated. In addition, methods of extraction by maceration and assisted by ultrasound to obtain olive leaf extracts were studied. Afterwards, carrageenan films were made with and without the addition of OLE by the casting method. The films were evaluated for color, solubility, thickness, water vapor permeability and mechanical properties. The protective effect of films against antimicrobial activity on lamb meat packaging was also evaluated. The optimal conditions for microwave assisted extraction, using the desirability statistical tool, were: 100°C, 2 min and pH 6. Under these conditions it is possible to obtain AA of 92.87%, PC of 103.87 mgGAE.g–¹ (d.b), in addition to antimicrobial activity against E. coli, with a minimum inhibitory concentration value of 50 mg.mL-¹ and oleuropein content of 11.59 mg.g-¹ (d.b). When compared to the extraction technologies by maceration and ultrasound, the microwave technology proved to be more efficient, presenting a greater recovery of bioactive compounds of interest. The incorporation of OLE in the carrageenan matrix caused changes in the properties of the films, with an increase in thickness, elongation and permeability to water vapor, and a decrease in the tensile strength and elasticity modulus of the film. The solubility was not significantly affected by the addition of OLE, however the color difference with the addition of OLE was 64.72%. Another important result was the in vivo analysis of psychrophiles, that is, when applied to the packaging of lamb meat, carrageenan films with extract had an inhibitory effect on the count of psychrophiles. The study revealed the benefits of olive leaf extract, obtained by microwave incorporated in films based on carrageenan with potential for application as active packaging.