RESUMEN
Fusarium wilt, a vascular syndrome in a wide range of plants, is caused by the pathogen Fusarium Oxysporum. The objective of this investigation was to evaluate the antifungal effect of four essential oils (EOs) (Plectranthus amboinicus, Syzygium aromaticum, Lippia alba, and Rosmarinus officinalis), which were obtained by using microwave-assisted hydrodistillation (MAH), against F. oxysporum. The yield obtained from P. amboinicus with the use of MAH was 0.2%, which was higher than that of a conventional extraction; its extraction time was also shorter. For concentrations of 100 and 300 µL/L, P. amboinicus caused an inhibition rate of 27.2 and 55.7%, respectively, while S. aromaticum caused an inhibition rate of 23.1 and 87.3%, respectively. It was observed that increasing the concentration also increased the % inhibition rate. The extracts of L. alba and R. officinalis caused an inhibition rate of 14.5 and 14.7% at 500 µL/L, respectively, at 10 days of incubation, while at this concentration, P. amboinicus and S. aromaticum achieved 100%. The major chemical compounds of P. amboinicus were carvacrol (41.20%), o-cymene (11.61%), caryophyllene (11.45%), α-bergamotene (7.71%), and caryophyllene oxide (4.62%), and these monoterpene hydrocarbons were responsible for the biological activity. The essential oil of P. amboinicus in appropriate concentrations is a potent antifungal agent that could be used for the control of F. oxysporum.
RESUMEN
The curing process (CP) of Vanilla planifolia pods, which is a long and tedious process, is necessary to obtain the natural vanilla extract. This research evaluated the application of microwave (M) and ultrasound (U) during the "killing" stage of the CP and its effect on vanillin content and ß-glucosidase activity. The pods were immersed in a container with water or with moistened samples for the M treatments. In U treatments, the pods were immersed in an ultrasonic bath. After this stage, the samples were subjected to an additional U treatment. The results show that the application of these technologies significantly improves vanillin yield (p < 0.05) and the curing time is reduced to 20 days. U treatments subjected to additional sonication at 38 °C obtain more than double the yield of vanillin regarding control. The effect of M and U on cell structure damage increases with additional sonication, but at 15 min, ß-glucosidase inactivation decreases the final yield. Disposition of samples in M also affects the final vanillin content. There is no significant correlation between ß-glucosidase and vanillin in the different treatments. The application of M and U with the appropriate parameters reduces the CP time without affecting the compounds of interest.
RESUMEN
This study evaluated the effectiveness of spraying juices, during shortwave ultraviolet irradiation (UVC) treatments as an alternative to promote more contact area, by means of ultrasonic atomization (UA) and pneumatic atomization (PA). Four juices with dissimilar physical characteristics were processed to assess the effect of suspended solids and turbidity. Antioxidant activity, anthocyanins, ascorbic acid, and inactivation of Saccharomyces cerevisiae inoculated in the juices were evaluated. Five decimal reduction cycles were reached after two passes of orange or grapefruit juice through the UVC + UA arrangement. On the other hand, five decimal reduction cycles were achieved after three passes in the UVC + PA arrangement. Losses of 11% and 14% of ascorbic acid were observed in orange and grapefruit juice, respectively, while anthocyanin content presented losses of 50% and antioxidant activity decreased by 40% for pomegranate and blueberry juice, correspondingly.
