The current study deals with an innovation in the hot air convective drying process consisting of the application of two consecutive drying steps. Temperatures ranging between 60 and 80 ℃ for times between 200 and 600 s were applied for the first stage, and from 40 to 80 ℃ for the second stage. Salvia officinalis, an aromatic, medicinal Mediterranean plant with remarkable antioxidant properties, was selected for this study. A management of the process regarding the antioxidant capacity of S. officinalis extracts and energy consumption was carried out: (i) artificial neural networks were applied to model the evolution of the antioxidant capacity and moisture content of the product in the drying process; (ii) a genetic algorithm and a multiobjective genetic algorithm were selected to optimize the drying process, considering the antioxidant capacity and/or the energy consumption in the objective function. The results showed that the optimum values depended, logically, on the controllable variables values (hot air temperatures and drying times), but also on the uncontrollable variable values (room air temperature and relative humidity and the product's initial mass and moisture content).
Water shortage throughout the world, especially in arid regions in the later decades has led to search for alternatives to save potable fresh water. Treated wastewater (TWW) appears to be an opportunity for irrigation. However, it could represent a stress factor for plants, and influence their metabolism, changing their secondary metabolites and, consequently, their biological properties. Eucalyptus camaldulensis essential oil (EO) had been reported to possess phytotoxic activity. The main objective of this work was to compare the chemical composition and herbicidal activity of E. camaldulensis EO obtained from leaves of young plants and old trees irrigated with well water (WW) and TWW. Germination tests were performed in vitro against Amaranthus hybridus, Chenopodium album, Echinochloa crus-galli and Lolium perenne. The EOs composition was analyzed by gas chromatography and gas chromatography/mass spectrometry. A high percentage of oxygenated monoterpenes, with 1,8-cineole as main compound, was found in the EOs from leaves of young plants irrigated with both types of water. The EO from leaves of old trees irrigated with WW contained a main fraction of monoterpene hydrocarbons (45.17%) with p-cymene as principal compound. The highest herbicidal potential was shown by the EO from young plants irrigated with TWW. It completely inhibited A. hybridus and L. perenne germination, and nearly blocked the others at all concentrations assayed. It also showed strong phytotoxic activity on seedling length. The results suggest the possible use of TWW to irrigate Eucalyptus crops as it enhances the EOs herbicidal potential that could be used as natural herbicides.
In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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