Management of Surface Drying Temperature to Increase Antioxidant Capacity of Thyme Leaf Extracts (Thymus vulgaris L.)

[EN] Thyme leaves are an important source of essential oils with antioxidant activity; these compounds are located in trichomes on the leaf surface. The drying conditions affect not only the drying time but also the antioxidant activity. In the literature, a drying temperature of 70 ºC appears to be the best for drying thyme leaves according to their antioxidant capacity. Considering drying periods at different temperature also could be quality beneficial. From these considerations, the goal of this work was to establish a drying strategy with which to manage a drying temperature on the leaf surface which will enable the drying time to be shortened and improve the antioxidant capacity (AC) of the extract of dried thyme leaves. The drying strategy consisted of two consecutive drying periods in order to manage the drying temperature on the leaf surface. The first drying period was carried out at 80°C (Ta1) until the sample surface reached a temperature of 70 ºC, which then immediately being set to 70, 60, 50 and 40 °C (second drying period (Ta2)), at a different air velocity (v) (1 and 2 m s-1). Compared with constant drying conditions, two consecutive drying periods were found to improve the drying kinetics, the AC increased from 10.5% to 27.4 % while reducing the drying time by 14.5% to 39.2 %. The use of this drying strategy was found to be an interesting means of intensifying the convective drying of thyme leaves and its application should be considered when drying similar materials with bioactive compounds on the surface.The authors of this work acknowledge financial support from the "Ministerio de Educacion y Ciencia" in Spain, Consolider Ingenio 2010 (CSD2007-00016) and PROMETEO/2010/062.Rodríguez Cortina, J.; Melo, E.; Mulet Pons, A.; Bon Corbín, J. (2014). Management of Surface Drying Temperature to Increase Antioxidant Capacity of Thyme Leaf Extracts (Thymus vulgaris L.). Drying Technology. 32(16):1931-1941. https://doi.org/10.1080/07373937.2014.917094S19311941321

Role of friction in pattern formation in oscillated granular layers

Particles in granular flows are often modeled as frictionless (smooth) inelastic spheres; however, there exist no frictionless grains, just as there are no elastic grains. Our molecular dynamics simulations reveal that friction is essential for realistic modeling of vertically oscillated granular layers: simulations of frictionless particles yield patterns with an onset at a container acceleration about 30% smaller than that observed in experiments and simulations with friction. More importantly, even though square and hexagonal patterns form for a wide range of the oscillation parameters in experiments and in our simulations of frictional inelastic particles, only stripe patterns form in the simulations without friction, even if the inelasticity is increased to obtain as much dissipation as in frictional particles. We also consider the effect of particle friction on the shock wave that forms each time the granular layer strikes the container. While a shock wave still forms for frictionless particles, the height and time dependence of the hydrodynamic fields differ for the cases with and without friction.Comment: final version appeared in Phys. Rev.

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

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