Ethephon and fosetyl residues in fruits from São Francisco Valley,Brazil

ABSTRACT

This survey describes the occurrence of Ethephon (ETH) and Fosetyl in fruits intended for export produced in the São Francisco Valley, Brazil. The determination of these compounds was carried out by the QuPPe-method (Quick Polar Pesticides Method), which was optimised and successfully validated according to the SANTE/11813/2017. From January 2016 to December 2018 a total of 1048 samples were analysed for ETH residues. In 547 (53%) of the samples, residues below the EU MRL of 1 mg kg^?1 were present. In 17 samples (2%) ETH residues were above 1 mg kg^?1. Overall, the mean ETH level decreased after 2016. Analyses of fosetyl showed that (18%) of 109 mango samples were positive for this compound. Phosphonic acid was found in concentrations ranging from 0.12 to 3.2 mg kg^?1 and 5% of the measurements were above the EU MRL of 2 mg kg^?1. The results emphasise the quality control of fruits produced in this region.     

Antitumour properties of the leaf essential oil of Xylopia frutescens Aubl. (Annonaceae)

The aim of this study was to investigate the chemical composition and anticancer effect of the leaf essential oil of Xylopia frutescens in experimental models. The chemical composition of the essential oil was analysed by GC/FID and GC/MS. In vitro cytotoxic activity of the essential oil was determined on cultured tumour cells. In vivo antitumour activity was assessed in Sarcoma 180-bearing mice. The major compounds identified were (E)-caryophyllene (31.48%), bicyclogermacrene (15.13%), germacrene D (9.66%), δ-cadinene (5.44%), viridiflorene (5.09%) and α-copaene (4.35%). In vitro study of the essential oil displayed cytotoxicity on tumour cell lines and showed IC₅₀ values ranging from 24.6 to 40.0 μg/ml for the NCI-H358M and PC-3M cell lines, respectively. In the in vivo antitumour study, tumour growth inhibition rates were 31.0–37.5%. In summary, the essential oil was dominated by sesquiterpene constituents and has some interesting anticancer activity.     

Thermal and mechanical properties of the açaí fiber/natural rubber composites

The açaí fruit industrial processing produces a large amount of waste, mainly seeds and fibers, which is a serious environmental and public health problem. The objective of this work was to use these fibers to obtain composites with natural rubber from different clones. The effect of the addition of açaí fibers and the type of clone were investigated using thermogravimetric analysis (TGA) under inert and oxidative atmospheres, differential scanning calorimetry (DSC), water sorption, and mechanical properties. The açaí fibers exhibited a thermal behavior comparable to other natural fibers industrially used in polymeric composites. The addition of the fibers did not influence the thermal stability of the composites. There was no significant effect of the type of clone and the addition of the fiber on the glass transition temperature, which was approximately ?59 °C for all samples. Water sorption behavior of the compounds and of the composites was similar to that of the other materials with natural rubber that are reported in the literature. The promising performance of the composites with açaí fibers opens a new area of use for such fibers.     

Uptake-curves for the determination of diffusion coefficients and sorption equilibria for n-alkanes on zeolites

Sorption capacities and diffusion coefficients were measured for n-alkanes on a 5A-zeolite and ZSM-5 with a gravimetric setup. Significant heat effects were observed during the experimental determination of diffusion coefficients, which complicate the interpretation and the analysis of the experimental Uptake-curves. This effect depends significantly of the sorption rate, heat of adsorption and dissipation of heat. Taking into account these heat effects, reliable transport coefficients can be extracted. These agree well with diffusion coefficients obtained from other techniques, like PFG–NMR or ZLC. With the carbon chain-length the measured diffusivities decrease from 1.6 × 10⁻¹² to 0.5 × 10⁻¹² m²/s for propane to n-hexane for 5A-zeolite at 473 K. For n-butane and n-hexane values about 8 × 10⁻¹¹ and 4.6 × 10⁻¹¹ m²/s on MFI-type zeolites at 303 K are measured.From the equilibrium data, heats of adsorption were calculated and compared with literature data. The heat of adsorption for 5A-zeolite changes with the carbon chain-length from 32 to 44 kJ/mol for n-butane to n-octane, respectively. The heats of adsorption of alkanes on ZSM-5 were 60 kJ/mol for n-butane and 57 kJ/mol for hexane. Due to different adsorption sites in MFI-type zeolites two heats of adsorption were calculated for each alkane.     

Profiles of xylose reductase,xylitol dehydrogenase and xylitol production under different oxygen transfer volumetric coefficient values

BACKGROUND: Xylitol is a sugar alcohol (polyalcohol) with many interesting properties for pharmaceutical and food products. It is currently produced by a chemical process, which has some disadvantages such as high energy requirement. Therefore microbiological production of xylitol has been studied as an alternative, but its viability is dependent on optimisation of the fermentation variables. Among these, aeration is fundamental, because xylitol is produced only under adequate oxygen availability. In most experiments with xylitol‐producing yeasts, low oxygen transfer volumetric coefficient (K_La) values are used to maintain microaerobic conditions. However, in the present study the use of relatively high K_La values resulted in high xylitol production. The effect of aeration was also evaluated via the profiles of xylose reductase (XR) and xylitol dehydrogenase (XD) activities during the experiments. RESULTS: The highest XR specific activity (1.45 ± 0.21 U mg_protein^?1) was achieved during the experiment with the lowest K_La value (12 h^?1), while the highest XD specific activity (0.19 ± 0.03 U mg_protein^?1) was observed with a K_La value of 25 h^?1. Xylitol production was enhanced when K_La was increased from 12 to 50 h^?1, which resulted in the best condition observed, corresponding to a xylitol volumetric productivity of 1.50 ± 0.08 g_xylitol L^?1 h^?1 and an efficiency of 71 ± 6.0%. CONCLUSION: The results showed that the enzyme activities during xylitol bioproduction depend greatly on the initial K_La value (oxygen availability). This finding supplies important information for further studies in molecular biology and genetic engineering aimed at improving xylitol bioproduction. Copyright © 2008 Society of Chemical Industry     

Ultraviolet‐induced crosslinking of poly(vinyl alcohol) evaluated by principal component analysis of FTIR spectra

The crosslinking of poly(vinyl alcohol) (PVA) films under ultraviolet irradiation for between 1 and 4 h was studied in air at 25 °C in the presence of sodium benzoate by Fourier‐transform infrared spectroscopy (FTIR) using the attenuated total reflectance technique (ATR). Principal component analysis (PCA) is a mathematical procedure that allows treatment of the entire infrared spectrum and is very appropriate for analysing the chemical modifications initiated by sodium benzoate which occur in PVA upon UV irradiation. By PCA it was possible to clarify the mechanism of crosslinking of PVA. From this FTIR–PCA study, it is suggested that a free radical arising from the photolysis of sensitizer would abstract a tertiary hydrogen atom from the polymer chain to yield a polymeric radical. This radical reacts with O? H groups, leading to the formation of ether bonds between the polymeric chains and hence to crosslinking and insolubilization of the PVA. © 2001 Society of Chemical Industry