Effect of temperature and air velocity on drying kinetics, antioxidant capacity, total phenolic content, colour, texture and microstructure of apple (var. Granny Smith) slices

Abstract

22The production of condensate compounds from the degradation of benzene by OH radical 23 chemistry was studied. Secondary organic aerosol (SOA) formation was investigated in the 24 EUPHORE (European Photoreactor) simulation chambers. Experiments were performed under 25 different OH-production conditions -addition of H 2 O 2 , NO or HONO -, in a high-volume 26 reactor, with natural light and in the absence of seed aerosols. The consumption of 27 precursor/reagents, the formation of gas-phase and particulate-phase products and the temporal 28 evolution of aerosol were monitored. Several aerosol physical properties -mass concentration, 29 overall aerosol yield, particle size distribution and density -were determined and found to be 30 clearly dependent on OH radical production and NO x concentrations. Furthermore, the use of 31 one and/or two products gas-particle partitioning absorption models allowed us to determine the 32 aerosol yield curves. The SOA yield ranged from 1.6 to 9.7 %, with higher SOA formation 33 under low-NO x conditions. Chemical characterization of the SOA was carried out, determining 34 multi-oxygenated condensed organic compounds by a method based on the gas 35 chromatography-mass spectrometry technique. Several ring-retaining and ring-cleavage 36 products were identified and quantified. The compounds with the highest percentage 37 contribution to the total aerosol mass were 4-nitrobenzene-1,2-diol, butenedioic acid, succinic 38 acid and trans-trans-muconic. In addition, a multigenerational study was performed comparing 39 with the photo-oxidations of phenol and catechol. The results showed that although the mass 40 concentration of SOA produced was different, the physical and chemical properties were quite 41 similar. Finally, we suggest a general mechanism to describe how changes in benzene 42 degradation pathways -rate of OH generation and concentration of NO x -could justify the 43 variation in SOA production and properties. 44 , and it plays a critical role in atmospheric chemistry. Atmospheric studies on benzene 50 acquired greater relevance when this volatile organic compound (VOC) became established as a 51 petrol additive, thus increasing its direct emission. Other benzene sources are the chemical 52 industry, biomass burning, cracking of aromatic hydrocarbons, solvent usage and industries 53 related to vegetable oil processing. The increasing levels of this pollutant -up to 5 g m -3 54 higher than European Directive 2000/69/EC stipulates -are of great concern not only because 55 benzene can promote carcinogenic effects and lung disease in humans but also because it is an 56 important precursor of ground-level ozone (Martin-Reviejo and Wirtz, 2005). 57The atmospheric transformations of VOCs, including aromatic hydrocarbons, have been 58 widely examined using simulation photoreactors which reproduce reactions isolated from 59 meteorological variations or dispersion (Volkamer et al., 2002 the atmospheric degradation is mainly initiated by adding the OH radical to the aromati...

Total phenolics, antioxidant capacity, colour and drying characteristics of date fruit dried with different methods

“…The decrease could also be related to interactions between antioxidant compounds and other fruit constituents (Di Scala et al, 2011). These results disagree with some previous studies that reported that drying at low temperatures with long drying times decreases of antioxidant capacity (Garau et al, 2007;Vega-Gálvez et al, 2012).…”

“…During studies using the convective drying method, the total phenolic content declined when the drying temperature was increased from 60 to 80 ºC (P < 0.05). The decrease in total phenolic with increasing drying temperature has also been reported in studies of pear (Santos et al, 2014) and apple (Vega-Gálvez et al, 2012). The increase in total phenolic content in dried samples may occur because the drying treatments accelerate bound phenolic compounds as part of the breakdown of cellular constituents (Chang et al, 2006).…”

Influence of different drying techniques on drying parameters of mango

“…Rising drying temperature from 60 °C to 80 °C reduced the phenolic content significantly (P<0.05). In virtue of the rise at drying temperature, the decrease in total phenolic has also been reported by some studies in pear samples (Santos et al, 2014) and apple samples (Vega-Gálvez et al, 2012). In sum, amid the three distinct drying techniques, microwave drying technique attained greater TPC values, and then freeze and hot air drying techniques respectively.…”

“…For this reason, incrementing the level of the microwave power and temperature led to a considerable decline in the drying duration. Identical outcomes were also obtained by Vega-Gálvez et al (2012) and Doymaz & Ismail (2012) at the hot air drying technique applied on apple and pear by Chayjan et al (2015) and Duan et al (2015) for the microwave drying technique applied on hawthorn and lychee fruits, respectively. Table 2 exhibits the statistical analysis data, containing the model constants and R 2 , RMSE and χ 2 values, for all thin-layer drying models suitable with the moisture ratio data.…”

“…The color reading was realized for rind of the fruit sample then finally, the mean value of ten color readings which were taken from random points of the each sample was noted as color value. In addition, the Chroma C, hue angle a and total color variations ΔE were calculated by using the formulas below (Vega-Gálvez et al, 2012): …”