Effect of dry heat, microwave and ultrasonic treatments on physicochemical properties of potato starch with or without pectin

Purpose: To investigate the effects of dry heat, microwave and ultrasonic treatments on the physicochemical properties of potato starch alone or blended with pectin. Methods: The physicochemical properties of potato starch gels prepared using microwave, ultrasonic and dry heat treatments were assessed. Pasting properties, gel strength, thermal properties and crystal texture of the potato starch were determined using Rapid Visco analyzer, texture profile analyzer, differential scanning calorimeter and x-ray diffractometer. Results: Dry heat and ultrasonic treatments significantly increased the peak viscosity of the potato starch, and significantly decreased its setback and pasting temperatures (p < 0.05). Dry heat treatment significantly increased the hardness, while dry heat and ultrasonic treatments significantly improved retrogradation of the potato starch (p < 0.05). Transparency of potato starch paste was significantly increased by the different treatments, except microwave treatment (p < 0.05). Potato starch gels blended with pectin and subjected to any of the treatments exhibited significantly increased hardness, when compared with raw potato starch (p < 0.05). The retrogradation of the potato starch was significantly improved by the different treatments. Dry heat and ultrasonic treatments significantly decreased the syneresis of potato starch with or without pectin (p < 0.05). The three treatments also significantly affected the gelatinization enthalpy of the potato starch with or without pectin, and exerted some effects on the crystallinity of the gels. Conclusion: The results obtained in this study suggest that differences in physicochemical properties of potato starch gels are due mainly to the degree of damage to starch granules caused by different treatments. The addition of pectin to potato starch gel greatly improves its hardness and retrogradation

Reaction between Azidyl Radicals and Alkynes: A Straightforward Approach to NHâ 1,2,3â Triazoles

Reaction between nitrogenâ centered radicals and unsaturated Câ C bonds is an effective synthetic strategy for the construction of nitrogenâ containing molecules. Although the reactions between nitrogenâ centered radicals and alkenes have been studied extensively, their counterpart reactions with alkynes are extremely rare. Herein, the first example of reactions between azidyl radicals and alkynes is described. This reaction initiated an efficient cascade reaction involving interâ /intramolecular radical homolytic addition toward a Câ C triple bond and a hydrogenâ atom transfer step to offer a straightforward approach to NHâ 1,2,3â triazoles under mild reaction conditions. Both the internal and terminal alkynes work well for this transformation and some heterocyclic substituents on alkynes are compatible. This mechanistically distinct strategy overcomes the inherent limitations associated with azide anion chemistry and represents a rare example of reactions between a nitrogenâ centered radicals and alkynes.Get radical! Although the reactions between nitrogenâ centered radicals and alkenes have been studied extensively, their counterpart reactions with alkynes are extremely rare. Herein, the first example of reactions between azidyl radicals and alkynes is described (see scheme).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137186/1/chem201504515.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137186/2/chem201504515-sup-0001-misc_information.pd

Impact of aerosol composition on cloud condensation nuclei activity

The impact of aerosol composition on cloud condensation nuclei (CCN) activity were analyzed in this study based on field experiments carried out at downtown Tianjin, China in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS) of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC), whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%), and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5±2.6% to 12.8±6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reached up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7±19.0% to 46.5±12.3% correspondingly. The calculated <i>N</i><sub>CCN</sub> based on the size-resolved activation ratio and aerosol number size distribution correlated well with observed <i>N</i><sub>CCN</sub> at high SS (0.4%), but this consistence decreased with the falling of SS. The slopes of linear fitted lines between calculated and observed <i>N</i><sub>CCN</sub> are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4% respectively. Moreover, the stand deviation (SD) of calculated <i>N</i><sub>CCN</sub> increased with the decreasing of SS. A case study of CCN closure analyses indicated that the calculated error of <i>N</i><sub>CCN</sub> could reach up to 34% at SS of 0.1% if aerosol composition were not included, and the calculated error decreased with the raising of SS. It is decreased to 9% at SS of 0.2%, and further decreased to 4% at SS of 0.4%