Xue-Hui Fan

Free radical generation induced by ultrasound in red wine and model wine: An EPR spin-trapping study

Direct evidence for the formation of 1-hydroxylethyl radicals by ultrasound in red wine and air-saturated model wine is presented in this paper. Free radicals are thought to be the key intermediates in the ultrasound processing of wine, but their nature has not been established yet. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-l-pyrrolin N-oxide (DMPO) was used for the detection of hydroxyl free radicals and 1-hydroxylethyl free radicals. Spin adducts of hydroxyl free radicals were detected in DMPO aqueous solution after sonication while 1-hydroxylethyl free radical adducts were observed in ultrasound-processed red wine and model wine. The latter radical arose from ethanol oxidation via the hydroxyl radical generated by ultrasound in water, thus providing the first direct evidence of the formation of 1-hydroxylethyl free radical in red wine exposed to ultrasound. Finally, the effects of ultrasound frequency, ultrasound power, temperature and ultrasound exposure time were assessed on the intensity of 1-hydroxylethyl radical spin adducts in model wine.

Preliminary study of the effect of ultrasound on physicochemical properties of red wine

Ultrasound is regarded as a potential alternative method for improving the quality of some wines. This study was initiated with the objective of evaluating the effects of ultrasound on some important physicochemical properties of red wine such as chromatic characteristics (CC), electrical conductivity (EC), pH, titratable acidity (TA), total phenolic compounds (TPCs) and DPPH (1,1-diphenyl-2-picryl-hydrazyl) free radical scavenging activity (DFRSA). The operational parameters assessed were ultrasound power, ultrasound frequency, exposure time and bath temperature. Results illustrated that there were significant changes in CC, EC and TPC while pH and TA hardly changed except for samples treated at high temperatures. DFRSA was correlated to TPC during ultrasonic treatment. Application of principal component analysis to the experimental data suggested that exposure time was the factor with the greatest ability to induce changes on wine. Results suggested that ultrasound may be applied to improve some physicochemical properties of red wine.

Changes of gallic acid mediated by ultrasound in a model extraction solution

Ultrasound has been widely used as a new kind of auxiliary extraction technique in food industry, but its effect cannot be ignored on the potential degradation of the extracted target compound. In this paper, a model extraction solution was constructed with the standard gallic acid as target compound to be extracted, and its change was monitored by using high performance liquid chromatography (HPLC) under different ultrasonic extraction conditions, namely, solvent types, extractant concentrations, extraction time, extraction temperature, ultrasound power and frequency, in order to understand the effect of ultrasound on the extract during ultrasonic extraction and provide an objective evaluation of ultrasonic extraction of polyphenols. The results indicate that ultrasonic parameters had definite effect on the degradation of gallic acid during ultrasonic extraction, which implies that the extraction yield should not be over-focused in actual extraction applications of ultrasound, more attention should be paid to the potential degradation of the extracted target compound induced by ultrasound.

Mathematical modeling of debittered apricot (Prunus armeniaca L.) kernels during thin-layer drying

ABSTRACT In this paper, the effect of drying temperature was investigated on the drying kinetics of the debittered and skin-removed apricot kernels, and the thin-layer drying model was also constructed by fitting the eight mathematical models such as Henderson and Pabis, Logarithmic, Midilli et al. and Approximation of diffusion model, Among them, the Midilli et al. and Approximation of diffusion models were selected to describe the drying characteristics of apricot kernels due to their relatively higher coefficient of determination (R2), and lower chi-square (χ2) and root mean square error (RMSE). Beyond that, the moisture loss and the effective moisture diffusivity (Deff) of the kernels during drying were also described and estimated by Fick’s second law and the data obtained, getting a range of 1.39×10−8 to 3.5×10−8 m2/s, respectively. The temperature dependence of the diffusivity coefficients was described with the activation energy (Ea) value of 16.5 kJ/mol. All these results are beneficial for better understanding and controlling the drying of apricot kernels.

Online monitoring of electrical conductivity of wine induced by ultrasound

ABSTRACT We assessed the effects of ultrasonic frequency, power, temperature and exposure time on the electric conductivity (EC) of wine to evaluate the feasibility of the online EC monitoring as an indicator to reflect the changes of wine quality under the ultrasound irradiation. Results showed that the continuously monitored curve of EC was significantly different from the values recorded at the beginning and end of sonication. An abrupt rise and a rapid drop of wine EC were observed at the start and end points of sonication, respectively, in all working conditions. With regards to the assayed wine temperatures, the effect exerted by this parameter on EC before sonication was totally different from that observed when the samples were cooled down after ultrasound treatment. All in all, these results suggest that the online EC monitoring of wine may be used as an efficient indicator to control and reflect the real changes of wine under ultrasound treatment.

Optimization of Pyrogallol Autoxidation Conditions and Its Application in Evaluation of Superoxide Anion Radical Scavenging Capacity for Four Antioxidants.

In this study, some factors influencing pyrogallol autoxidation, including EDTA, temperature, and solvent, were systematically investigated to improve its feasibility in the evaluation of antioxidants for the first time. Subsequently, the improved pyrogallol autoxidation conditions were used to assess the superoxide anion scavenging activity (SASA) of four commonly used antioxidants, namely, ascorbic acid, rutin, catechin, and gallic acid, by both the reaction rate method and the terminated method. The results indicate that pyrogallol autoxidation could be successfully used to determine the antioxidant capacity of ascorbic acid and rutin, which correspondingly suggests the feasibility of its use to measure the superoxide anion radical scavenging activity of polysaccharides and flavonols, because these compounds have a similar basic structural unit as ascorbic acid and rutin, respectively. Unexpectedly, however, pyrogallol autoxidation cannot be used to evaluate the SASA of catechin and gallic acid, although their good antioxidant capacity was confirmed by the 1,1-diphenyl-2-picrylhydrazyl assay. Together, these results suggest the importance of noting the conditions used for pyrogallol autoxidation when assessing the SASA of targeted compounds.

Physicochemical properties and in-vitro antioxidant capacity of Semen Astragali Complanati wine

ABSTRACT In this paper, the physicochemical properties of the Semen Astragali Complanati wine was first investigated including the pH, electrical conductivity (EC), titratable acid, alcohol content, residual sugars, chromatic characteristics and flavonoids, and thereafter the in-vitro antioxidant capacity and its correlation with the total phenolic and flavonoids content were systematically evaluated and analyzed for the different fractions of the Semen Astragali Complanati wine by six antioxidant assays and the Pearson product–moment correlation, respectively. On a whole, there are no significant differences between the Semen Astragali Complanati wine and the grape wine regarding most of the conventional enological parameters. The antioxidant assays showed that the Semen Astragali Complanati wine exerts great antioxidant capacity, which is attributed to the high content of polyphenols and flavonoids contained such as complanatoside A and rhamnocitrin, since high correlations exhibited between the total content of phenols and flavonoids, and the in-vitro antioxidant activity, respectively. All these results indicate that the Semen Astragali Complanati could be fermented to wine and be as a natural source of antioxidants preventing damage associated with free radicals and offer alternatives to develop high value-added products to enhance health benefits.

Chemical compositions and antioxidant capacity of by-products generated during the apricot kernels processing

ABSTRACT The compositions and antioxidant capacity were investigated about the by-products (blanching water concentrate (BWC) and debitterizing water concentrate DWC) produced during the industrial processing of apricot kernels, to evaluate the by-products’ potential utilization. The results indicate that the by-products contain a great number of compounds like amygdalin, protein, phenolics, and flavonoids. Among them, the amygdalin has the highest content both in BWC and DWC, which is 33.48 ± 0.04 and 23.89 ± 0.03 (g/100 g dry base weight), respectively. Furthermore, the by-products exert good antioxidant functions including the higher reducing power and radical-scavenging capacity on the 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and hydroxyl radicals, which is mainly attributed to the phenolic compounds, not the highest content of amygdalin by the principal component analysis and verification test of DPPH radical-scavenging capacity. In conclusion, the by-products definitely have great potential for utilization and should be recycled from the wastewater in the apricot kernels processing industry, especially for amygdalin.

Antioxidant Evaluation and Composition Analysis of Extracts from Fuzhuan Brick Tea and Its Comparison with Two Instant Tea Products.

In this paper, the antioxidant capacities and compositions of two commercialized tea products and extracts from Fuzhuan brick tea (FBT) were investigated using three HPLC methods comparing the retention times of injected standards. Principal component analysis and DPPH-spiking HPLC analysis were used to analyze correlation between antioxidant capacity and the compounds detected to screen which compounds contribute to antioxidant activity. Results indicated that all samples contained high amounts of polysaccharides, phenols, and flavonoids and had good antioxidant activity and a high level of correlation among them. Furthermore, gallic acid, epigallocatechin, epicatechin, and epigallocatechin gallate were screened and found to be stronger antioxidant candidates. In summary, the quality of the FBT extracts was not inferior to that of commercialized tea products, suggesting the feasibility that extracts may directly act as instant tea products.