Qing-An Zhang

Ultrasound-assisted extraction of phenolics from wine lees: Modeling, optimization and stability of extracts during storage

The ultrasound-assisted extraction process of phenolics including anthocyanins from wine lees was modeled and optimized in this research. An ultrasound bath system with the frequency of 40 kHz was used and the acoustic energy density during extraction was identified to 48 W/L. The effects of extraction time, extraction temperature, solvent-to-solid ratio and the solvent composition on the extraction yields of total phenolics and total anthocyanins were taken into account. The extraction process was simulated and optimized by means of artificial neural network (ANN) and genetic algorithm (GA). The constructed ANN models were accurate to predict the extraction yields of both total phenolics and total anthocyanins according to the statistical analysis. Meanwhile, the input space of the ANN models was optimized by GA, so as to maximize the extraction yields. Under the optimal conditions, the experimental yields of total phenolics and total anthocyanins were 58.76 and 6.69 mg/g, respectively, which agreed with the predicted values. Furthermore, more amounts of total phenolics and total anthocyanins were extracted by ultrasound at the optimal conditions than by conventional maceration. On the other hand, the stability of phenolics in the liquid extracts obtained from ultrasound-assisted extraction during storage was evaluated. After 30-day storage, the total phenolic contents in extracts stored at 4 °C and 20 °C decreased by 12.5% and 12.1%, respectively. Moreover, anthocyanins were more stable at 4 °C while tartaric esters and flavonols exhibited a better stability at 20 °C. Overall, the loss of phenolics during storage found in this study could be acceptable.

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.

Extraction, antioxidant capacity and identification of Semen Astragali Complanati (Astragalus complanatus R. Br.) phenolics.

A study about the ultrasonic extraction, antioxidant capacity and identification of phenolics from Semen Astragali Complanati was undertaken. The optimised extraction condition with an orthogonal experiment design of L9(3(4)) was 50°C, 30min and 15:1 (methanol solution:sample, mL:g). An extraction yield of 40.12±1.10mg gallic acid/g dry seed and the antioxidant capacity of 0.85±0.13mg dry extract/mg DPPH were obtained with the optimum condition, respectively. For each extraction set, the antioxidant capacity by 2,2-diphenyl-1-picrylhydrazyl radical assay highly correlated to its total phenolic content by Folin-Ciocalteu method. Twelve phenolic components obtained with the optimised extraction procedure were tentatively identified by Ultra Performance Liquid Chromatography coupled with Q-TOF Mass Spectrometer (UPLC-Q-TOF) according to their mass spectrometry, UV/vis spectrometry, and related literature reports. Furthermore, the ultrasonic effect on the particles microstructure of Semen Astragali Complanati was also investigated by scanning electron microscopy (SEM) analysis.

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.

Evolution of some physicochemical properties in Cornus officinalis wine during fermentation and storage

In order to modify the sharp sour and astringent mouthfeel of fresh consumption, an alcoholic beverage was developed for the first time from the fruit of Cornus officinalis. Evolution of some physicochemical properties such as titratable acidity, total phenolic content (TPC) and free radical-scavenging capacity during fermentation and storage was monitored in the C. officinalis wines fermented with two different techniques. Overall, the studied parameters had a rapid increase during fermentation, then followed by a decrease until the end of storage, except titratable acidity and gallic acid which kept increasing throughout the winemaking process. Strong positive correlations were observed between free radical-scavenging capacity and TPC (0.7378xa0≤xa0R2xa0≤xa00.9555), suggesting that total phenols in C. officinalis wines are the main compounds responsible for the antioxidant capacity. Considering the content of constituents and antioxidant capacity, the wine fermented with C. officinalis pomace is better than that without pomace, indicating the former is the feasible fermentation protocol for C. officinalis wine. While regarding the rapid decrease in some parameters during storage, it suggests that this fruit wine should be suitable for fresh consumption and not be aged for longer time. In a word, all the results pointed to the importance of fermentation methods and also revealed that most of the studied parameters might be as feasible indicators to monitor the C. officinalis wine’s fermentation status, quality and ageing potential in oenological industry.

Effect of ultrasound irradiation on the evolution of color properties and major phenolic compounds in wine during storage

In this paper, the effects of ultrasound irradiation were investigated on the evolution of color properties and major phenolic compounds during wine storage. The results indicate that the changing trends of color parameters are very similar in both the ultrasonically-treated and untreated wines, meanwhile the evolutions of malvidin-3-O-glucoside, monomeric flavan-3-ols and phenolic acids also demonstrate some similar patterns in all wines during storage, respectively. In summary, the ultrasound irradiation does not only temporally influence the color characteristics and phenolic compounds of wine, but also have a longer effect on their evolutions during wine storage. Furthermore, the ultrasonically-treated wine had a quicker changing trend than that of the untreated wine regarding the studied parameters. All these results indicate that the ultrasound might be as a feasible and promising novel technology for wineries to produce more red wines with the similar quality as the traditionally-aged wine in a shorter time.

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.