Juan Francisco García Martín

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.

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.