The elemental analysis was carried out using an inductively coupled plasma mass spectrometer (ICP-MS), Perkin–Elmer SCIEX, model ELAN 6000 (Thornhill, Canada) coupled to a cross flow nebulizer and a Scott spray chamber. The operational parameters are listed in Table 1. Red grapes from the V. labrusca L. varieties Concord, Isabel and Bordo, were manually harvested in Videira, South Region of Brazil, and kindly

donated by the Agricultural Research Company of Santa Catarina State (EPAGRI). All the varietal grapes were harvested at the stage of technical maturity, with soluble solids readings between 16 and 18 °Brix. This parameter was determined according NLG919 cost to OIV (1990). The ripened grapes from the three cultivars were brought to the laboratory and the fresh grapes were washed with tap water to remove adhering

dust and dirt. Grapes were ON-01910 cost kept separately at −12 °C and all varietal grape juices were prepared within a period of sixty days, followed by the analysis. Previously to juice preparation, grape samples were gently defrosted in a thermostatically controlled water bath at 20 °C for 5 min. Grape seeds of each variety were manually collected from the berries and washed separately with ultrapure water. The grape seeds were dried at room temperature (24 °C) for 15 min and weighed, followed by maceration with berries. Samples were then manually crushed and macerated with seeds under agitation in a thermostatic water bath at 24 °C for 5 min. Grape berries were separated from the rachis and 20 g of randomly selected berries of each cultivar were individually weighed in triplicate. Grape seeds of each cultivar were added at concentrations of 50, 100 and 200 g/kg of grape berry. A blank sample for each cultivar was weighed and macerated without the addition of seeds. Samples were macerated under agitation at 24 °C for 5 min, followed by the addition of 50 mL of ultrapure water. The mixture was transferred to 100 mL flasks and sonicated on an ultrasonic bath at 24 °C for 15 min, followed by the addition of the pectinolytic enzyme Pectinex®

Ultra Color at concentration of 1 mL/L and incubated in a thermostatically controlled water bath CYTH4 at 50 °C for 60 min. After the enzymatic treatment, the grape mash was manually pressed for 1 min using nylon filter bags, and the extracted juices were heat processed at 80 °C for 5 min. Finally, grape juices were filtered through a Whatman n°1 filter paper and packed in clean amber glass bottles. Total phenolic content of the grape juices was determined spectrophotometrically using the Folin–Ciocalteu colorimetric method (Singleton & Rossi, 1965). The reaction with the Folin–Ciocalteu reagent was carried out at room temperature (24 °C) for 90 min, with the samples kept in dark. The absorbance of the juice samples and the blank was measured at 760 nm.