Spectrophotometric Determination of Arginine in Grape Juice Using 8-Hydroquinoline

Arginine in grape juice can be metabolized by wine yeasts and malolactic bacteria to precursors of ethyl carbamate, known as carcinogen. The aim of this study was to develop a simple, fast, and accurate method for determining arginine in grape juice with Sakaguchi reaction by separating arginine with strong cation-exchange resins. Parameters were optimized including the concentrations of 8-hydroquinoline and sodium hydrobromite. The color stability lasted for 4 min, which is sufficient to finish the measurement. The method is simple, reproducible and accurate, and can be applied for quick measurement of arginine in grape juice to take necessary measures for controlling the level of ethyl carbamate.

Tropical Isabella Grape Juices： Bioactive Compounds and Antioxidant Power Depends on Harvest Season

Grapes are important sources of antioxidants compounds and one of the most used varieties to elaborate juices is ＂Isabel＂, or ＂Isabella＂, as it is called in North-America. This study aimed to evaluate the antioxidant activity of Isabella grape juices from the tropical semi-arid climate produced in Brazil on March and September, 2010. Total phenolics and anthocyanins were determined, as well as the antioxidant capacity by DPPH, FRAP and hydrophilic ORAC methods. Test T was used to compare statistical difference at 5% of significance level. As expected, the results showed that the season can play a significant role on phenolics content and antioxidant power. Polyphenols content in juices varied from 82.9 ± 0.92 to 102.2± 1.59 mg GAE 100 mL1- and anthocyanins content ranged from 44.3 ± 2.01 to 129.5 ± 2.82 mg cyanidin-3-glucoside 100 mL-1. Regression analyses showed a high correlation of antioxidant capacity and anthocyanins content. Grapes from Sao Francisco River Valley demonstrated to be a good source of antioxidant for human diet.

Purple Grape Juice,an Important Flavonoids Source,Influence in Biochemical Parameters in Offspring of Wistar Rats

Our objective was to evaluate the effect of chronic gestational treatment and post-breast feeding with purple grape juice on the biochemical parameters in offspring of dams. We used 40 male offspring from 14 Wistar rats which received purple grape juice or water by gavage daily for 42 days at a dose of 7 microliters/g. The offspring were divided into groups of water or juice. All received daily purple grape juice or water by gavage for 30 days after completion of their nursing period at a dose of 7 microliters/g. At the end of the treatment period, the offspring were euthanized by decapitation with its truncal blood collected and subsequently separated the serum from the blood. The measurements were performed by automation or by manual dosing. Considering the gestational factor, grape juice was able to reduce levels of total cholesterol, triglycerides, urea, alanine aminotransferase (ALT), and not alter the levels of creatinine and aspartate aminotransferase (AST) in serum of the offspring. When considering the post-breast feeding factor, grape juice resulted in an improvement in HDL-C. We concluded that purple grape juice was able to produce a beneficial effect on certain biochemical parameters in offspring.

Estimation model for electrical conductivity of red grape juice

The equations for predicting the electrical conductivities of red grape juice at different concentrations have been evaluated in this study.Three samples of red grape juice having concentrations of 10.5,12.5 and 14.5°Brix were ohmically heated by applying three different voltage gradients(10,12 and 15 V/cm)in the temperature range of 25-80℃.The mathematical models using multiple linear regression analysis indicated that electrical conductivity depended on temperature and concentration.The predictions of electrical conductivities using the mathematical models was found to be highly accurate with R2 value of 0.9975 when compared with the experimental data of red grape juice with concentration of 11.5°Brix.The reducing chi-square(χ^(2))and the root mean square error(RMSE)from the mathematical models were calculated and compared with the experimental data.As the results,multiple linear regressions on the coefficients of the mathematical model of electrical conductivity prediction have given highest values of the R2 and lowestχ^(2)and RMSE so the established model was confirmed as highly accurate when estimating electrical conductivities of red grape juice.