Phospholipids of the grape

In the berries of the cultivated grape vineVitis vinifera L. nine phospholipid fractions have been identified, the main ones being phosphatidylcholines and phosphatidylethanolamines. The composition and position distribution of the fatty acids has been studied.Physicochemical Institute, Academy of Sciences of the Ukrainian SSR, Odessa. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 1984.     

One step purification of the grape vacuolar invertase

Invertase is a major protein of grape juice and wine. Accordingly, in order to study the biochemical and structural characteristics of this protein and for a better understanding of its physico-chemical properties, large amounts of the pure protein are needed. A simple method for the purification of the grape vacuolar invertase in a preparative-scale is described in this work. The grape protein was isolated and purified from must by ultrafiltration and anion exchange chromatography. The identification and purity determination of the grape invertase fraction were assessed by SDS-PAGE, and were then confirmed using nanoLC-chip-MS/MS analysis. The laboratory fractionation procedure presented in this work generated large quantities of pure grape vacuolar invertase from must.     

Statistical-probability simulation of the organoleptic properties of grape wines

Approaches to the evaluation of generalized wine quality indices based on a set of the quantitative characteristics of single parameters and their organoleptic rating were studied with the use of statistical-probability simulation methods. A general linear model (multiple linear regression) was constructed to predict degustation evaluation values from the concentrations of volatile substances (acetaldehyde, ethyl acetate, methanol, higher alcohols, acetic acid, and furfural) and wine quality classes (high, medium, low, and adulterated). The wine quality class was identified by discriminant analysis based on the concentrations of the above volatile substances. A program module was developed for the automation of a calculation procedure. The average absolute deviation of predicted values from degustation evaluation data in a test sample was 5.8%.     

Comparison of pesticides levels in grape skin and in the whole grape by a new liquid chromatographic multiresidue methodology

The increasing interest in the study of pesticides in grapes is justified from an enological point of view, since some pesticides can interfere with fermentative microflora used in wine production, as well as, with the consumer’ safety. Considering that washing grapes before consumption is the standard procedure, the study of the effect of washing on the residue concentration is required to assess real consumer exposure. In this work, pesticide mobility in grapes was studied, by comparing their residual concentration in the skin with that of the whole grape. The efficiency of water washing to remove pesticides from grape skins was also evaluated.One variety of grapes from the Northern region of Portugal, Trajadura, sampled at two maturation periods of the 2001 crop, were analysed by a new validated methodology involving liquid chromatography with diode array detection.It was concluded that, although there were no significant differences between some pesticide levels found in the whole grape (skin and pulp) and in the grape skin, pyrimethanil was preferably found in the pulp, while metalaxyl was detected in the skin but not in the whole grape.The removal of pesticides from grapes by washing did not exceed 70% (procymidone). Never the less, it was concluded that consumer intake of the pesticides from grapes studied in this work should be significantly decreased as a result of water washing of the grapes.The concentration levels found for the pesticide residues were below both the Portuguese and the FAO Maximum Residue Levels (MRLs), thus causing no problems in terms of food safety.     

Cholesterol-lowering activity of the major polyphenols in grape seed

The major polyphenols in grape seed have been shown to have beneficial health effects in the prevention of dyslipidemia and cardiovascular diseases. In this present study, we investigated the cholesterol-lowering activity of three major polyphenolic compounds found in grape seed. The results showed that gallic acid, catechin, and epicatechin significantly inhibited pancreatic cholesterol esterase in a concentration-dependent manner. Moreover, they bound to taurocholic acid, taurodeoxycholic acid, and glycodeoxycholic acid at levels ranging from 38.6% to 28.2%. At the concentration of 0.2 mg/mL, gallic acid, catechin, and epicatechin reduced the formation of cholesterol micelles 27.26 ± 2.17%, 11.88 ± 0.75%, and 19.49 ± 3.71%, respectively. These findings clearly demonstrate that three major polyphenolic compounds present in a particular grape seed have cholesterol-lowering activity by inhibiting pancreatic cholesterol esterase, binding of bile acids, and reducing solubility of cholesterol in micelles which may result in delayed cholesterol absorption.     

Composition of the complex of biopolymers of the cell walls of the grape

The complex of high-molecular-weight substances of the cell walls of the grape has been studied. It has been shown that the complex contains polysaccharides, proteins, and phenolic substances presumably linked through O-glycosidic bonds."Magarach" Scientific-Research Institute of Wine-Making and Wine-Growing, Yalta, M. V. Frunze Simferopol' State University, Khimiya Prirodnykh Soedinenii, No. 5, pp. 564–567, September–October, 1984.     

Stability of anthocyanins extracted from grape skins

Summary The extractability and stability of anthocyanins from the skins ofVitis vinifera were determined at different pH values. Anthocyanins were extracted using acetone, partitioned with chloroform and pre-purified by solid-phase extraction (SPE). They were analysed by RP-HPLC, and the kinetic parameters of decomposition were calculated. The total monomeric anthocyanin content was determined by spectrophotometry. Anthocianins were well separated by RP-HPLC. The efficiency of extraction depended strongly on the pH of the extracting agent and on the character of the pigment to be extracted. The amount of anthocyanins decreased with increasing duration of storage, more so at elevated temperatures. Presented at Balaton Symposium '01 on High-Performance Separation Methods Siófok, Hungary, September 2–4, 2001.     

Monoterpenes in grape juice and wines

The importance of monoterpenes on varietal flavour of wines has been reviewed. These compounds were mainly found linked to sugar moieties in the grape juice and wines, showing no olfactive characteristics. In this way, mechanisms to liberate terpenes were studied, making a comparative study between acidic and enzymic hydrolysis of terpene glycosides. Finally, analytical techniques developed to study these compounds, in both free or glycosidically forms, and also to fractionate glycosidic precursors, have been discussed.     

Novel flavanol derivatives from grape seeds

Viniferone A, an oxidative derivative of catechin, together with viniferone B and C, presumably the oxidative derivatives of epicatechin, were isolated from grape seeds. Their structures were elucidated by spectroscopic methods. The X-ray structure of viniferone A is presented.