Oxidation of Grape Juice 2-S-Glutathionyl Caffeoyl Tartaric Acid by Botrytis cinerea Laccase and Characterization of a New Substance: 2,5-di-S-Glutathionyl Caffeoyl Tartaric Acid

The evolution of caftaric acid derivatives in grape juice samples exposed to air was monitored by high performance liquid chromatography. 2-S-glutathionyl caftaric acid was shown to be oxidized by laccase from Botrytis cinerea but it was not a substrate for grape polyphenoloxidase. In the presence of glutathione, 2,-5-di-S-glutationyl caftaric acid was formed; this was identified by proton NMR. Its production involved laccase oxidation of 2-S-glutathionyl caftaric acid into the corresponding orthoquinone and substitution of the latter by glutathione. When no glutathione was available, polymerization of the quinones led to browning of the juice.     

Oxidation of Grape Juice Phenolic Compounds in Model Solutions

Oxidation of caftaric acid, catechin, epicatechin, epicatechin gallate, procyanidins B1 to B4 and 2-S-glutathionyl caftaric acid (GRP) in grape must-like model solutions containing grape polyphenoloxidase was monitored by HPLC. Caftaric acid was degraded faster than catechin, epicatechin, and epicatechin gallate. Procyanidins and GRP were oxidized very slowly when incubated alone with the enzyme. Oxidation of two-component mixtures in the presence of polyphenoloxidase was studied. Caftaric acid induced coupled oxidation of other compounds. The order of redox potentials was determined. Oxidation of catechin-caftaric acid mixtures was studied, and the oxygen consumption measured. A reaction sequence including enzymatic oxidation, coupled oxidations and the formation of caftaric acid and catechin copolymers was proposed.     

Effect of pre‐ and post‐veraison water deficit on proanthocyanidin and anthocyanin accumulation during Shiraz berry development

Background and Aims: Water deficit is known to influence berry development as well as flavonoid metabolism. The aim of this study was to investigate the influence of pre‐ and post‐veraison water stress on the proanthocyanidin and anthocyanin accumulation on berry samples selected at comparable physiological maturity, especially after veraison while avoiding sugar influence. Methods and Results: Three irrigation treatments were applied by a drip irrigation system on three rows of 30 vines from an experimental Shiraz vineyard. Pre‐veraison water stress had no effect on total proanthocyanidin accumulation but increased accumulation of all anthocyanins except malvidin and p‐coumaroylated derivatives, whereas post‐veraison water stress enhanced the overall anthocyanin biosynthesis, particularly malvidin and p‐coumaroylated derivatives. Conclusions: Pre‐ and post‐veraison water stress affected the anthocyanin composition differently, suggesting a differential regulation of the genes involved in the last steps of anthocyanin biosynthesis pathway. Significance of the Study: The study identifies the effect of pre‐ and post‐veraison water stress while avoiding sugar influence on anthocyanin accumulation which could be maximised since both stresses differently impacted hydroxylation and methylation of anthocyanins.     

A PLACE FOR AREA‐BASED POLICY? THE SURVIVAL AND GROWTH OF LOCAL FIRMS IN DUTCH RESIDENTIAL NEIGHBORHOODS

ABSTRACT: Although their market scope often exceeds the neighborhood level, for most entrepreneurs of small‐scale firms the neighborhood is the relevant arena for both their professional activities and their personal affairs. Dutch local economic policy aims to stimulate new firm formation and firm survival in (disadvantaged) neighborhoods by conditioning economic, social, and physical aspects of the neighborhood such as economic zoning and clustering, livability, and the quality of the built‐up area. Although substantial differences in firm success exist across neighborhoods, it is not clear whether area‐level factors contribute to these differences, suggesting that area‐level policies are useful, or whether differences are due to either urban effects or to microlevel entrepreneurial and firm composition effects. This article distinguishes neighborhood effects from composition effects on local firm survival and firm growth, thereby also taking into account spatial dependence across neighborhoods. Our results suggest that aspects of the local livability of neighborhoods and of economic agglomeration are significantly related to individual firm survival and firm growth. The models provide proof for spillover effects of livability problems and market potential between adjacent neighborhoods. Neighborhoods and cities are therefore potentially places for area‐based policies, aiming at the survival and growth of local firms.     

Sugar Content Measurement in Fruit Tissue Using Water Peak Suppression in High Resolution 1H Magnetic Resonance

Sugar content of muskmelon tissue was measured using 200 MHz ¹H magnetic resonance (MR). Single pulse resolved water and sugar resonances, but both were broadened. The sugar peak from low sugar (≦8.0%) samples was not detectable with the single pulse. Selective saturation to suppress the water peak was inefficient. The T₁ of water was almost twice that of sugar. Therefore, inversion-recovery (IR) pulse sequences could be applied for water suppression. Separation of the sugar peak was remarkably improved allowing its detection in low sugar (1.8%) samples. Measured sugar correlated linearly with peak intensity (r≧0.94). Results suggest that ¹H MR could be used to measure sugar in intact fruits and vegetables.     

Stability and Color of Unreported Wine Anthocyanin-derived Pigments

Grape anthocyanin-3-glucosides and unreported natural pigments characterized as vinylphenol anthocyanin-3-glucoside adducts were studied. Our investigations were undertaken to compare color and stabilities when processed and stored under identical conditions. Studies of molecular concentration, color density and Hunter color values were done at pH levels. Grape anthocyanin-3-glucosides were less stable than their 4-vinylphenol derivatives and the color stability of the unreported pigments was higher than that of anthocyanin-3-glucosides. Moreover, the compounds were resistant to SO₂ discoloration whereas anthocyanins were completely bleached.     

Bitterness and astringency of grape and wine polyphenols

Extracts containing anthocyanins (ACN), and skin tannins (SKIN) and seed tannins (SEED) were prepared from Vitis vinifera cv. Cabernet Franc grapes grown in the Loire Valley, and characterised. Phenolic fractions from Cabernet Franc wines made from three Loire Valley locations were also isolated and characterised. Bitterness and astringency of ACN, SEED and SKIN as well as the wine extracts were evaluated by time intensity procedures in citric acid solution and in a base white wine. SEED and SKIN were equally astringent when tasted at the same concentration in spite of differences in tannin composition. The lower molecular weight (MW) of SEED was equal in astringency to larger MW SKIN which had a lower percentage of galloylation. The SEED fraction was slightly more bitter than the SKIN fraction in the citric acid solution, although no difference could be detected between samples in base white wine. Astringency of ACN alone was much lower than either SKIN or SEED. Addition of ACN to either tannin fraction produced very small sensory effects in citric acid. In wine, addition of ACN to either SEED or SKIN increased astringency significantly over either fraction alone, but had no effect on bitterness. The wine fractions differed only in astringency, which was correlated with tannin units as determined by thiolysis.