Purification and characterization of a cysteine protease in Vitis vinifera L. grapes (Macabeo variety)

Protease from Vitis vinifera L. (Macabeo variety) was partially purified (15-fold) by PVPP and Sephadex gel G-100 filtration and characterized afterwards by gel electrophoresis. The enzyme had an optimum pH of 2.50 and a Km value of 0.32 mM for haemoglobin. The results of applying diagnostic inhibitors indicated that the enzyme studied was a cysteine-protease.     

Effect of chemical treatments on ochratoxigenic fungi and common mycobiota of grapes (Vitis vinifera)

The effect of the application of two fungicides (cyprodinil alone and a mixture of cyprodinil and fludioxonil) on the mycoflora of grapes, especially ochratoxigenic fungi, was studied. Different doses and application times were analyzed. Grape mycobiota was isolated and identified, and the classification of black aspergilli was carried out. We found that 81.7% of the isolates belonged to Aspergillus niger aggregate and 18.3% to Aspergillus carbonarius. The ability to produce ochratoxin A (OTA) was studied on Czapek yeast extract agar (CYA) medium in 238 isolates. Most A. carbonarius (97.2%) produced detectable amounts of OTA, while only 2.9% of the A. niger aggregate were OTA producers. Most of the isolates (58%) produced less than 2.5 microg OTA per g of CYA. That, together with the highest levels of black aspergilli detected near harvest, proved the reported theory that they are primarily responsible for OTA in grapes. The fungicides studied had a significant effect on black aspergilli in three of the four vineyards sampled, as the natural increase of black aspergilli when approaching harvest was in general lower in all the fields treated with fungicides as compared to the control treatment. A mixture of cyprodinil (37.5%) and fludioxonil (25%) applied at veraison and 21 days before harvest was the most effective treatment to prevent black aspergilli in grapes, together with a single application of this mixture at veraison followed by an application of cyprodinil (50%) 21 days before harvest. No OTA was detected in musts (n=112) produced from either the control treatment or the treated grapes.     

Rate of degradation of λ-cyhalothrin and methomyl in grapes (Vitis vinifera L.)

Rates of degradation of λ-cyhalothrin and methomyl residues in grape are reported. The dissipation behavior of both insecticides followed first-order rate kinetics with similar patterns at standard and double-dose applications. Residues of λ-cyhalothrin were lost with pre-harvest intervals (PHI) of 12.0-12.5 and 15.0-15.5 days, corresponding to the applications at 25 and 50 g a.i. ha^-1, respectively. In the case of methomyl, residues were lost with PHI of 55.0 and 61.0 days, following applications at 1 and 2 kg a.i. ha^-1, respectively. The PHI, recommended on the basis of the experimental results, was shown to be effective in minimizing residue load of these insecticides below their maximum residue limits (MRLs) in vineyard samples.     

Development changes of anthocyanins in Vitis vinifera grapes grown in the Douro Valley and concentration in respective wines

Grapes of Touriga Nacional and Touriga Francesa red Vitis vinifera varieties have been sampled from two vineyard sites at different altitudes during three consecutive vintage years (1997, 1998 and 1999) in the Douro Valley. The total anthocyanidin monoglucosides (AMGs) detected by HPLC/DAD and the red colour of grape skin extracts were monitored during the last month of maturation. Microvinifications were performed with the grapes studied and the resulting Port wines were analysed. Malvidin 3‐glucoside and its acylated esters were the major AMGs irrespective of cultivar at harvest date. Vineyard altitude, together with other variables, was found to be an important factor contributing to the amount of anthocyanin compounds found in grapes of Touriga Nacional and Touriga Francesa. Overall, the climatic conditions observed at higher vineyard sites appeared to be advantageous, resulting in larger amounts of AMGs in grapes. The same outcome was obtained in the resulting wines, which showed higher levels of AMGs when made from grapes grown at higher altitude, especially for Touriga Francesa. © 2002 Society of Chemical Industry     

Factors influencing sensory quality in red wines of the variety Aghiorghitiko (Vitis vinifera L.) from Nemea

Sensory quality in wines from the indigenous Greek cultivar Aghiorghitiko of Nemea, in 2 years, was studied with multivariate modelling. The appearance, aroma and oral attributes were assessed separately using rank-rating in 13 red Nemea wines, dominated (10 of 13) by Aghiorghitiko, and headspace congeners (51) quantified by solid phase microextraction with gas chromatography. Partial least squares regression (PLS) and discriminant PLS studied relationships between sensory data and congeners, viticultural and oenological data, producers and influence of wood maturations, respectively. Principal component analysis (PCA) spaces for aroma (11 attributes; 64% variance, 3 PCs), congeners (51; 72%, 7 PCs) and oral characters (13 attributes; 77%, 3 PCs) showed similarities in product clustering. Modelling showed clear relationships between sensory character and plant density, wood maturation and producer, respectively. Sensory characters in Aghiorghitiko wines were primarily differentiated by oak maturation and producer influences. A part of the results of this work was presented at the Second International Symposium on the Evaluation and Exploitation of Grapes of Corresponding Terroir through Winemaking and Commercialisation of Wines, 1–3 June 2006, Santorini.     

Cell wall anthocyanin adsorption by different Saccharomyces strains during the fermentation of Vitis vinifera L. cv Graciano grapes

This work reports the adsorption of anthocyanins by the cell walls of different strains of Saccharomyces during the production of red wine from Vitis vinifera L. cv Graciano grapes. The anthocyanin derivative contents of the yeast cell walls were substantially different to those of their corresponding wines. Cinnamoyl derivatives (6-p-coumaroyl and 6-caffeoyl) were strongly adsorbed while vitisins (adducts of pyruvic acid and acetaldehyde) were weakly adsorbed. The mean total anthocyanin concentration of the wines was 507.64 mg L^?1 with the following distribution: 3-glucosides (3G), 82.2%; vitisins, 0.97%; 6-acetyl derivatives, 7.44%; 6-caffeoyl derivatives, 1.81%; and 6-p-coumaroyl derivatives, 7.54%. A mean of 18.57 mg of anthocyanins were adsorbed by the lees corresponding to 1 L of wine; this quantity was distributed: 3G, 52.60%; vitisins, 0.15%; 6-acetyl derivatives, 4.06%; 6-caffeoyl derivatives, 6.61%; and 6-p-coumaroyl derivatives, 36.58%. Large differences were seen between the different yeast strains examined with respect to the quantities of anthocyanins adsorbed. The mean adsorption percentage was 3.67%, but this varied between 1.60% (strain 3VA) and 5.85% (strain 9CV). The adsorption percentage of 6-p-coumaroyl derivates for strain 3VA (7.61%) was fourfold less than that of 9CV (28.37%). Strains 2EV and 3VA showed no vitisin adsorption.     

Rootstock effects on salt tolerance of irrigated field-grown grapevines (Vitis vinifera L. cv. Sultana).: 1. Yield and vigour inter-relationships

Vegetative growth and yield of grapevines grown in the field on their own roots or grafted to a range of rootstocks were investigated under drip irrigation with water of three salinity levels (0.40, 1.75 and 3.50 dS/m) over a five‐year period. Rootstocks were Ramsey, 1103 Paulsen, J17–69 and 4 hybrids (designated R1, R2, R3 and R4) derived from parentage involving Vitis champini, V. berlandieri and V. vinifera. Of measured yield components (bunches per shoot, bunches per vine, weight per bunch, weight per berry and total yield), only weight per berry was significantly reduced by high salinity (3.50 dS/m) in each year of the trial with the exception of Sultana on 1103 Paulsen and R2 in 1991 and Sultana on Ramsey in 1993. Weights of one‐year‐old pruning wood were also reduced by high salinity in all years for own roots and all rootstocks, with the exception of R2. Mean yield values at each salinity level over the five‐year period of the trial were highest for Sultana on Ramsey, 1103 Paulsen and R2. High salinity had no effect on five‐year mean yields of Sultana on Ramsey, 1103 Paulsen and R2. Yield (five‐year means) of Sultana on Ramsey and R2 at 1.75 dS/m were significantly higher than at 0.40 dS/m by 14.6% and 13.4% respectively. In contrast, 5‐year mean yields of Sultana on J17–69, own roots, R1, R3 and R4 at 3.50 dS/m were reduced by 54, 30, 20, 30 and 30% respectively. Yield of Sultana on J17–69, R1 and R4 rootstocks was reduced by 47, 20 and 24% respectively at 1.75 dS/m. When yield was regressed against bunches per vine and weight per bunch for Sultana on own roots and on Ramsey rootstock, bunches per vine was the main determinant of yield, while weight per berry showed a poor correlation with yield at all salinity levels. Rootstock ranking for salt tolerance based on yield at high salinity was the same as rankings for pruning wood weights at high salinity. The same occurred at medium salinity, demonstrating that vigour imparted by the rootstock was a major factor in Sultana salt tolerance as measured by yield. Mean root weighted soil saturation paste electrical conductivities (RWEC_e) (determined from soil saturation paste salinities and root length densities) were in the range 2.0–2.6 dS/m for the low salinity treatment, increasing to approximately 5.4 dS/m with increasing salinity of irrigation water. Yield reduction for own‐rooted vines for each 1.0 dS/m increase in RWEC_e above 2.6 dS/m was 9.3%.     

Capsaicin,an inhibitor of Ochratoxin A production by Aspergillus section Nigri strains in grapes (Vitis vinifera L.)

ABSTRACT

Food decay by spoilage fungi leads to significant economic losses and hazards to consumers’ health due to the potential of mycotoxin occurrence. Ochratoxin A (OTA) is a mycotoxin known as nephrotoxic and carcinogenic to humans. Natural capsaicin was evaluated for its effectiveness against the growth of five Aspergillus section Nigri strains and accumulation of OTA in inoculated black grapes. Results showed that capsaicin was effective in inhibiting fungal growth and OTA production by new four Aspergillus section Nigri strains (ATHUM 6997, 6998, 6999, 7000) and by Aspergillus carbonarius as well. Moreover, capsaicin addition exhibited maximum inhibition of OTA produced by ATHUM 6997, 6998, 6999, and 7000 in black grapes at 28.9%, 8.6%, 68.4%, and 78.1%, respectively. Inhibition percentage of OTA production by A. carbonarius in grapes treated with capsaicin was estimated at 61.5%. These results suggest that capsaicin influences the OTA biosynthesis pathway of all Aspergillus section Nigri strains and therefore could be used as an effective natural preservative against OTA contamination of vineyards. Risk assessment revealed that when grapes are treated with capsaicin, consumers are less exposed to OTA.     

Comparison of major volatile compounds from Riesling and Cabernet Sauvignon grapes (Vitis vinifera L.) from fruitset to harvest

Background and Aims: Research on concentration changes of volatile compounds during grape physiological development has focused on the period from veraison to harvest. This study compared the developmental changes in the major volatile compounds released after the crushing of Riesling and Cabernet Sauvignon grapes sampled from fruitset to harvest during the 2007–2008 season. Methods and Results: Volatile compounds were extracted from the headspace of crushed Riesling and Cabernet Sauvignon grapes sampled throughout berry development using solid-phase microextraction and analysed by gas chromatography–mass spectrometry. A multivariate statistical approach coupled with analysis of variance was applied to compare the developmental changes in volatile compounds for the two cultivars. In both cultivars, E-2-hexenal was the most abundant volatile compound, and it showed a significant increase in concentration after veraison. Benzene derivatives discriminated ripe Cabernet Sauvignon grapes, whereas monoterpenes and sesquiterpenes discriminated both cultivars pre-veraison with a broader range of terpenes observed in the Cabernet Sauvignon samples compared with the Riesling samples. At veraison, terpene production in both varieties was low, but Riesling grapes produced some terpenes (geraniol and α-muurolene) post-veraison. Generally, esters and aldehydes were the major class of compounds from Riesling grapes, while Cabernet Sauvignon showed a greater tendency to form alcohols. Conclusions: Both Riesling and Cabernet Sauvignon grapes had a more complex volatile compound composition pre-veraison than post-veraison. This study suggests that some compounds that contribute to grape aroma may be produced pre-veraison, and not simply accumulate after veraison. Significance of the Study: Understanding the timing of volatile compound production and cultivar differences will guide viticulture researchers and growers in the optimisation of vineyard strategies to enhance grape aroma attributes that may, in turn, contribute to wine aroma.     

Vascular function in berries of Vitis vinifera (L) cv. Shiraz

Anatomical studies on the movement of a xylem tracer dye were combined with functional studies on changes in grape berry volume during final stages of berry ripening to gauge xylem effectiveness. Movement of a xylem tracer dye into pre-veraison fruit was compared with movement into post-veraison fruit by feeding a solution of acid fuchsin to excised shoots with bunches still attached, and then sectioning fruit for photo-microscopy. Those comparisons confirmed published studies showing an apparent blockage to dye movement along major vessels within the brush tissue of post-veraison fruit. However, our functional approach yielded a different impression of vascular activity. A continuation of xylem transport in ripening fruit was inferred from comparisons of berry volume where pedicels were either girdled (phloem interrupted, but xylem intact) or excised (both phloem and xylem interrupted). Volume changes in manipulated berries were compared with immediately adjacent intact control berries within the same bunch. Control fruit lost volume subsequent to 78 days after flowering (DAF) while manipulated fruit lost volume from the first day of treatment at 67 DAF. By harvest time at 95 DAF, both control fruit and girdled fruit had fallen to 91% and excised fruit to 46% of maximum volumes recorded around 78 DAF. Berry volume loss in girdled fruit was further enhanced by deficit irrigation. We conclude that xylem flow into those Shiraz berries must have continued beyond veraison despite dye evidence of a vessel blockage within the brush region of analogous post-veraison fruit.     

Quality response of table grapes (Vitis vinifera L.) during cold storage to postharvest cap stem excision and hot water treatments

Berry quality, total phenol, sensory characteristics and decay incidence of grapes (V. vinifera cvs. Mü?küle and Red Globe) as affected by prestorage hot water immersion with or without cap stem excision treatments were investigated with 7‐day interval during storage at 1 °C for 21 days. Weight loss occurred mainly up to the second week and was more pronounced for the untreated control samples subjected to the stem excision. In Mü?küle, the least weight loss value was obtained from hot water–treated grapes (0.62%), while the highest loss occurred in control grapes of stem‐excised berries (0.96%). Immersion of stem‐retained grapes in hot water was the best applications for maintenance of overall storage quality for both cultivars. According to panellist scores, it is evident that hot water has positive effect on maintaining the minimally processed table grapes without altering the flavour and taste of the commodity. Stem‐retained berries of hot water treatment had the highest score for both Mü?küle and Red Globe, with their values 3.8 and 4.2, respectively, while the least values were obtained from stem‐excised berries of untreated control group of both the cultivars (1.9 and 3.0, respectively). At the end of three‐week storage, the least decay rates were determined in stem‐retained berries that received hot water treatment (5.3% for Mü?küle and 1.1% for Red Globe). Attenuate influence of brief high temperature exposure on ripening parameters (SSC, TA, MI, pH) was also observed. Postharvest hot water treatment may be used as a nonchemical means to extent storage life of minimally processed grapes with its alleviating effect on physiological disorders. Cap stem retaining in minimal processing can be recommended to maintain the quality of grapes.     

Combining microsatellite markers and capillary gel electrophoresis with laser-induced fluorescence to identify the grape (Vitis vinifera) variety of musts

In this work, a new method that combines the use of microsatellite markers (VVMD5 and ZAG79) together with capillary gel electrophoresis with laser-induced fluorescence (CGE–LIF) is developed and applied to the identification of Albariño and Moscatel Grano Menudo musts. The GCE-LIF method uses commercially available products including polymers, DNA-intercalating dyes and bare fused silica capillaries to provide reproducible and sensitive separations of DNA fragments for grapevine characterization. The CGE–LIF procedure offers highly resolved separations of DNA fragments from 48 to 1031 bp in ca. 30 min with efficiencies up to 1.8×10⁶ plates/m allowing the separation of fragments that differ in 4 bp. The use of different DNA standards (i.e., 100 bp ladder, Ф×174 and pBR322) and their effect on size assignment of the amplified DNA is also investigated. It is demonstrated that the microsatellite markers (VVMD5 and ZAG79) provide DNA amplification patterns specific for Albariño and Moscatel Grano Menudo grapes that can be adequately differentiated by using CGE–LIF. Moreover, the DNA sizes determined by this CGE–LIF method are corroborated using a more standard procedure (i.e., an automatic genetic analyzer with a commercial kit) demonstrating the usefulness of this new methodology.     

Regional characteristics of anthocyanin and flavonol compounds from grapes of four Vitis vinifera varieties in five wine regions of China

Anthocyanins and flavonols are important flavonoid metabolites in grapes, making a dominant contribution to the color, the mouth feel and even the flavor of grapes and wines. The accumulation of these flavonoids in grapes is greatly influenced by a many, diverse but interacting factors, of which variety and climate are among the most important ones. In the present study, the anthocyanin and flavonol profiles of four grape varieties (Vitis vinifera L.), Cabernet Sauvignon, Carmenere, Syrah and Merlot, from five major wine regions in China were examined for two consecutive years (2006 and 2007). The results showed that the total anthocyanin content of the berry skins in these cultivars tended to increase from east to west in China, yet the proportion of the acylated anthocyanins displayed the opposite trend. It seemed possible that the western grape regions, with their high altitude and low annual rainfall, had an advantage in producing high level of anthocyanins. In addition, a high proportion of trihydroxylated flavonols were always found in the western region grapes, whereas dihydroxylated flavonols were more prominent in the lower altitude eastern regions. This suggested that the relative amounts of these flavonoid compounds may depend on their corresponding cultivar characteristics, while the amounts are more affected by the environmental factors where they were growing.     

Relationships between different berry components in Tempranillo (Vitis vinifera L) grapes from irrigated and non‐irrigated vines during ripening

The impact of water availability on Vitis vinifera L cv Tempranillo grape yields and juice composition over a 3 year period was studied. Grape juice composition during the different stages of berry growth was compared. The analytical data collected were used to investigate the relationships between some of the different components studied in these berries during the ripening period. The object was to determine whether the relationships could be used to derive mathematical equations for use as indicators of the changes taking place in the different parameters considered and thus of the optimum time for harvesting the grapes for a given wine‐making process. Very similar equations were derived for this grape variety irrespective of the culture conditions (use or non‐use of irrigation) or the different ripening conditions employed. A high degree of correlation between some of the components considered was observed. In any case, cause‐and‐effect relationships could only be established for certain of the parameter pairs considered (total acidity/pH, pH/potassium, °Brix/glucose + fructose, total acidity/tartaric acid and malic acid). For other parameter pairs (berry weight/°Brix, °Brix/pH, °Brix/total acidity) the relationship found was attributable to accumulation and breakdown processes which took place concurrently or overlapped in time. In two cases only there was uncertainty as to whether the relationship observed between the parameters was a cause‐and‐effect relationship or whether the parameters were so closely related that they acted as mutually limiting factors (°Brix/proline, °Brix/total anthocyanins). © 2002 Society of Chemical Industry