Content Of Grapes Research Articles

Ultraviolet-C and Induced Stilbenes Control Ochratoxigenic Aspergillus in Grapes

This study investigated the efficacy of ultraviolet-C (254 nm) and induced stilbenes to inhibit Aspergillus carbonarius and Aspergillus tubingensis and control ochratoxin A production in grapes. In addition, the stilbene synthesis as a response to UV-C treatment and to infection of ochratoxigenic Aspergillus was compared. The initial microbial inactivation by a previously optimized UV-C illumination protocol for increasing trans-resveratrol content in grapes (50 W/m (2), 40 cm, 60 s) was similar on undamaged and damaged grapes, achieving 1.2 and 1.3 log conidia/100 g reductions, respectively. After 5 days of storage at 22 degrees C, UV-C treatment and the stilbenes induced by UV-C inhibited ochratoxigenic Aspergillus growth in undamaged grapes. UV-C elicited the biosynthesis of trans-resveratrol, while microbial infection and tissue damage triggered the biosynthesis of trans-piceid. trans-Resveratrol was not synthesized as a consequence of ochratoxigenic Aspergillus contamination. However, when trans-resveratrol was synthesized by UV-C, it contributed to inhibiting the development of ochratoxin A producing aspergilli. Furthermore, UV-C treatment also contributed to decrease ochratoxin A production by ochratoxigenic aspergilli. Therefore, UV-C is a promising emerging technology either for reducing the potential ochratoxigenic risk in grapes, which is of particular interest to the wine industry, and also for increasing trans-resveratrol content of grapes, which would provide an added value to the wine.

Nondestructive Estimation of Leaf Chlorophyll Content in Grapes

Leaf chlorophyll content provides valuable information about the physiological status of plants, and there is a need for accurate, efficient, practical methodologies to estimate this biophysical parameter. Reflectance measurement is a means of quickly and nondestructively assessing, in situ, the chlorophyll content in leaves. The objective of this study was to develop a precise, efficient, nondestructive technique to estimate leaf total chlorophyll (Chl) content in grapes. A relationship was established between Chl content and the red-edge chlorophyll index, based on reflectances in the red-edge (710–720 nm) and near-infrared (755–765 nm) spectral ranges, and the algorithm for Chl retrieval was calibrated. The accuracy of Chl prediction using an independent data set, containing sampled leaves from three field-grown grape cultivars (Edelweiss, Saint Croix, and DeChaunac), was evaluated with no re-parameterization (adjustment of the coefficients) after initial calibration. Although Chl in the validation data set was widely variable, from 3 to 506 mg m⁻², the calibrated algorithm was capable of accurately predicting grape leaf Chl with RMSE <30 mg m⁻². Such an approach has potential for developing simple hand-held field instrumentation for accurate nondestructive Chl estimation and in analyzing digital airborne or satellite imagery to assist in vineyard management decision making.

Individual anthocyanins and their contribution to total antioxidant capacity in response to low temperature and high CO 2 in stored Cardinal table grapes

In this study, we have analyzed the profiles of individual anthocyanins in the skin of Cardinal table grapes and their contribution to the total antioxidant capacity (TAC) in response to low temperature (0 °C) and high CO 2 levels (20% for 3 days). An analysis of the representative colour parameters of this red-violet variety was also determined. The anthocyanin composition was determined using high-performance liquid chromatography coupled to diode array detector and mass spectrometry (HPLC–DAD–MS). The contribution of individual anthocyanins to the TAC value of table grapes was calculated on the basis of their concentration and antioxidant capacity measured as the TEAC value (slope of the anthocyanin/slope of Trolox). Chromatographic analysis identified six anthocyanins, including pelargonidin 3-glucoside (Pg-3-G), in the skin of Cardinal table grapes. Short-term storage at 0 °C in air had an increasing effect on the concentration of each of the identified anthocyanins. After 3 days at 0 °C, untreated grapes had the highest anthocyanin content (27.55 mg/100 g FW) and displayed the largest TAC value (52.45 mM TE/100 g FW). Peonidin 3-glucoside (Pn-3-G) was the predominant anthocyanin, and it was mainly responsible for the rise in the calculated TAC value in untreated grapes. Pn-3-G had a low average TEAC value (1.73 mM), but its contribution could be explained by the sharp increase in the content of this anthocyanin the first days of storage at 0 °C. In contrast, the Pn-3-G content in grapes at the end of the 3-day CO 2 treatment did not change, and both the total anthocyanin content and the calculated TAC value remained significantly constant in comparison to the levels in pre-stored grapes. In addition CO 2 treatment had a positive effect on the amount of Pg-3-G concomitant with a pronounced decline in delphinidin 3-glucoside (Dp-3-G) and smaller decreases in petunidin 3-glucoside (Pt-3-G) and malvidin 3-glucoside (Mv-3-G). These effects of high CO 2 levels on the profile of individual anthocyanins were progressively lost when grapes were transferred to air. Indeed, after prolonged low-temperature storage when the colour of the berries become dark violet, similar calculated TAC values were quantified in untreated grapes and in those exposed to 20% CO 2. These data provide new insights about the effect of low temperature and high CO 2 levels on the concentration of the individual anthocyanins identified in cardinal table grapes.

Potássio em uvas II: análise peciolar e sua correlação com o teor de potássio em uvas viníferas

O objetivo deste trabalho foi acompanhar a evolução da absorção de potássio pelas uvas durante o processo de maturação e verificar sua influência no pH, bem como tentar correlacionar ambas com os teores encontrados nos pecíolos na época da floração. Amostras das uvas foram coletadas durante o processo de maturação de três variedades: Pinot noir, Cabernet Sauvignon e Merlot. Durante os dois anos de estudo, ocorreram variações nos teores de potássio absorvidos pelos frutos durante a maturação, sendo o aumento acompanhado pela elevação do pH; a redução no teor de potássio foi acompanhada pela estabilização dos valores de pH, fato também influenciado pela queda nos teores de acidez titulável. Sugere-se, assim, que os altos valores de pH encontrados nos vinhos elaborados com uvas destes vinhedos, em anos anteriores, estão relacionados com a absorção de potássio e a diminuição da acidez total durante a maturação da uva. A retirada de amostras peciolares na floração e trinta dias após mostrou-se um mecanismo eficiente na avaliação do teor de potássio nos tecidos próximos aos grãos. Dessa forma, a análise peciolar, além de ser utilizada para monitorar os níveis de potássio na planta e avaliar a necessidade de adubações e tratos culturais, pode servir de diagnóstico futuro para os teores de potássio nas uvas e nos vinhos.

Elicitation of trans-resveratrol by laser resonant irradiation of table grapes

Table grapes were irradiated with UV nanosecond laser pulses in searching for resonant photo-elicitation of trans-resveratrol, a known antioxidant compound naturally produced by grapevines and other plants. To this end, the irradiation time as well as the wavelength dependence of the induced trans-resveratrol content was investigated by comparing the elicitation level of this compound at two laser wavelengths. One wavelength was selected right at the maximum of the absorption band (302.1 nm, the resonant wavelength for this compound) while the second was selected (300 nm, a non-resonant wavelength) such that trans-resveratrol absorption is negligible. It was found that the resonant irradiation enhances the resveratrol content in grapes by up to six times more than that of non-resonant irradiation, the rest of the conditions being the same. This work demonstrates how selective laser excitation of fruits can open new possibilities for the development of functional foods with enhanced nutritional and beneficial properties.

A NEW TECHNIQUE FOR GRAPE INSPECTION AND SORTING CLASSIFICATION

Sorting and classification of fruits are the main problem specially for Superiorand King Ruby varieties which represent more than 50% of grape production inEgypt. A usual procedure to carry out this task is based on human visual inspectionconsidering general fruit attributes like color, size, shape, firmness and sugar contentof grape cluster. Color contains important information about fruit status and in somecases it is decisive for fruit quality differences. This paper provides a new techniqueto investigate the applicability of color classification, sugar content and firmness ofgrape. Standard RGB color chart, artificial neural network and a potential of nearinfrared(NIR) reflectance as a means for nondestructive measurements of grapefirmness and sugar content were used. NIR spectral data were collected from the twovarieties of grape in the spectral region between 800 nm and 1700 nm. Statisticalmodels were developed using the partial least square method to predict the firmnessand sugar content of grape. The models gave relatively good predictions of thefirmness of both Superior and King Ruby, with corresponding r values of 0.80 and0.65. The NIR models gave excellent prediction for grape sugar content with valuesof 0.71 % and 0.65 % Brix for Superior and King Ruby, respectively.

Development of Proanthocyanidins inVitis viniferaL. cv. Pinot noir Grapes and Extraction into Wine

The effect of grape maturity on proanthocyanidin concentration, composition and transfer into wine was studied. <i>Vitis vinifera</i> L. cv. Pinot noir grapes (Pommard clone) were monitored for three consecutive vintages (2001 to 2003). Proanthocyanidin content was monitored by reversed-phase HPLC after acid-catalyzed cleavage in the presence of excess phloroglucinol (phloroglucinolysis). After three growing seasons, results indicated that an increase in heat summation between fruit set and veraison was associated with an increase in proanthocyanidin content in grapes and wine. Maturity did not have a consistent effect on the total proanthocyanidin content in wine, but the proportion of seed-derived proanthocyanidins extracted consistently increased with maturity.

Effect of Lobesia botrana damages on black aspergilli rot and ochratoxin A content in grapes

Sixty-nine wine grape samples of two varieties (Bombino Nero and Uva di Troia) were collected from four vineyards in a high ochratoxin A (OTA) incidence grape-growing area in Apulia, southern Italy, during the 2001 and 2002 crop harvests. The levels of toxin, measured in the two year harvests, ranged from 0.02 to 681 ng/g of fresh berries. In both surveys, higher levels of contamination by black aspergilli and OTA were found in both intact and rotten berries originating from bunches damaged by Lobesia botrana larvae as compared to bunches without L. botrana attacks. All berry samples with an OTA level > 1 ng/g were contaminated by black aspergilli with a CFU > 10 6, and all but one of these samples belonged to the Lobesia damaged berries group. This is the first evidence of an interaction between L. botrana damaged berries and OTA contamination, in field.

Short anoxic treatments to enhance trans-resveratrol content in grapes and wine

In a search for a method to improve the (endogenous) trans-resveratrol content in post harvested grapes, several short anoxic treatments with dry nitrogen have been assayed. A significant enhancement of the trans-resveratrol content was obtained, especially for treatments under 24 h; moreover, with shorter treatments (e.g. 6 or 15 h) the induced higher content of trans-resveratrol was maintained during several days with no appreciable anoxic damage of the grapes. These results allowed the design of an anoxic treatment protocol for wine grapes prior to the vinification process that led to a trans-resveratrol enriched wine.

Development of a fast spectroscopic enzyme assay for on-site measurement of total polyphenol content in grapes and wine

In recent years interest in polyphenols as a nutrient in vegetables and fruits has increased because of polyphenols' positive effects on human health. The interest focuses on the sensory properties of polyphenols and their influence on the taste of fruits and derived products. This article presents the development of a bioanalytical measurement technique enabling the determination of the total polyphenol content (TPC) of fresh grapes within a few minutes. Furthermore this technique allows the control of TPC during production processes, e. g. fermentation of wine.

SUSCEPTIBILITY OF SOME GRAPEVINE CULTIVARS IN AREA OF VINEYARDS OF PODGORICA ON THE ATTACK OF EUROPEAN GRAPE BERRY MOTH - LOBESIA BOTRANA DEN &amp; SCHIFF, LEPIDOPTERA, TROTRICIDAE

Economically the most important pest of grapevine in area of vineyards of Podgorica is Lobesia botrana Den. et Schiff. (Lepidoptera, Tortricide). Larvae feeding in flower buds, flowers, green and mature grape berries cause damage. Larvae might finish their development even on young leaves. Not all the cultivars have the same susceptibility to the moth attack. This depends on the bunch compactness, as well as on the composition and thickness of berry epidermis and sugar content in grapes. Investigations were conducted during 1998 and 2000 on three grapevine cultivars: Vranac, Rkaciteli and Cardinal on second generation of moth. On 25 randomly chosen grapevine plants, 4 bunches of grapes were examined in detail to check moth presence and calculate the number of cocoons on 100 bunches of grapes. For the first moth generation in the period of full bloom, all bunches of grapes from 25 grapevine plants of nine cultivars (Vranac, Kratosija, Krstac, Cardinal, Ribier, Pleven, Early Afus Ali, Clotild Prosperi and Caus × Bulgar), were examined during the period of investigation. Average number of cocoons on 100 bunches of grapes was calculated. The most important attack of the grape berry moth was in Krstac cultivar, which is one of the most represented autochthonous cultivar with white epidermis, followed by Vranac and Kratosija. According to the observations, those three cultivars had the most compact clusters. The highest percentage of infested bunch of grapes in the second generation was in Vranac cultivar that also had the most compact bunch of grapes. Considering that the most susceptible cultivars to the moth attack were those with compact clusters and bunches of grapes, and also that females lay eggs on the bunches protected from the direct sun, the training system that allows the better plant aeration possible, should be chosen, during the grapevine growth.

Non-volatile analysis in fruits by laser resonant ionization spectrometry: application to resveratrol (3,5,4′-trihydroxystilbene) in grapes

A laser desorption (LD) coupled with resonance-enhanced multiphoton ionisation (REMPI) and time-of-flight mass spectrometry (TOFMS) technique for non-volatile trace analysis compounds is presented. Essential features are: (a) an enhanced desorption yield due to the mixing of metal powder with the analyte in the sample preparation, (b) a high resolution, great sensitivity and low detection limit due to laser resonant ionisation and mass spectrometry detection. Application to resveratrol content in grapes demonstrated the capability of the analytical method with a sensitivity of 0.2 pg per single laser shot and a detection limit of 5 ppb.

Organoleptic impact of 2-methoxy-3-isobutylpyrazine on red bordeaux and loire wines. Effect of environmental conditions on concentrations in grapes during ripening.

The 2-methoxy-3-isobutylpyrazine content in grapes and red wines was assayed by stable isotope dilution gas chromatography-mass spectrometry, following vapor extraction and purification on a cation resin microcolumn. The threshold beyond which the green bell pepper character is marked in wines has been determined. From a comparison of the 2-methoxy-3-isobutylpyrazine concentrations of 50 red Bordeaux and Loire wines from different vintages and grape varieties (Cabernet Sauvignon, Cabernet franc, and Merlot) with the intensity of the green bell pepper character as perceived on tasting, the threshold value was estimated to be 15 ng/L. Statistical analysis of the 2-methoxy-3-isobutylpyrazine concentrations of 89 red Bordeaux wines showed that Cabernet wines were more commonly affected by this vegetative character. Changes in the 2-methoxy-3-isobutylpyrazine concentration as the grapes ripen are affected by the environmental and cultural conditions (soil, climate, training system, etc.). A very good correlation was shown between the breakdown of malic acid and 2-methoxy-3-isobutylpyrazine as the grapes ripened, irrespective of grape variety, type of soil, or weather conditions.

EVOLUÇÃO DA ACIDEZ DURANTE A VINIFICAÇÃO DE UVAS TINTAS DE TRÊS REGIÕES VITÍCOLAS DO RIO GRANDE DO SUL

The acidity influences the wine stability and coloration and it is one of the most important sensory attributes of wines. The total acidity and the pH vary with the salification of tartaric acid and the K content in grapes. This work evaluated the acidity evolution during vinification of three red grape varieties (Merlot, Cabernet Franc and Cabernet Sauvignon) from three viticultural regions of the state of Rio Grande do Sul, Brazil. The vineyards were uniforms and with the same trellising and pruning systems and grafted on the SO4 rootstock. The wines were elaborated by the microvinification process in the 1995 vintage. The evolution of pH, total acidity, tartaric acid and K were evaluated in five vinification phases: 1) immediately after crushing; 2) after draining; 3) after alcoholic fermentation; 4) after malolactic fermentation; 5) after tartrate stabilization. Results show that wines from Sant'Ana do Livramento presented the lowest values of total acidity and the highest increases of pH. The acidity evolution was associated with the initial K and tartaric acid levels found in the grape musts.

Variation in phenol content in grapes during ripening: low-molecular-weight phenols

Variations in low-molecular-weight phenolic compounds in different parts (must, skin, and seeds) of berries ofV. vinifera, variety Cencibel during ripening were studied using HPLC andTLC. Twenty-five different compounds were identified. The differences were chiefly quantitative, although some quantitative differences were also recorded.

Effect of Temperature Change on the Release Rate of Sulfur Dioxide from Two-Stage Sodium Bisulfite Generators

Sodium bisulfite two-stage SO₂ generators were packed with 9Cardinal9 grapes at room temperature in unvented containers with polyethylene-coated curtains. During cooling and at 32°F the concentration of SO₂ around the fruit reached 28 ppm in 4 days then dropped to 3 ppm after 21 days. The concentration in containers moved to 75°F on the 21st day, increased to 40 ppm on the 22nd day, dropping to 1 ppm on the 24th day. Concentrations in containers kept at 32°F dropped gradually to zero by the 42nd day. However, concentrations in containers moved to 75°F on the 42nd day, increased to 12 ppm by the 43rd day, dropping to less than 1 ppm on the 45th day. Concentrations in containers moved to 75°F on the 59th day rose from zero to 3 ppm on the 60th day, then dropped to zero on the 61st day. No SO₂ was detected in containers warmed up on the 79th day. Patterns were similar but lower in containers with kraft unvented curtains but with no vapor-barrier film, especially on the 4th and 22nd days. Total SO₂ content of grapes and bleaching injury were related directly to air concentrations and time of exposure to the gas. Amount of decay showed an inverse relation to gas exposure.

Accumulation of tartaric acid in the ripening process of grapes

1. Tartaric acid content in grapes gradually increased with ripening and reached a plateau about 50 days after flowering. 2. Tartaric acid synthesis from 14C02 was predominant in an early ripening stage. When the berries were exposed to 14CO2 8 days after flowering and examined two days later, 30% of the total 14C fixed was found in tartaric acid. Subsequently, a part of the tartaric acid decomposed, but the greater part remained in the berries in a salt form. At the last stage of the ripening process (82-100 days after flowering), some of the tartarate was again converted to free acid. No 14CO2 was incorporated into tartaric acid when berries were exposed 61 days after flowering. 3. L(+)-Tartaric acid-l,4-14C fed to the berries was catabolized to 14CO2. The ratio of radio activity recovered as 14 CO2 to that fed was nearly constant throughout the ripening process. The cause of tartaric acid accumulation in grape berries is not thought to be due to a lack of catabolizable enzymes, but to formation of an insoluble salt which is scarcely effected by such enzymes.

Growth and senescence of the grape berry*

Benzothiazole-2-oxyacetic acid (BTOA) was applied to bunches of grapes (Vitis vinifera cv. Shiraz) at different times during their development and its effect on their subsequent growth was followed by measuring changes in berry weight, reducing sugars, malate, and tartrate. It lengthened the slow growth phase of berry development and this delayed ripening. It had no effect on the course of the first or second rapid growth stages. Greatest response to a single application was obtained when BTOA was applied at the end of the first growth stage or during the first week of the lag phase. Two and three applications made at 2-weekly intervals lengthened the lag phase more than a single application. During the prolonged lag phase malate continued to increase and reached a higher maximum than in untreated grapes. No consistent effect of BTOA on the tartrate content of grapes was apparent. The response of grapes to treatment with BTOA and other auxins is discussed in relation to growth and senescence of the grape berry. * This work was initiated at the Australian Wine Research Institute, Glen Osmond, S.A. 5064, Australia.