Postharvest ethylene and 1-MCP treatments both affect phenols, anthocyanins, and aromatic quality of Aleatico grapes and wine

Aleatico grapes (Vitis vinifera L. cv. Aleatico) picked at 20.4–20.6^oBrix were treated with air containing 500 mg/L ethylene for 15 h, or 1 mg/L 1‐MCP (1‐methylcyclopropene) for 15 h, or 1 mg/L 1‐MCP for 15 h + 500 mg/L ethylene for further 15 h, or air (control). All treatments were imposed at 20^oC and 95–100% relative humidity. Samples undergoing treatment were then held in air at 20^oC and 85% relative humidity for 13 days. Ethylene production from ethylene‐treated grapes was very high (25 μL/kg.h) immediately after treatment, and declined progressively until day 6; 1‐MCP‐ethylene‐treated grapes showed lower ethylene production (10 μL/kg.h). This high ethylene production was mainly due to in‐out diffusion of ethylene absorbed during the treatment, but a potential effect of 1‐MCP is postulated, since 1‐MCP‐treated grapes did not show ethylene production for 2 days after treatment, whereas control grapes produced constant amounts (3–4 μL/kg.h) of ethylene. After day 6, no significant difference was observed among samples. No difference in respiration was revealed. Total phenols were increased significantly by ethylene treatment from 520 mg/L up to 710, while total anthocyanins were lost in air‐treated samples (from 175 mg/L to 120) and remained constant in ethylene and 1‐MCP‐treated grapes. HPLC analyses of anthocyanins confirmed this result: air‐treated samples lost anthocyanins rapidly while this loss was delayed in gas‐treated samples. Terpenols, esters, alcohols, and C6 compounds were increased by ethylene treatment. Conversely, 1‐MCP‐treated grapes showed a significant loss of terpenols and esters, although maintaining alcohols, especially hexan‐1‐ol. Berry pathology was also affected, with 1‐MCP and 1‐MCP‐ethylene treated grapes hosting a diffuse attack of grey mould. Wine analyses revealed higher concentrations of phenols and anthocyanins in wine from ethylene‐treated grapes, although aromatic compounds were lost, and thus the aroma profile of those wines was diminished.     

Residues of the fungicide famoxadone in grapes and its fate during wine production

Famoxadone is a recently applied fungicide to vines that belongs to the oxazolidinedione family. The fate of famoxadone was studied by considering the decay ratio of this fungicide during the maturation of grapes and wine production. The main factors affecting the presence of fungicide residues such as fruit growth, photodegradation, evaporation, thermodegradation and co-distillation were studied with model systems. An experimental field was treated with a commercial product containing famoxadone at the recommended dose. After this application, residues of famoxadone were found in grapes at 0.27 ± 0.06 mg kg^-1. In this field experiment, the half-life (t_1/2;) of famoxadone, which is described by pseudo-first-order kinetics (R² = 0.74), was 18 ± 6 days, resulting from the photodegradation. The famoxadone residue levels in grapes were below the established maximum residues level for Europe (2 mg kg^-1), whilst levels in wine, carried out with and without maceration, were below the calculated limit of detection of the method.     

Effect of postharvest dehydration on the composition of pinot noir grapes (Vitis vinifera L.) and wine

This study was conducted in order to improve our understanding of how phenolics and aroma compounds change in wine grapes during postharvest dehydration. Pinot noir grapes grown in the Willamette Valley of Oregon were harvested at 22.0 and 24.0 °Brix. Grapes harvested at 22.0 °Brix were divided into three equal lots with one lot immediately used for wine production, and the remaining two lots placed inside an air tunnel with an air speed of 1.0–1.8 m s⁻¹, 38% relative humidity and a temperature of 22 °C. The soluble solids content and weight loss were measured daily and wines were made from grapes when they reached 24.8 and 26.7 °Brix. The soluble solids of grapes increased about 1 °Brix per day; therefore, on the third and fourth day the berries reached the desired concentration; weight loss was 14 and 16%, respectively. Results from berry phenolic analysis indicated that per berry anthocyanin amount remained unchanged during dehydration. The composition of proanthocyanidins isolated from berries changed during dehydration. Volatile compounds in wines made from dehydrated grapes contained more terpenes and norisoprenoids (β-ionone, β-damascenone) when compared to wine made from the original fruit. Wines made from increasingly dehydrated grapes tended to resemble the composition and flavour profile of wines made from grapes left on the vine (i.e. with extended ripening). The results of this study suggest that postharvest flavour changes consistent with changes during fruit ripening can occur in grapes when harvested early and allowed to dehydrate under controlled conditions prior to fermentation.     

Screening of grapes and wine for azoxystrobin, kresoxim-methyl and trifloxystrobin fungicides by HPLC with diode array detection

The Quinone outside Inhibitors (QoI) are one of the most important and recent fungicide groups used in viticulture and also allowed by Integrated Pest Management. Azoxystrobin, kresoxim-methyl and trifloxystrobin are the main active ingredients for treating downy and powdery mildews that can be present in grapes and wines. In this paper, a method is reported for the analysis of these three QoI-fungicides in grapes and wine. After liquid-liquid extraction and a clean-up on commercial silica cartridges, analysis was by isocratic HPLC with diode array detection (DAD) with a run time of 13 min. Confirmation was by solid-phase micro-extraction (SPME), followed by GC/MS determination. The main validation parameters for the three compounds in grapes and wine were a limit of detection up to 0.073 mg kg^-1, a precision not exceeding 10.0% and an average recovery of 93% ± 38.     

Headspace volatile compounds during osmotic dehydration of strawberries (cv Camarosa): Influence of osmotic solution composition and processing time

The influence of the type of sugar in the osmotic solution and of the time of processing on the volatile compounds of strawberries was studied, in order to optimize the technique as a pre-treatment to further processing. Strawberries of cultivar ‘Camarosa’, cut into 1 cm thick slices, were subjected to osmotic dehydration at 30 °C for 1, 2, 4 and 6 h using either 60% (w/w) sucrose or 60% (w/w) sorbitol solutions. Volatile compounds of fresh and processed strawberry slices were analyzed by static headspace—gas chromatography. Osmotic treatments provoked a loss in volatile compounds due to the migration, mainly of esters, into the osmotic media. The variations in the volatile pattern depended on both time of treatment and type of osmotic solution. The greater changes occurred after 2 h in sucrose; with a promotion of fermentative volatiles (acetaldehyde, ethyl acetate), and a decrease in the other volatiles. Using sorbitol as osmotic agent, the major variations in the volatile pattern occurred after 4 h of osmosis, and the fermentative process was less important than in sucrose, as sorbitol could be less effective in forming a peripheral layer at the fruit surface and/in reducing tissue porosity.     

Postharvest dehydration of wine white grapes to increase genistein, daidzein and the main carotenoids

Wine white grape bunches of the Grechetto variety were dehydrated at 10, 20 and 30°C, RH 45% and forced air ventilation of 1.5m/s. Chemical and metabolic changes due to the effect of dehydration were studied at various stages of weight loss: 10%, 20%, 30% and 40%. Berry colour at 10 and 20°C tended to become greener with dehydration but at 30°C, at the final sampling, the colour darkened. Acidity decreased in all samples, while sugars increased. Total phenol content increased at 10°C until 30% weight loss was reached and then declined, while at 20 and 30°C the concentration decreased immediately. The contents of lutein and β-carotene (respectively 68 and 58mg/kg d.w.), representing the 80% of total carotenoids, did not change significantly until the 30% of weight loss, when at 30°C the value increased above all for lutein while at 10 and 20°C, the contents decreased significantly. Daidzein, at 10°C, rose significantly from about 150μg/kg d.w. to 1434μg/kg d.w. at 20% weight loss and then declined; at the same weight loss percentage, the genistein concentration began to increase. At 20°C both isoflavones rose until the end of the experiment, reaching values similar to the sample at 10°C. A temperature of 30°C was deleterious to grape isoflavones. A discussion on the changes in isoflavones related to temperature and time is reported.     

The effects of copper and high sugar concentrations on growth, fermentation efficiency and volatile acidity production of different commercial wine yeast strains

The effect of high sugar concentrations or the presence of copper residues on fermentation efficiency and volatile acid (VA) production were examined for selected commercial wine yeast strains. Fermentation rate as measured by accumulated mass loss appeared to be least affected by high sugar concentrations during the first few days of fermentation for strains VIN13, WE14, N96 and RJ11. It was, however, only fermentations using VIN13, WE372, N96 and L2056 that contained less than 11 g/L fructose after 21 days. VIN13 and RJ11 produced the lowest VA in the 21^o, 25^o and 28^oBrix musts. Fermentation efficiency of six strains was also studied in must containing 0.25 mM Cu²⁺. Results indicated that strains NT50, Collection Cépage Cabernet (CC) and D80 were not significantly affected, whereas VIN13, NT112 and RJ11 contained significantly more glucose and fructose after fermentation in the must containing copper. Copper addition also increased VA production, with strains RJ11 and NT50 being the most affected.     

Effect of intra and interspecific interaction on OTA production by A. section Nigri in grapes during dehydration

The aim of this study was to assess the colonizing capability and OTA production of different populations of Aspergillus section Nigri spp. in grapes, as affected by the interactions with other fungi, during a simulated in vitro sun-drying. Mature white grapes were divided into two lots of healthy and artificially injured grapes and inoculated with A. section Nigri spp. (A. carbonarius OTA producer, A. niger aggregate OTA producer, A. niger aggregate OTA non-producer), Eurotium amstelodami and Penicillium janthinellum, in different combinations. The drying process was simulated adjusting water activity firstly at 0.98 a(w) and gradually decreasing it to 0.76 a(w) for a total of 20 days. Colonizing grape percentages were recorded after 5, 10, 15 and 20 days of dehydration and OTA content was measured after 5, 7, 10, 12, 15, 17 and 20 days. Colonization of grapes increased with time in all treatments. A. niger aggregate OTA-positive showed the highest colonization percentage, followed by A. carbonarius, and finally their mixed inoculum. When the two OTA-producing strains were combined, addition of any other microorganism increased the percentage of infection by A. section Nigri. A. carbonarius was the highest OTA producer in pure culture, followed by A. niger aggregate OTA-positive. In general, when competing fungi were added to A. carbonarius inoculum, the OTA content was reduced. E. amstelodami was the only competing fungus which increased OTA accumulation. The sun-drying process may be conducive to OTA accumulation in dried grapes. The complex fungal interactions which may take place during this process, may act as an additional control factor, given that the higher presence of A. niger aggregate OTA-negative inhibits OTA accumulation by OTA producing species.     

Nitrogen addition influences formation of aroma compounds,volatile acidity and ethanol in nitrogen deficient media fermented by Saccharomyces cerevisiae wine strains

The effects of nitrogen addition into nitrogen deficient/depleted media on the release of aroma compounds post-fermentation were investigated in three commercial yeast strains of Saccharomyces cerevisiae which highlight the yeast strain effect as well as nitrogen effects. By comparing the two timings of nitrogen addition, prior to fermentation or later at stationary phase (72 h), it was shown that nitrogen addition at stationary phase significantly decreases ethanol and acetic acid formation and significantly increases the following compounds: 2-phenylethanol, ethyl isobutyrate, 2-phenylethyl acetate, ethyl 2-methylbutyrate and ethyl propionate in the three strains, and also isovaleric acid, isoamyl alcohol and ethyl isovalerate in both PYCC4072 and UCD522. The strain EC1118 produced significantly less medium chain fatty acids, hexanoic, octanoic and decanoic acids and their respective esters after nitrogen addition. Therefore, timing of nitrogen addition to a ferment media can vary the concentration of certain aroma compound and might provide a means for varying wine composition.     

The effect of ethephon and clone on physical characteristics and sensory quality of Crimson Seedless table grapes after 1 month storage

Colour is one of the most important quality parameters of table grapes. Ethephon can be applied to improve the colour of table grapes. Trials were conducted in Western Australia to investigate the effect of ethephon on low berry colour and other quality parameters of two new clones (306 and 314) of Crimson Seedless table grapes developed in Western Australia. The ethephon effect was studied in comparison with clone 5560, which was the standard clone imported from California. The grape clones were established at two locations in Western Australia having different types of soil and environmental conditions. Ethephon was applied (300 ppm Ethrel^®) to improve the colour development. Physical measurements demonstrated that clones 306 and 314 were better than the imported standard clone in terms of berry weight, length and width. Sensory evaluation by 70 panellists revealed that clone 314 with ethephon application received significantly higher sensory scores for sweetness, crispness, flavour and overall acceptability compared with the standard clone. The acidity level was higher in clone 314 than the standard clone at the same °Brix level and had a positive effect on flavour and overall acceptability. Ethephon treatment reduced the berry crispness in the standard clone and clone 306 but had no effect on the crispness of clone 314.     

Effect of osmotic dehydration on dielectric properties,microwave vacuum drying kinetics and quality of mangosteen

Mangosteen (Garcinia mangostana Linn.) with and without osmotic dehydration (OD) in sucrose solution was dried by microwave vacuum drying at 1200, 1440 and 1680 W. Because of water loss (49.12–49.98 g 100 g^?1) and solid gain (9.31–11.62 g 100 g^?1) during OD, dielectric constant, loss factor and loss tangent of mangosteen were significantly increased (P ≤ 0.05) to 24.82–25.12, 11.52–14.18 and 0.47–0.50, respectively. With the decreased initial moisture content and the modified dielectric properties, drying time of osmotically dehydrated mangosteen was shorter than that of mangosteen without OD. Moreover, an increase in microwave power enhanced drying kinetics. With OD, Tg of dried mangosteen was increased from ?7.01, ?3.00 to 11.11–25.96 °C. Hardness and lightness (seedless part) were significantly increased (P ≤ 0.05). Structure of dried seedless mangosteen was well protected, resulting in the improved rehydration ability (P ≤ 0.05). Nonetheless, rehydration ability of the mangosteen containing seed was not improved (P > 0.05).     

Fate and distribution of pyrimethanil,metalaxyl, dichlofluanid and penconazol fungicides from treated grapes intended for winemaking

Tempranillo grapes were immersed in solutions of pyrimethanil, metalaxyl, dichlofluanid and penconazol fungicides at different concentrations for several different times. Determinations of the fungicide residues was carried out by GC-NPD, with an additional confirmation by GC-MS. The percentage absorption was determined as well as the distribution between surface, skin and pulp of the grapes. The percentage absorption ranged from 7.2 to 85.5%. These values depended on the time the grapes were in contact with the fungicide solutions. Residues were mainly found in skins, with percentages in skins ranging from 66.3 to 90.3% of total residues. In pulp, these values ranged from 3.5 to 31.0%. The overall methodology was applied to the determination of pyrimethanil in Tempranillo grapes treated with the recommended doses, respecting the safety period. Pyrimethanil residues found in treated grapes were higher in the skin. In grapes collected within the safety period (21 days), the levels found for fungicide residues were below maximum residues levels.     

Implications of nitrogen nutrition for grapes, fermentation and wine

This review discusses the impacts of nitrogen addition in the vineyard and winery, and establishes the effects that nitrogen has on grape berry and wine composition and the sensory attributes of wine. Nitrogen is the most abundant soil‐derived macronutrient in a grapevine, and plays a major role in many of the biological functions and processes of both grapevine and fermentative microorganisms. Manipulation of grapevine nitrogen nutrition has the potential to influence quality components in the grape and, ultimately, the wine. In addition, fermentation kinetics and formation of flavour‐active metabolites are also affected by the nitrogen status of the must, which can be further manipulated by addition of nitrogen in the winery. The only consistent effect of nitrogen application in the vineyard on grape berry quality components is an increase in the concentration of the major nitrogenous compounds, such as total nitrogen, total amino acids, arginine, proline and ammonium, and consequently yeast‐assimilable nitrogen (YAN). Both the form and amount of YAN have significant implications for wine quality. Low must YAN leads to low yeast populations and poor fermentation vigour, increased risk of sluggish/stuck/slow fermentations, increased production of undesirable thiols (e.g. hydrogen sulfide) and higher alcohols, and low production of esters and long chain volatile fatty acids. High must YAN leads to increased biomass and higher maximum heat output due to greater fermentation vigour, and increased formation of ethyl acetate, acetic acid and volatile acidity. Increased concentrations of haze‐causing proteins, urea and ethyl carbamate and biogenic amines are also associated with high YAN musts. The risk of microbial instability, potential taint from Botrytis‐infected fruit and possibly atypical ageing character is also increased. Intermediate must YAN favours the best balance between desirable and undesirable chemical and sensory wine attributes. ‘Macro tuning’, of berry nitrogen status can be achieved in the vineyard, given genetic constraints, but the final ‘micro tuning’ can be more readily achieved in the winery by the use of nitrogen supplements, such as diammonium phosphate (DAP) and the choice of fermentation conditions. This point highlights the need to monitor nitrogen not only in the vineyard but also in the must immediately before fermentation, so that appropriate additions can be made when required. Overall, optimisation of vineyard and fermentation nitrogen can contribute to quality factors in wine and hence affect its value. However, a better understanding of the effect of nitrogen on grape secondary metabolites and different types of nitrogen sources on yeast flavour metabolism and wine sensory properties is still required.