Berry skin thickness as main texture parameter to predict anthocyanin extractability in winegrapes

Red grapes are the only source of anthocyanins in wines and therefore the assessment of their extractability is important for wine quality. To date, a mathematical equation relating skin mechanical properties and anthocyanin extractability has never been performed for different ripening stages and vineyards located in a given production area. The main aim of this work was to assess anthocyanin extractability attempting to its relation with skin textural parameters. Morphological parameters, skin texture characteristics, total anthocyanin contents and extractability percentages were determined in Mencía grape berries (Vitis vinifera L.) from several vineyards and calibrated according to their density at three amounts of soluble solids. Skin mechanical properties were measured by Texture Analysis; a rapid and low-cost analytical technique. In most vineyards, an increasing tendency of texture parameter values was observed with the ripening stage but the differences were not statistically significant. The accumulation of anthocyanins in berry skin usually increased with the ripening stage. Anthocyanin extractability was no influenced by ripening stages for each vineyard studied. The study allowed to establish a skin texture parameter as predictor of anthocyanin extractability for a given production area. Thinner skins seem to be characterized by a greater release of red pigments.     

水杨酸和壳聚糖处理对‘白罗莎里奥’葡萄留树保鲜效果的影响

以‘白罗莎里奥’葡萄为试材,叶面喷施不同浓度的水杨酸和壳聚糖,进行果实成熟后留树保鲜试验。通过测定留树期间果实品质、烂果率、生理指标及休眠期冬芽发育的变化,分析评价水杨酸和壳聚糖在留树保鲜中的应用效果。结果表明:两种药剂对果实留树保鲜的效果良好,表现较佳的水杨酸使用浓度为1.5 mmol/L,壳聚糖使用浓度为0.1%。高浓度的水杨酸和低浓度的壳聚糖均可有效延缓葡萄留树期间果实品质的变化,降低葡萄果实中丙二醛的含量和多酚氧化酶活性,减少烂果,同时又能促进冬芽的发育。因此认为,水杨酸和壳聚糖可以作为保鲜剂延长葡萄的挂果期。     

“赤霞珠”葡萄转色后不同成熟度指标的变化

研究酿酒葡萄转色后不同成熟度指标的动态变化规律。以“赤霞珠”葡萄为试材,分别测定了技术成熟度和总酚成熟度指标,并进行了浆果感官评价。结果表明：转色后果实物理性状参数和糖含量迅速增加,转色后第4周达到最大值,成熟后期略有下降。果实中总花色苷含量逐渐增加,在转色后第6周达到最高,随后有所降低。浆果中可提取花色苷含量持续增加。细胞成熟指数、种子成熟指数和总酚指数总体上逐渐降低。果皮单宁含量变化较小,种子单宁含量在成熟前期显著降低（P＜0.05）,后期变化较小。不同分子大小聚合色素的含量逐渐增加,转色后第6周时达到最大值。浆果感官评价中各种成熟度的得分逐渐增加,果肉香气成熟度和果皮成熟度得分均在转色后第7周时最高,成熟后期变化较小。     

Consumer Acceptability of Fresh‐Market Muscadine Grapes

The objective of this research was to investigate the acceptability of muscadine grape (Vitis rotundifolia) genotypes (cultivars and selections) and to correlate overall liking to other quality measurements to determine the main drivers of liking. Twenty‐two genotypes grown at the Univ. of Georgia–Tifton Campus were evaluated. Four retail commercial grape genotypes (Vitis vinifera and “Concord”) were also evaluated for comparison. Panelists familiar with muscadine grapes used the hedonic general labeled magnitude scale (HgLMS, –100 = strongest disliking of any kind ever experienced, +100 = strongest liking of any kind ever experienced) to rate overall liking and the liking of appearance, flavor, pulp texture, and skin texture. Puncture testing was done to assess grape berry texture, and compositional attributes soluble solids and pH were also measured. The sensory results indicated that the grapes were variable with overall liking scores from 12.2 to 39.6. The factors highly correlated with overall liking scores were muscadine flavor, pulp and skin liking, while a significant negative correlation was found between skin liking and skin texture and mechanical texture measures. The muscadine grapes with the highest overall liking scores were Ga. 5‐1‐34 and Ga. 2‐8‐21. Principal component analysis confirmed that grapes with a thinner skin and a higher pH tended to group around overall liking and flavor points. These results indicate that even among panelists familiar with muscadine grapes, skin thickness is a negative characteristic. Breeding for thinner skins may be a positive step in muscadines gaining a more widespread appeal in the fresh fruit market.     

新疆伊犁地区赤霞珠葡萄成熟过程中花色苷组成及含量变化研究

本实验以新疆伊犁产区的赤霞珠酿酒葡萄为原料,采用液相色谱-质谱(HPLC-MS)联用检测分析伊犁地区2016年整个生长发育过程中赤霞珠酿酒葡萄果实中花色苷组成和含量上的变化规律,从中分析不同类型的花色苷在葡萄果实成熟的不同阶段的比例变化。实验表明:在伊犁地区,葡萄果实中的花色苷主要以甲氧基化形式存在,甲氧基化花色苷占总花色苷的比例在葡萄的成熟发育过程中变化不大。3’5’-取代花色苷在两地区均是葡萄果实成熟发育过程中的主要花色苷类型,占花色苷总量的70%以上,当葡萄果皮中花色苷积累至最大值后,随花色苷总量的减少3’-取代花色苷占总花色苷的比例均降低;乙酰化花色苷和香豆酰化花色苷占总花色苷的比例在葡萄果实成熟发育过程中的变化不同。伊犁地区花色苷在葡萄生长发育过程中均有下降趋势,香豆酰化花色苷占总花色苷的比例在伊犁地区葡萄果实成熟发育过程中呈现无规律的变化。     

Fungi and mycotoxins in vineyards and grape products

Many fungi may occur on grapes during growth in the vineyard, but the main concern from the viewpoint of mycotoxin contamination is the black Aspergilli, Aspergillus carbonarius and A. niger. These fungi are capable of producing ochratoxin A (OA) which may contaminate grapes and grape products such as wine, grape juice and dried vine fruit. Understanding the ecology and physiology of the black Aspergilli can provide tools for management of OA at all stages of grape production and processing. In the vineyard, careful management of cultivation, irrigation and pruning can assist in minimising the levels of black Aspergilli in the soil, which in turn, can minimise contamination of grapes by these fungi. Minimising damage to grapes on the vine by the use of open vine canopies, grape varieties with resistance to rain damage and by the management of insect pests and fungal diseases (e.g., mildew, Botrytis bunch rot) can reduce the incidence of Aspergillus rot in mature berries. The risk of OA in table grapes can be minimised by careful visual inspection to avoid damaged and discoloured berries. In wine, harvesting grapes with minimal damage, rapid processing and good sanitation practices in the winery assist in minimising OA. During vinification, pressing of grapes, and clarification steps which remove grape solids, grape proteins and spent yeast can also remove a significant proportion of OA. For dried vine fruit production, avoiding berry damage, rapid drying, and final cleaning and sorting to remove dark berries can reduce overall OA levels in finished products.     

Influence of the heterogeneity of grape phenolic maturity on wine composition and quality

Nowadays, consumers demand red wines with deep colour, soft tannins and fruit scents, but these wines can only be obtained from grapes with complete phenolic maturity. Diverse methods have been proposed for measuring phenolic maturity. However, all these methods only provide the average value and do not consider any possible heterogeneity. Throughout ripening, grapes were separated according to their density, which revealed the existence of a large heterogeneity. Grapes at harvest were also separated by density in three groups. The higher the density of the grapes the higher ethanol content, pH, colour intensity, total phenolic index and anthocyanin and proanthocyanidin concentrations, and the lower the titratable acidity and bitterness of the wines. When the grapes were denser the wines were also better balanced in flavour and mouthfeel sensation. These results suggest that grape heterogeneity may influence the final wine composition and quality and therefore it should be considered at harvest.     

On-Vine Monitoring of Grape Ripening Using Near-Infrared Spectroscopy

This study evaluated the ability of near-infrared (NIR) spectroscopy to characterise the behaviour of white and red grapes during on-vine ripening, as a function of grape position in the bunch (high, middle and low) and bunch orientation (north, south, east and west) and to distinguish between different ripening stages with a view to optimising harvesting times depending on the grape variety and the type of wine to be made. A total of 24 bunches of two wine-grape varieties (cv. Pedro Ximénez and cv. Cabernet Sauvignon) were labelled and analysed directly on the vine using a commercially available handheld micro-electro-mechanical system spectrophotometer (1,600?C2,400?nm). Principal component analysis was performed to study relationships between the various configurations (grape position and bunch orientation), ripening stages and spectral data. Results for the white-grape variety showed that grapes high on the bunch behaved differently during ripening from those in central or low positions and that east-facing bunches behaved differently from the rest. For both varieties, analysis of bunch spectral characteristics enabled three stages of ripening to be distinguished: early, middle and late. Subsequently, the ability of NIR technology to classify wine grapes as a function of reducing-sugar content, with a view to optimising harvest timing, was evaluated by partial least squares discriminant analysis: 88?% of white grapes and 88?% of red grapes were correctly classified while over 79?% of samples were correctly assigned to representative groups. These results confirmed that NIR technology in the spectral range 1,600?C2,400?nm is an appropriate technique for on-vine monitoring of the ripening process, enabling selective harvesting depending on the type of wine to be made.     

Changes in sour rotten grape berry microbiota during ripening and wine fermentation

This study investigated the microbiota of sour rotten wine grapes and its impact on wine fermentations. Yeasts, lactic acid bacteria (LAB) and acetic acid bacteria (AAB) were enumerated and identified on sound and sour rot grapes during the ripening stage. The alteration of the ecological balance induced by sour rot was particularly evidenced by the unequivocal increase of yeast and AAB counts on rotten grapes, since the beginning of ripening. Yeast and AAB species diversity in rotten grape samples were much higher than those found in sound grapes. LAB populations were low detected from both healthy and sour rotten grapes. The yeast species Issatchenkia occidentalis, Zygoascus hellenicus and Zygosaccharomyces bailii and the AAB species Gluconacetobacter hansenii, Gluconacetobacter intermedius and Acetobacter malorum, were recovered from damaged grapes and resulting grape juices in the winery. Acetobacter orleaniensis and Acetobacter syzygii were only recovered from sour rotten grapes. Dekkera bruxellensis and Oenococcus oeni were only recovered after wine fermentation induced by starter inoculation, irrespective of grape health, probably originating from cellar environment. After malolactic fermentation, racking and sulphur dioxide addition the only remaining species were the yeast Trigonopsis cantarellii and Saccharomyces cerevisiae, independently of the grape health status.     

Effect of Esca disease on the phenolic and sensory attributes of Cabernet Sauvignon grapes,musts and wines

Background and Aims: The impact of Esca, a cryptogamic disease affecting woody tissues of grapevines (trunk, branches and shoots), was investigated on phenolic and sensory qualities of Cabernet Sauvignon grapes, derived musts and wines. Methods and Results: Global phenolic analyses revealed no major difference between healthy and affected grapes whereas high‐performance liquid chromatography analyses showed decreases in the skin concentrations of catechin and epicatechin and of anthocyanins for the two vintages assessed. Proanthocyanidin characteristics, and particularly mean degree of polymerisation, were strongly decreased in skin proanthocyanidin polymeric fractions. Chemical analyses of wines made with different percentages of fruit from Esca infected grapevines confirmed the moderate impact of Esca on phenolic composition. Nevertheless, sensory analyses revealed a loss of wine sensory quality perceptible with as little as 5% of affected fruit in wines. Conclusions: Phenolic variations in grapes and in derived wines may be related to changes to grapevine physiology caused by Esca fungi that impact on flavonoid metabolism. The chemical and sensory variations between wines can also be related to the delayed ripening delay of fruit from Esca infected grapevines. Significance of the Study: Esca moderately affected the phenolic composition of grapes and decreased the sensory quality of wines, suggesting a dramatic increase in the economic importance of Esca if no control methods are found.     

Possible use of texture characteristics of winegrapes as markers for zoning and their relationship with anthocyanin extractability index

Ribeira Sacra Denomination of Origin is a steep slope viticulture area located in Galicia (northwest of Spain), and it is divided into five different subzones. Taking into account that grape composition depends not only on the grape cultivar used but also on the environmental factors and cultural practices, texture analysis has been proposed to assess the grape mechanical properties of those subzones. With the aid of principal component analysis, berry skin break energy measured on bottom side and berry cohesiveness have been suggested as the best mechanical properties for the subzones differentiation. Moreover, significant correlations among mechanical parameters and anthocyanin extractability index were found. A regression hyperplane allowed estimating anthocyanin extractability from berry skin thickness and Young′s modulus measured on the lateral side of grapes. The speed of mechanical analysis facilitates the planning and management of pressing and maceration processes as a consequence of the drastic reduction in sample treatment time.     

The influence of ripeness grade on the composition of musts and wines from Vitis vinifera cv. Tempranillo grown in a warm climate

Fruit ripeness has an influence on the phenolic and aromatic composition of grapes and musts and, therefore, on the sensorial characteristics of the resulting wine. The aim of the work described here was to assess the influence of the harvest date on the analytical composition of the musts and wines from the Vitis vinifera cv. Tempranillo grape grown in a warm climate. A hydroalcoholic medium was employed to extract the musts and simulate a traditional maceration process. Phenolic compounds were analysed by colorimetric methods and aroma compounds by gas chromatography/mass-spectrometry. Furthermore, the wines were tested by a sensory panel. A good correlation was obtained between the parameters measured in the must and in the corresponding wine, as well as in the scores recorded in the sensory analysis. In summary, grape ripening was found to have a marked influence on the wine composition and it was possible to establish the key parameters that need to be measured in the must during ripening to identify the optimal harvest date to obtain the best quality wine.     

不同采收期对黑比诺葡萄及葡萄酒品质的影响

为研究不同采收期对黑比诺葡萄及葡萄酒品质指标的影响,于葡萄转色后每7 d取样1次,监控葡萄果实理化指标及多酚含量的变化,并对不同采收期葡萄酿造的葡萄酒感官指标进行定量描述分析(QDA),以确定宁夏青铜峡黑比诺葡萄的最佳采收期;对不同采收期葡萄和葡萄酒的多酚指标进行主成分分析(PCA),筛选出对其品质影响最大的指标,达到简化实用的目的。结果表明,在葡萄成熟过程中,还原糖含量、糖酸比不断增加,总酸含量不断降低;果皮和籽中的多酚指标含量基本都呈先降低后逐渐升高的趋势;QDA分析结果表明,随着采收期的推移,相应葡萄酒的感官质量也逐渐提高;PCA分析结果表明,籽总类黄酮、皮总类黄酮和皮总花色苷对葡萄及葡萄酒品质的影响最大,并且其含量分别达到52.02±0.13 mg/g,29.95±0.28 mg/g和7.09±0.02 mg/g时,葡萄多酚成熟度相对较好,所酿葡萄酒的品质较佳;以期指导该地区黑比诺葡萄采收期的确定。     

First steps towards the development of a non-destructive technique for the quality control of wine grapes during on-vine ripening and on arrival at the winery

NIR spectroscopy was used as a non-destructive technique for the assessment of changes in certain internal quality properties of wine grapes (Vitis vinifera L.) during on-vine ripening and at harvest. A total of 108 different wine grape samples were used to construct calibration models based on reference data and NIR spectral data, obtained using a commercially-available diode-array spectrophotometer (380-1700 nm). The feasibility of testing bunches of intact grapes was investigated and compared with more traditional methods of presentation, such as berries or must. Predictive models were constructed to quantify changes in soluble solid content (SSC, °Brix), reducing-sugar content (g/l), pH-value, titrable acidity (g/l tartaric acid), tartaric acid (g/l) and malic acid (g/l), these being the major parameters used to chart ripening. NIRS technology provided good precision for the bunch analysis mode assayed for SSC (r² = 0.89; SECV = 1.41 °Brix), for reducing-sugar content (r² = 0.87; SECV = 17.13 g/l) and for pH-value (r² = 0.69; SECV = 0.19). Models developed for testing other fruit acidity parameters yielded results sufficient to provide a screening tool to distinguish between low and high acidity values in intact grapes. Significantly, the results obtained with bunch presentation were similar to those obtained with berries and must, thus justifying further implementation of NIRS technology for the non-destructive analysis of quality properties both during on-vine ripening and on arrival at the winery. This method allows musts to be processed separately depending on initial grape quality, assessed with a single spectrum measurement and in a matter of seconds.     

The effect of bunch shading on berry development and flavonoid accumulation in Shiraz grapes

Opaque boxes were applied to bunches of Shiraz grapes prior to flowering to determine the effect of sunlight on berry development and accumulation of flavonoids. The boxes were designed to maintain airflow while excluding light and thus to minimise changes in temperature and humidity. There was no significant effect of shading on sugar accumulation and in two of the three seasons studied there was no effect on berry weight. Chlorophyll concentration was much lower in the shaded fruit, which appeared pale yellow until veraison. The fruit coloured normally in the shaded bunches and in two of the three seasons there was no significant change in anthocyanin content. Expression of the gene encoding UDP-glucose flavonoid-3-O-glucosyl transferase (UFGT), a key gene in anthocyanin synthesis, increased after veraison and was similar in both shaded and exposed fruit. Anthocyanin composition was altered in the shaded fruit, which had a greater proportion of the dioxygenated anthocyanins, the glucosides of cyanidin and peonidin. Shading had no significant effect on the levels of condensed tannins in the skin or seeds of ripe fruit. Shading significantly reduced the levels of flavonols in the grape skin. In the exposed fruit, flavonol concentration was highest around flowering then declined as the berries grew, but there was an increase in flavonols per berry during ripening. When the boxes were applied before flowering, shaded fruit had much lower levels of flavonols throughout berry development and at harvest the level of flavonols were less than 10% of that in exposed fruit. A gene encoding flavonol synthase (FLS) was expressed at flowering and during ripening in exposed grapes but its expression was greatly reduced in shaded fruit. The results indicate that shading had little effect on berry development and ripening, including accumulation of anthocyanins and tannins, but significantly decreased flavonol synthesis.     

湿度条件对巨峰葡萄贮藏过程中水分及质构变化的影响

研究辽西地区巨峰葡萄在不同相对湿度90%、50%及环境湿度条件下贮藏时的水分变化规律,并与感官品质、全质构分析各参数（硬度、黏聚性、胶黏性、咀嚼性、弹性和黏附性）建立相关性联系。结果表明,90%相对湿度条件下葡萄贮藏效果要优于其他两个湿度条件。葡萄浆果总水分含量在贮藏期内总体呈现下降趋势,90%相对湿度贮藏时葡萄组织含水量相对较高,束缚水和自由水的变化也相对平稳,因此该条件更有利于维持葡萄水分的稳定。相关性分析结果表明,在高湿环境下（90%相对湿度）贮藏葡萄,对葡萄束缚水含量的追踪可以更好地表征和预测葡萄的贮藏品质;在低湿度环境下（50%相对湿度）贮藏葡萄,总水分含量是更合理的指标;环境湿度条件贮藏时,对自由水和总水分含量测定来间接表征葡萄贮藏品质较合理。     

BRNING TIME AND SMOKING INFLUENCE ON ACCEPTABILITY OF IDIAZABAL CHEESE

Brining time and traditional smoking effects on sensory characteristics (appearance, odor, texture, taste and aftertaste) during ripening of Idiazabal cheese were studied in terms of acceptability. The range of brining time (12, 24 and 36 h) considered in this study showed little effect on sensory parameters. In longer brined cheeses, an improvement of rind acceptability was observed especially at the beginning of the ripening period. In young products the texture of the more salted cheese was preferred, in hard cheeses consumers preferred the less salty ones. The traditional smoking process had a greater effect on sensory parameters perceived by consumers than brining time did. It was observed that smoking had a positive influence on acceptability of rind, paste color and eyes. Smoking also increased odor and texture acceptability.     

Auxin treatment of pre‐veraison grape (Vitis vinifera L.) berries both delays ripening and increases the synchronicity of sugar accumulation

Background and Aims: Pre‐veraison auxin treatments can delay grape berry ripening, but there is little information about their effects on berry development and wine composition. The aim of this study was to further investigate these effects and explore the practical implications of delaying ripening. Methods and Results: Treatment of pre‐veraison Vitis vinifera L. cv. Shiraz berries with 1‐naphthaleneacetic acid (NAA) significantly delayed ripening as measured by the accumulation of total soluble solids (TSS) and anthocyanins. The onset of the post‐veraison phase of berry size increase was delayed in NAA‐treated fruit, but these fruit were significantly larger than Control fruit at harvest. NAA‐treatments significantly increased the synchronicity of berry sugar accumulation. GC‐MS analysis of wine headspace volatiles showed significant, but largely small, differences in the concentration of 19 compounds. No significant difference in sensory properties was found between replicate small‐scale wine lots made from Control and NAA‐treated fruit. Conclusions: Auxin treatment delayed berry ripening, increased the synchronicity of sugar accumulation between berries, increased berry size and changed the levels of some volatile compounds, but did not affect wine sensory properties. Significance of the Study: We propose that NAA sprays might be used to delay grape berry ripening and increase the synchronicity of sugar accumulation, and therefore ripening, without deleterious effects on wine quality. This may be useful in controlling winery intake and fruit composition.