Australian Journal of Grape and Wine Research最新文献

The wine sector is actively working to add value, increase sustainability, and reduce waste streams. One great example is to use thinned grapes, that are usually left to rot, to make verjuice. As verjuice has no identity standard, there is a wide scope for producers to innovate. Decisions regarding sensory characteristics and packaging are currently made by the verjuice producers, mainly winegrowers and winemakers but also chefs, without fully understanding the needs and wants of consumers. Using discussion groups and interviews, this study explored both consumer and producer views towards commercial verjuice regarding perceived sensory characteristics, possible end-uses, packaging, and desirable label elements. Similarities and differences were discovered between consumer views and verjuice producer practices. Consumers reported a diverse range of attributes beyond the sourness and sweetness that was the focus of producers, indicating potential for a broader range of applications of verjuice than currently considered. Sweeter variants were generally preferred for drinking, while sourer ones were favoured for cooking, although exceptions to this trend existed across consumers. Additionally, a mismatch between producer packaging choices and consumer preferences was identified, highlighting potential for producers to optimise packaging to better cater to consumer needs. This research explored an opportunity to create verjuice with desirable sensory characteristics for specific end-uses, providing product diversification for the wine industry’s revenue stream. Uncovering these consumer insights is key to better inform promotion of verjuice by producers and the agrifood sector seeking to enhance the value of their by-products.

Background and Aims. Grapevine phylloxera, Daktulosphaira vitifoliae (Fitch), feeds on roots and leaves of Vitis spp. Susceptibility to phylloxera differs among rootstocks, such that Vitis spp. grafted onto resistant rootstocks can safeguard vineyards from phylloxera-induced damage in the long term. Diverse phylloxera genetic strains, however, vary in their ability to survive on different rootstocks. The 5C Teleki rootstock (V. berlandieri × V. riparia) is widely planted worldwide, but its resistance to phylloxera has not been characterised against the genetically diverse phylloxera strains present in Australia. Methods and Results. 5C Teleki roots and Vitis vinifera L. (positive control), either excised in Petri dishes or planted as whole plants in pots, were inoculated with eggs of six phylloxera strains (G1, G4, G19, G20, G30, and G38). On excised roots, G19, G20, G30, and G38 phylloxera survived to reproductive adults. The G1 and G4 phylloxera did not survive past the first instar stage. In potted vines, G4, G19, G20, G30, and G38 phylloxera strains induced nodosities on roots, but adults were only found on roots inoculated with G19 and G20 phylloxera strains. Conclusions. Results showed that 5C Teleki is resistant to the G1 phylloxera and susceptible to G19 strains. Performance of G4, G20, G30, and G38 differs depending on the assay used. 5C Teleki is likely tolerant of these strains. Significance of the study: the 5C Teleki rootstock is resistant to the G1 phylloxera strain but likely tolerant of others present in Australia. This implies that the rootstock can still host a population of phylloxera, and strict farm-gate hygiene should be employed to stop spread among vineyards and regions.

Background and Aims. The assessment of grapevine trunk disease symptoms is a labour-intensive process that requires experience and is prone to bias. Methods that support the easy and accurate monitoring of trunk diseases will aid management decisions. Methods and Results. An algorithm was developed for the assessment of dieback symptoms due to trunk disease which is applied on a smartphone mounted on a vehicle driven through the vineyard. Vine images and corresponding expert ground truth assessments (of over 13,000 vines) were collected and correlated over two seasons in Shiraz vineyards in the Clare Valley, Barossa, and McLaren Vale, South Australia. This dataset was used to train and verify YOLOv5 models to estimate the percentage dieback of cordons due to trunk diseases. The performance of the models was evaluated on the metrics of highest confidence, highest dieback score, and average dieback score across multiple detections. Eighty-four percent of vines in a test set derived from an unseen vineyard were assigned a score by the model within 10% of the score given by experts in the vineyard. Conclusions. The computer vision algorithms were implemented within the phone, allowing real-time assessment and row-level mapping with nothing more than a high-end mobile phone. Significance of the Study. The algorithms form the basis of a system that will allow growers to scan their vineyards easily and regularly to monitor dieback due to grapevine trunk disease and will facilitate corrective interventions.

Background and Aims. Dried grapes from Sunmuscat compose more than 50% of Australia’s production. Sunmuscat is late ripening which can lead to suboptimal drying conditions and darkening of the final product. The response of Sunmuscat to varying cane number per vine was studied with the aim to promote earlier ripening and optimise berry size and yield, without detrimental effects on dried product quality. Methods and Results. The study was conducted in a trellis dried, commercial vineyard with pruning level treatments of 6, 9, 12, and 15 canes per vine over 3 seasons. It included assessment of budburst and fruitfulness in spring; monitoring of grape ripening; measurement of yield, bunch number, and moisture content at harvest; and post-harvest assessment of dry berry mass and fruit colour. Traits strongly affected by season were fruitfulness, yield, berry development, juice composition (TSS, pH, and TA), and dried grape quality (colour, dry berry mass, and sugar per berry). Retention of high cane numbers produced a slight delay in ripening (i.e., a mean of 1.1°Brix), small berries, and an asymptotic yield response without an effect on dried fruit colour or moisture. A linear response for bunch loss between spring and harvest was found with increasing cane number. Conclusions. Retention of fewer canes increased berry size and promoted earlier ripening, but at the expense of yield. Significance of the Study. Bunch loss between spring and harvest was the major yield determinant being more important than budburst, shoot fruitfulness, or berries per bunch.

Mapping and monitoring cluster morphology provides insights for disease risk assessment, quality control in wine production, and understanding environmental influences on cluster shape. During the progression of grapevine morphology, cluster closure (CC) (also called bunch closure) is the stage when berries touch one another. This study used mobile phone images to develop a direct quantification method for tracking CC in three grapevine cultivars (Riesling, Pinot gris, and Cabernet Franc). A total of 809 cluster images from fruit set to veraison were analyzed using two image segmentation methods: (i) a Pyramid Scene Parsing Network (PSPNet) to extract cluster boundaries and (ii) Otsu’s image thresholding method to calculate % CC based on gaps between the berries. PSPNet produced high accuracy (mean accuracy = 0.98, mean intersection over union (mIoU) = 0.95) with mIoU > 0.90 for both cluster and noncluster classes. Otsu’s thresholding method resulted in <2% falsely classified gap and berry pixels affecting quantified % CC. The progression of CC was described using basic statistics (mean and standard deviation) and using a curve fit. The CC curve showed an asymptotic trend, with a higher rate of progression observed in the first three weeks, followed by a gradual approach towards an asymptote. We propose that the X value (in this example, number of weeks past berry set) at which the CC progression curve reaches the asymptote be considered as the official phenological stage of CC. The developed method provides a continuous scale of CC throughout the season, potentially serving as a valuable open-source research tool for studying grapevine cluster phenology and factors affecting CC.

Background and Aims. Stubble burning is an agricultural practice employed by some grain growers to prepare farmland for sowing and/or to control weeds and pests. Grapegrowers and winemakers have questioned whether the resulting smoke can contaminate grapes in nearby vineyards. This study therefore sought to determine the potential for smoke from three different stubble burns to taint grapes and wine. Methods and Results. Excised bunches of mature Cabernet Sauvignon grapes were exposed to smoke from prescribed burning of wheat, oat, and Balansa clover stubble windrows. Environmental sensors monitored the concentration of particulate matter as a measure of smoke density, while chemical and sensory analysis established the extent to which grapes and wine were tainted by smoke. Only grapes that were positioned among the burning wheat windrows or downwind, but in close proximity (∼200 m) to the oat stubble burn, were exposed to sufficient quantities of smoke to result in a detectable concentration of volatile phenols (up to 12 µg/kg), as chemical markers of smoke taint. These grapes yielded wines with two to threefold higher volatile phenol concentrations (up to 18 µg/L) than other wines, including the control wine, and low intensity, but perceptible smoke-related sensory attributes, indicative of low-level smoke taint. Conclusions. Chemical and sensory analyses suggest the risk of smoke taint from stubble burning is low, except where vineyards are immediately downwind and/or prolonged or repeated smoke exposure occurs. However, stubble moisture content and prevailing weather conditions affect smoke density and dispersion, and will therefore affect the potential for smoke contamination by grapes. Significance of the Study. This study will assist colocated grain growers and grape and wine producers to undertake commercial operations, without negatively impacting one another.

Climatic conditions play a major role in wine production. Given the increasing impacts and risks posed by climate change, it is important to understand the effects it will have on the wine sector and different wine-producing regions worldwide. This study provides an in-depth examination of the scientific discourse on wine and climate change from 2000 to 2022 by conducting a bibliometric analysis of the literature published on the Web of Science database, which included 1,314 publications. The use of quantitative and qualitative methods allows us to investigate how research has evolved over the years. Our analysis uncovers the most productive countries, institutions, and journals leading the research in this domain, while emphasising the multifaceted approach to studying wine and climate change. Nevertheless, numerous research areas are yet to be adequately explored. Through co-citation analysis and bibliographic coupling, we identify dominant thematic clusters in previous and current scientific literature and reveal emerging research trajectories in this field. The main thematic clusters found include the assessment of climate change effects on viticultural regions worldwide, climate change’s impact on grape composition, and the impact on grape phenology. Our results can be useful not only to understand the main themes studied until now but also to orientate researchers towards less explored aspects and disciplines in scientific research.

Background and Aims. Previous work in Australia has demonstrated the value of data-driven approaches to terroir analysis but, like other terroir research, focussed predominantly on the natural resources (soils, topography, and climate) on which winegrowing depends. In only very few cases have metrics of production performance also been considered. In this study, focussed on the Marlborough region of New Zealand, we integrated data pertaining to vineyard performance with biophysical data (soils and climate) describing the conditions under which grapes are grown to give a more holistic indication of regional-scale variation in the terroir of the Marlborough production system. Methods and Results. Digital map layers describing variation in climate, soil properties, and the yield and harvest date of Sauvignon Blanc (Vitis vinifera L.) were assembled and analysed for similarity in their patterns of spatial variation over six vintages (2014–2019) using k-means clustering. The results suggest that the Marlborough region has a characteristically variable Sauvignon Blanc production with crop phenology and harvest date strongly influenced by variation in temperature, and yield variation impacted by soil properties. Spatial variation in seasonal rainfall did not appear to impact on vineyard performance. Importantly, the Wairau and Awatere valleys which, hitherto, have been considered together as parts of a single Marlborough region, are shown to be distinct. Conclusions. This analysis is strongly suggestive of the Marlborough terroir being variable at the within-region scale. It also lends weight to the idea that estimates of vineyard performance in some parts of the region may be used to predict performance in others. Significance of the Study. The results have potentially important implications for the management of both vineyard operations and winery logistics, for wine marketing and for whole-of-industry planning around expansion or contraction. The methods used are free of any bias introduced to many previous studies of terroir zoning through adherence to historical or geopolitical boundaries, expert opinion of wines, and other heuristics.

Sustainability in grapevine cultivation requires the precise use of water and fertilizers, particularly nitrogen (N), to produce grapes of the highest quality for winemaking, while simultaneously avoiding harm to the surrounding waters and atmosphere by reducing NO₃⁻ losses and N₂O and NH₃ emissions from the vineyards. To address the challenge of optimizing N use in viticulture, many N fertilization trials have been carried out over the last decades, and a compilation and analysis of worldwide trials was therefore needed. The present study tackled this challenge through a meta-analysis of published research, which included 374 fertilization trials. From the compiled data, six vine production parameters and eight grape quality traits were extracted and normalized to enable comparisons between experiments. The Mitscherlich law of diminishing returns was able to satisfactorily describe the set of vine production parameters against nitrogen application rate, and the same occurred with the yeast assimilable nitrogen (YAN). In vines, both reproductive and vegetative growth similarly responded to the N application rate. In general, the nitrogen requirements for 95% of the maximum grape yield amounted to rates between 30 and 40 kg·N·ha⁻¹, which increased nitrogen use efficiency (NUE) to values between 0.27 and 0.36 t·kg·N⁻¹. Although several grape quality traits could not be described against the N rate in terms of any mathematical relationship, an N rate between 20 and 25 kg·N·ha⁻¹ could be considered as maximizing grape quality for winemaking. Such N fertilization range increases NUE up to values between 0.41 and 0.47 t·kg·N⁻¹, thus almost doubling the known NUE standards when grape quality is targeted instead of yield, although soil fertility could be exhausted in the mid-to-long term. Whatever the case, anthocyanins and polyphenols are well preserved in red grapes at such low N rates, although YAN is not. The results of this work will be useful for guiding new vine N nutrition research and N nutrition management in vineyards, thus increasing wine growing sustainability.

One of the major challenges that global warming poses to viticulture is the maintenance of adequate acidity at maturity in white grapes for sparkling winemaking. This issue arises from three main occurrences: (i) with higher temperatures, degradation of malic acid is significantly enhanced; (ii) with a general advancement in grapevine phenology, grape maturity may occur under suboptimal climatic conditions; and (iii) harvesting grapes at “traditional” dates results in overripe fruits for sparkling destinations. In this biennial work, we compared the fruit and must composition of a local, widely grown white grape variety in the Colli Piacentini area (cv. Ortrugo, ORT) with those of a minor autochthonous variety, namely, Barbesino (BRB). Furthermore, we compared the composition, aromatic, and sensory profiles of wines obtained from ORT and BRB grapes picked on the same date and, in addition, of a second Barbesino wine from late harvest (BRB-LH). ORT and BRB had a similar sugar accumulation dynamic, whereas BRB exhibited a delayed loss of titratable acidity. In more details, BRB had lower malic acid degradation rates when malate concentration was <9 g/L. As a result, with comparable yield and total soluble solid content (TSS) (∼20°Brix), BRB had a higher berry titratable acidity and malic acid concentration at harvest than ORT. BRB wines showed the highest titratable acidity (TA), while ORT had the lowest TA and a higher pH, and as expected, BRB-LH had the highest pH and a lower TA than BRB although still higher than those of ORT wine. The aroma profiles of wines were mainly characterized by fermentative aromas, including esters, fatty acids, higher alcohols, and C₆ compounds, and BRB-LH wines showed the highest concentration of higher alcohols, while the fermentative esters were higher in ORT wines. Panelists considered BRB significantly fresher and with bigger aroma intensity than ORT, confirming that the higher acidity detected in BRB musts is well preserved in final wines. Our work demonstrates that local minor varieties can be reconsidered in light of the new climate change-related issues impairing viticulture sustainability today. In particular, currently neglected cultivars could help preserve must acidity as compared to traditional varieties having early ripening, maintaining the links with terroir and local traditions at the same time.