Paul R. Petrie

Unripe Berries and Petioles in Vitis vinifera cv. Cabernet Sauvignon Fermentations Affect Sensory and Chemical Profiles

Petioles, rachis, and leaves are all matter other than grape (MOG), and although originating from vines, they potentially contaminate primary fermentations of red grape must. Fruit contaminated with high levels of MOG may be downgraded or rejected at the winery; however, management practices such as hand harvesting or fruit sorting may reduce MOG. Petioles are the most common form of MOG to be included in the must, yet little is known about their chemical composition and resulting effects on the sensory and chemical properties of red wines. A descriptive analysis panel (n = 12) examined the sensory profiles of Cabernet Sauvignon wines to which 0.5% or more of MOG (petioles or unripe berries) had been added. This sensory analysis showed that an addition of 10% petioles to the must had a perceived impact on sensory wine qualities, increasing floral aromas and reducing bitterness relative to the sensory qualities of control wines, and resulting in a fuller body than that of wines made with unripe (i.e., green) berries. These sensory results are related to increased terpene concentrations as petioles increase in concentration in the wine must. Methoxypyrazines can also be detrimental contaminants to Cabernet Sauvignon wines. Concentrations of the predominant methoxypyrazine in the wines, 3-isobutyl-2-methoxypyrazine, increased with increasing additions of unripe berries to the must. Wines made with 0.5% or more of unripe berries during fermentation were associated with increased perceived acidity in the sensory analysis and an aroma that was more leafy and vegetal green than the aromas of some wines made with added petioles. The results of this study provide winemakers with important information to better understand how grape-harvesting choices may affect the perceived quality and chemical composition of their wines.

Evaluation of Sensory Thresholds and Perception of Sodium Chloride in Grape Juice and Wine

Poor water quality and lack of rainfall can lead to higher salt loads in vineyard soil and the production of wine with sodium chloride (NaCl) concentrations that may affect wine quality or exceed regulatory limits. Here, study 1 aimed to determine NaCl sensory thresholds in grape juice and wine so that better harvest and processing decisions could be made regarding salt-affected fruit. A whole-mouth gustatory method was used to determine detection and recognition thresholds of NaCl in water, red and white juices, and wines. The NaCl sensory thresholds were often within legal boundaries; thus, a significant proportion of wine consumers may detect salt in wines at concentrations below the legal NaCl limits. The detection and recognition thresholds of NaCl in grape juice and wine increased with panelist age. Study 2 investigated how NaCl affects wine sensory properties. Sensory evaluation using a trained descriptive analysis panel (n = 9) and chemical and elemental analyses were conducted on four Chardonnay wines made from separate vineyards where the fruit was perceived to contain varying degrees of saltiness and results were compared to Chardonnay wine samples spiked with 0.5 or 1 g/L NaCl. Wines made from fruit grown on salt-affected vines and wines spiked with NaCl had similar sensory characteristics. Salty and soapy attributes were correlated and associated with higher Na and Cl concentrations. Fruit expression was associated with wines containing less Na and Cl. When determining acceptable salt concentrations in juice and wines, winemakers need to consider sensory impacts, legal requirements, and who conducts the sensory assessment.

Late pruning and carry-over effects on phenology, yield components and berry traits in Shiraz

Background and Aims n nGlobal warming is shifting vine phenology, compressing harvests and altering the balance of fruit traits relevant to wine. Our aim was to test late pruning as a tool to delay maturity and to assess carry-over effects from repeated late pruning on phenology, yield components, dynamics of leaf area and berry traits of Shiraz grown in the Barossa Valley of Australia. nMethods and Results n nA trial was established in a commercial vineyard comparing three pruning times during four consecutive seasons: (i) winter (Control), (ii) budburst and (iii) 2–3 leaves emerged. Compared with the Control, TSS in berries of vines pruned at 2–3 leaves reached 12°Be 7 days later in the first three seasons, and 14 days later in the last season; the budburst treatment was intermediate between that of winter and of 2–3 leaves. Yield was unchanged by late pruning in three seasons and increased in one. Leaf area index at harvest in 2–3 leaves was greater or similar than in the Control. Late pruning shifted the onset of anthocyanin accumulation against TSS, increasing the anthocyanin concentration and the anthocyanin-to-sugar ratio in two seasons. nConclusion n nLate pruning delayed maturity with neutral or positive effects for yield and berry traits. Carry-over effects on phenology, yield, leaf area and berry traits were negligible. nSignificance of the Study n nIn a context of global warming, delaying pruning to 2–3 leaves can effectively spread the harvest and partially restore the anthocyanin : sugar ratio with no penalty for yield in Barossa Valley Shiraz.

A Fast Method to Measure Stomatal Aperture by MSER on Smart Mobile Phone

A fast image processing method is proposed for detecting stomata and measuring stomatal aperture size in individual images. The accuracy of aperture measurements is 97%. A prototype mobile application is developed to assist field measurements.

Late pruning impacts on chemical and sensory attributes of Shiraz wine: Late pruning impact on wine

Background and Aims n nWarming has two major effects on the wine industry: compressing harvest duration, thus stressing the current capacity of wineries to process more fruit in a shorter time, and compromising fruit composition and wine style. Late pruning can effectively delay vine development and contribute to decompressing harvest, but its impact on wine is unknown. Our aim was to measure the effects of late pruning on wine chemical and sensory attributes. nMethods and Results n nWe compared wines made from Shiraz vines pruned in winter (Control), and in two late pruning stages, when Controls reached budburst and 2–3 leaves in two vintages. Late pruning consistently increased wine anthocyanin, tannin, pigmented tannin and colour density and altered the wines sensory profiles over two vintages. In 2014, colour intensity, fruit aroma, fruit flavours and body were more intense in wine made from late pruning treatments. In 2015, wine made from late pruning treatments showed more intense savoury flavours with a dryer palate and a smoother texture tannin (roughing sub‐quality). The colour improvement was associated with cooler temperature 1 week after veraison in the late‐pruned vines. nConclusions n nLate pruning consistently improved wine chemical composition and altered sensory profiles of Shiraz under Barossa Valley conditions. nSignificance of the Study n nLate pruning is a cost‐effective tool to decompress harvest, with neutral effects on yield and positive effects on wine chemical attributes with enhancement of fruit and colour intensity perception in an extended vintage (2014), and smoother tannin texture with dryer perception in a short and compressed vintage (2015).

Late Pruning and Elevated Temperature Impact On Phenology, Yield Components and Berry Traits in Shiraz

Recent warming has shortened and compressed vintages and has altered enologically relevant berry traits. Late pruning can decompress harvest and preserve fruit quality. Here, we were interested in exploring the interactive effects of late pruning and heating on Shiraz development and composition. We established a factorial experiment that combined two thermal regimes (ambient versus heated) with open-top chambers, and three pruning times (late pruning at budbreak and at two to three leaves, a winter control) in Shiraz vines over three seasons in the Barossa Valley. Late pruning delayed budbreak by up to 23 days, flowering by up to 17 days, and veraison by up to 16 days. Heating advanced flowering in late-pruned vines by up to seven days, with a minor effect in winter-pruned controls. Heating advanced veraison by up to seven days, with greater advances in years with warmer springs. Pruning weights were unaffected by late pruning and were increased by heating. Yield was increased in a single season by late pruning and heating, but it remained unchanged for the pooled three-year data. Late pruning delayed maturity in four of six cases; the largest delay was 17 days in unheated vines pruned when two to three leaves had emerged. Late pruning maintained the anthocyanin-to-sugar ratio, which decreased with heating in two seasons. There was an interaction between the timing of pruning and heating, whereby late pruning enhanced the berry tannin-to-sugar ratio in heated but not in unheated control vines. Late pruning delayed the harvest by shifting the onset and rate of ripening, with a higher degree of response in the warmest season in both ambient and heated treatments.

Microscope image based fully automated stomata detection and pore measurement method for grapevines

BackgroundStomatal behavior in grapevines has been identified as a good indicator of the water stress level and overall health of the plant. Microscope images are often used to analyze stomatal behavior in plants. However, most of the current approaches involve manual measurement of stomatal features. The main aim of this research is to develop a fully automated stomata detection and pore measurement method for grapevines, taking microscope images as the input. The proposed approach, which employs machine learning and image processing techniques, can outperform available manual and semi-automatic methods used to identify and estimate stomatal morphological features.ResultsFirst, a cascade object detection learning algorithm is developed to correctly identify multiple stomata in a large microscopic image. Once the regions of interest which contain stomata are identified and extracted, a combination of image processing techniques are applied to estimate the pore dimensions of the stomata. The stomata detection approach was compared with an existing fully automated template matching technique and a semi-automatic maximum stable extremal regions approach, with the proposed method clearly surpassing the performance of the existing techniques with a precision of 91.68% and an F1-score of 0.85. Next, the morphological features of the detected stomata were measured. Contrary to existing approaches, the proposed image segmentation and skeletonization method allows us to estimate the pore dimensions even in cases where the stomatal pore boundary is only partially visible in the microscope image. A test conducted using 1267 images of stomata showed that the segmentation and skeletonization approach was able to correctly identify the stoma opening 86.27% of the time. Further comparisons made with manually traced stoma openings indicated that the proposed method is able to estimate stomata morphological features with accuracies of 89.03% for area, 94.06% for major axis length, 93.31% for minor axis length and 99.43% for eccentricity.ConclusionsThe proposed fully automated solution for stomata detection and measurement is able to produce results far superior to existing automatic and semi-automatic methods. This method not only produces a low number of false positives in the stomata detection stage, it can also accurately estimate the pore dimensions of partially incomplete stomata images. In addition, it can process thousands of stomata in minutes, eliminating the need for researchers to manually measure stomata, thereby accelerating the process of analysing plant health.