Cross-sectional models are useful for estimating the impact that climate and climate change have on grape prices due to changes in grape composition. The aim of this study is to estimate the impact of growing season temperature (GST) on grape prices in Australia using cross-sectional data.
We use data on average price by cultivar and region for a 10 year period. We estimate a model using (area-) weighted least squares and variables from a principal component analysis to control for 103 characteristics that relate to the production system used in each of 26 regions. Results suggest that a GST increase of 1°C leads to a decrease of 9% in the average price of grapes. A LASSO model that we use as a robustness check suggests similar results: a GST increase of 1°C leads to a decrease of 7.3% in the average price of grapes.
Failing to control for characteristics that relate to the production system overestimates the impact of GST on grape prices, suggesting that changes to variables in a production system may mitigate deleterious changes to grape composition due to climate change.
This study contributes to the understanding of the issue of omitted variable bias in cross-sectional models, and how to deal with this issue when analysing the impact of climate and climate change in grape and wine research.
Terpenes are volatile organic compounds that influence the composition of many winegrape cultivars. Terpene accumulation is variable between seasons and locations, influencing vintage composition. Crop load management (CLM) is a cultural practice utilised to improve grape composition; however, the impact of CLM on terpene biosynthesis and accumulation in winegrapes remains largely unknown.
Crop load management was applied to Gewürztraminer vines at two developmental stages: bunch closure [early (E)] and veraison [late (L)], and two crop loads: 50% removal [light crop (LC)] and 25% removal [medium crop (MC)] and compared to a Control [high crop (HC)] over three seasons. We considered early-harvest (22.5°Brix in HC) and harvest (23.4°Brix in HC) dates. The LC treatments improved TSS at both harvests; however, LC-E accelerated ripening compared to LC-L. The concentration of total free terpenes was highest in LC-E only at early-harvest. Free α-phellandrene, β-citronellol, geranic acid, geraniol, myrcene and nerol dictated this pattern. Although LC-E increased glycosylated geraniol at early-harvest, the concentration of total glycosylated terpenes was not altered. The expression of four terpene synthase (TPS) genes was increased by LC-E at early-harvest.
The LC-E treatment accelerated technological maturity, and increased the expression of TPSs and free terpene accumulation at the early-harvest stage.
This work provides valuable insight into the capacity of CLM to modulate terpenes in aromatic winegrapes.
3-Isobutyl-2-methoxypyrazine (IBMP) is a compound whose aroma is reminiscent of green capsicum and is found in many winegrape cultivars, such as Cabernet Sauvignon and Sauvignon Blanc. A high concentration in grapes can lead to excessive greenness in the resulting wine products, thus reducing quality. This study sought to determine the impact of using non-Saccharomyces yeast during fermentation on the concentration and perception of IBMP in wines.
As a potential postharvest remediation strategy, 11 strains of non-Saccharomyces were evaluated through fermentation of juices containing IBMP. Wines fermented with Kazachstania servazzii, Metschnikowia pulcherrima, K. aerobia, Hanseniaspora uvarum, Meyerozyma guillermondii and Candida krusei were rated with a higher level of fruitiness and less greenness in sensory analysis, even though no significant difference was observed amongst yeast treatments for IBMP concentration.
In mixed fermentation, in which Saccharomyces cerevisiae yeast strain EC1118 was sequentially inoculated, several non-Saccharomyces yeast strains differentially masked the perception of IBMP.
The selective use of non-Saccharomyces yeast may be a strategy for modulating the excessive perception of greenness in wines derived from grapes containing a high concentration of IBMP.
The effect of amino acids, and their interactions with volatiles and other non-volatiles, on in-mouth sensory properties of red wines is not known. This knowledge gap has been studied in a series of comprehensive sensory experiments.
A solvent-assisted flavour evaporation extract of Shiraz wine volatiles, a de-aromatised polyphenolic extract and amino acids were added to model wine and wine systems. Using full factorial designs, samples were evaluated by sensory quantitative descriptive analysis. Volatiles enhanced Viscous mouthfeel (F = 20.0, P < 0.001), Sweetness (F = 26.5, P < 0.001) and Body (F = 81.4, P < 0.001), while the phenolic extract directed Astringency (F = 170.5, P < 0.001) as well as Bitterness (F = 7.3, P < 0.001) and suppressed Sweetness (F = 16.5, P < 0.001). An amino acid by volatile interaction (F = 4.2, P < 0.05) was found, and further experiments showed that L-proline enhanced Viscosity (F = 5.0, P < 0.05), Sweetness (F = 14.4, P < 0.001), Red fruit flavour (F = 7.8, P < 0.001) and suppressed Astringency (F = 6.1, P < 0.05) and Bitterness (F = 7.0, P < 0.01), while L-glutamic acid imparted an Umami taste (F = 5.0, P < 0.05) at wine-like concentration.
For the first time, these causal experiments showed that amino acids can influence the taste, mouthfeel and flavour of red wine.
This work provides insight into a new class of wine compounds of sensory significance that can be targeted by producers to directly influence wine flavour.
Water deficit modifies the concentration of the aroma compounds of grape berries, but little information is available on the effect of deficits applied at different phenological stages. We evaluated the effect of deficit irrigation on glycosylated volatile organic compounds (VOCs) responsible for the aroma of berries of Sangiovese and Merlot cultivars grafted on 1103P or SO4 rootstocks.
Vines were subjected to either pre- or post-veraison water stress, and berry composition compared against that of fruit of fully irrigated vines. At harvest, a higher concentration of glycosylated VOCs was measured in berries from vines stressed pre-veraison, but while it increased as water deficit increased in Sangiovese, this occurred only at a low or moderate level of stress in Merlot. Post-veraison water stress had a negative or negligible effect on the concentration of glycosylated VOCs in berries at harvest. The rootstock affected the concentration of glycosylated VOCs, particularly in vines stressed pre-veraison, with higher glycosylated VOCs observed for SO4 grafted vines than for 1103P grafted vines.
Pre-veraison water deficit enhanced the concentration of berry glycosylated VOCs, while post-veraison deficit did not. The rootstock–scion interaction might amplify the irrigation effect on berry glycosylated VOCs.
Modifying the timing and volume of irrigation might allow management of berry flavour for improved fruit and wine composition. Irrigation protocols should be tailored for specific cultivar–rootstock combinations.
These last years, minor cultivars have gained attention as they provide an opportunity to offer original products in a global market and to combat global warming. Recent evidence brought to light the existing diversity within the group of autochthonous cultivars from Argentina and other South American countries, commonly known as criollas. The objective was to prospect, rescue and identify grapevine phenotypes recovered in ancient vineyards as putative criollas, in the western provinces of Argentina.
We collected 60 samples in 11 locations. Their identity and pedigree were analysed through nuclear simple sequence repeat (nSSR) markers. The 60 samples were grouped in 45 different genotypes, 19 of them corresponding to previously registered cultivars, while 26 were new genotypes, with no correspondence in international databases. The majority (18) of the 26 new genotypes were related with the criollas group while other genotypes presented a totally different genetic profile and its origin remains to be elucidated.
The diversity within the South American cultivars is higher than previously thought. Ancient vineyards, located in isolated valleys, are reservoirs of minor cultivars, and growers have played a key role in maintaining and conserving them.
This genetic diversity constitutes a valuable tool to explore alternatives for diversification and adaptation to climate change.
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