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Using a “pied de cuve” to manage indigenous fermentations

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By: Karien O'Kennedy

The aim of the study was to evaluate the impact of a vineyard-derived pied de cuve (fermentation starter culture) compared to spontaneous and commercial yeast inoculated fermentations, on the microbial, chemical and sensory characteristics of wines.
PROJECT LAYOUT Two pied de cuves were prepared from Ugni blanc and Sauvignon blanc grapes four days before the harvest. After fermenting two days at 20˚C ammonium phosphate and thiamine were added to the two 12 litres of must. Temperatures and sugar concentrations were measured daily. After 30 – 50% of alcoholic fermentation completion the pied de cuves (PdCs) were subjected to microbial, chemical and sensory analyses. The PdCs were then inoculated into 225L barrels containing cold settled Sauvignon gris juice. Two additional barrels of the same Sauvignon gris juice underwent spontaneous and commercial yeast inoculated (Zymaflore X5) fermentations.Microbial, chemical and sensory analyses were performed on all the barr…

Saccharomyces cerevisiae and Saccharomyces uvarum co-fermentations

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By: Karien O'Kennedy

Saccharomyces uvarum is a cryotolerant yeast specie that naturally occurs in spontaneous fermentations. It has been observed to contribute positively to fermentation and final wine quality and at least one commercial S. cerevisiae / S. uvarum blend exists (Enartis), as well as a S. cerevisiae / S. uvarum hybrid yeast (Maurivin). The aim of this study was to observe the interactions between a commercial S. cerevisiae yeast strain and an indigenous S. uvarum strain at two temperatures in controlled Chardonnay fermentations.
PROJECT LAYOUT Commercial yeast Lalvin QA23 and indigenous yeast S. uvarum SU01 were inoculated into sterile-filtered Chardonnay juice from South Australia in five different ratios (1c | 0u, 10c | 1u, 1c | 1u, 1c | 10u, 0c | 1u). Fermentations were conducted at both 15 and 24°C on small scale (250 ml glass Schott bottles).Sulphur dioxide and pH measurements were also conducted on the juice before fermentation.Samples were taken from the must on …

Production of dimeric stilbenes to control fungal diseases

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By Lucinda Heyns

In this project, researchers aimed to synthesize oligomeric stilbenes from natural resveratrol by oxidative coupling using metals. Stilbenes are produced by grapevine plants, in response to stress conditions, such as when exposed to pathogens. Stilbene or resveratrol oligomers are synthesized by vines to act as the active compounds that have anti-microbial properties to inhibit pathogen growth in grapevine defence systems. Even though resveratrol is plentiful in grapevine canes or other natural sources, obtaining enough raw material for the effective production of large volumes of oligomers to be used in crop protection could be challenging. Some studies have reported that oligomeric stilbenes can however be produced from resveratrol hemisynthesis using metals, this knowledge formed the basis of this study.
Project layout Resveratrol was extracted and purified from grapevine cane extract.Oxidative coupling of resveratrol was conducted in methanol using silver acetate as c…

Grapevine physiological response to row orientation-induced spatial radiation and microclimate changes

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Background and aims

Terroir factors and vineyard practices largely determine canopy and root system functioning. In this study, changes in soil conditions, multi-level (vertical, horizontal) light interception (quantitative, photographic, schematic, 3D modelled), leaf water potential and photosynthetic activity were measured during the grape ripening period on NS, EW, NE-SW, and NW-SE orientated (Southern Hemisphere) vertically trellised Shiraz grapevine canopies.
Methods and results
It was hypothesised that the spatial radiation interception angle and radiation distribution of differently orientated and vertically trained grapevine rows would affect soil conditions and vine physiological activity. Soil water content showed an increase and soil temperature a decreasing gradient with soil depth. In the afternoon, soil layers of EW orientated rows reached their highest temperature. This, along with measured photosynthetic active radiation received by canopies, complimented the diurnally-ca…

Effect of canopy management practices on grapevine bud fruitfulness

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Background and aims

Bud fruitfulness is a key component of grapevine reproductive performance as it determines crop production for the following growing season. While canopy microclimate can impact bud fruitfulness, the effects of canopy management practices on bud fruitfulness are not well known. The objective of this study was to investigate the effects of common canopy management practices on bud fruitfulness and the relationships with shoot growth capacity, bud microclimate and bud carbohydrate level.

Methods and results

Different canopy management practices, (shoot thinning, bunch thinning, leaf removal and lighter pruning) were applied to Semillon and Shiraz grapevines. Light interception at the bud zone was measured after canopy management practices were applied. Bud fruitfulness at dormancy was assessed using bud dissection analysis. The number and size of inflorescence primordia, and the incidence of primary bud necrosis were recorded. The results were correlated with measuremen…

Effect of weather conditions on yield components

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By Lucinda Heyns

Aim of the study
In this project, researchers aimed to quantify the relationship between yield components and the climatic conditions at critical growth stages for wine grapes in a cool climate environment.
Project layout This was a long-term field study on Sauvignon blanc in Marlborough, New Zealand.Four different vineyards were established in 2004, both containing two-cane and four-cane trained VSP vines. Phenology and yield (bunch number, berry mass) were monitored up to 2019 in some of the vineyards.This data was combined with meteorological records and then a multi-variable mixed linear model was used to assess the relationship between various yield components and weather conditions.Results
The critical periods for each yield component and weather factor were optimised based on the maximum likelihood returned from the mixed linear model. The results showed that temperatures during the pre-flowering (mainly before 50% flowering) period, significantly impacted all yiel…

Sequential fermentations to reduce the alcohol content in wine

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Background
Over the last decades, the average alcohol content of wine has increased due to climate change and consumer preferences for particular wine styles that resulted in increased grape sugar levels at harvest. Therefore, alcohol reduction is a current challenge in the winemaking industry. Among several strategies under study, the use of non-conventional yeasts in combination with Saccharomyces cerevisiae plays an important role for lowering ethanol production in wines nowadays.
Project layout
In the present work, 33 native non-Saccharomyces strains were assayed in sequential culture with a S. cerevisiae wine strain to determine their potential for reducing the alcohol content in Malvar white wines.
Results Four of the non-Saccharomyces strains (Wickerhamomyces anomalus 21A-5C, Meyerozyma guilliermondii CLI 1217, and two Metschnikowia pulcherrima (CLI 68 and CLI 460)) studied in sequential combination with S. cerevisiae CLI 889 were best able to produce dry wines with decreased alco…