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Showing posts from April, 2018

Manipulation of sugar accumulation in Shiraz

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By Lucinda Heyns

In this project, researchers wanted to gain a better understanding of the relationship between berry sugar concentration and wine flavour and aroma. This can help to identify methods for mitigating accelerated sugar accumulation in a in a warming climate.

Project layout  Sugar uptake of berries were restricted by peduncle girdling of bunches, performed at three post veraison stages in a Shiraz vineyard. Grapes were harvested separately and berry analysis was done.

Results -Restricting sugar uptake at 10–14°Brix had severe effects on the accumulation of a number of amino acids, cytokinins and, by inference, the cellular redox status. Consequently, wine made from these berries displayed changes to a large number of esters, higher alcohols and C13-norisoprenoids, which would potentially result in a substantial difference in wine flavour and aroma; -When grapes reached 18°Brix, peduncle-girdling caused only minor modification of berry amino acid concentration and wine volatile…

Delayed pruning to postpone ripening in Pinot noir

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By Lucinda Heyns

The aim of this project was to investigate what the effect of delayed pruning is on cane pruned, trellised Pinot noir, over more than one season. Researchers also wanted to validate whether this technique can be used to preserve acidity and contain yields, especially considering sparkling wine production.

Project layout

Mature Pinot noir vines were subjected to the following pruning strategies over a period of three years: -Standard winter pruning (WP); -Double pruning (DP): In mid winter, fruiting cane and spur were selected and retained and previous season’s bearing cane removed. In spring, the cane was shortened to 10 nodes and tied to the cordon wire; -Late pruning (LP): All pruning operations were postponed until spring and performed in one day. -With both DP and LP, shoot growth from node 10 of unpruned canes reached an average stage where three leaves have unfolded before being pruned back to 10 buds. Phenological and ripening dynamics, yield components and must co…

Evaluation of the yeast Schizosaccharomyces japonicus for use in wine production

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By Karien O'Kennedy

The aim of the study was to evaluate the use of S. japonicas for winemaking.

Project layout
·S. japonicus was compared with Saccharomyces cerevisiae Lalvin EC 1118 in free form, in immobilised form, in co-inoculation with EC 1118 (free and immobilised) and in sequential inoculation, where EC 1118 was inoculated 48 hours after immobilised S. japonicas. ·Fermentations were conducted at 22°C in 500 mL Erlenmeyer flasks containing 350 mL Trebbiano juice. ·Viable yeast count, wine protein stability and volatile compounds were measured.
Main results
·The fermentation speed of EC 1118 was negatively affected only in the sequential fermentations where it was inoculated 48 hours after S. japonicas inoculation. ·S. japonicas flocculated after the second day of alcoholic fermentation when it was used in the non-immobilised form. ·S. japonicas consumed a lower amount of ammonia and amino acids than EC 1118 as a result of arrested cell growth due to stressful fermentation condit…

Compositional variability in commercial tannin and mannoprotein products

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By Karien O'Kennedy

The aim of the study was to evaluate commercial tannin and mannoprotein products in terms of their composition and molecular size distribution.
Project layout
14 grape-based enotannins and eight mannoprotein products commonly used in the Australian wine industry were evaluated.
Enotannins: ·Tannin products were labelled skin, seed, or skin and seed, according to the information on the product’s origin given by its supplier. ·All enotannins were dissolved in a model alcoholic solution at 3 g/L and the total tannin concentration measured by the MCPT assay. ·Subsequently the tannins were purified and subunit composition, mean degree of polymerisation (mDP) and molecular mass was determined. ·The un-purified tannins were also analysed to determine the concentrations of monomeric phenolics such as catechin, epicatechin and gallic acid. ·Anthocyanins were also measured.
Mannoproteins: ·Powdered and liquid mannoproteins were reconstituted in model wine at 1 g/L. ·Total poly…