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Why your should stay away from fermentation temperatures above 30°C

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By Karien O'Kennedy

Spanish researchers from Argentina and Spain evaluated the effect of cold and hot temperature shocks on fermenting yeasts. These temperature shocks are usually referred to as thermal shocks in scientific literature and the “how to use guidelines” of commercial yeast companies. The researchers also looked at the effect that DAP addition, before the thermal shocks, had on the recovery of the yeast after such a shock.
What they did The researchers exposed two different yeasts to cold shocks and three different yeasts to heat shocks in small scale fermentations conducted in synthetic grape juice. The cold shocks comprised abruptly lowering fermentation temperature to either 9°C or 1.5°C for 16 hours; two, six, 10 or 14 days after the start of fermentation. A daily cold shock variable was also included where the temperature was lowered to 1.5°C every night and allowed to return to room temperature (26°C) during the day. Three yeasts were exposed to three heat shock tre…

Dead yeasts adsorb red wine colour

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By Karien O'Kennedy

It was previously found that yeasts can negatively affect wine colour in two ways: via their β-glycosidase enzymatic activity (removing the sugars from monomeric anthocyanins and thus rendering them colourless), and through direct adsorption of anthocyanins on the yeasts’ cell walls. Brazilian researchers evaluated the effect of five different commercial yeasts on red wine colour. The yeasts were previously grouped into three categories namely low, medium and high yeast pigment adsorption phenotypes. This grouping was done by the same researchers during their development of a method to test the adsorption capacity of yeasts.
The current research Small scale fermentations were conducted using a 50/50 Merlot/Tannat must combination that underwent a laboratory scale thermovinification process. The researchers measured the anthocyanin adsorption overall, as well as that of individual cells.
What they found The researchers found that yeasts begin to adsorb anthocyanins…

Fighting vineyard pathogens with UV light

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By Lucinda Heyns
The aim of this project was to determine if UV light can be used to reduce or eliminate the incidence of powdery and downy mildew in vineyards.
Project layout: - Two different UV light treatments (100 J/m2 and 200 J/m2) were applied weekly to Chardonnay vines using a UV light array on a tractor drawn carriage. Based on previous laboratory trials, it was expected that these treatments should stop 80% - 100% of the powdery mildew conidia from germinating.  - Treated vines received only UV light, no other fungicides.  - In another treatment, vines received only conventional fungicides.  - There was also a control where no fungicides or UV light were applied.  - The trial was done in a year where powdery mildew pressure was moderate and downy mildew pressure was severely high.
Results Powdery mildew - Severity of powdery mildew in the control vines were 15%. - Both UV treatments significantly reduced the severity of powdery mildew on berries to 5%. - Fungicide treatments reduce…

Do mychorrizal fungi survive root pruning?

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By Lucinda Heyns

In this study, researchers wanted to determine whether trimming of roots of young vines prior to planting affects mycorrhizal fungi on the roots.
Arbuscular mycorrhizal fungi are symbiotic fungi which are beneficial to plants by helping plants to capture nutrients from the soil. They are sometimes applied as biofertilizers to young vines before planting, with the intention to aid establishment of the vines once they are transplanted into the field. Often the roots of the young vines are trimmed prior to planting to avoid J-rooting and to ensure the roots fit comfortably into the planting hole. It is not known whether root trimming removes active mycelium, therefor losing all the benefits of the inoculation.
By means of a greenhouse experiment, researchers tested how root trimming affects mycorrhizal fungi on vine roots.
Conclusions: Mychorrizal symbiosis persisted on roots, despite root trimming. This is probably because the fungal structures left on roots after trimmi…

Phenolic and sensory potential of new disease resistant cultivars

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The aim of this study was to evaluate nine monovarietal wines from new red grape varieties resistant to downy and powdery mildews in terms of their total phenolic, anthocyanin and proanthocyanidin contents, anthocyanin profile, volatile composition, and sensory attributes. The question was whether these hybrid grapes (≥97.5% of Vitis vinifera genome) can produce wines with organoleptic properties similar to those of Vitis vinifera wines that consumers are used to?
PROJECT LAYOUT NineredBouquetvarietiesamongthirtywereconsideredinthepresentresearch:HG-A,HG-B,HG-C,HG-D,andHG-Ewith98.7%ofVitisviniferagenome;andHG-F,HG-G,HG-H,andHG-Iwith99.2%ofVitisviniferagenome (Tabel 1).All of them shared the same vineyard location, cultivation system, climate, soil type, vine cultivation practices since 2009, and harvesting time at the experimental unit of Pech Rouge from INRA (Gruissan, France).Microvinification assays were carried out separately for each hybrid grape to obtain the corresponding monovar…

It’s all about the bass

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By Karien O'Kennedy

The aim of the study was to determine if low frequency sounds can influence wine tasters’ perception of body (mouthfeel), aromatic intensity and acidity.
PROJECT LAYOUT: 50 people took part in the main study, 25 in Oxford in the UK and 25 in Sydney Australia. Participants comprised 18 males and 32 females. Their ages were between 22 and 73 years. They had different levels of wine tasting expertise. Both groups of participants tasted identical wines under identical circumstances. Two wines were tasted: the 2015 Torres Sangre de Toro (Garnacha from Spain) and the 2015 Brancott Estate Letter Series “T” Marlborough Pinot noir from New Zealand. Both wines were described, though professional sensory assessment, to be medium bodied and medium in aromatic intensity.20 mL measurements were given to participants in dark glasses in randomised order in a quiet room. The participants went in one at a time. Participants were given basic training prior to the experiment on what …

How will mandatory nutrition and ingredient labelling affect the wine industry? A quantitative study of producers’ perspectives.

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PURPOSE: The purpose of this study is to examine producers' perspectives on the mandatory labelling of nutrition and ingredient information for wine, as suggested by the European Commission. Producers’ expectations about consumer reactions to new label information, the consequences of mandatory labelling on production processes and relative competitive advantages for different producer sizes are assessed. METHODOLOGY:Data for this survey was collected from producers using the quantitative research method of an online survey. In total, 483 German wine producers, covering a substantial share of the country's wine acreage, took part in the survey, comprising 434 estate wineries, 29 cooperatives and 20 large bottling wineries. FINDINGS:The study concludes that mandatory nutrition labelling will have several effects on the wine industry. Producers' expectations of consumer reactions largely agree with the findings of recent qualitative studies focusing on wine consumers. While nut…