Expertise documents

CERTAIN SELECTED WINE BACTERIA ACT AS BIOCONTROL TOOL AGAINST BRETTANOMYCES

The concept of biological control or protection also called  "biocontrol"  is a method known and applied since the beginning of agriculture even without knowing it. Agriculture development was necessarily linked with the need to protect cultures with various methods including biocontrol. With the development of chemistry applied to the agri-food sector biological control tools were put aside for many years. With a growing awareness of the environmental and health issues due to the use of chemicals, alternative methods such as biocontrol were studied again with improved knowledge and scientific approach. Biocontrol appears to be a great natural way to protect crops against pests and diseases. For more information on the subject, please read the attached article.WE#10 Certain selected wine bacteria act as biocontrol tool

STUCK FERMENTATION

WE #9 Stuck Fermentation A stuck fermentation is one in which fermentation has ceased prematurely or the rate of fermentation is considered too low for practical purposes, leaving a higher residual sugar content than desired in the wines at the end of the fermentation (Bisson, 1999; Henschke, 1997). Not only does it delay the completion of the AF, but it can also lead to off-aromas formation. A residual sugar concentration of less of 2 g/L is considered dry or completed by winemakers (Bisson, 1999). What are the factors leading to a stuck fermentation? Continue reading the attached article on Stuck Fermentation.

THE MANY ROLES OF NITROGEN IN ALCOHOLIC FERMENTATION

Nitrogen is a key factor that has a significant impact on wine fermentation. It is the most important yeast nutrient, influencing both fermentation kinetics and wine quality. Nitrogen is present in grape must in different forms: ammonium, amino acids, peptides, and proteins. The part of nitrogen that can be used by yeast during alcoholic fermentation is called ‘assimilable nitrogen’. Yeast cells also contain nitrogen in the form of proteins, peptides – particularly tripeptides – and amino acids Nitrogen is essential to yeast growth and yeast metabolism. In winemaking............... WE#8 ENG PWV-Jan-2016-Nitrogen-Roles-article

H2S PRODUCTION BY WINE YEAST DURING ALCOHOLIC FERMENTATION

Hydrogen sulfide (H2S) is an important contributor to the so-called ‘reductive’ off-flavor present in some wines, with an odor threshold of only 0.9-1.1 μg/L for white wine and 1.6 μg/L for red wine. Even at a level that can’t be detected by a human nose, H2S can impact the wine aroma negatively, masking the fruit, and giving a ‘closed’ sensation. Moreover, the chemical reactivity of H2S can lead to the formation of other negative compounds such as sulphides and mercaptans especially during aging. Research has shown that all yeasts, indigenous or selected produce H2S and the capacity of the yeast to do so is genetically determined. The wine yeast will also respond differently to different environmental factors, for example, nutritional status of the must, which can impact H2S formation. Continue reading for more in-dept researh on the topic and how to manage H2S in your wine. WE #7 - H2S production by wine yeast  

SO2 PRODUCTION BY WINE YEAST DURING ALCOHOLIC FERMENTATION

Sulphur dioxide is used during several steps of the winemaking process. It is added to prevent the unwanted developments of microorganisms, as an anti-oxidant, as an antioxidasic to inhibit polyphenol oxidases (laccase and tyrosinase) and as a dissolvent. However, sulphites can have a negative impact on wine sensory properties, can delay the onset of malolactic fermentation, and can cause some health concerns in case of high concentrations in the final wine. That’s why SO2 levels in wine are regulated. Please continue reading the Wine Expert #6 for more information.WE#6 SO2 production by wine yeast
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