Fermentation kinetics

• Strong fermenter even at low temperatures, ferments slower towards the end of fermentation
• Sensitive to micro-nutrient shortages
• Conversion factor: 0.58 – 0.63

Technical characteristics

• Cold tolerance: 13 °C (55 °F)
• Optimum temperature range: 13 – 16 °C (55 – 61 °F)
• Optimum must clarity: 100 – 150 NTU
• Osmotolerance: 24 °Brix, 13.3 Baumé
• Alcohol tolerance at 15 °C (59 °F): 14.5%
• Foam production: medium
• Inoculation temperature: no lower than 15 °C (59 °F)

Metabolic characteristics

• Glycerol production: 5 – 7 g/L
• Volatile acidity (VA) production: 0.4 – 1.8 g/L
• SO2 production: none to very low
• Nitrogen requirement: requires a complete nutrient source

Phenotype

• Killer: sensitive
• Cinnamyl decarboxylase activity: low positive (POF+)

GUIDELINES TO MINIMISE VA FORMATION

• Propagation lowers sugar tolerance and enhances glycerol/acetic acid production; do not propagate VIN 7.
• Do not inoculate at lower than 15 °C.
• Avoid pH 3.2 and lower.
• Avoid 50 ppm S0₂ and higher at crushing.
• Do not ferment at temperatures lower than 13 °C.
• Ascorbic acid will enhance VA, but can be mitigated with the addition of “oxygen substitutes”, such as inactivated yeast based complex nutrients.
• Botrytis infection: do not use.
• Flotation of must: ensure sufficient micronutrients and NTUs (100 – 150) after flotation and before inoculating with VIN 7.
• Pasteurisation of must: do not use.
• Initial must sugars exceeding 24 °Brix will increase level of VA.

Origin 

ARC Infruitec-Nietvoorbij, the vine and wine research institute of the Agricultural Research Council, Stellenbosch, South Africa.

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