Fermentation Monitoring

Constant assessment of your fermentation is advised to insure that quality is being maintained and no problematic fermentations are developing. Use only clean equipment for this monitoring to help avoid spoilage. The sampled wine can be returned to the fermentor after being tested. The following assessments should be done once or twice a day during fermentation:

• Sugar Level: Several different means of measuring sugar are available, but the easiest and most commonly used is a hydrometer to measure density. A sample is drawn from the fermentation and is placed in a narrow cylinder. The hydrometer is then floated in the liquid. The reading is taken at the base of the liquid level touching the hydrometer, not where the liquid rises up on the hydrometer stem. Care should be taken that carbon dioxide gas from the fermentation is not adding extra buoyancy to the hydrometer.
• Temperature: A temperature reading is taken to monitor changes in the fermentation temperature over time as well as to calibrate the hydrometer used to measure sugar. Density will increase or decrease depending on the difference between the must temperature and the calibration temperature of the hydrometer. Several hydrometer models sold for home use have a built-in thermometer with a correction scale.
• Aroma and Taste: A sensory evaluation of the fermenting wine should also be performed when measuring the sugar. The fermenting juice will typically smell very fruity and candy-like from fermentation esters formed by the yeast and will have a fruity as well as yeasty/bread taste. The sensory evaluation is more to determine if any flaws or spoilage characters are developing in the wine.