Analysis Request – Juice
All wines start as juice and all juices start as grapes. Through chemical analyses winemakers are provided with a complete picture of their must composition at harvest and ultimately their wine. Various chemical analyses requested at this juice stage allows planning of appropriate winemaking strategies, nutrient additions and intervention if necessary.
What?
Balling, pH and TA are generally the most important chemical parameters tested by winemakers’ pre-fermentation, followed by yeast assimilable nitrogen. As fermentation progresses the sugar content can be measured as the sum of the glucose and fructose. Malic acid also comes into play should the final wine have to go through malolactic fermentation. Turbidity, volatile acidity, and phenolics are also useful tools in managing your fermentation.
Why?
The sugar content of the juice, being the sum of glucose +fructose, provides a sound basis for estimating your potential alcohol in the wine. Acid balance, a complex composition of free hydrogen ions, acids, acid salts and cations, is essential in achieving and maintaining a pH favourable to optimum wine balance and microbiological stability. Turbidity and Yeast Assimilable Nitrogen are both indicators of potential stuck fermentations. Juices that are too clean are likely to be deficient in yeast nutrients.
How often?
Balling and temperature should be monitored daily in the cellar until juices are considered dry. Routine monitoring of pH, TA, YAN and malic acid is recommended to effectively monitor fermentations.
When?
Balling, pH and TA of grapes should be measured before harvesting, as well as, prior to inoculating. Malic acid and YAN levels should also be determined before inoculation.
Who?
Everyone involved in these critical first stages of the winemaking process, whether an assistant winemaker, winemaker or cellar master.