Water addition at the juice or must stage in winemaking is a tool that can be used to reduce sugar levels in high sugar musts and avoid potential issues such as stuck or sluggish fermentations. An additional benefit may be to help manage the logistical problems caused by compressed vintage periods, when it is sometimes not possible to harvest fruit at the optimal time.
In 2017 an amendment was made to standard 4.5.1 of the Australia New Zealand Food Standards Code (FSC) to expressly permit the limited addition of water to high sugar must and juice to reduce the chance of problems arising during fermentation.
The amendment establishes that water may be added to grape juice or must to reduce the sugar level of the juice or must to a minimum of 13.5 degrees Baumé.
This is in addition to the maximum 70 mL/L currently allowed under the FSC to allow the incorporation of permitted additives or processing aids, and for other reasons incidental to the winemaking process.
Application and helpful hints
The common types of water used in wineries include rainwater, mains/potable water, water from boilers or treated river water. Bore water is not generally recommended for human consumption. However, as most wineries are unlikely to have the volumes of rainwater required for must dilution, it is advised to use mains/potable water where possible. It is recommended to treat water to remove chlorine/chloramines before addition to must to minimise risks of fermentation problems and/or chlorine-related taints. It is not uncommon for wineries to carbon filter water that is to be used in the cellar, which is a practice the AWRI also recommends.
The volume of water to add to the tank must first be calculated (see calculator below). Water can be added using flow meters (if available) and confirmed by measuring the tank dip post-water addition. It is important to ensure that the tank has the capacity to take the extra volume before water is added, and this should be done after the cap has risen. Following water addition, it is recommended that the ameliorated must be mixed thoroughly and re-analysed to obtain a starting Bé/Brix, pH and titratable acidity and any adjustments be made based on this data not the initial juice parameters.
Calculating the amount of water needed to decrease the Bé to a particular value can be done via the AWRI water addition calculator, which is accessible from the AWRI Winemaking Calculators App or the calculators page on the AWRI website.
Cowey, G. 2017 Making water additions to high sugar must. AWRI Tech. Rev. (227): 9-12.
Cowey, G. 2017 Ask the AWRI: Adding water to high sugar must. Aust. N.Z. Grapegrower Winemaker (639): 88-89.
Anon. 2017 What actually happens when you add water to must? Aust. N.Z. Grapegrower Winemaker (640): p. 55.
Petrie, P.R., Teng, B., Smith, P.A., Bindon, K.A. 2019. Managing high Baume juice using dilution. Wine Vitic. J. (1): 36-37. (in press)