# Calculation Methods for Winemaking Adjustments

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## Introduction

The ability to calculate accurate adjustments in winemaking empowers the winemaker to meet precise goals. This is of increased importance when a winemaker wishes to control certain winemaking parameters. Some winemakers are, however, daunted by the mathematics this might involve. The following article outlines simple mathematical approaches to common winemaking adjustments.

## Sugar

It is often required that a must or wine be chaptalised (i.e., have sugar added to it). As sugar is added to a must/wine, the volume of the must/wine changes due to the addition. This volumetric increase can significantly off-set the concentration of sugar in the liquid. Thus, when calculating sugar additions to meet a target sugar concentration, both the quantity of the addition and the volume change should be taken into account. The following calculation assumes that the addition of 1600 g of sugar to must/wine raises the volume by 1 litre. This value has proved to be relatively accurate in practise.

The amount of sugar, A, to add to a must of volume, Vi, and sugar content, Si, is equal to: where
A = the quantity of sugar to add to the must [g]
Vi = the initial volume of must [L]
Si = the initial sugar concentration in the must [g/l]
Sf = the desired (final) sugar concentration in the must [g/l]
b = number of grams of sugar required to raise volume by 1 litre [g] = 1600
Note: the b factor here has been determined from a number of winemaking sources and, whilst volume changes due to sugar additions are not strictly linear, the value of 1600 is relatively accurate for use over a wide range of typical sugar additions in winemaking.

Following the addition, the final volume of must, Vf, will be approximately: For example, the SG of the must is 1.030. From the table (first table under Hydrometer/Sugar/Alcohol Tables) this is approximately equivalent to 83 g/l of dissolved sugar. It is desired to take the must to SG 1.090, which is approximately equivalent to 242 g/l of dissolved sugar. The volume of the must is 12 litres.
Using the second equation above, the quantity of sugar required to make this SG rise is: Thus, 2248 grams of sugar are required to make this SG rise. The must volume after this addition has been made will be: Thus, when the SG has been raised to 1.090 with the addition of 2248 g sugar, the new volume of the must will be 13.4 litres.

## Inverse Stock Solution Make-up Calculation

Sometimes a winemaker wishes to make up a stock solution such that a specific volume of stock solution will result in a particular increase of a compound in a given volume of must/wine.

The total stock solution volume will be T (ml). It is desired that the stock solution will deliver D (mg/l) of compound when S (ml) of this stock solution is added to V (litres) of must/wine. The stock solution is made by weighing out Q (mg) of compound and adding water to volume T, where Q is: For example, it is desired that bentonite be added to a must/wine at a rate of 20 mg/l when 5 ml of 500 ml bentonite slurry solution is added to a 30 L volume.
T = 500 ml
V = 30 L
D = 20 mg/l
S = 5 ml To make the solution, weigh out 60 g of bentonite and make up the volume to 500 ml with water. A 5 ml dose of this slurry will add 20 mg/l bentonite to a 30 L volume of must/wine.

## Blending

Wine A has an abv/TA of Ca, and wine B has an abv/TA of Cb. It is desired to add wine B to wine A to achieve an abv/TA of Ct. Wine A has a volume Va and wine B has a volume Vb. What volume (V) of wine B is required to be added to the total volume Va of wine A to achieve this? This can be used for alcohol or TA. Note that this is not applicable to pH due to the impact of buffering compounds in wine.

For example, wine A has a TA of 4 g/l and wine B has a TA of 10 g/l. It is desired to add enough of wine B to wine A to obtain a TA of 6 g/l. There is 20 L of wine A. Thus, 34 L of wine B must be added to the 25 L of wine A to obtain the desired TA of 6 g/l in the blended wine.

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