Lesson 6 - Wort Separation Process Control

We need a way to determine the concentration of sugars in our wort. A traditional method is to use a saccharometer, which is a specialised hydrometer. This measures SG or ˚Plato. Nowadays, however, instruments called densitometers are available to do this quickly and accurately.

If we know the Specific Gravity of our wort, then we can calculate the extract quantity in one of two ways. The method chosen depends on how we measure the extract in the malt. Malt extract can either be expressed as % w/w (using EBC method) or L˚/kg (litre degrees per kg) (using IoB method). Other regions outside Europe may us other methods.

So, what is a L˚ (litre degree)? It is the product of volume (L) x degrees gravity. So, if our malt extract has 300 L˚/kg, then one kg of malt will produce varying possibilities of volume and gravity, but their product will always be 300.

If 300 L˚ of extract are dissolved in 15 L of wort, the gravity will calculate as:

                            300 L˚/15 L = 20 ˚ (SG 1.020). 

If the gravity is 60˚ (SG 1.060), then the volume will calculate as:

                            300 L˚/60˚ = 5 L.

If our malt analysis is % w/w, then our extract calculations will be kilograms of extract.

For a quick mental comparison, 1% w/w extract is 3.86 L^˚/kg extract.

Care needs to be made as to whether the malt extract value is expressed on a ‘dry’ basis or an ‘as is’ basis. If we have a dry basis extract value, we need to correct this so that the moisture content of the malt (around 5% w/w) will provide us with the actual ‘as is’ extract of the malt we are weighing out.

Calculating the Extract Added

Let us first consider calculating kg of extract, where our malt analysis is expressed as % w/w. In this example, the malt extract is 82% w/w on a dry basis, and has a moisture content of 5% w/w. How much extract is there in 10,000 kg of this malt?

Point of reflection: Have a go at calculating this. When you have finished click ‘Next’ to continue this lesson.