Fruit based spirits are getting popular these days. They are distilled using a single column device with careful fraction separation, which helps to achieve high quality and exceptional fruit taste. This is accomplished by analyzing spirit smell, and depends on operators' experience. If performed on a group of columns -- result will end up to be a mixture of pure ethanol and a number of fractions. In this case spirit will have artificial taste.
Given the situation, a choice is forced to be made between unique taste and mass production.
In order to improve quality, we need a tool that’s able to analyze rectification column parameters and perform spirit separation automatically. The tool has to be non-destructive to spirit, easy to use and universal.
So, where do we look for a solution? Let’s start from the fact that fruit based spirits are not a pure water-ethanol mixture: they always contain some extra elements like aldehydes, ethers, etc. What if we record the same parameter in different ways and compare the result? For example, measure spirit mass in real time and compare it to ideal water-ethanol mixture mass. Such measurements are quick and reliable. Calculation can be done by software.
Spirit mass can be measured in real time and ideal water-ethanol mixture mass can be calculated based on ABV, temperature and reference table.
For the test let’s take two different types of mash:
sugar based mash -- 2,5 dal, 18% alc;
black currant based mash -- 3 dals, 7% alc.
Rectification done on a single 4-inch column with four theoretical plates and human controlled fraction separation. Sugar mash test results are shown on pic 1. Berry mash test results are shown on pic 2.
For both types of mash lines cross on the left side of the graph. This is the point of Head fraction separation. It matches human organoleptic experience.
Tail fraction separation is more complicated. Sugar mash does not provide any clear way to see Tail fraction start. However, the berry based spirit changes its density on Tails. There is a tremendous ABV change without spirit mass changes. So, the density of the ideal water-ethanol mixture under these conditions would change from 800 kg/m3 to 900 kg/m3.
For fruit based spirits real time mass measurement with comparison to ideal water-ethanol mass provides clear Head fraction separation data. Same calculations can be used for sugar based mash.
Tail fraction separation method still needs to be investigated.