The production of quality schnapps (rakija) starts with alcoholic fermentation (fruit fermentation), and ends with distillation at home and leaving the schnapps to stand some time. Further in the article we will explain what is fermentation and how to do it in your home the best way you can.
First the fruit must be washed well in cold water and after that comes chopping. While chopping the fruit you must be careful not to break the pit. Broken pit releases poisonous compound that gives unpleasant taste and smell to schnapps. Depending of what kind of schnapps we want, we choose fruit we put in. On Balkan Peninsula the most common are Slivovitz (plum), Viljamovka (sort of pear)…
Dish for fermentation or barrel (plastic) is filled with chopped fruit, never over 80% of capacity of the dish so it doesn’t come to overflow of the fruit mash.
Alcoholic fermentation of the fruit represents a process of fruit transformation, with yeast activity, into alcohol and carbon dioxide. That the yield can carry out it’s process they need to have enough “food”, first of all nitrogen and phosphorous. In the husk itself before the start of fermentation there are: water, fruit sugar, albumin, fruit acid, mineral materials, vitamins, nitrogen…. Of course the quantity of these materials depends of the quality, variety and kind of the fruit.
Alcoholic fermentation formula
C6H12O6 → 2C2H5OH + 2CO2 + 117,8 kJ
The beginning of the alcoholic fermentation signalizes the appearance of “the hat”, bubbles on the surface of the husk. This appearance comes when the carbon dioxide is produced during fermentation, the same way appears foam and wheezing while the gas is coming out.
The length of fermentation of the fruit is not always the same, it depends from the temperature, if the yield is added, content of sugar in husk, and how much is the fruit chopped. When the bubbles go away and the wheezing stops it is a good indicator that the fermentation is over, of course, that always needs to be checked with saccharometer. The best temperature for fermentation is 15-23 degrees, if the temperature goes below 15 degrees the fermentation can come to an end. It is not desirable to have significant variations of the temperature in the room and direct exposure to the sun should be avoided.
You must be careful about the temperture durring fermentation, it can not be to high because that is a good environemnt for the bacteria that create acetic acid. If, however, comes to the creation of acid, the cause of termination of alcoholic fermentation, it is necessary to neutralise the acid with calcium carbonate (CaCO3) or with slaked lime (Ca(OH)2). Be careful with acids, call experts!
Fermentation in open barrel
Fruit fermentation in closed dishes (the old way) implies that the top side of the dish is open. They are filled with minced ripe, sweet plum near the top of the barrel. However, with dishes with open fermentation you must leave at least 15-20cm space in case if it comes to violent fermentation (sudden release of CO2) when bubbles and foam are created and they are lifting the husk and causing overflow, or so called „seethe“, defilement of the dish from outside, which enables increased development of vine flys.
With prescence of air ethanol is converted into acetic acid, CO2 and H2O and on that way contributes to reducing content of alcohol and it’s acidification with acetic acid in upper surface part of the kit. The consequence of all this is acidifikation of the whole schnapps.
Fermentation in closed barrel
To ensure quality fermentation of the fruit mash (husk) in closed dish-barrel, which is considered to be the new time technology, the next needs to be done:
- fruit fermentation should happen in closed kit, cistern and other dishes where flies and other insects.
- stirring and ventilation of the fruit mash must be done with the help of specially produced probes, at least every 3-4 days during violent fermentation in first 14-20 days.
- for the fermentation to start in closed process it is recommended to add yeast into fruit mash.
- in case of unsufficient ventilation ie. not leting in enough oxigen it can come to creating conditions for „anaerobic fermentation“ that leads to forming milk acid, development of mold, fungus and other processes that have very bad effect on the production of schnapps.