Different types of Fermentations
As we said in the previous article, fermentation brief, depending on the yeasts and bacteria involved in the process, we will have different types of fermentation, such as lactic fermentation, alcoholic fermentation, acetic fermentation, and others which we will see later and which will take their name from the most important substance produced.
Alcoholic fermentation is a chemical-biological process that results in the transformation of sugars into ethyl alcohol and carbon dioxide. This process is the basis for the production of the main alcoholic drinks (wine, beer) and also for the leavening of the bread; as in any type of fermentation it is activated by micro-organisms, single-cell fungi called yeasts which, in this case, break down the glucose molecules in the absence of oxygen, transforming them into alcohol and carbon dioxide and can occur spontaneously which involves the creation of a selective environment for the proliferation of desired microorganisms or artificially with the addition of a fermentation starter and which involves the use of selected and specialized yeasts for each type of fermented.
In addition to transforming sugars into alcohol and carbon dioxide, microorganisms also provide for a transformation in the values of pH, alcohol and sugar concentration and temperature and it is essential to become aware of these values, through essential tools such as pH meter, Brixometer, Alcoholometer and Thermometer, so as not to fall into errors that can be harmful.
In the case of fermentation with starter, all the values are reported by the producer on the label allowing us to ferment our raw material in the best way respecting the indicated parameters; on the market, there are selected yeasts for any type of fermentation, but of course, it is also possible to produce them by themselves, creating the opportunity to be able to reuse them.
500 g pineapple
1.5 l water
50 g white sugar
75 g raw sugar
25 g whole sugar
Spices (1/2 cinnamon stick, 1-star anise, 5 cloves)
Wash the pineapple well and remove the top with the leaves. Cut it into small slices without removing the peel, insert it in the fermentation container (sterilized glass jar) and add the other ingredients except for the spices. Cover the mouth of the used container with a sheet of absorbent paper or cloth and make sure it is firmly attached to it (use an elastic band or a cloth tape to tie it to the mouth of the container). This system will allow the entry of the yeasts naturally present in the air while preventing insects attracted by the sugar content of the compound from settling. After 2 days, remove the sheet of paper or the cloth used to cover the mouth of the container and close it with a cap with a one-way valve (bubbler or other types of the vent) to which water will be added to ensure the action of the yeasts and therefore the alcohol production. Leave to ferment for another 5 days at room temperature. 1/2 days before the end of the week add the spices. Filter everything, bottle, and label. Store in the fridge for 1-2 weeks. To make the drink sparkling, best filter the liquid by eliminating as much as possible the solid parts, pour it into bottles with mechanical cap and seal (like craft beer) or crown cap, and leave them at room temperature to continue fermentation. Label the bottles with the day and time of bottling. After 24/36 hours the fermentation should have produced the quantity of CO2 necessary to make the drink sparkling. Then keep in the fridge and consume it within 7 days to avoid possible breakage of the bottles due to the excessive pressure created.
It is also possible to check the pressure inside the bottles using an aphrometer (an instrument for checking the pressure level reached by the compound in the bottle or other container). The internal pressure must not exceed 4 bar, while for the service it is always preferable to cool the drink and go below 3 bar.
An example of homemade starter is the Ginger Bug, which of course is created from ginger root (or any similar root) with water and sugar placed in an airtight container; in this way the metabolism will be very active and will have to be nourished every day by adding quantities of ginger and sugar.
Ginger Beer with Ginger Bug
80 g peeled ginger per liter of water
50-100 g sugar (the quantity will vary according to the desired sweetness)
½ squeezed lemon
5-10 ml ginger bug
Pour all the ingredients except the Ginger Bug into a container and blend everything. Then filter the mixture obtained with a super bag (dense mesh bag) of about 200 microns (1 micron equals 1 thousandth of an mm). The clearer the liquid obtained by filtration, the greater the quantity of CO2 incorporated.
Add the Ginger Bug to the mixture and mix.
Then pour the mixture into special bottles with a crown cap or hermetic seal capable of resisting the pressure generated by the increase in CO2 (e.g. beer).
Leave to ferment for about 48-72 h.
Check the internal pressure using an aphrometer.
Store in the fridge and use within 1 week.
In this recipe, we can also replace fresh ginger with a decoction of ginger (10-20 min heated with water, cool before use). The results obtained will be different.
In the case of lactic fermentation, glucose is transformed into lactic acid by the LAB (lactic and bacteria) and is more commonly used in the food industry for the production of acidic foods such as yogurt for example, but in recent years we have also found it in many drink recipes in different bars around the world. We know two different types of the latter fermentation:
Homolactic fermentation ferments glucose producing almost exclusively lactic acid;
Heterolactic fermentation instead ferments glucose producing about 50% of lactic acid, acetic acid (or ethanol) and carbon dioxide.
To start this fermentation it is necessary to put the salt in contact with the ingredients and it is the simplest and most effective way to start it, but we can obtain Lacto-fermented foods also using starters or ingredients that already have a good nature. salt content.
To implement it, it is necessary to consider three fundamental elements such as the quantity of oxygen, the quantity of salt, the temperature, and the pH; like alcoholic fermentation this occurs in the absence of oxygen and it is essential to create the right conditions. To create the right environment for LABs and an inhospitable environment for other unwanted microorganisms, non-iodized salt is used in certain percentages and also a favorable condition is created by the temperature which conditions each other with salinity; For example, in summer the temperature is high and the fermentation could be faster and more difficult to control, therefore it may be useful to increase the quantity of salt to control the production of lactic acid; Fermentation will start by putting the salt in contact with the ingredients (dry spontaneous lactic fermentation) or creating a brine.
Recipe for dry spontaneous lactic fermentation;
Fruits or vegetables (peeled and chopped if large cut)
Salt in% of the weight of fruit or vegetables (the percentage can vary between 2.5 and 20% depending on the turgidity of the raw material)
Combine the ingredients and put them under a vacuum. Wait about 24-48 hours until the salt begins to extract the water contained in the raw material chosen by osmosis, completely covering it and creating a natural brine. For this type of preparation, it is, therefore, advisable to use fruit or vegetables that are fairly juicy and rich in water. Fermentation will last about 2-3 weeks.
Calculation of the % of salt concerning the weight of the raw material
Pmp = raw material weight
Ps = percentage of salt we want to reach
Qs corresponds to the exact amount of salt that we will have to add to reach the percentage of salt established.
100 g lemons
8% salt we want to reach
Following the formula described above:
100-8 = 92
100/92 × 8 = 8.69
8.69 g corresponds to the exact amount of salt to be added to the lemons to reach the established percentage of salt (8%).
Even if it is defined as “fermentation”, acetic fermentation is not in the metabolic sense of the name as it is an oxidative metabolism therefore aerobic and works in contrast to the fermentations discussed so far where the transformations take place in the absence of oxygen .
Acetic fermentation takes place in the presence of oxygen; ethanol (alcohol) contained in beverages such as wine, beer, but also in some foods, is transformed into acetic acid by Acetobacter bacteria.
To start the fermentation we will have to leave a fermented (alcoholic) product in the air, preferably with an alcohol content of less than 12 ‘, covered with gauze or similar; after more or less four weeks an acetic mother will be created that will allow fermenting any sugary substance with which it comes into contact becoming a starter for acetic fermentation; in any case today it is possible to buy anything and on the market, we find starters for kinds of vinegar where we can follow the manufacturer’s procedures.
It is very important to cover the compound inserted in a jar with gauze or similar to avoid the formation of the “Turbatrix aceti” commonly called “vinegar eel”, a worm that feeds and multiplies in the acetic solutions and to minimize any type of risk at the end of the process it would be advisable to pasteurize the result.
Cucumber and Gin vinegar
London Dry Gin
Lower the alcohol content of the Gin to 12 ° using the cucumber extract. Mix everything and pour it into a jar or other container without sealing or airtight cover. Cover with gauze and let it brew.
It is possible to speed up the oxygenation and therefore oxidation process by using an aquarium oxygenator for about 7 days in contact with the compound. After about 7 days, stop forced oxygenation and leave the compound covered for another 2 weeks. During this time the so-called acetic mother will be formed.
Celery and Vodka extract
Tomato and Tequila extract
Formula to lower the alcoholic strength of a distillate
Gi = initial alcoholic strength of the distillate
Gf = final grade that we want to obtain
Gf / Gi = x
X corresponds to the quantity of distillate to be subtracted from 1 liter of water to calculate the value of the water to be added to the final compound.
Vodka = 40° = Gi
Final gradation that we want to obtain = 10 ° = Gf
10 / 40 = 0,25
We subtract 0.25 to 1 and get 0.75.
1 – 0,25 = 0,75
0.75, therefore, corresponds to 750 ml of water (0.75×1000) to be added to 250 ml of vodka (0.25×1000) to make the distillate reach the desired 10 °.
0,75 x 100 = 750 ml
0,25 x 100 = 250 ml
750 + 250 = 1000 ml
In any case, there are many other types of fermentations such as, for example, the one via Scoby in the production of Kombucha or Kefir, or Tibicos; which however take place with processes other than those listed above if you want to know more about it click here.
written by Pasquale Bergamo