Something delicious happens I can tell you that! But fermenting is a special kind of magic essentially it involves a battle between the forces of good and the forces of evil.
In a bacterial fermentation the battle is between the good bacteria and the bad bacteria that are harmful to us (you will also recall that there are different types of fermentation using yeasts and molds however the basic ideas are similar).
Provided you do it right the good bacteria win! Yeah go good guys!
The food actually enters a kind of suspended animation where it will stay fresh for many months or even years under the right conditions.
This process preserves the food, and also creates beneficial enzymes, b-vitamins, omega-3 fatty acids, and various strains of probiotics.
Bacterial Fermentations
We will describe what happens when you do a bacterial fermentation as opposed to fermenting with yeast or mold.
Bacterial fermentations involving Lactobacillius bacteria are the easiest (often called lacto-fermentations) for beginners and to describe. For very detailed descriptions of what goes on in Kombucha and other ferments you probably need a food science degree!
Fermented food is called ‘a living food’
It is called a ‘living food’ because it’s full of good bacteria that are munching away on carbohydrates in the food and it won’t go rotten, at least not until the sugar party runs out, and that can take a very long time!
All the bacteria really want is carbohydrates (including sugars which are a simple type of carbohydrate) which occur naturally anyway in vegetables and fruit (sometimes we can add a little extra so they are not hungry). In return they multiple like little rabbits and their bacteria poo (which is mainly lactic acid and carbon dioxide) makes your food very tasty and sometimes slightly fizzy!
The lactic acid also conveniently acidifies the ferment (lowers the pH) quite quickly and therefore also makes it safe as bad bacteria don’t like acid conditions pH<4.6 (read Safety and Food Fermentation for more information)
Mother nature is pretty smart with this sort of stuff isn’t she?! It really is like nature’s refrigerator!
In fact the good bacteria you want are found naturally on fruit and vegetables (especially organic or pesticide free ones). We sometimes add extra ‘good guys’ in the form of a ‘starter’ culture if we want but it’s usually not necessary. The starter culture can be as simple as 10% of the pickle juice from a previous successful ferment.
Sauerkraut Fermentation Example
Sauerkraut is a lacto-fermented vegetable and a common one for newbies to start with. Ideally the fermentation takes around 3-4 weeks at 21°C .
Scientists have studied the bacteria when sauerkraut ferments and essentially there are different waves of different bacteria over the 3-4 week period. So one group of bacteria predominate in the first few days then as they produce acid conditions that favours a different type of bacteria and so and so forth with each different stage of fermentation giving different layers of flavour. All of those bacteria were present at the beginning it’s just different environmental conditions favours certain types.
Other Types of Fermentation
Fermentations involving yeasts and molds (rather than bacteria) work slightly differently. Yeast fermentation’s produce alcohol (yup like beer and wine) which will if exposed to air actually eventually break down to vinegar (acetic acid). If you leave a bottle of red wine out it will eventually turn into red wine vinegar all by its self! And then eventually to water!
But these are more advanced fermentations so will leave all this all here for now while everyone is still awake.