Fermented vs. Rotten: What’s the Difference Anyway?

Most of us are aware of what rotten food smells like! It is offensive, noxious, and does not entice us to eat it! The decay of food, or rotting, and fermentation both use bacteria in their processes. So what is the difference between fermented and rotten food?

When things rot, the bacteria that cause decay proliferate on the item and begin to break it down. Fermentation is the introduction of good bacteria that inhibit the growth of the bacteria that cause decay. This has the effect of preserving the food item for longer, and even enhancing its nutritional value due to the presence of the good bacteria!

Most of us who have been in the survival, prepping, or homesteading community for any length of time have heard of fermenting food as a means of preserving it for future use. What is the difference between fermented food and rotten food, and is fermented food safe to eat?

Fermented Vs. Rotten

There is a vast difference between rotten and fermented when it comes to food, especially when it comes to homesteading and prepping!

In both processes, bacteria are involved, but they are different bacteria and perform different roles! Essentially, we differentiate between these bacteria by calling them good bacteria and bad bacteria.

We humans are not alone! We have bacteria living in our gut that are an essential part of our overall good health. These “good” bacteria help to improve digestion of our food and keep “bad” bacteria under control. Basically, the by-products of good bacteria are toxic for the bad bacteria and thereby don’t allow them to proliferate in your system. If the good bacteria in your system die off, the bad bacteria proliferate, and it is difficult for the good bacteria to get back to full strength.

What Happens In The Rotting Process?

Bad bacteria caused decay and disease. In food that starts to rot, the bacteria that infest the food are of the type that breakdown the tissues of the food and cause it to decay or rot. The by-products of this process are the gasses, which are the smells that come off the food that indicates to us that the food is rotting and not good to eat!

The process of decay also produces toxins as a by-product, which can be harmful to humans, causing severe illness, which can result in death in severe cases.

Eating food that has started to rot will introduce the bad bacteria and the toxins into your gut, which can overpower the good bacteria that are already there and cause food poisoning, vomiting, diarrhea and make your system susceptible to attack from other illness-causing bacteria.

Due to these harmful effects that can occur through eating rotten food, caution needs to be taken when eating any animals in the wild that you find dead. First of all, you don’t know what killed the animal, and secondly, you don’t know how far along the decay process is and what bad bacteria and toxins you could introduce into your system, which could make you extremely sick. Eating rotten food is something to be especially avoided if you are in a survival circumstance where you need to forage for food to sustain yourself.

What Happens In The Fermenting Process?

The fermenting process is when good bacteria are used to our advantage and are encouraged to proliferate to the point that they inhibit the growth of the bad bacteria and thereby prevent the process of decay.

The food treated in this way becomes preserved and can be stored for longer periods of time without the process of decay being allowed to begin.

Fermented foods are not only a method of preserving food but also have health benefits that include improving digestion and boosting our immune system.

The Fermenting Environment

The method used to ferment food, particularly fruits and vegetables, is usually in a medium that promotes the growth of the good yeasts and bacteria that are already on the plant material. This same medium inhibits the growth of molds and the bad bacteria until the good bacteria is established and can limit the growth of the bad bacteria.

This can be in brine, or saltwater solution, or in brine where bacteria found in dairy products such as milk kefir whey, are added to give the good bacteria a good start. This process of fermentation is often referred to as Lacto-fermentation since it is the growth of the lactobacilli bacteria that is encouraged.

The bacteria in the fermentation process produce an acidic environment in which the food is pickled and preserved. Pickling food in vinegar is the same as fermentation, as the environment is designed to inhibit the growth of the unwanted bacteria that cause decay!

Because the fermentation results in an acidic environment, the food preserved in this way tastes like it has been pickled in vinegar, but the vinegar taste is not as strong. Fermented vegetables usually stay crisp and crunchy and can be eaten right out of the jar or included in soups and stews, sauces, and relishes!

What Food Can Be Fermented?

Most garden vegetables can be fermented to preserve them for out of season use and to enhance their nutritional value. The recipe you use for each type of vegetable may vary slightly depending on how soft the vegetable is.

For example, soft vegetables like tomatoes can be fermented, but it is best to ferment them whole. Therefore the small cherry tomato varieties are more suitable for fermenting. It is possible to ferment the larger ones, but you won’t be able to fit many in the fermentation jar!

Similarly, most fruits can also be successfully fermented in much the same way, but in some cases, different starter cultures are used for the start of the fermentation process.

What Food Cannot Be Fermented?

Most foods can be successfully fermented, including eggs, meat, and other food products. The only issue is that not all foods taste good after fermentation.

If you want to begin fermenting food, it is best to stick to the more common foods and fermentation methods until you develop your knowledge and skill.

Once you have advanced to this level, you can branch out and try fermenting more unusual types of foods.

How Long Do Fermented Foods Last?

The length of time that fermented foods can last depend on the type of food and the conditions the food is stored in, and the containers used for storage.

The fermentation process can preserve foods for anywhere from 4 months to 18 months, but you will need to do your research regarding the food you want to ferment and its expected shelf life.

There are many factors that can affect the longevity of your fermented food. The best precaution to take is to inspect your stored food regularly for signs of spoiling, and if in doubt, throw it out!

Are There Dangers To Fermenting?

Fermenting is an activity that most homesteaders and preppers get into at some point. When starting out, you should find a tried and proven recipe to ferment the product you have in mind and then stick to the recipe religiously.

It is important to stick to the correct temperatures, fermentation times, and hygiene practices for your hands and fermenting equipment. Failure to follow the correct protocols can introduce harmful bacteria, yeasts, and mold into your ferment, which can out-compete the good bacteria.

This will result in the food spoiling and becoming unsafe to eat. You can usually tell if your ferment did not work and your food spoiled due to an unpleasant odor that will make you not want to eat the food. This is a clear indication that the food has spoiled and should be discarded.


Fermented food and rotten food are very different, even though they are both the result of the action of micro-organisms on the food item.

Fermented foods are good for you to eat, provide health benefits, and are an important method of preserving food for future use. This is especially significant when you have a bumper crop of vegetables in your garden and need to preserve the excess before it begins to rot.

Fermenting vegetables and fruit can even become an income-generating activity on the homestead, as you can sell your fermented products to friends and family and at local markets.

Rotten food, on the other hand, is not good to eat, and will invariably make you sick. The illnesses you can contract from eating rotten food can be severe, even to the point of being life-threatening.

Fermentation is a worthwhile activity to pursue on the homestead and is a skill that you will find useful. Just ensure you adhere to the rules and safety protocols to do it safely!

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