What’s the Difference Between Fermenting and Rotting?

Short Answer:
When comparing food that is fermented vs rotten, the rotting is an uncontrolled act of food decomposing. Bacteria take over the food in question, breaking it down to a dangerous and foul state. Rotting kills the food.

Fermentation is a controlled process that creates an environment in which the food is placed (jar, crock…); when done correctly, the beneficial microbes will break down sugars and starches into alcohols and acids, making food more nutritious and preserve it, so it can be stored for long periods of time without spoiling.

Is fermentation the same as rotting? No, fermenting is just the opposite.

What is the difference is between fermentation and rotting food?

If you are in the middle of making a batch of fermented vegetables and are wondering if it has fermented or spoiled, check out my post How To Tell If Fermented Food Has Gone Bad.

Fermentation vs. Rotten: Grapes

Is fermented food rotten or spoiled?

No, fermented food is not spoiled food. The process of fermenting food is a method of preservation that raises the population of beneficial bacteria and breaks down the properties of the food so that they remain edible.

How the fermentation process works:

The process starts with the pH lowering, which creates an inhospitable environment for the harmful bacteria. They no longer thrive. The beneficial bacteria will then outcompete the harmful bacteria. It’s the survival of the fittest on the microscopic level.

The results are delicious fermented foods such as kimchi, sauerkraut, and so on.

In fact, because humans have generally moved away from eating unpasteurized fermented foods, which we have been doing for thousands of years. Studies indicate this has negatively impacted our systems.

What is the difference between fermenting and rotting foods?

Food spoilage takes place when microscopic organisms feast on food items that you leave unattended. The microscopic bacteria are what cause food to spoil. These tiny organisms, called spoilage bacteria, eat unprotected food, and produce waste products.

Bacterial waste is easy to detect by its foul smell, rotten appearance, and vile taste.

It’s all relative to the process, and humans have developed senses that warn us of harmful things. Think of how you react to a putrefying smell; you start to gag uncontrollably. That is your body protecting itself.

During the fermentation process, microorganisms such as bacteria, yeast, or fungi convert organic compounds, such as sugars and starch into alcohol or acids.

For example, starches and sugars (carbohydrates) in vegetables and fruits are converted to lactic acid, and this lactic acid acts as a natural preservative.

The lactic acid is how the food gets its good stuff, the distinctive, intense, slightly sour flavors to common in kimchi, sauerkraut, pickles, beet kvass, and the like.

It’s a balancing act. The challenge is to balance both the good and bad bacteria.

Humans have both good and bad bacteria living in their guts. The good bacteria are called probiotics. Probiotics are what line your gut and support nutrient absorption and a healthy immune system.

Eating fermented foods on a daily basis will help you build up the colonies of good bacteria and achieve a healthy gut.

It will help your body digest, absorb, and get better use of the foods you’re eating. More health benefits of eating fermented foods include:

  • Stronger immune system
  • Promote repair of damaged tissues
  • Improved digestion
  • Increased energy from the production of vitamin B12
  • Better breath because probiotics destroy candida
  • Healthier skin, since probiotics improve eczema and psoriasis
  • Reduced cold and flu
  • Healing from leaky gut and inflammatory bowel disease
  • Weight loss

Probiotics have also been shown to help slow or reverse some diseases, improve bowel health, aid digestion, and improve immunity!

Signs you have too much bad gut bacteria:

  • Constipation
  • Excess intestinal gas
  • Too little or no intestinal gas
  • Chronic diarrhea
  • Chronic bad breath

In this post, I covered exactly what the difference between fermentation and rotting is. You should now be able to safely distinguish the difference. Or, just trust your nose and taste buds. They won’t lead you astray.

Specifically, I described how fermenting is purposeful spoilage using Lactobacillus (or LAB), which ferments foods by converting sugars. It wards off the bad bacteria. For this reason, you can store fermented foods for a long time.

While, rotting is bad bacteria breaking down food. It’s uncontrolled spoilage, and not suitable to eat because it can make you sick. You will know because it has a very unpleasant smell and taste.


Hello! I’m Katie, mom, hobby fermenter, gardener, canner, and boundless experimenter. Here at Fermenters Kitchen, our team of enthusiast aims to encourage readers to embark on a fermentation journey with us, one bubbly jar at a time.