When we don't know if a food we have in the fridge is bad, our first instinct is automatically to smell it. If it does not give off strange aromas, we assume that it is good and that we can eat it calmly. But the reality is that smell is not enough to determine if our food is safe, or if it has already gone bad.
Odors in food are produced by the metabolism of different types of microbes that, when feeding, produce gases and in some cases release aromas. An example is the yeasty smell of freshly baked bread, which would indicate the presence of good microbes that help leaven the bread. But the same does not happen with some microorganisms that can contaminate our food and make us sick, as explained by the English microbiologist Matthew Gilmour. Bacteria such as listeria and salmonella do not give off odors that are perceptible to humans, so the sniff test may fail to detect if food is contaminated in this case.
Although pathogens such as listeria and salmonella cannot be detected through the sniff test, this can be used to determine if some food has gone bad. For example, smelling milk is the best test to see if it is still in good condition, or if it is better to throw it away.
The portfolio of aromas in food is so extensive that we cannot reduce ourselves to thinking that odors mean that a food is bad. This is the case of some cheeses, such as Roquefort, or certain fermented foods such as kimchi, whose strong odors are not indicative of rot.
Although the smell of cured or fermented foods does not indicate their state of preservation, the same does not happen when we talk about fresh ingredients. In the case of fruits, vegetables and some dairy products, it is better to be careful that they do not start to give off strange odors, since that would indicate that they are no longer in good condition and that they have not been properly preserved. This is why it is recommended to store them at an adequate temperature and plan the best time to consume them, which would avoid possible poisoning and reduce food waste.
