It's obviously very clean, why is there still a strange smell in the refrigerator?

Review expert: Wang Guoyi, Postdoctoral Fellow in Nutrition and Food Safety, China Agricultural University

Have you ever encountered this kind of question: the refrigerator is clean and tidy, but you can still smell unpleasant odors. When eating iced watermelon, you can taste the taste of chives, and when you open a piece of bread, it tastes like pickles.

Why does the refrigerator smell bad? What substances produce these unpleasant smells? And how can we effectively remove the odors?

1

Sources of refrigerator odor

There are three main sources of odor produced by food in the refrigerator: the odor of the refrigerator itself, the odor of food, and the odor caused by food spoilage .

Yes, you read that right, refrigerators themselves can emit odors, especially if they are new. This is because the plastics that make up the refrigerator can release volatile compounds, such as benzene, acids, alcohols, vinegar, and other compounds that have pungent odors.

In addition to the smell of the refrigerator itself, different foods also have different smells, and poor stability is one of the main characteristics of food flavor substances. So, when you put a box of durian in the refrigerator without covering it, as the small molecules of odor naturally diffuse, when you open the refrigerator again, you will find that "everything is durian."

Image source: Wikipedia

In addition, the biggest culprit for the odor in the refrigerator is food spoilage . Although the low temperature of the refrigerator can inhibit the growth and reproduction of microorganisms, it cannot eliminate microorganisms, especially low-temperature resistant microorganisms. When food is kept in the refrigerator for a long time, bacteria will decompose nutrients such as protein, sugar and fat in the food and produce small molecular compounds, among which compounds containing elements such as nitrogen and sulfur will emit a foul odor.

Source: "Research on Refrigerator Deodorization, Sterilization and Freshness Preservation Technology"

In short, long-term storage or failure to clean the refrigerator properly will create a breeding ground for bacteria.

2

Odor-causing bacteria

Different bacteria can produce different types of odors. Let’s take a closer look at these bacteria and the odors they produce so we can better address refrigerator odor issues.

Common psychrophilic bacteria in refrigerators include Shigella, Listeria, Salmonella, Yersinia , etc. These psychrophilic bacteria produce many metabolic gases during their growth and metabolism, such as methane, hydrogen sulfide, methyl mercaptan, methylamine and other volatile compounds with a strong smell of rotten eggs. If you smell a foul odor similar to rotten eggs when you open the refrigerator door, it is likely that these bacteria are at work.

These four strains of bacteria can generally survive in the refrigerator for 3 to 4 months. July and August each year are the peak periods for intestinal infectious diseases caused by these strains.

Storing things like raw pork (affects the content of amines and alkanes in the refrigerator), tofu (increases the content of oxygen-containing compounds in the refrigerator), and green vegetables (leads to an increase in styrene content) in the refrigerator will provide bacteria with suitable nutrients and promote the production of odor.

Image source: Wikipedia

3

Effective ways to remove odors

How can we effectively remove these odors?

Once the refrigerator has a strange smell, it means that the food is no longer fresh. Therefore, it is very important to check and clean the food in the refrigerator regularly. Make sure the food is dry and clean before storing it, and try to wrap the food well to reduce the transfer of odor .

At the same time, proper storage of food, use of sealed containers, and regular cleaning of the refrigerator are all effective measures to prevent bacterial growth. When cleaning, you can use a mild detergent to wipe the inside of the refrigerator, especially the sealing strips, drawers, corners and other hard-to-reach places, which are more likely to breed bacteria and odors, so you need to pay more attention.
Once the odor has already occurred, some more convenient ways to remove the odor are needed.
Commonly used deodorization methods can be divided into four categories: masking deodorization, physical deodorization, chemical deodorization, and sterilization deodorization.

Masking deodorization , such as putting lemon peel, grapefruit peel, orange peel and other fruits in the refrigerator, using the aromatic substances volatilized by the fruits to cover up the original odor. Some air fresheners are the same, but choosing fruits is relatively safer for food and human body.

Physical deodorization is also called adsorption. You can use activated carbon to absorb odors in the air and replace it regularly. The used charcoal bag can be exposed to the sun for a day before being used again.

For chemical deodorization , you can put vinegar, baking soda, and rice wine in an open container and put it in the refrigerator. These things will adsorb odorous substances and then react with them to produce odorless substances to achieve deodorization.

Tea is the representative of sterilization and deodorization . In daily life, you can dry the soaked tea leaves in the sun, put them in gauze or a small cloth bag and put them in the refrigerator. The tea polyphenols in tea are an alkaline substance that can inhibit the activity of bacteria, thereby achieving a deodorization effect. And tea leaves can also be used repeatedly, isn't it very environmentally friendly!

Although the odor in the refrigerator is sometimes a headache, by understanding the source of the odor and the bacteria that produce it, and taking effective deodorization methods, we can keep the refrigerator fresh at all times. Regularly cleaning the refrigerator, separating food, using deodorizers and other methods can help us effectively remove refrigerator odors!