Can cheese go bad if left out?

In this brief article, we will look into the question, “Can cheese go bad if left out?” We will also explore cheese storage and cheese deterioration.

Can cheese go bad if left out?

Yes, cheese can go bad if left out through the action of bacteria and fungi [1].

Moreover, cheese can become rancid, undergo color modifications, and rind spoilage due to cheese dehydration and fat oxidation if exposed to light, or placed in a hot, low-humidity environment [2, 3]. 

The rate of spoilage depends on many factors, among them, I highlight the cheese type: fresh, soft, hard, and semi-hard cheeses.

According to the type, cheese can have different pH, fat and salt concentration, moisture, ripening periods, and microorganisms added to promote desired flavor development (e.g. lactic bacteria, molds).

Fresh and soft cheeses, like ricotta, mascarpone, and Feta, will generally spoil faster than hard or semi-hard ones because of their higher pH, moisture content, and water activity [3, 4].

Most spoilage and harmful bacteria prefer a pH close to neutrality (7.0) to multiply [4]. Fungi also develop well under this condition, but they are also able to grow at a pH as low as 3.5 [5].

Moisture, along with water activity (Aw), is the most important indicative parameter of food perishability. Generally, the higher the moisture, the more susceptible to spoilage the food is.

In practical terms, Aw is a technical concept that expresses the amount of water in food available for microbial growth and chemical reactions [5].  

The water activity of foods lies between 0 and 1. The closer to 1, the more water is available for microbial development, and the more perishable the food product [5]. 

Vrdoljak and others [3] and Jafarzadeh and others [4] reported that soft cheeses have a pH of about 6-6.5, and water activity above 0.95. Moreover, the moisture content of soft cheeses lies above 40%.

On the other hand, semi-hard and hard cheeses had a pH of about 5.4-5.8, a moisture content between 36% and 25% or less (for very hard cheeses), and water activity ranging from 0.9-0.7 [3, 4]. 

Moreover, hard and semi-hard cheese types usually contain more salt, which is an extra factor against microorganisms’ growth, as salt helps reduce the Aw.    

Thus, Vrdoljak and others [3] concluded that due to these distinct characteristics, soft cheeses are more supportive of the growth of spoilage bacteria and even harmful bacteria like Listeria monocytogenes than hard cheeses.

How long do different types of cheese last?

Hard cheese 

Hard cheeses last up to 6 months unopened and about 3 weeks after opening [4]. After opening, always wrap your cheese with an appropriate food-grade film. 

Among all cheese types, hard cheeses are the ones lasting more because generally they ripen for longer (usually 6-36 months), have lower moisture and water activity, besides higher salt content compared to others [4].

During ripening, cheese undergoes dehydration and a number of complex biochemical reactions that result in lower pH, moisture, and water activity compared to non-ripened cheeses. 

For instance, parmesan is a hard, highly ripened cheese (12-36 months of ripening), with a pH of 5.5, moisture of about 32%-37%, and 0.7-0.8 of Aw. 

This makes parmesan less susceptible to most spoilage and harmful bacteria growth [4]. 

However, Jafarzadeh and others [4] highlight that the surface of the cheese, even the hard ones, is still favorable to all types of microbial growth. For this reason, cheese should be always stored properly.

The precise shelf life of a hard cheese will depend on the characteristics of the cheese, such as salt concentration, water content, and ripening length. So follow the manufacturer’s instructions for your cheese.  

Semi-hard cheese

Cheeses that fall between the hard and soft categories, such as gouda, may be kept in the refrigerator for up to 4 months unopened, and two to three weeks after they have been opened, depending on their consistency.

The precise shelf life of semi-hard cheese can vary greatly for instance due to salt concentration, moisture content, and ripening length. So follow the manufacturer’s instructions for your cheese.  

 Fresh and soft cheese

As a result of their high moisture content, cheeses like brie, feta, and camembert are among the cheeses that deteriorate the most quickly. 

Before opening, they last 2 to 3 weeks. After opening, they can be stored for up to 5 days. Keep the cheese always wrapped in appropriate food-grade films [4]. 

Can you freeze cheese?

You can freeze cheese but it is not recommended if you intend to serve and enjoy it alone. Freezing can damage the cheese texture. The best way to use frozen cheese is in recipes, such as lasagna.

Hard and semi-hard cheeses may last for up to 8 months frozen, while soft cheeses can be frozen for up to 6 months [4]. 

Before using the frozen cheese, thaw it in the refrigerator overnight or until completely thawed.

How to tell the cheese has gone bad?

Be attentive to spoilage signs: 

Development of mold: in some cheese types, molds are desirable, for example in brie, camembert, Roquefort, and gorgonzola cheeses. 

However, in non-moldy cheeses, mold growth will result in an unpleasant appearance, and promote the development of off-flavors and off-odors. If your cheese shows mold, discard it.

Slimy surface:  it is caused by peptides and polysaccharides produced during the growth of harmless spoilage microbes [2]. Thus, a slimy surface may indicate a high microbial load in the cheese.

– Bitterness: occurs due to proteolysis and production of low molecular weight peptides. Proteolysis may be caused by enzymes from microorganisms or enzymes native to cheese. 

If you feel your cheese bitter, it just means that proteins were degraded to give harmless off-flavors. 

Rancidity: it is the result of fat oxidation. Rancidity happens more easily in high-fat cheeses. It can take place due to the activity of microbial enzymes or native enzymes in cheese.

Rancidity also occurs if the cheese is exposed to high temperatures during storage or maturation since fat oxidation is boosted by heat.  

– Irregular holes and swelling: In some cheese types, such as Emmental, holes are desirable and intentionally caused by selected microorganisms.

However, in certain cheese types, for instance, mozzarella, and gruyere, holes and swelling may indicate gas production from microbial proliferation. The gas is produced for some types of contaminating bacteria, like coliforms [2]. 

Thus, if you observe holes and swelling in cheese that is not supposed to have them, avoid consuming it.

Is it safe to eat expired cheese?

No, it is not safe to eat expired cheese, especially fresh and soft cheeses which are highly favorable for the growth of harmful microorganisms.

For instance, a number of studies report the occurrence of outbreaks involving the consumption of cheese contaminated with Listeria monocytogenes, a harmful bacteria that can affect mainly immunosuppressed people [6, 7].

Although many of these events were related to moist cheese, such as mozzarella, hard cheeses could also be affected, as L. monocytogenes can grow in refrigeration temperatures, low pH, and high salt concentrations [8].

Cheese surfaces are also  

Thus, eating expired cheese exposes you to food poisoning.

How to properly store cheese

As a general rule, cheese is better preserved in the refrigerator, regardless of the type. Chilling will prolong the shelf life by delaying undesirable chemical reactions and the growth of spoilage microorganisms. Harmful microbes will also be inhibited.

Importantly, keep the cheese always protected from light and air exposure, for instance, covered by foil paper or other food-grade films. Besides protecting from contamination, fat oxidation is also delayed. 


In this brief study, we answered the question, “Can cheese go bad if left out?” We also explored cheese storage and cheese deterioration.


1. Spoilage of Milk and Milk Products.  Food Microbiology: Principles into Practice2016. p. 307-36.

2. Robertson, G.L. (Ed.). (2009). Food Packaging and Shelf Life: A Practical Guide (1st ed.). CRC Press.

3. Vrdoljak J, Dobranić V, Filipović I, Zdolec N. Microbiological Quality of Soft, Semi-Hard and Hard Cheeses During the Shelf-Life. Macedonian Veterinary Review. 2016;39(1):59-64.

4. Jafarzadeh S, Salehabadi A, Mohammadi Nafchi A, Oladzadabbasabadi N, Jafari SM. Cheese packaging by edible coatings and biodegradable nanocomposites; improvement in shelf life, physicochemical and sensory properties. Trends in Food Science & Technology. 2021;116:218-31 

5.  Jay JM. Food – Microbiology. 6th Ed, Aspen Food Science, 2000.

 6. Li Y, Gao Y, Ling N, Shen Y, Zhang D, Ou D, et al. Rapid and simple quantitative identification of Listeria monocytogenes in cheese by isothermal sequence exchange amplification based on surface-enhanced Raman spectroscopy. Journal of Dairy Science. 2022;105(12):9450-62.

 7. Rivas PM, Carmo da Silva D, Lopes SM, Riboldi CI, Tondo EC. Assessing the Listeria monocytogenes transference during mechanical slicing of mozzarella cheese. Food Microbiology. 2022;105:104022.

8. Silva SPM, Teixeira JA, Silva CCG. Application of enterocin-whey films to reduce Listeria monocytogenes contamination on ripened cheese. Food Microbiology. 2023;109:104134.