Does parmesan cheese go bad?

In this short article, we will provide an answer to the question “Does parmesan cheese go bad?”. We will go over the shelf life of parmesan cheese as well as the best ways of storing it.

Does parmesan cheese go bad?

Yes, parmesan cheese goes bad if expired, improperly handled, or stored. When unopened and correctly stored, a block of parmesan is given a shelf life of 6 months [1]. 

After opening, it is advised to be consumed within 2 months for best quality. If grated or shredded, it lasts less.

Parmesan cheese is categorized as an extra-hard cheese. According to Gobbeti [2] and Poças and Pintado [1], parmesan cheese has a moisture content between  30-36% and values of fat of about 28-40%. 

Ripening takes from 6 to 24 months. Parmesan’s pH is around 5.5 and water activity averages 0.92 [1,3].  

Fox and others [3] stated that these features could help control bacterial growth, but are not enough to prevent the growth of yeasts and molds.  

Thus, parmesan cheese can keep its quality longer than soft cheeses for example but may be more easily spoiled by fungi.

Moreover, the surface of parmesan cheese is more susceptible to all types of contamination than the inner parts, as according to studies, it has acidity and high-water activity conditions that favor microbes multiplication [4]. 

Due to its high-fat content, parmesan cheese can also undergo fat oxidation and become rancid [2, 3]. 

If improperly stored – for instance, exposed to excessive heat, light, oxygen, and moisture loss – texture changes, the growth of mold, and fat oxidation may be promoted, reducing the shelf life of cheese.  

Grated and shredded parmesan cheeses are more prone to deteriorative changes than whole cheese because of a larger surface area exposed to light and air [1]. 

Besides, manipulation adds a source of contamination to the cheese, as verified in a study by Aguilar and others [5], who found significant levels of contamination in parmesan cheeses grated in supermarkets. 

Human handling and contact with non-sanitized utensil surfaces were pointed out as the most likely sources of contamination by the authors.

What is the shelf life of parmesan cheese?

Parmesan cheese blocks unopened and still in their original packaging are given a shelf life of 4-6 months in the refrigerator [1, 4]. After opening, it lasts for around 6 weeks in the fridge.

Grated or shredded parmesan cheese has a shorter shelf life than a whole piece of parmesan cheese. According to Poças and Pintado [1], unopened grated parmesan cheese is given a shelf life of about 3 months.

After being opened, manufacturers recommended consumption within 5 days. Always follow storing instructions printed on labels.

Ways to tell if parmesan Cheese has gone bad 

Development of mold: According to the recommendation of the United States Department of Agriculture [6], moldy parmesan cheese can be trimmed 2.5 cm around and below the moldy section.

The problem with mold development is related to the fact that some mold species produce poisoning compounds during their growth, known as mycotoxins.

However, the knowledge so far indicates that molds generally cannot penetrate into the food [6,7]. 

Research showed that mycotoxins produced by molds artificially inoculated in hard cheeses did not migrate further than 2 cm into the cheese [7]. 

Moldy shredded, grated or sliced parmesan cheeses are recommended to be discarded, as they could have been contaminated by the cutting instrument or human manipulation, and harmful bacteria can also be present [6]. 

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 in cheese. 

Rancidity: parmesan is a high-fat cheese, so it is susceptible to fat oxidation, which can take place due to the activity of microbial enzymes or enzymes in cheese.

Fat oxidation leading to rancidity also occurs if the cheese is exposed to oxygen, light, and high temperatures during storage. 

Trobetas and colleagues [8] found that fat oxidation of hard cheese stored under fluorescent light (used at home and in the supermarket) and in presence of oxygen was 20 times higher than in the cheese stored in the dark. 

Color change: may be attributed to the light-induced decomposition of pigments in cheese, such as carotenoids, and vitamins like riboflavin, which acts as a photosensitizer in photo-oxidation reactions [2, 8].

A previous study demonstrated that hard cheese exposed to fluorescent light showed significant discoloration compared to cheese kept in the dark [8]. The authors attributed the color loss mainly to carotenoid degradation. 

Moreover, the rise of dark spots in cheese may indicate mold development.   

Other signs of spoilage: off-flavors and off-odors, in general, indicate high microbial load, and it is advisable to discard the cheese (in blocks or grated). 

How to keep parmesan cheese fresher for a longer?

Store parmesan cheese in the refrigerator at a temperature of 4 to 8 °C always with plastic wrap or aluminum foil paper. Avoid light and oxygen exposure. 

Grated cheese often comes in a pouch that already provides light, moisture and oxygen barriers. In this case, keep the pouch properly sealed to maximize protection.

Jafarzadeh and others [4] stress that protecting cheese from moisture loss, oxygen, and UV (light) minimizes the activity of bacteria and fungi and leads to good textural and sensory properties of cheese.

Oxygen can favor the development of mold and rancidity [4]. UV (light) can also promote rancidity, as demonstrated by Trobetas [8] in a study conducted with hard cheese. Moreover, water loss may negatively affect the texture.

Can you freeze parmesan cheese?

Yes, you can freeze parmesan cheese to make it last longer, but freezing can change the texture of the cheese. In the freezer, parmesan cheese can last from 6 to 8 months [4].

It may be kept in an airtight box or freezer bag that has been firmly sealed. Always take precautions to ensure that as much extra air is removed as feasible.

To thaw it, place the cheese in the refrigerator overnight or until you notice it is completely thawed. 


In this short article, we provided an answer to the question “Does parmesan cheese go bad?”. We also discussed the shelf life of parmesan cheese as well as the best ways of storing it.


1. Poças MDF, Pintado M. Packaging and the shelf life of cheese. Em Robertson GL, editor, Food Packaging and Shelf Life: A Practical Guide. CRC Press. 2009

2. Gobbetti M. Extra-hard varieties. In: Fox PF, McSweeney PLH, Cogan TM, Guinee TP, editors. Cheese: Chemistry, Physics and Microbiology. 2: Academic Press; 2004. p. 51-70.

3. Fox PF, Guinee TP, Cogan TM, McSweeney PLH. Microbiology of Cheese Ripening. In: Fox PF, Guinee TP, Cogan TM, McSweeney PLH, editors. Fundamentals of Cheese Science. Boston, MA: Springer US; 2017. p. 333-90.

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. Aguilar CEG, Rossi Junior OD, Vidal AMC, Ribeiro LF, Rossi GAM. Microbial quality of industrial and retail market grated parmesan cheese in the State of São Paulo, Brazil. Cienc Rural [Internet]. 2016; 46(12):2257–63.


7. Olsen M, Gidlund A, Sulyok M. Experimental mold growth and mycotoxin diffusion in different food items. World Mycotoxin Journal. 2017; 10(2): 153–161.

8. Trobetas A, Badeka A, Kontominas MG. Light-induced changes in grated Graviera hard cheese packaged under modified atmospheres. International Dairy Journal. 2008;18(12):1133-9.