How long is grated parmesan cheese good for after opened?
In this article, we will answer the question ‘How long is grated parmesan cheese good for after opened?’ and discuss how to store grated parmesan cheese, the factors that cause grated parmesan cheese to spoil quicker and how to know if grated parmesan cheese has gone bad.
How long is grated parmesan cheese good for after opened?
Grated parmesan cheese lasts for a few days after being opened (2). The shelf life of grated parmesan cheese packed in a modified atmosphere packaging (MAP) is when kept unopened is about 3 months (1).
The shelf life of cheese is drastically reduced through grating, shredding, cutting or handling, due to the exposure of the product to possible sources of contamination (3). Other factors also affect the shelf life of grated parmesan cheese, which will be discussed in the following section of this article.
What determines the shelf life of grated parmesan cheese?
The shelf life of grated parmesan cheese can be determined by the following factors (1,2,3,4):
- Handling: microorganisms are able to contaminate the product through handling, cutting and grating, especially when the hygienic practices of food handlers are poor
- Equipment: grating equipment and cutting utensils, such as cutting boards and knives, even when properly sanitized, are able to contaminate cheese, reducing its shelf life
- Product quality: cheese produced with higher quality of the ingredients, including high quality milk and under better manufacturing conditions has a longer shelf life
- Storage conditions: low temperature of storage reduces the growth of microorganisms, while temperature fluctuations during storage and transporting can favor spoilage
- Packaging: modified atmosphere packaging (MAP) reduces the rate of microbial growth and oxidation of the cheese, as it reduces the oxygen concentration inside the cheese package, resulting in a longer shelf life
How to know if grated parmesan cheese has gone bad?
To know if grated parmesan cheese has gone bad, be aware of the possible signs of spoilage in parmesan cheese (1):
- Generation of off-odors and off-flavors: lipid oxidation and amino acid deterioration lead to the formation of off-odors, such as rancid, moldy, acid, and extreme bitter. Lipid and amino acid degradation can be caused my microorganisms as well
- Formation of slime: the presence of a watery biofilm on the surface can indicate bacterial growth
- Discoloration: formation of pigments, such as orange, purple, pink can indicate the growth of bacteria
- Loss of pigments: Exposure to light can lead to the loss of the characteristic color of cheese
- Growth of mold: many molds are able to grow in cheese, such as Mucor spp. and Rhizopus spp., Cladosporium herbarum and others, and form brown, black and green colonies
- Drying of edges and formation of rind: although the cheese is safe to consume, dryness leads to quality loss
Can you eat grated parmesan cheese after the expiration date?
Yes, you can eat grated parmesan cheese after the expiration date, unless no sign of spoilage is noticeable and the product has been stored under proper conditions (6).
Mold growth, slime formation, off-odors and off-flavors indicate the microbial spoilage of cheese and spoiled cheese should not be consumed, as it possesses a risk to health (1).
The risks of eating spoiled cheese are of having a foodborne illness, especially due to the infection of yeasts and molds and their toxins. Aspergillus and Penicillium are the most common fungi found in cheese which toxins can cause deleterious health effects (5).
Other FAQs about Parmesan which you may be interested in.
How to extend the shelf life of grated parmesan cheese?
To extend the shelf life of grated parmesan cheese, you should keep it in the original package till the consumption, especially when the cheese is packed in a modified atmosphere package (MAP) (2,3).
MAP can extend the shelf life of cheese, as it prevents the product from microbial contamination and reduces the oxidation reactions, as well as avoids the loss of moisture. Opening the package will allow contamination from the external environment to reach the cheese and reduce its shelf life.
To extend the shelf life of an opened package of grated parmesan cheese, place in a freezable airtight food container and store it in the freezer.
Freezing of cheese at -20°C (-4°F) can preserve the quality of the cheese for many years, especially in the case of high fat content, which helps the ice crystals not to grow considerably, reducing the negative effects in the texture due to the freeze-thawing process (4).
In this article, we answered the question ‘How long is grated parmesan cheese good for after opened?’ and discussed how to store grated parmesan cheese, the factors that cause grated parmesan cheese to spoil quicker and how to know if grated parmesan cheese has gone bad.
- de Fátima Poças, Maria, and Manuela Pintado. 6 Packaging and the Shelf Life of Cheese. Food packaging and shelf life. 2010.
- Alves, Rosa Maria Vercelino, et al. Stability of sliced mozzarella cheese in modified-atmosphere packaging. J Food Protect, 1996, 59, 838-844.
- Pala C, Scarano C, Venusti M, Sardo D, Casti D, Cossu F, Lamon S, Spanu V, Ibba M, Marras M, Paba A, Spanu C, De Santis EP. Shelf Life Evaluation of Ricotta Fresca Sheep Cheese in Modified Atmosphere Packaging. Ital J Food Saf. 2016, 5, 5502.
- Nájera, A.I.; Nieto, S.; Barron, L.J.R.; Albisu, M. A Review of the Preservation of Hard and Semi-Hard Cheeses: Quality and Safety. Int. J. Environ. Res. Public Health 2021, 18, 9789.
- Bullerman, L. B. Public health significance of molds and mycotoxins in fermented dairy products. J Dairy Sci, 1981, 64, 2439-2452.
- Food product dating. United States Department of Agriculture.