Time and storage space are the factors that influence the likelihood of food spoiling due to microbiological, chemical or physical causes.
From the manufacturer to the seller and the end consumer, the longer the chain of intermediaries and the greater the distance between the place where the food is produced and the end consumer, the greater the risk that fresh products will be contaminated, because they spend more time stored under conditions that are not always optimal.
When they reach the end consumers, the risk of spoiling also increases for the same two reasons – the time between when they are purchased and when they are consumed, and the conditions of domestic storage.
Fresh foodstuffs, such as milk, eggs and bread, spoil more frequently due to fungi and yeasts, and products with a higher proportion of water in their composition are also more likely to become contaminated with bacteria than those with less water.
Microbiological contamination is most common because microorganisms are everywhere, and except for moulds, they are also the most difficult to detect with the senses.
Furthermore, contamination by microorganisms means that the invaders “win” the battle against the usual bacterial flora. It is not an invasion, but instead a “victory,” as occurs with infectious diseases.
The table below summarises the most common types of changes that take place in cheeses, and relate them to the types of microorganisms that cause them.
Changes due to gas production are the result of unwanted fermentations that occur in the cheese’s ripening process, either at the beginning, or towards the end. The production of gas is apparent in the form of holes in the mass of the cheese, which cause the pieces of cheese affected to swell.
Cracking is also the result of the piece of cheese swelling, which even breaks through the rind.
Rancidity is apparent in the smell and taste, and is due to the degradation of fats. The bacteria that cause it are those that grow at temperatures below 7º C, i.e. it affects cheeses that are stored under refrigerated conditions.
Pink or whitish discolouration occurs in cheeses that take longer to ripen, and appears below the crust.
The following table, taken from the article Understanding spoilage microbial community and spoilage mechanisms in foods of animal origin, published recently in the journal Comprehensive Reviews in Food Science and Food Safety, summarises the conservation methods currently applied and researched worldwide that increase the storage time of cheeses:
The techniques included range from the use of preservatives (nisin, Natamycin, chitosan, etc.), modified atmosphere packaging and high pressure processes, to the most cutting-edge methods, such as edible and active coatings.
The techniques using coatings and films are in fact complemented with preservatives, since Natamycin and other preservatives are part of these coatings.
The authors of this publication argue that the detection technologies being investigated must be fast and sensitive, to help characterise the microorganisms that spoil cheese and other dairy products.