Cut apple that turns rust-colored, tomato that goes moldy, bread that shrivels up, and milk that tastes rancid: these are just some of the ways in which foods undergo so-called alterations.
By this word is meant all those changes, whether desired or not, that food may undergo if certain conditions arise.
These conditions are varied, multiple, and include biological, chemical, physical, and environmental factors.
Often, these factors coexist and cooperate in defining the alteration that the food will undergo.
The consequences of alteration include impairment of the quality of the food, as well as its safety and nutritional values.
This topic is of interest to anyone who likes to cook-or is forced to-because knowing about it helps us protect our food and keep it unaltered for as long as possible.
Of course, it is of enormous relevance not only on the household level, but also for public health and the food economy.
Finding ways to better package and preserve food makes it last longer, reducing the chance of it becoming waste before it even reaches our homes.
In addition, a well-preserved product is by definition also safer for consumers.
Disclaimer: Actually, the term alteration is not always meant in a negative sense.
Some of these changes are intentional, as in the cheese-making process.
In this case the alteration processes are necessary to achieve the desired organoleptic characteristics.
All fermented foods, which we have discussed in this article, are also intentional.
Among the many altering processes, today we discuss those that have a degrading and undesirable action.
Let us now go on to find out how many and what factors affect food spoilage.
Spoiler: more than you think!
Causes of food spoilage
Biological factors:
- Microorganisms: bacteria, yeasts and molds can grow on food, causing spoilage and potential risk of food poisoning.
Examples include Salmonella, E. coli, and Listeria. - Enzymes: Enzymes naturally present in food can catalyze chemical reactions that lead to changes in the flavor, texture, and appearance of food.
A common example is the browning of cut apples, caused by the enzyme polyphenoloxidase which, as its name suggests, oxidizes the polyphenols contained in the fruit.
This reaction occurs only following cutting, because the apple is exposed to oxygen that activates the enzyme.
Chemical and physical factors
- Oxygen: Oxygen causes oxidation of foods, which for example in fats can lead to rancidity by altering the taste and smell of foods.
Antioxidants are often added to food preparations at the industrial level to prevent this phenomenon.
Pepper, chili pepper, sage and rosemary are examples of natural antioxidants that slow down oxidation: it is no coincidence that the surface of some cured meats is covered with pepper! - Temperature: excessive heat and cold can alter the structure and quality of foods.
Freezing can cause the formation of ice crystals that damage food cells, and heat can speed up degradation and rotting processes. - Moisture: High levels of moisture can promote the growth of microorganisms in fresh foods, damage to dry foods such as seeds, softening of baked goods, and formation of lumps in foods such as flours and sugars; conversely, the absence of moisture can cause foods to dry out, dehydration in vegetables, and “blanching” in frozen foods with formation of whitish spots.
Environmental factors:
- Light: Exposure to light can degrade vitamins (A, B2 and C) and pigments, as in the case of riboflavin in milk.
How might these factors combine?
The most famous alteration
We will talk here mainly about food spoilage occurring due to biological causes, although we can always keep in mind that the remaining factors are capable of speeding up or slowing down the process. We will talk about her, the most important and well-known enemy of refrigerators and pantries, the vip of the wastebasket…MARCESCENCEYeah, what happens when food rots?
We know that fruits, vegetables, fish and meat rot if they are left in the refrigerator for too long or, even faster, if they are left at room temperature.
We can smell it by the odor, which is annoying and repulsive; by the texture, which becomes soft and saggy; and by the taste, which is pungent and unpleasant.
And again by the changes in color, the formation of mucilage and any surface moldiness!
Rotting is due to the action of enzymes, special types of proteins in the foods themselves, and contamination by microorganisms or insects, for example.
Even in the case of microbial contamination, degradation occurs through the action of proteins that alter food molecules.
The two phenomena can then occur simultaneously, speeding up the process.
Alterations to proteins involve hydrolysis and putrefaction. In organic chemistry, hydrolysis indicates the breaking of a strong bond, such as the one that holds amino acids, the building blocks that make up proteins, together. Putrefaction, on the other hand, involves microbial enzymes, which initiate a series of biochemical reactions that can break, again, the bonds that hold proteins together.
One of the most common reactions involves amino acids such as cysteine, which are degraded releasing hydrogen sulfide.
This acid can bind to myoglobin, which is contained in meat, causing the green color that informs us of impending rotting!
Another very common reaction is that from the breaking of certain internal bonds in amino acids gives rise to amines, which are responsible for the disgusting odors typical of spoiled food.
Two of these amines, in particular, take the names of cadaverine e putrescent.
Non c’è bisogno di aggiungere altro, direi, a parte il fatto che per essere un po’ più precisi va detto che l’odore di marcio è composto da non due ma almeno 400 diverse molecole!
Disgusting for us, delicious for them
It is always interesting to make the mental effort to reverse our point of view.
Indeed, it comes naturally to us to perceive the world through our filter, the human one.
In doing so, however, we forget the perspective, the relativity by which everything works.
We miss the broader keys to understanding nature.
For example, the molecules that are released when foods rot are as repulsive to us as they are neutral or even attractive to other organisms.
Like the very culprits responsible for contamination and the formation of those molecules, which, according to some studies yet to be investigated, would gain priority over the food they contaminated.
A kind of VIP pass at the first come, first served, which in this case it eats.
Indeed, it would seem that the rotting caused by one or the other microorganism can gross out, and thus drive away, not only large beasts like us mammals, but also other microorganisms!
Prevention and best practices
What can we do to prevent food spoilage as much as possible?
AVOIDS CROSS-CONTAMINATION
Also called cross-contamination, it is the passage of microorganisms or dirt from one food to another.
It can occur in a manner:
- indirect: through contact of hands, work surfaces or kitchen utensils used first on one food and then on others;
- direct: When two or more foods come into contact with each other.
In general, it is important that raw food not come into contact with cooked food.
In fact, cooked food is likely to be free of biological contaminants since it has reached high temperatures during cooking; on the other hand, raw food that has not yet been thoroughly washed can carry microorganisms, which find fertile ground on the dishes.
For this reason, it is always advisable to use appropriate (closed) containers for storage in the refrigerator, paying attention to the symbols on them (especially those made of plastic) so as to avoid physical contamination due precisely to the materials in the container.STORE FOOD PROPERLYThis topic is so important that it deserves a separate article, which, in fact, you can find here -> the refrigerator vademecum: how to arrange food and use it to best effect.GOOD PRACTICES.In addition to these cautions, there are simple rules to follow to ensure fresh, undamaged food:
- Grocery shopping several times a week by buying less fresh produce.
Compared to shopping once a week is more challenging and requires more time organization, but it is the best way to manage fresh produce.
Fruits, vegetables, meat, and fish will be present in the right quantity and thus avoid unnecessary waste - If you really cannot or want to, then make a weekly plan.
It doesn’t need to be super precise or then follow it to the letter, but it will help you figure out what amount of food to buy so you don’t overdo it - The freezer: an often underestimated ally, we can use it in two different ways.
The first goes in the direction of philosophy prep, which involves cooking more fresh food at once, portioning and freezing it and then thawing it during the week as needed.
The second is even faster, because we just buy some fresh and some frozen, so that we have an always-ready supply of vegetables.
Don’t worry about the nutritional properties; they are not significantly altered!
In short, understanding the mechanisms of food spoilage is critical to preserving food quality and safety.
Through proper storage practices, contamination prevention and careful stock management, we can minimize waste and ensure that our food stays fresh longer.
Awareness and adoption of good practices not only protect our health, but also contribute to a more sustainable and efficient food economy.
Sources:
– Patrizia Cappelli, Vanna Vannucchi, Food chemistry storage and processing., Bologna, Zanichelli, 1990, ISBN 88-08-06788-2.
– Food Technology By Bruno Zanoni
– Pircher, A., Bauer, F. & Paulsen, P.Formation of cadaverine, histamine, putrescine and tyramine by bacteria isolated from meat, fermented sausages and cheese. Eur Food Res Technol 226, 225-231 (2007). https://doi.org/10.1007/s00217-006-0530-7– Goldberg S, Kozlovsky A, Gordon D, Gelernter I, Sintov A, Rosenberg M. Cadaverine as a Putative Component of Oral Malodor. Journal of Dental Research..
1994; 73 (6): 1168-1172.
doi: 10.1177 / 00220345940730060701
