Why does food break down?
The main causes of decomposition by vital phenomena are microorganisms (such as bacteria in the environment and parasites in food itself) and enzymes present in food. Enzymes are biological type compounds through which specific chemical reactions are catalyzed. Microorganisms and enzymes cause decomposition by intervening in processes, physical and chemical transformation of the substances that make up food.
But food is also altered by non-vital processes. Among the causes of this can be mentioned: excesses of temperature, humidity, light, oxygen or simply time. All these factors cause various physical and chemical changes, which are manifested by changes in the color, smell, taste, consistency or texture of the food.
Can you prevent food spoilage?
Previously mentioned as the main causes of food alteration, microorganisms and food enzymes themselves as responsible for vital phenomena. For these phenomena to occur certain appropriate conditions are required: air access, humidity and temperature. Thus, to prevent these undesirable vital phenomena from occurring, excessive air, water and heat must be removed. Methods that prevent biological agents from altering food are called Indirect Preservation Methods.
Indirect Conservation Methods
Vacuum packed: food in glass containers
Dehydrated: milk powder, sachets, tea powder, jams, dried fish (cod)
Refrigerated: fruits, vegetables
Frozen Foods: ice cream, fish, fruit
Sterilized with heat: canned in general
Pasteurized: milk and dairy products (butter) in refrigerators
Vacuum packaging: It consists of the elimination of air or oxygen from the appropriate containers and packaging for this purpose. In this way the food is prevented from having contact with microorganisms in the air or the environment. Conveniently packaged foods are also protected against dirt and other possible contamination. Tomato is a food that can be preserved by this technique.
Dehydration or drying: It allows the elimination of water. Dehydration is a methodical, progressive and continuous process, in which the amount of heat necessary to extract water from food is applied. As an example we have powdered milk, which is the dry residue obtained after dehydration of the milk. Another way to remove moisture is to add highly soluble substances such as common salt and sugar to food. Salting fish and meat has been practiced since ancient times. Sugar is used above all in canned fruits: jams, preserves, etc.
Refrigeration: refrigeration and freezing methods avoid the effects of heat on food. Refrigeration consists of lowering the temperature of the food to values close to 0º C, but without reaching the formation of ice. Refrigerators are an example of the use of refrigeration to preserve food. Refrigeration is also used at the industrial level to store large quantities of products (fruits, vegetables, meats, etc.) and in transport (trucks, rail cars, ships). Refrigerated foods can be kept for a period of time ranging from one or two days (seafood, fish) to months (eggs).
Freeze a food is to lower its temperature below 0º C. Frequently freezing is used, ultra-fast freezing to temperatures between 18º and 40º C. This prevents large ice crystals from forming, which would alter the texture of the products. When defrosting deep-frozen foods, they retain characteristics much more similar to those of fresh foods. Deep freezing destroys up to 50% of the microorganisms that may contain food. Both in industry and in households, freezing and deep-freezing are increasingly used in the preservation of raw seafood, fish, meat, fruit and vegetables, and also for preserving prepared and semi-prepared meals.
Indirect preservation methods prevent the action of microorganisms and enzymes, but in general these methods do not destroy all microorganisms and enzymes in food. To destroy them, one must resort to Direct Conservation Methods.
Direct conservation methods
These methods include heat sterilization, pasteurization, and the use of additives.
Microorganisms and enzymes need a certain degree of temperature to alter food, but excess heat destroys them. This is why heat sterilization is used to preserve food, especially canned food. The filled and hermetically closed cans are subjected to high temperatures (between 100º and 150º C.) for a certain time. Once the cans are sterilized, and as long as they do not open and deteriorate, the products in them will remain unchanged for a long time. For this reason it is useless to keep canning cans in a refrigerator before opening them.
This method consists of raising the temperature of the food between 60º and 80º C during a period between a few seconds and 30 minutes. This destroys the most dangerous microorganisms or those that can produce alterations more frequently. Since pasteurization does not eliminate all the microorganisms that can be contained in the treated products, this method only allows temporary storage and under certain conditions. Pasteurized foods, sometimes called semi-preserves, should be kept in a refrigerator, even if the packaging has not yet been opened. This is the case of milk that comes in a carton, butter, margarine, among others.
Both vital and non-vital processes can be avoided by adding certain chemicals called additives. These additives can have different missions:
- Eliminate microorganisms (antibiotics);
- Prevent microorganisms from multiplying or proliferating (inhibitors);
- Avoid alterations due to oxidation (antioxidants), among others. Each country has strict food regulations to regulate the use of additives and ensure that they are not harmful to the consumer.
Fresh food or canned food?
Many people think that when fresh food is bought and cooked, all its nutrients are preserved; But when the food itself goes through an industrial process of preservation, the nutrients are largely or completely destroyed. This belief is false. Actually, from a nutritional point of view, there is no significant difference between meals made at home with fresh foods and those made with preserved foods.
Some nutrient losses are inevitable. Many food preparation processes, whether domestic or industrial, involve applying heat or treating with water. In both cases some loss of nutrients occurs. If losses occur during industrial food processing, this will also inevitably occur when cooking food at home. The exact opposite is often the case: industrially processed foods outperform fresh foods in some respect. In addition, some industries enrich food by adding vitamins and mineral elements. However, chemical additives to keep food in good condition can be harmful to health.
Remember: We can only have some fresh food for a limited period of time. If no preservation method is used, there are few fresh foods that can be stored or transported.