Food Preservation

Importance of Food Preservation:

Food preservation refers to the processes you use to prepare food for safe, long-term storage, whether you plan to use it at home, for prep in a commercial kitchen, or to sell directly to consumers. Preservation methods help inhibit bacterial growth and other types of spoilage, meaning the food is safe and satisfying to eat in the future.

There are three reasons why food preservation is important:

1. To minimize pathogenic bacteria – food in long-term storage is at serious risk of spoilage due to bacteria such as coli, Salmonella, and other pathogens. Bacteria only need warmth, moisture, and time to rapidly multiply in food, but food preservation inhibits one or more of these conditions and stops their growth.
2. To keep food at its best quality – food deteriorates over time due to spoilage. In many cases, mild spoilage doesn’t make food unsafe to eat, but it significantly affects its taste, texture, and appearance. Proper food preservation can help retain some of these qualities, as well as the nutritional value of certain foods.
3. To save money – waste is costly, both at home and in a commercial setting. Ideally, you should avoid buying more than you can use, but various preservation methods – if done safely – help you keep vegetables, fruits, meat, etc. well past their usual expiration so there’s no need to bin them.

Certain food preservation methods can be tricky, but chances are you’ll gain a real sense of satisfaction and pride when you successfully apply them. Also, as many preservation methods require precision and care to maintain food safety, you’ll strengthen your awareness of food hygiene risks and good practices.

Common Methods of Food Preservation:

Food preservation methods range from the simple process of chilling to more complex procedures such as canning. Many are creative options that help you mix things up at home or sell food in various forms of packaging. Others help you keep your inventory in a commercial kitchen for much longer, which means you reduce waste and increase profit.

Traditional Methods of Food Preservation:

Food preservation is one of the most important inseparable parts of human life. To increase the shelf-life of the food products, application of various methods such as drying, storage in vinegar under acidic condition, canning, freezing, fermenting, dry salting, curing, smoking, and sealing have been suggested. Although the traditional methods of food preservation guarantee its safety, application of these methods in food systems promotes the loss of temperature sensitive compounds, denaturation of proteins, alteration of food structures, change of color and taste of the products, and formation of new undesirable substances. Thus, today there is a growing interest in using nonthermal processing methods for preservation of food products.

Bottling and canning

• Bottling and canning are processes of preserving food by heating and then sealing it in an airtight container.
• The food is boiled to kill microorganisms and then sealed to prevent other microorganisms from getting in.

 Pickling

• Pickling food in vinegar or other acids, makes it difficult for microorganisms to live. Commonly pickled food includes onions, parkias, soya beans and chillies.
• Sugar can also be used in pickling fruits such as nutmegs, mangoes and cherries.
• The concentrated sugar solution used draws water from the fruit thus preventing the growth of microorganisms.

Drying

• A lot of food is preserved by drying under the sun.
• Drying removes most water from food. Most bacteria die or become inactive when the food is dried.

Salting

• Salting is an age-old way of preserving food. The salt draws out moisture and prevents microorganisms from growing. In this process, food such as fresh fish are gutted, washed and coarse salt is rubbed into it.

Vacuum Packing

• Vacuum packing keeps food by sucking air out from its packaging. Food is thus prevented from spoiling because there is no air.

Cooling and Freezing

• Cooling and freezing are the most common forms of food preservation.
• Cooling slows down the action of microorganisms, thus it takes longer to spoil. It allows fruit from different parts of the world to appear on our supermarket shelves. (0 to -4 0 C)
• At freezing temperature, microorganisms become inactive, thus food cannot spoil when it is frozen. (-18 0 C)

Waxing

• Waxing of fruit and vegetables is also common. Apples, oranges, eggplants and tomatoes are dipped into liquid wax to prevent growth of fungi and loss of moisture.

Pasteurization

• Pasteurization means heating food to a certain temperature for some time followed by rapid cooling. Heating at such high enough temperature kills most bacteria. However, it does not affect the taste and nutritional value of the food.

Boiling

• As food is heated and cooked, the heat kills the microorganisms.
• Boiling kills most bacteria. However, those not affected by heat will grow when the conditions are suitable.

Smoking

• Smoking is the process of drying food with smoke for a long period of time. This method is mainly used for fish, meat and fruit such as banana.
• The drying effects of smoke and the chemicals produced from the smoke help to preserve the food.

Principles of Food Preservation:

1. Inhibit the growth and activity of Microorganisms
2. Asepsis (to keep out microorganisms)
3. Removal of microorganisms
4. Stopping the growth and activity of microorganisms (low temperatures, drying or chemicals)
5. Destruction of MO (heating or radiation)
6. Protecting against self-decomposition of food
7. Inhibit the activity of Endogenous Enzyme (Phenolase)
8. Delay or inhibit chemical reactions (Non-enzymatic browning)
9. Protection from invasion and spoilage by insects and rodents
10. Protection against losses by mechanical causes

Techniques of Food Preservation:

• Physical
• Chemical

Physical

--freezing and canning (rely on killing the microorganisms or at least stopping their growth for long enough)

--drying, gamma irradiation, exposure to ultraviolet or high intensity white light, ultra-high pressure and filtration

Chemical

• Preservatives
• Work either as:
• Direct microbial poisons or,
• Reducing the pH to a level that prevents the growth of Micro-organisms
• Chemicals used today are:

1. Nitrates and Nitrites -- to preserve meats
2. Sulphites -- to prevent the browning of fruits and vegetables, -- to prevent fungal spoilage