Food Preservation Methods - Discover Food Tech

When you open a packet of chips or canned food have you ever wondered that how months older manufacturing keeps the food product safer and delicious without hampering its nutritional quality. The food which we prepare in our homes get spoiled within a day or 2 (until and unless some preservation techniques are applied) but how these products can be consumed after a long period of time. Well, there comes a concept and a technique called FOOD PRESERVATION. Let’s study Food Preservation Methods in detail.

What Is Preservation Of Food?

Food preservation is the science which deals with the process of prevention of decay or spoilage of food thus allowing it to be stored in a fit condition for future use. Preservation aims to prevent and retard the growth and activity of microorganisms and also the oxidation of fats to cause rancidity. Food preservation also aims that there is no discoloration and aging. Preservation methods should be applied such that it does not compromise much with the nutritional qualities and taste of the food.

Food Preservation Methods | Discoverfoodtech.com

Commonly Used Food Preservation Methods

• DRYING-Drying is defined as the application of heat under controlled conditions to remove majority of water normally present in a food by evaporation (except in freeze-drying where the food is first frozen and then water is removed by sublimation). It is the oldest method of food preservation. In ancient times, drying was the only method of food preservation where food products were dried either by sun or wind.

Advantages Of Drying

1. After drying, the moisture content reduces to a large extent thus increasing the shelf life of the product.
2. Decreased shipping cost.
3. More amount of product per container.

Methods of drying- Broadly, the methods of drying has been classified into 3 classes:

1. Direct contact drying:

Example- Sun dryer, Tunnel Dryer, Tray dryer, fluidized bed dryer, Spray dryer, etc.

2. Indirect contact drying:

Example-Drum dryer

3. Infrared dryers/ Microwave dryers

• SUGARING- You know it was a common practice in ancient times to store fruits in honey. Sugar tends to draw water from microbial cells thus leaving them dehydrated. Dehydrated microbial cells thus die because water is necessary for any living form for survival. Sugaring is done by preparing sugar syrup. Sugaring is done for fruits and brining is done in the case of vegetables. If we do brine in the case of fruits then perhaps there will be a loss of flavor and aroma of fruit. Sugaring is done with apples, pears, peaches, apricots, plums, etc.
• SALTING AND PICKLING- Addition of salt even at 20% of its concentration disturb the osmotic balance of microbial cells as a result of which they die. Salting is also known as curing, curing removes the moisture from foods like meat. Pickling means preserving the food product in brine (salt solution) or marinating in vinegar (acetic acid). Pickling is of 2 types chemical and pickling and fermentation pickling. In chemical pickling, we add the brine, vinegar, alcohol, and vegetable oil. These chemicals kill the various microorganisms thus increasing the shelf life. In fermentation pickling, bacteria produce organic acids which work as a preservation agent, best example of fermentation pickling is sauerkraut. Pickling Of Vegetables | Image Source – epicurious.com
• CANNING- Canning is defined as the preservation of food products in sealed containers which usually implies heat treatment for the prevention of spoilage. In conventional canning, the food is placed inside the container, the air is removed by vacuum and cans are hermetically sealed. The cans are then placed in a retort and sterilized with steam

Principle of Canning- It is based on the principle that fruits and vegetable being perishable are spoiled by microorganisms and the application of heat kill those microorganisms or their enzymes

• FREEZING- It is a low-temperature food preservation technique in which food product is frozen. The low temperature does not allow the growth and multiplication of most of the microorganisms. Freezing does not sterilize the food but it reduces the microbial load. The shelf life of frozen food is much high

• PASTEURISATION- It is a mild thermal treatment of food products for a specific period of time to decrease the microbial load. Pasteurization can be batch or continuous. Based on temperature-time combination pasteurization can be High-Temperature short time (HTST) in which the food product is heated at 72 degrees Celsius for 15 minutes while the other one is Low-temperature long time (LTLT) in which food product is heated at 63.5 degrees Celsius for 30 minutes. Depending upon the microbial load and the degree of reduction in the microbial population, specific temperatures and times are required.
• IRRADIATION-Irradiation is exposing the food to ionizing radiations for a specific time to either kill or reduce the microbial population. Not all type of food product is suitable for thermal treatment or low-temperature treatment, so in those food products irradiation has proved to be very successful. Food Irradiation | Discoverfoodtech.com

• MODIFIED ATMOSPHERIC PACKAGING- It is defined as the enclosure of food in a package in which the atmosphere inside the package is modified or altered to provide an optimum atmosphere for increasing shelf life and maintaining food quality. The principle of MAP is to store products under high Carbon dioxide content (gases like nitrogen and ethylene are also added) and low oxygen content. The addition and removal of gases are such that the atmospheric composition of food products is different from that of air.

• PULSED ELECTRIC FIELD ELECTROPORATION (PEF)- Brief electric pulses of a strong electric field is provided to food containing microbes. In PEF, a substance is placed between two electrodes. The electric field enlarges the pores of the cell membrane which kills the cells and releases the contents. In food technology, it is being developed.
• HURDLE TECHNOLOGY- In this method, the microbial load in the food products is reduced by introducing various hurdles like temperature, water activity, acidity, redox potential preservatives, and competitive microorganisms. The hurdles must keep the normal population of microorganisms in the food under control. The microorganism present in the food should be able to overcome the hurdles inherent in the food. If the hurdles in food are known and the interaction between various hurdles are also known then the microbial stability and safety of this food might be optimized by changing the intensity and quality of these hurdles.

• STERILISATION- It is a high-temperature treatment given to food products to increase their shelf life. The shelf life of sterilized food products ranges in months. Sterilization is done either by using moist heat or dry heat. Sterilization by chemical methods is used nowadays. It’s much more effective than pasteurization. The index microorganism for sterilization is Clostridium botulinum.