When you open a packet of chips or a 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 about Food Preservation Methods in detail.
What Is Food Preservation?
Food preservation is the science which deals with 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 oxidation of fats to cause rancidity. Food preservation also aims that there is no discolouration and ageing. Food preservation methods should be applied such that it does not compromise much with the nutritional qualities and taste of the food.
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.
Related Read: Freeze Drying Explained!
Advantages Of Drying
- After drying, the moisture content reduces to large extent thus increasing the shelf life of product.
- Decreased shipping cost.
- 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, fluidised bed dryer, Spray dryer etc.
2. Indirect contact drying:
3. Infrared dryers/ Microwave dryers
- SUGARING- You know it was a common practice in ancient times to store fruits in honey. Sugar tend 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 case of vegetables. If we do brining in case of fruits then perhaps there will be the loss of flavour and aroma of fruit. Sugaring is done with apples, pears, peaches, apricots, plums etc.
Related Read: How To Improve Shelf Life Of Food
- 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 brine, vinegar, alcohol, and vegetable oil. These chemicals kill the various micrrorganisms thus increasing the shelf life. In fermentation pickling, bacteria produce organic acids which works as a preservation agents, best example of fermentation pickling is sauerkraut.
- 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, air is removed by vacuum and cans are hermetically sealed. The cans are then placed in retort and sterilised with steam
Principle of Canning- It is based on principle that fruits and vegetable being perishable are spoiled by the microorganisms and the application of heat kill those micoorganisms or their enzymes
- FREEZING- It is 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 sterilise the food but it reduces the microbial load. The shelf life of frozen food is much high
Related Read: Freezing Of Food In Depth
- PASTEURISATION- It is a mild thermal treatment to food products for a specific period of time to as to decrease the microbial load. Pasteurisation can be batch or continuous. Based on temperature time combination pasteurisation can be High Temperature short time (HTST) in which the food product is heated at 72 degree Celsius for 15 minutes while the other one is Low temperature long time (LTLT) in which food product is heated at 63.5 degree Celsius for 30 minutes. Depending upon the microbial load and the degree of reduction in microbial population, specific temperature and time is required.
- IRRADIATION-Irradiation is exposing the food to ionising 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.
- MODIFIED ATMOSPHERIC PACKAGING- It is defined as 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 is such that atmospheric composition of food products is different from that of air.
Related Read: Modified Atmosphere Packaging In Detail
- PULSED ELECTRIC FIELD ELECTROPORATION (PEF)- Brief electric pulses of 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 cell membrane which kills the cells and releases the contents. In food technology, it is being developing.
- HURDLE TECHNOLOGY- In this method, the microbial load in food product 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 a food are known and the interaction between various hurdles are also known then the microbial stability and safety of this food might be optimised by changing the intensity and quality of these hurdles.
Related Read: Hurdle Technology In Depth
- STERILISATION- It is high temperature treatment given to food products to increase their shelf life. The shelf life of sterilised food products ranges in months. Sterilisation is done either by using moist heat or dry heat. Sterilisation by chemical methods are used nowadays. It’s much more effective than pasteurisation. The index microorganism for sterilisation is Clostridium botulinum.