It is the treatments which are given to food products so as to increase their longevity and stop or slow down their spoilage of nutritional value. It prevents the growth of bacteria, yeasts, fungi and other micro-organisms and also retards the oxidation of fats which cause rancidity. The processes include heating, oxidation, and ozonization, toxic inhibition, dehydration, osmotic inhibition, low temperature inactivation and ultra high water pressure. The different preservation methods are as follows:
a) Drying- It is an ancient technique which reduces water activity sufficiently to prevent or delay bacterial growth.
b) Refrigeration- In this process food is preserved by slowing down the growth and reproduction of microbes and the action of enzymes which cause food rotting.
c) Freezing- It is one of the common preservation process used for preserving food items which do not require freezing when unprepared.(in unprepared state).
d) Vacuum Packing- It is done in airtight bag or bottle. It removes the oxygen needed for the survival of bacteria. It is mostly used for storing nuts.
e) Salting- It withdraws the water from the food product, and hence is used as a preservation technique.
f) Sugaring- It is used to preserve fruits such as apples, pears, peaches and apricots etc.
g) Artificial Food Additives- Commonly used food additives are calcium propionate, sodium nitrate, sodium nitrite, sulfites and disodium EDTA which are used as antimicrobial agents.
h) Pickling- In this method food is preserved as an anti-microbial liquid which inhibits or kills bacteria and other micro-organisms. The typical pickling agents include brine, vinegar, alcohol, and vegetable oils. Sometimes chemicals are also added such as sodium benzoate and EDTA which enhance the shelf life of the food.
i Lye- The chemical sodium hydroxide is known as lye and it is often added to food for its preservation as it makes the food alkaline and prevents bacterial growth, it also saponifies the fat in the food and changes its flavor and texture.
j) Canning And Bottling- It involves the sealing of cooked food in sterile jars and bottles and boiling the container to kill or weaken any other form of microbes.
k) Jellying- It is the cooking of food in a material which solidifies it in the form of gel, such as gelatin, agar, maize flour, and arrowroot flour.
l) Potting- Mainly used for meat, by setting it in a pot and sealing it with a layer of fat.
m) Irradiation- It is the exposure of food to ionizing radiation; either high energy electrons or X-rays or by gamma rays. This treatment kills bacteria, molds and insect pests, reduces ripening and spoiling of fruits and also induces sterility.
n) Pulsed Electric Field Processing- It is a method of preservation by strong electric field.
o) Modified Atmosphere- It is a way of preserving food by operating on the atmosphere around it and sometimes the oxygen content is lowered and the carbon content is increased which prevents from insects and molds. Also nitrogen gas is used to kill bacteria effectively.
p) High Pressure Food Preservation- Through this method of preservation we can retain the flavor, texture and nutrients, while it also disables harmful microorganisms and slows down spoilage.
q) Biopreservation- It is the use of natural and controlled antimicrobial agents for preserving and increasing the shelf life of the food. it is a natural technique and hence preferred over the other methods.
r) Hurdle Technology- It is the application of more than one preservation technique on food so that it becomes impossible for microbes to survive in the food product. The different hurdles used are high and low temperature, reducing water activity, increasing the acidity, using biopreservatives and removing the oxygen content of the food.
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