Microwave Heater is a kind of heat drying equipment where microwaves produced in a magnetron are reflected into the oven cavity. The frequency of microwaves ranges from 2450 MHz to 22125MHz.These waves when reflected from the oven walls and absorbed cause any substance to heat up. Heat is produced in the form of microwaves due to constant variation in the polarity of the electric field at a particular frequency.
A microwave heater is mainly used for heating food items. As it constitutes one of the factors required that affect the temperature requirement of thermal processing, it is best used for sterilization. Here the advantage is heat energy is directly absorbed by the food rather than equipment. Although there are some reports regarding its usage, it is considered very safe.
It does not require a combination of any other factors as required in hurdle technology.
Another disadvantage is as this heating process does not guarantee shelf life, refrigeration may be required in contrast to hurdle technology.
Hurdle technology is a combination of specific factors used for controlling microorganisms. The factors are heating, chilling, water activity, pH, redox potential, preservatives, and modified atmosphere. This technology is mainly used in the processing of intermediate and high moisture foods when individual factors fail to hinder the growth of undesirable microorganisms. The advantage of this technology is enhanced nutritional and organoleptic quality with no need for refrigeration. Hence, it is the best strategy when used in combination with necessary factors and ensures a good shelf life of 3 months for food products.
Since this technology requires other factors a wide range of food items can be preserved.
However, the disadvantage is time-consuming and laborious when compared with the single microwave heating process.
UHT (Ultra High-Temperature processing) is a process of killing microorganisms at a temperature of 1945K. It is mainly used in the distillery and dairy industries. This technology mainly targets yeasts, non-spore-forming bacteria, Brucella abortus, Mycobacterium tuberculosis, Salmonella seftenberg, etc. It always relies on exceptionally high temperatures followed by parallel refrigeration. Hence huge voltage of electricity is mandatory to ensure successful inhibition of microorganisms. Since this process does not require other factors as in hurdle technology, it is not tedious. But it has no nutrient enhancing features. The disadvantage is low shelf life of 3 –weeks and it does not have good implications for solid food.
Food packaging is one of the essential processes of inactivating microorganisms by heat. It makes use of cartons, plastic and glass bottles, pouches, and plastic trays. Here food is sterilized by sealing in a container subjected to saturated steam under a pressure of 1psi approximately. This technology mainly depends on a yet another time-consuming process known as ‘in container processing’ that involves food preparation, heat treatment, washing, and filling cans the most essential step cooling. There are many prerequisites for cans intended to be used in this process like dimensions, nature of metal, soldering, and decoration.
This process does not require extremely high temperatures as seen in UHT.
This method is only reliable for preserving food additives up to some weeks. Hence shelf life is limited. There is no requirement for any other factors as essential for Hurdle technology.
The disadvantage is it is not specific for killing a variety of food born microorganisms.
As this technology is dependant on containers, it seems very expensive in contrast to microwave heating, hurdle technology, and OHT