Ever since man discovered fire, cooking is a ritual firmly ingrained in his culture. Heating any food before consumption is an instinctive behavior special to man because he wants the food to be safe from dangers associated with contamination and spoilage. It was only later that man learned how cooking enhances the sensory pleasure and many developments in cooking technology made it easy to create a variety of eating sensation through aroma, taste and texture. Cooking does destroy some nutrients naturally present in the food but also increases the nutritive value of many foods by inactivating undesirable enzymes and reducing levels of harmful constituents.
Domestic cooking till about 5 decades ago was centered around open hearths using fire wood, charcoal, dried cow dung, agricultural wastes and similar fuels easily available at close proximity. Advent of fossil fuels and organized generation of electricity reduced dependence on smoke-spewing open hearths and scientifically designed stoves using gas and/or electricity became the norm. Liquid Petroleum Gas (LPG) has become ubiquitous in to day's urban house holds with almost 100% coverage and it is percolating down to rural homes near towns, cities and semi urban areas. Electricity is losing its edge due to uncertainty of supply from the public grid, uncontrolled price escalation and inefficient heating mode. With international prices of crude oil fluctuating wildly, uncertainties associated with LPG supply and cost, its reliability is also under a cloud. Large scale oil exploration within India has raised hopes that the country may have comfortable sources of cooking gas which are being piped in some cities for delivery to users, in stead of the bottled version.
What about the most convenient and customer-friendly microwave cooking? It is doubtful whether this mode of cooking will ever be able to have a strangle hold on Indian house wives, as is the case in many industrialized countries. Microwave heating, ever since it was accidentally discovered in 1940 in the US, is based on non-ionizing microwave radiation at a frequency of 2.45 giga herz (GHz). When passed through the food the latter absorbs the energy, makes the molecules of water and other liquids which are bipolar in nature, rotate to align themselves with the electric field created and generating heat in the process of colliding amongst them selves. Fat or oil, though less polar than water, exhibits faster rate of heating due to its lower specific heat which is less than half that of water. Dissolved salts, being ionic in nature also generate heat in the electric field, due to theses ions colliding with each other. A typical MW oven has a rating of 1100 watts load but the out put is about 700 watts of microwave power but wastage of energy for heating the container is avoided making it as efficient as conventional heating
There are some misconceptions and apprehensions about microwave use (MW) for heating foods. Just like normal heating MW heating also heats up the surface first though many mistakenly believe that MW heats the core first before heating outer layers. True, MW has high penetrating power and in relatively dry foods, the surface does not get heated fast since MW penetrates into the center of the food heating it first and the heat conducted outward there after. MW is not related to ionizing radiation as with X-rays or irradiation and fear of cancer causing artifacts like dioxines, is totally misplaced. Nutritional damage to foods is much below that caused in conventional cooking, though blind opposition to MW makes at least some people believe this canard. MW ovens are designed to make them user friendly and accident proof by integrated electronic circuitry and most ovens do not leak radiation beyond 5 milli watts per square centimeter at 2 ft distance from the surface of the oven as per international specifications.
Containers used for MW heating pose much more danger if no proper attention is paid in their selection. Ceramics with safe glazes and glasses with no trapped micro-air bubbles are considered safe while plastic containers do raise some pertinent safety questions. Lack of awareness about the dangers of using non-food grade plastics for food contact applications is one of the risks using MW heating. Since temperature in MW oven can be as high as 100C, high melting plastics only are suitable for fabricating MW compatible containers and manufacturers have to declare this information on each of these containers. Use of brown papers, plastic grocery bags, aluminum foil, paper towels made with recycled fiber and dyes or chemicals, thin storage bags is not advisable. Explosive spurting of over heated water and bursting of closed containers without vents can also pose some danger to the users. Convection microwave ovens are designed to take care of higher temperature needs like baking. New designs incorporating high power halogen bulbs help to heat surfaces to get desirable browning or crust are emerging to lure more customers.
Why MW ovens may not catch up n India? In a country like the US 90% of the house holds have at least on MW oven where as in India the corresponding figure is an abysmally low, being less than 1%!. The annual sale of 1.2 million pieces of MW ovens, claimed to be growing at 25% per year, reflects the lack of universal acceptability of this system in the country. The severe limitations of container system, frequent power failures, high temperature cooking practices involving frequent stirring, non uniform heating, perceptional non-satisfaction with foods cooked with MW and mistaken association of MW with irradiation, all contribute to this situation. Probably MW oven may at best be an occasionally used kitchen appliance, just for heating foods before serving rather than as a gadget for cooking.