Energy, money and time saving cooking by applying simple principles of science.
Posted on April 14th, 2013

Dr Hector Perera         London

Now it the time of the most traditional times of the year, Sinhala Awrudu season then the people would like to resort to traditional ways doing all things including cooking. Its nothing like preparing “ƒ”¹…”Kiribath’ on firewood stoves because it’s the traditional way Sri Lankans have been preparing this festive seasonal food. Honestly I cannot describe the happy atmosphere created during this time of the year but let me show some energy saving cooking ideas by gas fires because some people have gas cooking facility than firewood cooking.

By definition cooking means to prepare food by boiling, roasting, baking, broiling, etc to make food suitable for eating by using fire or heat.

My aim is to show the general public how to cook scientifically in order to save energy, money and time involved in cooking. Some people are under the wrong impression that cooking means it’s a tedious, time consuming and a nasty thing because of the cooking smells that are likely to get deposited while cooking. I am sure this wrong attitude can be changed if the following steps are taken. Some scientific terms are involved but let me simplify just a few only for the sake of majority of the people.

 Always put lids on pans when cooking, the reason is this speed up the cooking process by up to 6 per cent. Scientifically all the gaseous molecules trying to escape are pushed back into the pan so due to intermolecular and interamolecular reactions so the food gets cooked faster. The molecules have more collisions with different kinds of molecules in the cooking pan and with each other when the lid is closed than when it is left open. Honestly I haven’t seen a single molecule but one needs to visualize these things. Visualisation and imagination leads to creations that is what I think.

Apart from these mentioned reactions there are other forces acting such as different vapour pressures from different volatile ingredients. When the lid is closed the environment remains even so that cooking takes place almost evenly or harmoniously and there is not much difference of temperature gradient from top to bottom within the cooking pan.  Most Sri Lankan ladies open the rice pots when it froths then froth goes down then there is an uneven temperature gradient from the bottom of the pot to the top. Further some people put a long handle to check the water then add some water, then they say it’s gone for six or pear shaped. No wonder rice forms the roasted form or “Dankuda”. I am sure they are unaware of the fact that when they open the lid the above mentioned reactions are interrupted.

Whether you have a new budget or you are looking for ways to save more money, the kitchen is a great place to start.  If you are committed to cooking more efficiently, then you probably already know that eating at home, rather than at restaurant saves money. You can save more money without making sacrifices on quality or taste by making these changes. Two other issues of home cooking are they are healthy and clean.

The modern way of living is in apartments or in flats in high rise blocks for example just visit areas like Battramulla, Gampaha or Jaela apart from Colombo, many people live in these forms of limited space dwellings unlike in country houses. In England only the rich and wealthy can afford to live in country houses but in Sri Lanka it’s not always the case. I am certain they cannot use traditional firewood stoves unlike in villages. They have to rely on nothing but on gas or electric cooking. When I visited back home, I noticed the way they cooked their daily meals such as rice and curries on firewood as well as on gas cooking. I gave some practical helpful ideas to save energy only to some people who were really interested in energy saving. By following these steps you will be able to use less cooking gas (liquid petroleum gas LPG) without compromising your cooking.

The higher the temperature within a cooking pan the quicker the cooking, however when the temperature is too high the food may burn. In cases of rice when water evaporates quickly or not enough water to cook rice, no wonder it burns. This is the reason why these ladies always check the water using a long handled spoon like checking the oil in a car with a dip stick. Temperature and pressure are directly proportional to each other that mean when the temperature decreases the pressure as well, if the temperature is increased the force of molecules hitting the contents in the pan increases and this increases the pressure. This relationship of temperature and pressure is called Gay-Lussac’s Law and makes up part of the ideal gas law. I will try and back up my ideas with respect to science so there will be less controversy. Once the liquid runs out, temperature inside the cooking pan tends to increase gradually then we call the things get burn for example if water runs out of cooking rice then rice gets burn forming “dankuda”. This is where one needs to be aware of controlling the temperature otherwise food gets burn and waste energy as well.

 I cannot remember any British TV celebrity cook mentioned anything like that before and not applying any principles of energy saving. They are time conscious, rush rush from one to the other and not paying any attention to energy wastage. One of the reasons is they are not scientifically applying any knowledge or make any effort to save any energy. This principle is used even in fractionating column for separating liquids of different boiling points. Here is a point where most people waste energy.

Maintain shiny outer surface on cooking pans. The shiny surfaces reject heat (by convection) at a lesser rate than any dull or black surfaces do. As you know stainless steel pots and pans have shiny surfaces and clay pots have dull or black surfaces. It has been found by experiment that black surfaces loose heat quickly than a shiny surface that means clay pots loose heat more quickly than stainless steel pots. Just imagine, why these umbrella surfaces are made out of black clothes? Would you say the front of the space shuttles entering the earth’s atmosphere should be made out of shiny metals or with matt black tiles?

If you happened to measure the diameter of a base or the bottom of an ordinary stainless steel cooking pan, you would notice some of the larger ones have 20 to 22cm in diameter. Normally the clay pots have a round bottomed base just like some round bottomed flasks in chemistry laboratories. When clay pots are placed in firewood stoves, a good part of the base sinks into the fire so that fire directly hits the base. These pots are not designed to place flat on gas cookers just like the stainless steel pots but a little modification of the cooker ring can accommodate even clay pots.

To get the efficiency of the fire one must use a pot or pan that is wide enough to cover the flame but not allowing the fire to spread out of the base. If there was a huge gap between the fire and the pot or the pan, some of the heat looses due to unnecessary radiation. Have you witnessed the firewood stoves cooking? Quite often fire spreads surrounding the base then more than half way up the pot. In a way that is the nature of firewood stoves cooking, I must admit it’s lovely to see but does this type of cooking save energy? As I said before clay is a bad conductor of heat and a good surface to loose heat quickly so would you say clay pots are energy efficient?

Most Sri Lankans eat rice and curries immaterial of the country they live presently but some of them pretend that they have given up that since they left the country, is that true? There is a nice Sinhalese saying; a cat would always meow even if taken to Singapore.

Once a curry comes to boil, reduce the flame so that it is just enough to maintain boiling. Again this cannot be easily done in firewood stoves but it is easily done with gas or electric cookers. A boiling curry will be at about 100 degrees centigrade. In a curry how many spices and ingredients are found? The spices have aromatic chemicals for example in cinnamon there are over 12 chemicals, each with a different boiling point. How about other spices such as chillies, cloves, cardamom, cumin, fennel, coriander, turmeric, black pepper, mustard, curry leaves, “rampae” and lemon grass then garcinia  indica, “ƒ”¹…”goraka’ and tamarind? Anybody cared to find out how many different chemicals are there and their chemical structures?

When some curries are cooked with right ingredients sometimes they can be smelled from a distant, “Love is in the air”. Chillies have a chemical called capsaicin and the structure is fairly complicated with 16 carbons with a ring attached to a linear structure. I am not going to mention the all chemicals in spices over here but the point is they all have different boiling points and very likely lower than the boiling point of water. When a chicken curry is boiling and piping hot, just imagine how many different volatile chemicals escape along with water vapour? Who would like a spicy bath and some of it might deposit on you, if you open the lid of a boiling curry. I am sure no one likes to walk like a mobile kitchen with body sprays of chicken cologne or Asian cologne. In that case let me show a way to minimise this cooking smell, how scientifically.

No matter how high the flame is, it is impossible to increase the temperature beyond that until all the liquid evaporates.  Therefore maintain a minimum flame required to maintain boiling. During the preparation do not add excessive quantities of water expecting to reduce the quantity of water by cooking over a long time on a high flame. Instead add enough water so that cooking can be done on a lower flame for the required duration. Keep the pan closed whenever possible because an open pan will allow heat to escape more rapidly than a closed pan would. Escaping steam too is a loss of heat. Trapping this steam inside the pan will allow cooking on a lower flame.

Make sure the flame is colourless or blue. Yellow flames are an indication that incomplete burning is taking place. In a gas cooker if this happened it’s better to get it checked. That shows the full energy within the gas is not being harnessed.

In some cases if possible use a pressure cooker because in a pressure cooker the temperature is fairly high due to pressure and food gets cooked faster. Cooking at a higher temperature can significantly save reduce the cooking time. In my case I adapt the normal cooking pans to create some pressure by leaving the lid on while cooking. This cannot be achieved easily unless you carefully experiment a few times to find out to which level one should adjust the gas level when it is boiling constantly. I call this position thermodynamic equilibrium position which really helps in creating a constant boiling temperature within the cooking pan.

In some cases you may cook certain things a little excess so that it helps because of what you left from the previous cooking. One must be careful in case of rice leaving in excess for the use on the following day since certain bacteria called Bacillus cereous might grow on them if not properly preserved. Your comments welcomed [email protected]

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