What is cooking?
Posted on August 17th, 2012

Dr Hector Perera     London

We just assume what is meant by cooking without any proper definition. When we say cooking, it means applying some form of heat to food so that it transforms into edible, safe or more palatable form due to chemical changes.

When green vegetables, fish or meat are cooked it changes colour, the appearance and the texture. If for example a lump of beef is cooked, it loses the red colour, any fish the same but to my surprise in some British TV cooking demonstrations, I have witnessed, when the cooked beef is cut, sometimes it is still red or even blood dripping red meat. When it is cooked it should have the same colour throughout otherwise theoretically it is not properly cooked or under cooked. Usually when we cook beef, often we cut into small pieces than cooking as a lump but in some cooking demonstrations they use it a little log or lump form.

The rate of reaction

The reason we cut into smaller pieces is to make the cooking reaction faster, larger the surface area, faster the reaction, better absorption of the ingredients. According to science, smaller pieces have a larger surface area than a lump of beef. If one needs to cook as a lump, then it needs a reasonable time to cook than cooking quickly. One must understand that any food such as fish or any meat or even vegetables are bad conductors of heat, the molecules take sometime to conduct heat through them. According to the laws of solubility products, due to the presence of ingredients, the temperature of the liquid rises a little above the boiling point of water. When all the water is evaporated then the temperature rises again. When the lid of a boiling chicken or vegetable curry vessel is opened, the temperature gradient falls from the top due to the release of the vapour pressure. To achieve the boiling point and the same vapour pressure, it takes up more energy than in a closed position. These chemical changes are due to intermolecular and intramolecular reactions happening during cooking.

Love is in the air

Cooking food also causes other, less obvious changes too. Nutrients like vitamins can be destroyed or leached out, literally cooked away. Anytime you boil vegetables, some nutrients naturally dissolve into the cooking water or into the air via steam. Flavours can be lost in this same way, too.

When you smell the aroma of food cooking, what you smell are the flavour compounds evaporating into the air. And if they’re in the air, then they’re not in the food. Actually not all the flavours in the food escape but some are lost, for example if you are frying fish, dry fish or prawns, invariably you would smell these flavours but invisible like, “love is in the air”. These cocktail of flavours do not always come by itself but “Piggy back” water molecules. Before you disagree with my arguments, please fry some fish, dry fish, prawns or even bacon. What about frying some dried chilli, please don’t’ try, no chance unless you are experienced. Once the frying is over, try this acid test, sniff the hand all the way from the fingers, did you get the smell of whatever you fried? How the smells did come to you?

A cooking experiment to try

How about another common cooking experiment to check the smell? May be you like to cook some chicken curry, fish or even lamb with some Sri Lankan spices such as red chilli powder, mixed curry powder, curry leaves, cinnamon, cardamoms, and cloves also with the roasted mixed whole spices, sometimes it is labelled as “Pannch”. In any experiment, observation is quite important; I have observed how the others cooked chicken curry, rice and other things.

 My observation

This is what they done: added all these spices to chicken, fish or beef, mixed it up with a spoon, then put the lid on and start cooking, nothing unusual! When it is boiling, the “game begins”, they opened the lid and mixed again so that some on the top went to the bottom. That’s not the end, then checked the salt by licking the piping hot partially cooked gravy on the palm, have you not noticed? Often they cool it instantly by a blowing on the liquid. Try and see the facial expression at that moment, it’s amazing. Then the put the lid on and opened it again to double check then added some salt, then again checked, sometimes the process is repeated. So how many times they opened and closed this boiling chicken curry? What happened during this opening and closing times? Is it possible some spices and volatile oils vapours are dancing in the air, just above and around your face?

Remember now it is boiling, giving mixtures of chemical vapours from the different spices and due to reactions with each other then with chicken as well. Now would you agree that some of these volatile chemicals would escape with water vapour molecules? Looks like a kind of,” Piggy back” escape due to gain of kinetic energy. Then according to laws of science, these volatile vapours would condense on any cold surface by losing the kinetic energy in them.

My question is, is it possible some of these volatile chemicals to deposit on the person who cooks them, then on anything in the kitchen? Do you want me to name where some of them would deposit on you? Starting from the fingers, palm, all the way up on the arm, then on the face, hair, on clothes, if there was any jewellery on the hand or neck then on any clothes you wear as well are subjected to chemical condensation. Again before you disagree please, observe anybody cooking chicken curry or why not try it out? You might say, cooking smell is a part of cooking, quite right, perfect answer.

 How to avoid cooking smell

I know it for sure, this cooking smell is very appetizing, suddenly makes you feel hungry but not pleasant to wear or not ideal to walk about with the smell on you. If one works in a school as a teacher or works in a bank, or as a doctor in a hospital or in other profession, still they all need to eat some cooked food. Who would be expecting to eat raw carrots, salads and cucumber all the time because they are healthy, one must eat some cooked food as well. If one does not know how to cook without getting food smell on them, definitely needs to find out the technique to cook scientifically. This is where I can help how to cook scientifically, simultaneously save the wasting energy.

 Would this help the public?

In some British TV cooking demonstrations, the presenter always stands near the cooker for the camera while the chef hurry up and cooks carelessly. The time is limited in the show, so the cook just adds this and that, jabbering anything, rushing all over the cooking area, like a headless chicken, leaving the fire on full blast, toss the food once or twice then say it is cooked. Then served on the plate for the presenter to taste, no doubt he or she must say “yum” even when it is “yuck”. The smell of vaporising oil and ingredients invariably escape the hot cooking pan then you know the rest. I didn’t notice the chef made any care for the wasting gas or energy. Who would agree that kind of cooking would educate the public, including the children to learn home cooking?

 You made a cover up?

Most people just cover up this smell with another smell such as a scent or cologne. The truth is the cooking smell is there but you made a cover up. This is one of the reasons why some people prefer to eat takeaways or eat out than cooking at home. As I mentioned before there are ways to totally avoid or cut down this cooking smell depositing on you while cooking. Just one thing, cooking smell cannot be avoided spreading in the air because these are highly volatile chemicals but they would not deposit unless the conditions are correct, that must be remembered. When you visited the high street or a supermarket, you get so many smells in the air but they wouldn’t deposit on you unless the conditions are right.  Any comments please, perera6@hotmail.co.uk


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