Allan Wensky, Berkley, California. asked:
Recently a friend of mine was telling me about a pizza that he burned to the point of becoming a charred husk ten times smaller than the original. At that point I realised that this pizza had now become a very low-calorie alternative to its former self. My question is whether all types of cooking result in loss of calories as well?
John Fry, Food Scientist and Chemist:
Burning the pizza will certainly reduce its energy content because some of the energy that you might otherwise have digested and turned into you goes up in flames and smoke. The black carbon thatís left after youíve burnt the pizza has got a lot less energy in it than the original.
Other cooking processes also cause loss of fat. Roasting a joint of meat is a good example. Itís also common to rescue the fat and meat juices that drip from the joint for use in gravy or that great staple of my youth, bread and dripping.
Cooking can also directly increase the energy content of food by making it more digestible. Starch in particular is made more easy to digest by cooking it. Starch crops up as small tight granules in many cereals, vegetables and fruits. Humans have thought to find it easier to digest starch once these granules have been burst open and the starch released in a gelatinised form by cooking.
In short cooking can increase or reduce the energy content of a food depending what you do. If you want to eat pure calories then consuming less food is preferable to incinerating your pizza. Burnt food may have fewer calories but it also contains a lot of very toxic materials created by excessive heat and it doesnít taste that great.
What's a calorie?
Intuitively, one would guess that if you turn part of your pizza into smoke then it must lose mass and that means energy? chris, Wed, 11th Jun 2008
If the Pizza was not burned and cooked on a base with a covering of oil..would this then in fact increase the calories as the oil would be absorbed into the dough !
No but the charcoal from burnt pizza or toast is good for your digestion that is what my Mum told me.
definitely because the carbohydrates and other compounds which provides us energy are broken down into carbon particles which are not only harmful but also carcinogenic. The calories are cut down to a lower level but the free radical particles are more dangerous to us than the energy. qazibasit, Fri, 13th Jun 2008
Cooking usually involves some addition of oils and fats, doesn't it? So during the cooking process, before you get to the burning stage, you'd probably be adding some energy to food. I think that the heating of certain foods may also increase its digestibility, its availability for utilisation by the body, and consequently the amount of energy it is able to provide the body with. But then for other foods, the reverse may be true, so the net effect would depend on what you're cooking, how you cook it, for how long etc.
If I take a steak and grill it a lot of the fat melts and runs off. If I don't eat that fat I have saved a fair few calories.
Why not just EAT LESS of the nice stuff? lyner, Sat, 14th Jun 2008
Pizza isn't nice anyway! SquarishTriangle, Sun, 15th Jun 2008
Especially if it's of the "pavement" variety... chris, Sun, 15th Jun 2008
BTW - love the fact that the expert answering this foody question was called "john FRY"
Cooking Pizza is always very easy but the right cooking gear and the cooking temperature is very important while doing it.
You like cooking Sandra1980? Chemistry4me, Fri, 23rd Jan 2009
Looks like you're trying to advertise a website! I like getting my pizzas from PizzaHut How do you 'cook' your own pizza? Chemistry4me, Fri, 23rd Jan 2009
OK Hows this for an easy to understand answer. Bear in mind that there are a whole lot of different foods that gain different properties when cooked Foods that are mainly carbs Potatoes, cereals, wont increase their calorie content by cooking, but will increase their digestibility for humans or makes available more carbohydtrate than the raw product, but you must remember that doesnt mean you make it more nutritious, heat processing diminishes the nutritional aspect of food, vitamin, enzymes etc. The higher the temperature that the food is cooked the less nutritious it will be, coupled with the fact that you will introduce undesirable properties and other compounds within the food which in some cases might be and in others definately are carcinogenic compounds such as Acrylamides. Proteins such as meat and fish if cooked dry will lose calories as they will lose fat and oil content pulses such as beans, lentils dont increase their calorie content when heat processed in water, and most of those need to be heat processed because of enzyme inhibitors that need to be disrupted. there are other ways to process pulses that dont require heat to make their macronutrients available to humans. fats, gram for gram the most calorific food 1g of fat = 9 cals, protein and carbs are 4cals per gram. Assuming that you catch all you cook when it comes to fats there are no calorific gains or losses with respect to heat processing. Heat processing food decreases its water, oil and fat content, water being the greatest loss which of course is calorie free, therefore by virtue of weight by weight i.e 100grams of raw chicken will have less calories than 100g of cooked chicken. Other methods of cooking such as in oil will increase the calorie content of food, but that should be obvious because you are adding another food element to it. I hope the above helps Dickie, Wed, 10th Mar 2010