How cooking affects nutrients

Cooking food may destroy enzymes and the chemicals which plants produce in order to try to prevent them being palatable to animals. This may improve the flavour, texture and digestibility of the raw food.

Cooking foods in liquid and then throwing away the liquid is very wasteful of many nutrients, particularly the water soluble vitamins such as thiamin, riboflavin, niacin and vitamin C. There is almost never any need to discard cooking water if the right amount is used in the first place. Any surplus liquid should be used for soups and gravies, or even, as in China, served as a cold drink.

The most nutrients are lost at high temperatures and by prolonged cooking. Foods left to stand may also lose nutrients.

Microwave and infra-red cooking can improve the nutritional status of food by reducing the use of liquids and cooking times. They are a good way of reheating food, provided the food is heated right through.

Cooking protein and starches together results in destruction of the amino acid lysine, severely degrading the quality of the protein. Prolonged cooking of protein can also make it more difficult to digest.

How cooking affects nutrients

Posted by Brittany (message id=3175 )

i have carried out an expariment where i have taken 10 test tubes and in 5 test tubes put about .1866g of broccoli and in the other 5 put about .1866g of a green bean. one test tube was the control and the others were placed in boiling water for different amount of time. one for 10 one for 9 one for 7 and one for 5min. the same thing was done for the green beans. before they were placed in the boiling water 10 mL of Sodium hydroxide 10\% and 5-10 drops of copper soulution were droped in and stired. once all were boiled for apropriate time each liquid, leaving the solid in the test tube, was taken out and placed in a clean test tube. they were then placed in a machine that read for the Absorbance and \% transmittance. the only problem the results did not turn out like i would have hoped. the results i got barley showed me anything. they were a bunch of numbers scatered all over the scale. my hypotenuse was to have results that read that the vegetable lost nutrients when boiled longer, but instead i got a big scatered nothing. can you help in the conclusion at all or the analysis of what happend or went wrong? A concerned student Post a reply to this message, or post a new topic    Your Name:  Your Email:  Subject:  In reply to message (delete if not applicable):  Display heading   Security Code:

How cooking affects nutrients

Posted by Peter (message id=3176 )

Brittany The test that you are doing is a test for protein. I presume that your hypothesis is that protein will be leached out of the food into the boiling water as it cooks. However I would suggest that proteins tend to coagulate on cooking - think of what happens to a poached egg as you cook it. The egg sets into a solid rather than dissolving in the water. Broccoli is very low in protein, so I wouldn't expect enough to leach out to be measurable. Note that you must use exactly the same number of drops of your copper solution (not 5-10). Also try turning the testube round in the colourimiter. Does the reading stay constant? Traces of dirt, or just variation in the thickness of the glass may affect the results It is more likely that sugars would leach out on cooking, and also water soluble vitamins. You could test for sugar leaching out, but you would need to use a lot more vegetable as your starting point - say 100g vegetable in 100ml of water. Boil for the required time, then remove the vegetable from the water. Now boil the water to evaporate the water until you have only 5ml left, and now test this for sugar Post a reply to this message, or post a new topic    Your Name:  Your Email:  Subject:  In reply to message (delete if not applicable):  Display heading   Security Code:

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Copyright Peter Thomson 2008-August-29