How can you test vegetables for vitamins and minerals?

Question

I'm doing a science experiment for a school assignment, and i'm going to compare two methods of cooking vegetables; Boiling and Steaming. The aim is to determine which is a better method, in terms of which method preserves the most V & M's in the vegetables, because we all know boiling vegetables can destroy the V &M's. How can i test the vegetables for the pressence of V& M's? I know that i can test the water that the vegetables boil in for the pressence of V & M's but theres no water to test for the steamed vegetables.

Sorry if this is confusing, if anyone know's about any of this, please help.

Thank you :)

Answer 1

Professional food scientists do this using High Performance Liquid Chromatography (HPLC) http://www.answers.com/topic/liquid-chro... applied to blended samples of the foodstuffs. This is a very accurate technique that will reveal the very small differences in nutrient density you are likely to find being created by slight differences in cooking methods. Seriously, unless you boil vegetables until they are diluted mush, there isn't much nutritional difference between short, fast parboiling http://www.thefreedictionary.com/dict.as... and steaming. You'll be looking for difference of a few parts per million, at most, which is the nutritional difference easily overcome by eating an extra tablespoon of the "overcooked" vegetable.

And so far as steaming as a cooking method is concerned, home kitchen steamers are NOT generally working on high pressure, "dry" or "live" steam. Most work with very wet steam at nearly zero pressure, created over a boiling pot of water, condensing in the upper steaming basket, and dripping back to the water below. Operating a steamer so that it cooks by dry steam (which transfers heat rapidly, and leaves the pressure vessel before condensing and dripping back to the steam generation source) is difficult, because the high temperature and pressure required to keep steam non-condensing is hard to achieve safely with normal kitchen utensils. Commercial kitchens use convection pressure steamers http://www.atlantafixture.com/Summary.as... or combi ovens http://www.fesmag.com/article/CA6507784.... to cook with dry steam. You can emulate this at home with a pressure cooker, carefully loaded and quickly brought to high temperature for a couple of minutes, but this is a little dangerous, and rarely done by most home cooks. Home pressure cookers are really designed to work at temperatures slightly above boiling temperature, with fairly low pressure wet steam. Cranking them up for fast, dry steam operation, and immediately chilling them in a sinkful of ice water to achieve the kind of cooking cycle commercial pressure steamers achieve is not recommended.