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How are nutrients calculated?

chow_rk Oct 14, 2013 01:11 AM

We can find nutrients in a raw sweet potato and boiled sweet potato.
But, how is this actually calculated?

Reason I ask is...apart from 'is that info accurate?'...if I can calculate it myself, I can compare say an organic vegetable to non-organic one, raw one to cooked (boiled or steamed) one, cooked dish (this is almost impossible to accurately calculate), etc.

P.S. This might sound like an overkill, but with all the advancements in science, there should be easier ways to do this...

  1. fldhkybnva Oct 14, 2013 02:21 PM

    A bomb calorimeter - they combust the food and measure the energy production to calculate calories. The rest of it is pretty difficult and not sure possible at home but here is a quick description from an online post

    Ok, so first we'll address proteins, carbs, and fats. Fats, which are like butter, oil, or the white stuff around a steak, can't combine with water. So, we weigh how much the food weighs at first, then we use a solution called "ether," which is kind of like scientist's dawn, to wash away the fat from the food. Then we weigh the food again & figure out how much is left. Then we subtract how much is left to how much we started with & that gives us how much fat is in the food.

    Carbs & proteins are trickier since they are both water soluble. For proteins, we can't directly measure proteins like we can for fat & instead measure a substance called nitrogen, which is another pure element like oxygen & carbon. We measure nitrogen because all proteins contain nitrogen. Now, to find the amount of nitrogen in a food, we mix the food with sulfuric acid, which is like the acid that we see on cartoons that eats almost everything it touches. This sulfuric acid will make ammonia, which is that smell made by cleaning products. We then measure the amount of ammonia made & that tells as how much nitrogen and, therefore, protein is in the food.

    Carbs are fun to measure because we essentially put the food sample into a small washing machine & add different detergents to figure out how many carbs are in the food. Like when finding fat, we measure how much food we started with, then how much food we ended with, subject one from the other & find out how much of the food was carbs. (DO NOT PUT FOOD IN THE WASHING MACHINE!)

    For vitamins & minerals, there are individual different methods for each vitamin & mineral. For minerals, we can either do wet chemistries or atomic absorption spectroscopy (AAS). Wet chemistries which is we a scientist will add different solutions to the food till a chemical reaction occurs, like a change of color or a formation of a solid in a liquid solution. AAS is when we put the ash, or burnt up remains of the food, into water. We then fire a beam at the water & measure the light bounced out of the water, kind of like a prism. The color & amount of the light reflects what type & how much of mineral is present.

    For vitamins, every vitamin is a bit different. Often times, though, we compare a solution with a known certain of the vitamin to the food solution & calculate the difference between the two.

    Here's an online presentation http://www.uark.edu/ua/foodedu/Module...

    5 Replies
    1. re: fldhkybnva
      chow_rk Oct 14, 2013 04:44 PM

      oh boy! ... that is NOT possible for individual usage indeed :)

      thanks that was very informative

      1. re: chow_rk
        fldhkybnva Oct 15, 2013 06:48 AM

        No problem, I also keep track of macronutrients and calories but would never attempt it myself. I use nutritiondata.self.com for most information which is the USDA database which is also great and useful when the government isn't shut down.

        1. re: fldhkybnva
          chow_rk Oct 16, 2013 05:17 PM

          oh oh another shutdown joke ;) ...jk

          1. re: fldhkybnva
            grangie angie Oct 16, 2013 05:26 PM

            I think I heard a little snip about it just being re-opened??

            1. re: grangie angie
              fldhkybnva Oct 16, 2013 05:56 PM

              That's what my news alert suggests, counting on the house

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