Calling all you scientific boffins - why is this?

beccib2
beccib2 Posts: 44 Member
in Food and Nutrition
Hi All

Yesterday i was looking through my freezer at what to have. I have bought some Mccain Jacket Smilies which are small pre cooked jacket potatoes that are frozen so all you have to do is microwave them (or put them in the oven) and you have a lovely oven cooked potato.

Now my question is this - i was looking at the nutritional value to see how many calories etc they were and was given three different values on the pack....

Per potato frozen - 85kcal
Per potato oven baked - 127kcal
Per potato microwaved - 104kcal.

So why is it that without adding anything to the potato to cook it - the calories increase by as much as 42? And does this mean that all frozen products, the calories are labelled wrong depending on how it is heated. I.E if you had three different frozen products on your plate - took the value off the packet and them heated them in the oven, could you effectively be adding 120 extra calories to your plate without you knowing???

Interested in your ideas on this one as this could make huge calorie differences to some people (i don't normally eat frozen foods)

Help is appreciated to heal my curiosity :-)

Replies

  • ladybird1771
    ladybird1771 Posts: 99 Member
    I don't know... if it had been per 100g or something, then that would have been fine because the water lost in cooking would have made the food more calorie dense. But I've no idea when they're writing per potato! :huh:
  • myofibril
    myofibril Posts: 4,500 Member
    Was the nutritional listing by grams (so for example, per 100gs)

    If so, it is because of the water content of potatoes. If you weigh it from frozen it contains more water by weight and therefore has less calories. If you weigh it from cooked it has less water and therefore a higher calorie count as you are eating more actual potato overall.
  • saschka7
    saschka7 Posts: 577 Member
    I am so glad you asked this. I've seen stuff like this before and have always wondered myself!
  • yarwell
    yarwell Posts: 10,477 Member
    the frozen value is per 100g, not per potato, according to http://www.mccain.co.uk/mccain-products/kids-favourites/jacket-smiles/

    The GDA info says "Per 127g Potato Microwaved" 1.27 * 85 cals is 108 which is pretty close to 104 per potato.

    The 127g potato is alarmingly coincidental with 127 calories per oven baked potato, looks like an error.
  • beccib2
    beccib2 Posts: 44 Member
    Yeah - the site says that - but the box uses potato.....

    why would there be a difference between microwave and oven, and does this mean all frozen products need to be increased in calories to take out the density of the water it will lose.....
  • sbarella
    sbarella Posts: 713 Member
    I guess different types of cooking may make starch more absorbable and cause loss of fibers. Just a guess.
  • moondawg14
    moondawg14 Posts: 249 Member
    I would say that unless they have the most unbelievable quality-control ever, and they're cranking out 100g potatoes reliably....

    that the box is actually WRONG and should say "per 100g" instead of "per potato"

    there's no "magic" that happens chemically to the starches in the potato to make them different.
  • yarwell
    yarwell Posts: 10,477 Member
    Yeah - the site says that - but the box uses potato.....

    why would there be a difference between microwave and oven, and does this mean all frozen products need to be increased in calories to take out the density of the water it will lose.....
    It's just massively messed up as far as I can tell. They should employ someone who knows what they are doing instead.

    Adding or removing water has zero effect on calories. Weigh uncooked and use uncooked data is most reliable.

    I can see how oven cooking would remove more water than a microwave (longer time, drier air, higher temperature) so if the calories were expressed per 100g of cooked product they could be higher - but you would have less weight of cooked product.

    so take a 127g potato with 108 calories and lose 27g of water in the oven you still have 108 calories but now it is 108 cals per 100g of cooked potato rather than 85 calories per 100g of uncooked. As an example :-)
  • beccib2
    beccib2 Posts: 44 Member
    feeling like i need a phd lol :ohwell:

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