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I'm not technically minded, but if the friction of the blades in high powered (& expensive) blenders creates the heat when making hot soup, why when making smoothies are the smoothies not hot?

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    What leads you to believe that "the friction of the blades creates heat" ?
    – Tetsujin
    Dec 26, 2018 at 14:21
  • Because the manufacturers 'blurb' says so. Do you suspect otherwise? I'm interested to know.
    – Marian
    Dec 26, 2018 at 14:34
  • Can you provide a link to that claim, or picture of it, etc?
    – Tetsujin
    Dec 26, 2018 at 14:36
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    It very well could be the motor in addition to the blades. 1800 watts is a LOT of power for a blender, and some/a lot of that energy is going to convert to heat and transfer into the food if run long enough.
    – SnakeDoc
    Dec 26, 2018 at 22:25
  • @Tetsujin apparently it is a thing! See cooking.stackexchange.com/q/20981/17272
    – Erica
    Dec 26, 2018 at 23:56

1 Answer 1

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It is well known that the blades in high powered blenders create so much force that it can heat the liquids inside. In fact, I can put a can of tomatoes in mine and they will eventually become hot enough to be eaten as a warm soup.

That being said, creating this much heat takes time and also usually works best if you're starting from something already at least room temperature. A smoothie will not become warm because:

  1. Smoothies only take a few seconds to make, therefore not enough energy is transfered to make it warn.
  2. Ingredients often start somewhat cold from the fridge and don't heat up enough.
  3. Ice is usually added, which makes things very cold.

You could make a hot smoothie if you ran the machine maybe for 5-10 minutes, which I wouldn't suggest!

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    Well-known to everybody but me, so it would seem. Sorry about that - guess I've never run one long enough to find out :)
    – Tetsujin
    Dec 26, 2018 at 14:55
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    @Tetsujin it is an unpleasant side effect of most high powered blenders (and the named one is not that high on the scale, mine has 38 HP) and marketing people have tried spinning it into a positive "feature" - they advertise blenders as being capable of making hot soup on their own. For me, I prefer using the stove to heat things, and the extra heat is a minor annoyance, but as Behacad says, rarely enough to make that much of a difference.
    – rumtscho
    Dec 26, 2018 at 17:02
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    Extra heat being formed by friction in the bearing can easily build to the point where the plastic around the bearing begins to melt. That lets the blade tilt and enlarge the hole in the lid that the shaft goes through. If you use these high speed devices for long time runs, you'll find yourself having to buy new blade assemblies and bases on a regular basis. Dec 27, 2018 at 0:32
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    That sounds like a consequence of running these things for an outrageously long amount of time. Heating liquids is literally sold as a feature in these machines and some have "hot soup" settings. I very much doubt that would harm the machine!
    – Behacad
    Dec 27, 2018 at 0:46
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    @Behacad It does not always take that long to do damage. Attachments such as meat grinders can and often do put tremendous strain on the bearings and gears and generate excessive heat very quickly. I use a scraper blade in mine which I find wonderful for many applications, but ones which have butter than needs to remain cold it is not appropriate because even at the lowest speed and with a cold bowl with quickly heat the butter to near liquid from the silicon rubbing on the bowl generating heat.
    – dlb
    Dec 27, 2018 at 16:53

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