Blender companies state that a blender for smoothies should have speeds of at least 30000 rpm. They argue that only at 30000 rpm are cells of fruits and vegetables sheared enough to maximize nutrition and ease of digestion.

Would blending at lower speeds, such as 20000 rpm, be sufficient?

  • 2
    $\begingroup$ Could you explain what chlorophyll has to do with your question? $\endgroup$ – blep Mar 8 '13 at 20:00
  • 1
    $\begingroup$ Sounds very much like a marketing ploy... $\endgroup$ – nico Mar 8 '13 at 21:15
  • 1
    $\begingroup$ You might start by asking the company where they got their numbers and if they have published citations or data to back up their claims. They're making two claims, first that 30k rpm is necessary to shear cells, and second that shearing cells is desirable and improves the nutritional properties of the food. $\endgroup$ – octern Mar 9 '13 at 5:21
  • $\begingroup$ Related: cooking.stackexchange.com/questions/22639/… $\endgroup$ – Martin Dürrmeier Mar 10 '13 at 18:18
  • $\begingroup$ @dd3 thanks for editing. Chlorophyll has nothing to do with it $\endgroup$ – Martin Dürrmeier Mar 10 '13 at 20:31

I'm guessing that what they mean by 'maximize nutrition' for digestion is that they are assuming that the cells are broken open. This would make the co-factors we call vitamins, protein and sugars freely available to the digestive system and more easily absorbed.

I think it is a marketing literature claim, though the blender may have some valid advantages... details below.

Stainless steel waring blenders used to be typical pieces of lab equipment which could be used to homogenize tissue to extract proteins or DNA from tissue. These blenders would typically run from 10k-30k rpm. The web search for 'cell lysis blender' gives lots of examples of prepping DNA from plants at these speeds, but they don't complain for speeds towards the lower end of the range. A reputable looking example in my short search: This paper for tomato fruit cell wall preparations doesn't even give a speed the blender might have run at.

Cell lysis in the literature is not precise - the cell toughness, the strength of the tissue around it and other such factors all come into play. Putting woody stems into your blender and those cells won't really get opened up at all. Also in the cell literature cell lysis buffers may have detergents or other chemicals (the reference above is done in 50% ethanol) to weaken the cell walls. Not exactly what you'd want to use if you were making a health drink.

In experiments they have to contend with oxidation that happens when the cells are broken open with all the air whipping through the mixture. This is one reason you don't see blenders in labs to much anymore - hydraulic presses, sonicators, and bead beaters have taken their place - they have less aeration in the mixture and also deliver more power so that they can break open yeast and bacteria, which blenders really can't.

So there will be some vegetables where the cell walls won't break open and all the nutrients won't be so easily accessible. It must help to be running at the top end of the range, but there will always be some vegetables which won't be broken open. For most things like bananas and apples it sounds like you'll get similar benefit with other blenders too. Just have to think about how much more are you paying for that extra 10k of rpm I guess.

Is there a benefit to breaking open the cells and letting all the nutrients (as well as cell waste) break out into solution? It might give you a quick pulse of nutrition when you drink, but I'm pretty sure all the cells of a piece of fruit or vegetable will be pretty much broken down and extracted by the end. On the other hand, it sounds like it will save the digestive system some work... So there's that question too.

| improve this answer | |
  • $\begingroup$ Very nice but... how does all of that compare to the effects of HCl in the stomach? If HCl breaks apart food anyway (which it does...) the advantage of a >30K rpm blender are small or non-existent at all. $\endgroup$ – nico Mar 10 '13 at 16:57
  • $\begingroup$ you are correct I think. I've read that you actually don't need to chew your food. Including the action in the intestines, the conventional answer is that the digestive system does eventually break down all the nutrients you take in. Still, its not completely equivalent - it must be less work for the digestive tract if all the nutrients are in a juice than if you swallowed a bunch of cherry tomatos in their skin. $\endgroup$ – shigeta Mar 11 '13 at 14:49
  • $\begingroup$ sure I agree with that, but I was more puzzled by the fact that a 20K rpm blender would be worst then a 30K rpm one... $\endgroup$ – nico Mar 11 '13 at 16:51
  • 1
    $\begingroup$ Probably not a lot worse. I should have said that I think the differences are marginal, though its reasonable to assume that 30k will get a bit more than 20k. When I say a bit, it might be 80% vs 70% of cells. Not a big difference with many fruits and veggies. Most tissue will be liquified nicely at 20k if not completely. Running longer will lyse more cells, but will also heat the sample as well as oxygenate it, which can oxidize the contents. $\endgroup$ – shigeta Mar 11 '13 at 17:12

Not the answer you're looking for? Browse other questions tagged or ask your own question.