Do centrifugal juicers destroy vitamins through friction?

Question

I've read that in a couple of places.

Please name one of those places. This doesn't make much sense; how would friction destroy a chemical? — BobMcGee, Jul 09 '11 at 18:32
Not saying that this is the case, but friction causes heat, and heat _can_ alter chemicals, making them less effective. It is not a bad hypothesis to think that friction _may_ alter the chemicals that make up vitamins. see: http://wiki.answers.com/Q/How_does_cooking_vegetables_deprive_them_of_vitamins — Cos Callis, Jul 10 '11 at 04:33
@Cos Callis: Chemically speaking, vitamins and proteins are two **very** different things. That page says: "cooking will alter the vitamins' structures (heat denatures things like enzymes and proteins)" which is like saying that because moderate heat can melt ice it should also melt iron... — nico, Jul 10 '11 at 15:00
@nico, you miss the point entirely. OP asks if centrifugal juicers destroy vitamins through friction? @BobMcGee says, "That doesn't make much sense...` (as if OP has asked "are vitamins different on Tuesday?") My point was that if heat can alter vitamins _it is a plausible hypothesis_ that friction might also affect vitamins. Others have attempted answer OP's question, my point was more directed at @BobMcGee to say that it is a reasonable question regardless of the answer. — Cos Callis, Jul 10 '11 at 18:00
@Cos: I understood your point. I am just saying that whoever wrote the text in the link you provided is talking about vitamins and proteins like they were the same thing. — nico, Jul 10 '11 at 18:06
@Nico, `Eggs and Rocks will both be crushed by a large sledge hammer` does not treat "eggs and rocks" as "the same" except in respect to how they can be affected by a sledge hammer. Proteins and vitamins are similarly affected by heat, they undergo chemical changes when exposed to heat. That is the only similarity that **matters** _in the context of this question_. Both _are_ affected by heat, it is _plausible_ that they _may be_ affected by friction. I mean chemists never use anything that affect chemicals using centrifugal force, well, except a centrifuge... — Cos Callis, Jul 10 '11 at 20:20
@Cos: I'm sorry but there is a huge difference. Proteins denaturate with heat: that means that they lose their higher-order structure, which is taken together by weak bonds, easily broken by heat. Vitamins don't have secondary and tertiary structure so they cannot denaturate. The heat necessary to break up a vitamin (or a protein, for that matter) into its constituent atoms is definitely not reached in a juicer. Take any biochemistry book if you don't believe me. — nico, Jul 10 '11 at 21:00
@Nico, you still don't get the point. Fortunately you actually grant 100% of what I am saying when you said `Would be an interesting experiment to do though.` Beyond that you have been around the french too long. My ONLY point is that OP has a valid question, everything else you argue about is off point PERIOD. — Cos Callis, Jul 10 '11 at 22:09
@CosCallis let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/769/discussion-between-nico-and-cos-callis) — nico, Jul 11 '11 at 05:39

nico · Answer 1 · 2011-07-10T18:08:23.847

Short answer is no. Vitamins are organic compounds (that is, compounds based on a carbon skeleton) which are pretty small: most of them are formed by 20-30 atoms, not more than that.

Mechanical stress, as well as thermic stress, can indeed interfere with the structure of big organic compounds such as proteins or DNA, which are called macromolecules and are formed by thousands or even millions of atoms connected in complex 3D structures. However, this is not the case for vitamins.

So, in substance, continue to drink your orange juice and you'll be fine!

EDIT: standing what I wrote, it is also interesting to consider that certain vitamins can be enzymatically degraded. This is for instance the case of vitamin C: this article demonstrates how vitamin C degradation could happen when processing broccoli at <60°C, due to the action of an enzyme called vitamin C oxydase. Of course this does not necessarily apply to other vegetables/fruit or to other vitamins.

Personally, I think that the passage of a fruit in a juicer is sufficiently fast that I really doubt there would be enough time for the vitamins to degrade. Would be an interesting experiment to do though.

score 7 · Accepted Answer · answered Jul 09 '11 at 19:58

There are two explanations usually given for why centrifugal juicers lose some of the nutritional value:

frictional heating, supposedly from the higher speed of the moving parts (although it's never clearly explained where this comes into play, maybe from the juice splatting on the container)
aeration of the juice (since there's usually more frothing with a centrifugal juicer), which causes the juice to oxidize more and faster.

This page is fairly typical of the explanations.

I'm personally not convinced that either of these is a huge issue, but OTOH I do like the twin-gear masticating juicer we have because it can juice anything and doesn't suffer from those supposed disadvantages of the centrifugal type.

I just bought the Hurom Slow Juicer and it's very interesting. Slow squeezing of the items and plenty of juice. It even juices wheatgrass! — , Jul 11 '11 at 01:53

Do centrifugal juicers destroy vitamins through friction?

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