Comments on: Oh Lord, won't you buy me a new centrifuge The International Culinary Center's Tech 'N Stuff Blog Thu, 09 Jan 2014 18:17:16 +0000 hourly 1 By: Micah Wed, 11 Aug 2010 07:58:45 +0000 Greetings, a friend forwarded your site to me. I work as a biochemist by day and cook by night.

You have picked up a fine centrifuge, I work with a similar model with a built-in refrigeration unit (CR422). Those Jouan centrifuges are built like tanks… I would guess your machine is at least 20 years old if not more. Jouan as a company however hasn’t lasted as well and was bought out a few years back.

A few tips from an old hand…
Your rotor should have some important information stamped on it, serial number, model number and more importantly a MAX SPEED and EXPIRATION DATE.
Max Speed is the rated speed the rotor can handle with the maximum load (for this model probably 5k or 6k). For this model I would guess the load is the equivalent of all buckets containing a 500 ml flask (so 0.5 kg per bucket or 2 kg for a fully loaded rotor). It is not advisable to load the rotor beyond this as you risk a catastrophic failure (mass, acceleration, kinetic energy, metal fatigue blah blah blah). Centrifuge failures are a serious thing- there is a very real risk of damage and injury when these go- that’s why the chamber is made of steel armor. Try a Google image search for “centrifuge failure” and similar terms some time.
Expiration Date is the date when the manufacturer no longer guarantees the rotor to be suitable for use at max speed assuming a typical duty cycle. Many people use rotors for years (decades?) beyond this point without incident, but if it fails you can’t sue anyone. This gives you an idea of the age of your rotor and can you decide if operating it a max speed under a full load is really a good idea. Many labs will knock 500 or 1000 rpm from the old max speed and tape a note next to the speed dial, successfully depreciating (or “de-rating” in centrifuge jargon) an old rotor.

Keep your eyes open for flask holders for your buckets. Many of these flasks are perfect for centrifuging large quantities of liquid or slurry. Check out the various flasks what Nalgene sells… these could be a lot easier than using a vacuum sealer, plus the shape of many of these bottles are designed to make fractionation of your samples easier.

Your simple syrup idea reminds me of a technique called a sucrose cushion. It involves sedimenting large particles through a dense aqueous liquid (sucrose solution) at the bottom of a centrifuge bottle, everything that is soluble or too small to pass through the cushion is retained in the sample- it’s a great way to do fine fractionation. Make a saturated solution of sucrose (table sugar) in water, fill a pipette (or turkey baster) with the solution, put the tip at the bottom of the bottle (with your sample already in it) and gently expel the sucrose- do not blow out the pipette as air bubbles will disturb you gradient. After centrifugation you will see large debris below the sucrose, use a pipette to draw off the debris and the sucrose. Of course this only works when your sample can tolerate contamination with sugar (this might be useful for desert preparations?). Experiment with different speeds to get an idea of how fine of fractionation you can achieve with this technique. Bottom pipetting dense liquids is also a great way to make layered mixed drinks.

Finally, if you are interested in buying old laboratory equipment you should really check out the website DoveBid. They are a liquidation outfit that often sell off equipment from old pharmaceutical research labs. Lots of neat stuff shows up there and the prices are usually good (I attribute it mostly to the people running the auction not knowing what the things they are selling are). As these listings are not usually written by scientists there are some good typo bargains there too.

Love the site!


By: Chou Thu, 30 Jul 2009 03:16:54 +0000 Second the walk-in fridge idea, we kept one permanently in the 4C room. Now to find an ultra-fuge for a reasonable price . . . 15,000Xg does some fun stuff with DNA extraction, why not with food?

By: Dave A Wed, 29 Jul 2009 13:23:20 +0000 Paul,
Decidedly better than a salad spinner. Let us know if you find anything good. We are working on trying to flesh out our applications.

By: Paul A. Wed, 29 Jul 2009 04:07:59 +0000 I have a handful of fresh 15ml polypropylene tubes.

The RPM rating scrawled on the back of the machine is 3,146. The radius is about 250mm.

I see on the web that RCF = 1.12 times the radius, times (RPM/1000) squared. So I’m getting an RCF of about 2,770.

Better than a salad spinner!

By: Dave A Wed, 29 Jul 2009 01:07:31 +0000 Go on line and look up the RCF vs rpm values for your rotor/fuge combo. Also, do you have 15 ml tubes or are you putting stuff directly in the rotor?

By: Paul A. Tue, 28 Jul 2009 18:46:54 +0000 Just as we were talking about this, I found a fuge! It was in a pile of trash outside an animal hospital in Chelsea yesterday. Took it home and bleached the rabies out and it works perfectly.

The capacity is only 6 x 15ml, but the price was right.

I’m gonna try the kalamata separation. Any other suggestions for small-scale, quick-gratification My First Centrifuge projects?

By: robert millman Fri, 24 Jul 2009 17:19:47 +0000 You can run the centrifuge in a walk in to keep it cold.

By: alexgz Thu, 23 Jul 2009 23:55:51 +0000 I posted a reply about the nut centrifuge on the agar clarification page (silly me) proposing a simple explanation of what might be going on but I must commend Schinderhannes for his interjections, sounds like something worth doing.

By: derek Thu, 23 Jul 2009 23:52:00 +0000 would cerial grains work like the nuts? in refernce to beer brewing, powdered malt or malt extract is available. would be interesting to find out and to see the result used to brew a batch! what about hops? that has oils and resins. vita mixed corn? what about fish, how to they extract fish oils, how many fish do you need? do the beer one, and brew some up, i dont have the fuge or i would try it.

By: schinderhannes Thu, 23 Jul 2009 10:31:30 +0000 One more thought on breaking the very fine emulsion/suspension of your nut oil:

In a chemistry labe we very often use separatory funnels to seperate an aqueous layer from ans organic layer e.g. hexanes or ethyl acetate but fat (oil) would be the same story.

You shake water and your organic to transfer water loving stuff out of the organic into the water or vice versa. (Thinkin bout it there might be some cool uses for this in the kitchen on its own right, beyound straining the fat sauce from a roasted goose….)

Anyways once in a while your phases don´t separate nicely, you keep an emulsion.

The most effective additive to help break that emulsion is a few mls of methanol (stop, don´t try this :-) but ethanol (go head) does the trick as well.

Therefoe maybe adding a shot of booze to the nut puree will work like a charm!
As you certainly know, but maybe not all readers, glucose is a poly-alkohol, from a chemical standpoint, so maybe that does explain why SS is so effective….