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greensNbeans

Fluid gels

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Can somebody shed some light on this subject for me, please. Ive seen that Ludavic at Bastide also does it. Any comments will help - :blink:

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If you look in this month's Food Arts mag (if you're in the US), there's a piece on Heston which includes a discussion of fluid gels.

Basically, he uses a product called gellan gum to create a solid or set gel, and then uses an overhead lab mixer (which works at much slower speeds than a regular mixer, and so doesbn't incorporate any oxygen) to break up the gell into so many pieces, that it takes on the characteristics of a fluid, without actually becoming one. You can restrain the process at the point where it will behave like a puree, or continue until it's actually pourable.

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If you look in this month's Food Arts mag (if you're in the US), there's a piece on Heston which includes a discussion of fluid gels.

Basically, he uses a product called gellan gum to create a solid or set gel, and then uses an overhead lab mixer (which works at much slower speeds than a regular mixer, and so doesbn't incorporate any oxygen) to break up the gell into so many pieces, that it takes on the characteristics of a fluid, without actually becoming one. You can restrain the process at the point where it will behave like a puree, or continue until it's actually pourable.

So its gellan in a puree form. It does not lighten in color because of the amount of oxygen in it.

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I don't know about the discoloration. The issue, I believe (and I might be wrong) was to prevent it foaming, which the incorporation of air would have produced.

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I don't know about the discoloration. The issue, I believe (and I might be wrong) was to prevent it foaming, which the incorporation of air would have produced.

Does anyone have a copy of this magazine that they can upload and send me?

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Have sucessfully made fluid gels with a hand blender.

As Moby said it is basically a nearly broken gel. Make your main flavour ingredient, set with the gellan, then blend with a baa-mix or similar every now and again as it cools (around every 5 minutes or so), don't overdo it, just enough to break the setting of it. I have found no discolouration, but naturally can be a little frothy.

also what I have found the lower the pH the easier it is to bugger this up, flavoured milks are more foolproof then a strawberry or tomato fluid gel, and when you get to lemons or limes then it goes south very easily as the gellan loses hold on the liquid and you end up with lemon water with the odd lump in it, not quite the effect I was looking for!! :sad: !!

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Fluid gels are made by taking a gelling agent or gum (gellan, agar, or other hydrocolloids), hydrating it, letting it set, then shearing it to break the gel structure.

You can do it with many gelling agents - I've even made fluid gels with egg custards - you heat the egg custard until it JUST starts to set then you shear it.

Shear means mix with a device that produces high shear (side to side) forces - i.e. an immersion blender. In food labs or commercial production you would use a colloid mill which can generate far higher shear forces than an ordinary kitchen blender or immersion blender. However, the kitchen version will do.

Many gels have the property that their viscosity (thickness) depends on shear forces. Which means you can have something that seems set like a gel, until you shake (or otherwise produce shear forces) at which point it instantly thins and pours like a gel. Fluid gels have this property to a high degree.

There is a bottled beverage called Orbitz that has small colored "beads" of one gel, that are suspended in a clear liquid fluid gel. The beads stay put while the bottle is on the shelf, but when you go to drink it, it pours. Orbitz is made mainly of gellan, but I think there is some carrageenan (another hydrocolloid gum) in it too.

This is all a high tech way to say that fluid gels are basically Jello put in a blender.

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i did a lot of experimenting on this in the last 12 months

actually iam working on a range of "Molecular cuisine" products

together with germany´s biggest finefood wholesaler bosfood.de

the products will sell under the brandname "a cooks alchemy" and

cover usual suspects like the alginate & calcium cloride, but also

new products like "gellan 2.0" which is an enhanced form of gellan capable

of bearing extreme ph levels (like pure limejuice) and its far more easy to disperge in cold aquaeos systems than the original schtuff :-)

cheers

t.


Edited by schneich (log)

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This is all a high tech way to say that fluid gels are basically Jello put in a blender.

this is not correct

if you would apply strong sheer forces to a gelatin aka "jello" it would simply melt and reset. this doesnt happen with gellan, once set you can only remelt it with large amounts of heat ;-)


Edited by schneich (log)

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This is all a high tech way to say that fluid gels are basically Jello put in a blender.

this is not correct

if you would apply strong sheer forces to a gelatin aka "jello" it would simply melt and reset. this doesnt happen with gellan, once set you can only remelt it with large amounts of heat ;-)

Correct me if I'm wrong, but I think most people here, Nathan included, understand the impact of shear on gelatin. Nathan's statement inherently implies that it's a 'form of' jello put in a blender. A form of jello comprised of gelling agents that produce fluid gels when exposed to shear.

At least that's how I read it ;)

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This is all a high tech way to say that fluid gels are basically Jello put in a blender.

this is not correct

if you would apply strong sheer forces to a gelatin aka "jello" it would simply melt and reset. this doesnt happen with gellan, once set you can only remelt it with large amounts of heat ;-)

Correct me if I'm wrong, but I think most people here, Nathan included, understand the impact of shear on gelatin. Nathan's statement inherently implies that it's a 'form of' jello put in a blender. A form of jello comprised of gelling agents that produce fluid gels when exposed to shear.

At least that's how I read it ;)

Just to restate what Heston told me - he doesn't want a high velocity bamix or blender precisely because it begins to incorporate air into the mix. That's why he uses a slower overhead mixer to shear the cells without adding air. Otherwise you're making a foam, rather than a fluid gell.

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This is all a high tech way to say that fluid gels are basically Jello put in a blender.

this is not correct

if you would apply strong sheer forces to a gelatin aka "jello" it would simply melt and reset. this doesnt happen with gellan, once set you can only remelt it with large amounts of heat ;-)

Correct me if I'm wrong, but I think most people here, Nathan included, understand the impact of shear on gelatin. Nathan's statement inherently implies that it's a 'form of' jello put in a blender. A form of jello comprised of gelling agents that produce fluid gels when exposed to shear.

At least that's how I read it ;)

Just to restate what Heston told me - he doesn't want a high velocity bamix or blender precisely because it begins to incorporate air into the mix. That's why he uses a slower overhead mixer to shear the cells without adding air. Otherwise you're making a foam, rather than a fluid gell.

When the victorians were scoffing down moulded jellies like crack cocaine, to produce an opaque effect (say if you were making a layered jelly) a semi-solid jelly would be very vigorously whipped, to incorporate tiny air bubbles, then re-set.

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Btw, I don't know if this has been posted here or not, but I recently stumbled onto Wylie's recipe for gellan based fried mayonnaise:

http://www.starchefs.com/chefs/rising_star..._dufresne.shtml

the recipe itself is kinda nice but its wrong to say that gellan is "not thermoreversible" it can bear a lot of heat, but once you get to 100c it melts pretty quickly.

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Btw, I don't know if this has been posted here or not, but I recently stumbled onto Wylie's recipe for gellan based fried mayonnaise:

http://www.starchefs.com/chefs/rising_star..._dufresne.shtml

the recipe itself is kinda nice but its wrong to say that gellan is "not thermoreversible" it can bear a lot of heat, but once you get to 100c it melts pretty quickly.

Heat range of Gellan gum – if you get the right concentration and ph and salt levels, you can actually fry it.  You can cut a slice of Gellan and actually sauté it.  I once put it on the solid top to see what would happen. Or a deep fat fryer.

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Just about any gel can be made into a fluid gel, although some are better than others. Most gels are "thixiotropic" - also called "shear thinning" or "shear dependent viscosity" or "non Newtonian" - because their viscosity (thickness of the fluid) depends on shear, and typically "lets go' and at some threshold value.

Here is background on this http://bizarrelabs.com/slime.htm

Making a fluid gel involves either applying shear while the the gel sets (and thus preventing it from setting normally), or letting it set and then applying shear. You also need the right gel strength, and that depends on gel concentration, solid percentage, pH, ion concentration.....

Here are some references on fluid gels.

http://www.foodproductdesign.com/archive/1995/0195CS.html

http://www.foodproductdesign.com/archive/2005/0505CON.html

http://www.findarticles.com/p/articles/mi_...164/ai_17551651

Here is a good overview of hydrocolloids

http://www.foodproductdesign.com/archive/2002/0602AP.html

http://www.foodproductdesign.com/archive/1999/1299ap.html

Here is a discussion of the Orbitz drink previously mentioned

http://www.chemistry.org/portal/a/c/s/1/ac...rp1_orbitz.html

Gellan is one example of a hydrocolloid that has this property, but agar, xanthan and others do too. Most of them do, and under the right conditions you can make a fluid gel from any of them. However, some are better than others.

You typically do need a bamix or very high speed mixer to make a fluid gel, although that depends on the gel. I suppose that a weak enough gel could be converted with an ordinary stand mixer, but not in my experience.

Even if you don't need one to make the fluid gel you need a high speed mixer to hydrate the gel in the first place. These hydrocolloids are usually not easy to dissolve and hydrate smoothly without a lot of shear. Immersion blenders like Bamix are great for this. Laboratory style homogenizers, or colloid mills are better yet.

Certainly that is true with gellan and agar - both of them, as well as many other gelling agents can be turned into a fluid gel. This requires control both of the gel concentration and amount of shear.

Most hydrocolloids (including gellan, agar, xanthan, caregeenan) are polysaccharides - i.e. long polymer molecules related to sugars. Note that many of them are metabolized by the body as fiber rather than as a carbohydrate.

Here is a description that I excerpted from a Unilever patent (patents are public domain documents so excerpting this is allowed). This covers the issue pretty well:

======================

However, it has been discovered that when a sufficient amount polysaccharides or their derivative gelling agents such as Carrageenan or agar were dissolublized in the surfactant solution and hot solution is allowed to cool to room temperature, the surfactant solution will set to form a range of gel textures. These gels are stable at room temperature but can be remelted by heating above the gel temperature. On cooling the system will re-gel. The formation of gels by natural polysaccharides arises from the physical interaction between the polymer molecules. Hydrogen bonding is usually the major cause of the interaction. For a detailed description on the formation of gels in these types of polysaccharides see R. L. Whistler and J. N. BeMiller, Industrial Gum: Polysaccharides and their Derivatives, Academic Press, 1993. The gel will possess a strength dependent on the strength of intermolecular bonding. If the bonding is weak, it may be broken and the total gel structure disrupted by mild stirring. In this case, the weak gel is said to be thixotropic. When the intermolecular bonding is strong enough, a more identifiable gel forms that may not be easily broken by stirring. Once the gel is formed it may be strong enough that when under applied stress, the gel will separate or cleave as seen with gelatin gels. In some polymeric systems, once a gel is formed, the polymer molecules can further rearrange themselves by sliding over each other or simply moving together to strengthen the overall physical network structure which will cause a decrease in the water-filled spaces between the molecules. Hence water is exuded from the gel to produce a phenomena which is commonly know as syneresis.

During the cooling process if the polysaccharide surfactant solutions are subjected to shear either during or after the gelation process, the application of shear will disrupt normal gelation and result in a "fluid gel" that is pourable and cannot hold a shape (see G. O. Phillips and P. A. Williams, Handbook of hydrocolloids, CRC Press, Woodhead Publishing Limited, Cambridge, England, 2000).

(the patent is on a kid's shampoo made with a fluid gel http://appft1.uspto.gov/netacgi/nph-Parser...=DN/20040097385 )

================

The hydrocolloid handbook mentioned above is a good book on the topic, available from CHIPS books.

Most of these gels will NOT whip or retain bubbles when they are in the proper state to be turned into a fluid gel. So that is not really a concern. I am doubtful that it could be a concern, frankly, but I suppose it is possible. Note that very high speed shear rips the gel apart and will not allow bubble formation.

Gellan has a lot of properties other than being able to be made into a fluid gel. Thermoreversability is different than just melting - to be thermoreversable the gel needs to be able to set AGAIN (as per the passage above). Gellan can do this, but not always -it depends on whether you have high acyl or low acyl gellan, and also on the ion concentration.

High acyl gellan is fully thermoreversable, under the right conditions (concentration, pH etc). Low acyl usually isn't. Wylie uses low acyl in his fried mayonnaise - it is NOT a fluid gel, and is not thermoreversible.

Note that it is typical that the temperature for gelling is often different than the melting temperature (typically 35C gelling for agar, 85C to melt).

Other issues include gel texture (rubbery and "soft", brittle or "hard"), syneresis, flavor release etc.

Gelatin is a protein polymer that can cross link in a manner very similar to the polysacchride hydrocolloids.

WHen I said "jello in a blender" I was clearly speaking very loosely. However, you CAN make a fluid gel from gelatin - you just have to keep it below melting temperature, and have a weak gel to begin with. The degree of shear-thinning and the thixotropic threshold is not as strong as it is with others, so it is less interesting.

You can also make fluid gels from other cross linked protein gels, such as the egg custard case that I mentioned in a previous post.

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Wow, this is fun! Do any of you know where one can purchase some gellan gum? I found a manufacturer, CP Kelco, but it doesn't seem like you can purchase it directly from them.

Thanks in advance!

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nathanm, it's good to see you back, contributing and educating those of us who may not know as much. First sous vide, now this, where to next?

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