Tuesday, May 31, 2016

Ice Cream Stabilizers

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Shunned and embraced, demonized and defended, shouted and mispronounced, these ingredients are the most widely missunderstood, proving equally befuddling to ice cream lovers on all sides of the never-ending, stupid lively arguments. I’m hoping to shed some light here.


What Are They?


Stabilizers are any ingredients used to thicken the water in ice cream. They make ice cream smoother, by slowing the growth of ice crystals. And they can improve the texture generally, by adjusting the body, the speed of melt, and the finish.

Technically, they are hydrocolloids — suspensions of fine particles in water that form a network, increasing the water's viscosity, and in some cases forming a gel. When you thicken gravy with flour, make pudding with cornstarch, or mix Jell-o, you’re making hydrocolloids. Which is to say: you’ve probably been using stabilizers for a long time. 

Properly stabilized ice cream not only resists developing an icy texture over time, but will actually form smaller ice crystals to begin with.1 Improperly stabilized ice cream (like improperly cooked food) can indeed be awful. We'll be discussing how to use these ingredients well, with the belief that in most cases, it's possible to make a better ice cream with stabilizers than without.

Stabilizer Examples:


Egg Custard. Custard is indeed a stabilizer. It’s among the most effective at creating great textures, but only middling at slowing ice crystal growth. This is likely because custards exhibit synerisis, or weeping: they let water seep out of their gelatinous structure. The smoothest egg custard ice creams use additional stabilizers. Custard's other drawback is that it damps the release of flavors more than most other stabilizers—especially lighter and more aromatic flavors, and water-soluble flavors (fruits, etc.). 

Custard viscosity varies with the concentration of yolks and cooking temperature. For thickening and stabilization, ice cream requires at least 3% egg yolk by weight, which is between 1.5 and 2 egg yolks per liter. 4 to 6 yolks per liter is more common, and some people go higher, making a dessert that's more a frozen custard than an ice cream, with egg flavors and textures dominating.

Cooked egg flavor, like viscosity, increases with concentrationand cooking temperature, and possibly also with cooking time. With yolk concentrations below 4%, eggy hydrogen sulfide compounds will probably be undetectable except after extreme cooking. For more egg-rich recipes, it may be beneficial to keep the cooking temperature between 70°C and 72°C for longer cooking, or below 82°C for shorter cooking.


Refined Starches, like cornstarch and tapioca, are a staple in many ice cream traditions. Cornstarch is most famously used in Southern Italian gelatos, which are often made without eggs or even cream. It’s become popular in many home recipes because it’s easy to find and easy to use, and gives reasonably good texture and stability. Tapioca works similarly. Starches generally give better flavor release than custard, but not as good as gums.

I’ve seen some recipes that use arrowroot starch, which is possibly the best of the refined starches for savory applications, but should be avoided in ice cream. Arrowroot reacts with dairy ingredients to create unpleasant, snot-like textures.


Gelatin is the oldest known non-egg ice cream stabilizer. And it’s a very good one. Its ice crystal suppression and texture make it arguably superior to starches, and it’s equally easy to use. Gelatin has fallen out of favor partly because of cost, and partly because it’s an animal product. Even non-vegetarians are occasionally skeeved by knowing their ice cream contains rendered beef and pork tissue. But I would still encourage experimentation with gelatin, if you want to play with stabilizers but aren’t ready yet to buy a whole arsenal of hydrocolloids from the molecular ingredient sites.

Gums


These are the mack-daddy stabilizer ingredients. They work in minute quantities, have superior powers of ice crystal suppression, offer almost infinite textural possibilities, have no detectable flavor of their own, give superior flavor release (they don’t mute the flavors of the ice cream), and can be almost endlessly confusing.

We’re going to look at a small selection of gums individually, although much of the strength of gums comes from their synergies; they work best in combinations. The synergies are often such that the gums reinforce one another, and offer capabilities in combination that they did not offer individually. 1 + 1 = 3, etc.

The challenge in creating a gum blend lies is balancing the qualities of the individual gums with each other, as well as with the rest of the recipe, while taking into account the various synergies between those individual gums.

Gums are all polysaccharides—big molecules made up of lots of small sugar molecules linked together. They are close cousin to starches ... you can think of them as superstarches.

Locust bean pods

Locust Bean Gum, also called carrob bean gum, is made by milling the seeds of the locust tree. It’s been used as a thickener since at least 79 AD, and possibly much longer (look up traditional Indian recipes for cluster beans, another name for guar. They eat it by the bowl. We'll be using it by the milligram). LBG has the most powerful ice crystal suppression of all the conventional gums. It favors a smooth, creamy, natural texture that does not draw attention to itself. It manages this by forming a weak gel that is stable while frozen, but that is highly shear-thinning, so once the ice cream melts and starts moving, most of the added viscosity vanishes. These characteristics make it the most important of the gums in ice cream.

LBG needs to be heated to hydrate. Most varieties require heating above 80°C, which is higher than ideal for many ice cream processes. Varieties sold by TIC gums and Willpowder hydrate at much lower temperatures.


Guar beans

Guar Gum is milled from the seeds of the guar plant, which is a legume. Guar gum is chemically similar to locust bean gum, and the two are often used together. Guar is not quite as effective as LBG at ice crystal suppression, but gives greater viscosity than LBG at similar concentrations. In combination, guar and LBG strengthen each other—when using the two together, you can use a lower total quantity of gums.

Guar gum has only been in use since the 1950s, but the guar bean has been cultivated in India as a protein source for hundreds of years.

Guar’s main use, besides strengthening the effect of LBG, is to add body. In high concentrations, it can make ice cream that’s chewy and elastic—either a flaw or a benefit, depending on your point of view. In New England, they like a lot of guar.

Irish Moss / Carrageenan
Carrageenans are extracts from Irish Moss seaweed (chondrus cripus). They’ve been used as food thickeners since the 15th century. Modern versions of carraggeenan are divided into types based on the details of their molecular structure. The most common in the culinary world are Kappa, Iota, and Lambda. These types have different solubility temperatures, gelling characteristics, and interractions.

The most useful type in high quality ice cream is Lambda Carageenan, since the others form gels in the presence of calcium (dairy products). See note on gels, below).

Carrageenan has a moderate effect on ice crystal suppression, and a strong effect on texture, especially of the melted ice cream. Carageenan creates a rich and creamy mouthfeel similar to egg custard, but does so without adding any flavor of its own, and without muting other flavors. 

Carrageenan’s secondary role is to prevent wheying-off, a phenomenon of milk proteins preciptating out of suspension, aggregating, and creating grainy textures. Locust bean gum and carboxymethylcellulose can induce whey-off, so when these stabilizers are used you’ll usually see at least a minute amount of carrageenan.

Giant kelp / brown algae. Where we get the alginate.
Sodium Alginate is another seaweed extract, made from a brown seaweed grown in cold water areas. It’s a popular stabilizer, especially in low-fat and fat-free ice creams, because it forms a gel in the presence of calcium ions in the dairy. Its gelling quality makes it less useful in standard recipes (see the note on gels, below). The gel breaks into a fluid gel when the ice cream is spun, creating a unique body and viscosity. It’s quite effective at ice crystal suppression.

Sodium Carboxymethyl Cellulose: a big-ass molecule

Carboxymethylcellulos, also called cellulose gum, technically called sodium carboxymethylcellulose, is synthesized from plant cellulose. It may have the strongest ice crystal suppression of any known gum. It adds body and chew comparable to guar, and is synergistic with locust bean gum, guar, and carrageenans—it forms a gel in combination with these ingredients, with can be problematic (see note on gels, below).

There are low-viscosity varieties of CMC that suppress ice crystal formation with very little increase in base viscosity, if they're used in a non-gelling blend. These theoretically allow you to control iciness and texture completely independently. Examples include TIC Gums CMC PH-15.

CMC is not popular in higher quality ice creams, because it is a synthetic ingredient. While the word “natural” is rather ambiguous, CMC lies outside most interpretations of natural. This is perhaps more a marketing issue than a real one—there are no health concerns associated with the stuff. It's just a big polysaccharide like the gums that come from ground up seeds. Nevertheless, I’ve only experimented with it once and was dissuaded by its gel-forming with other gums.

You can get xanthan at the supermarket these days.

Xanthan Gum is created by bacterial action, when the organism Xanthomonas campestris chomps on glucose, lactose, or table sugar. It’s a fermentation product, much like cheese and booze. 

Xanthan is often called the “wonder gum,” because it’s easy to dissolve at any temperature, it thickens at any temperature, works at a wide range of acidities, can tolerate alcohol, freezing, thawing, and just about anything else.

While most gum recipes require a scale that reads to 0.01g and careful dispersion and heating, cooks find xanthan pretty friendly in an old-fashioned-ingredient way. Need to stabilize a vinnaigrette? Toss in a pinch of xanthan and whisk until it’s dispersed. Want to add a bit of body to a sauce? Make a slurry with a pinch of xanthan, and whisk in just as you would with cornstarch or arrowroot. 

Xanthan is not, however, my first choice in ice cream stabilizers. It does an acceptable job, but is not the most powerful ice crystal suppressor. And it forms a gel when used with locust bean gum. This makes the mix harder to handle. See note on gels, below. I do recommend xanthan for anyone interested in starting experiments with stabilizers. You can get it anywhere now, and it’s worth having around for a million other uses.

Dondurma vendor offering a cold chew.
Salep, Mastic, Gum Arabic, and Konjac Flour are specialty stabilizers used in Dondurma, a traditional taffy-like ice cream popular in Turkey and Azerbaijan. Also called MaraƟ, this ice cream is both chewy and resistant to melting. Salep (flour made from the root of the Early Purple Orchid), and Mastic (hardened sap the Mastic Tree) are traditional. Gum arabic (hardened sap of the Acacia Tree) and Japanese konjac flour (starch from the Konjac, aka Elephant Yam) are more readily available substitutes.  A combination of gellan gum (a microbial gum like xanthan, which forms gels) and guar can also substitute



Denatured Whey Proteins: Some of the whey proteins, which make up 20% to 25% of the total protein in milk and cream, can form a gel-like network when heated to the right temperature for the right amount of time. This network functions in the same way as the other hydrocolloids discussed here. Whey proteins may also be denatured chemically or enzymatically, using processes that are probably out of reach in the home and pastry kitchen. We don't know what they do at Haagen Dazs, but they're doing something. See extended discussion in the post on Emulsifiers.




Blends and Variations



Blend 1: Easy-to-find ingredients

Gelatin : Xanthan Gum

3 : 1

1g gelatin 0.33g xanthan For 1 liter of ice cream (0.15% total)


Gelatin hydrates when cooked to 60°C / 140°F. Any standard cooking step will take care of this.

Both the gelatin and the xanthan suppress ice crystals and increase the viscosity of the mix. 

The gelatin forms a weak gel that melts at body temperature and strengthens in the cold, so its effect is most pronounced on the ice cream in the frozen state. The xanthan gum’s activity is almost completely independent of temperature. So its effect is most pronounced on the ice cream in its melted state. So if you want more body, increase the proportion of the gelatin. If you want a creamier melt, increase the proportion of xanthan.

You can experiment freely, but be warned that at much higher concentrations, xanthan’s mouthfeel goes from creamy to slimy. If you’re not getting the results you want from this blend at modest concentrations, you should move on to the other gums.



Blend 2: General Purpose

Locust Bean Gum : Guar Gum : Lambda Carrageenan

4: 2 : 1

0.8g  0.4g  0.2g  for 1L  (0.15% total)

Mix should be cooked at least to the hydration temperature of the locust bean gum. TIC Gums versions hydrate at 74°C / 165°F—most brands hydrate at temperatures higher than what’s ideal for most ice creams. 

All three gums suppress ice crystals and affect texture, but not equally.

The Locust Bean Gum is the most powerful at suppressing ice crystals. It has a subtle effect on increasing the body of the ice cream and the creaminess of the melt.

The Guar amplifies the power of the locust bean gum, and has the strongest effect on the body of the frozen ice cream. Significantly increasing the guar will make the ice cream chewy and elastic.

The Lambda Carrageenan has the strongest effect on the consistency of the melted ice cream. Its mouthfeel is similar to that of custard, although it has a somewhat cleaner finish. If the melt feels too milky or watery, you can subtly enrich it with a bit more LCG.

I use this blend at 0.15% in a 15% milk fat ice cream that uses 2 yolks per liter. For a richer, more custardy mix, you could experiment with using as little as 0.1%. For a lighter ice cream, or one that needs a long shelf life, you could try 0.25%



Blend 3: Eggless Ice Cream [edited 10-2018]

Soy Lecithin: Locust Bean Gum : Guar Gum : Lambda Carrageenan

5: 2: 1.5: 1

2g 0.8g  0.6g  0.4g  for 1L  (0.4% total)

Mix should be cooked at least to the hydration temperature of the locust bean gum. TIC Gums versions hydrate at 74°C / 165°F—most brands hydrate at temperatures higher than what’s ideal for most ice creams. 
This is the same as the standard formula, but increased 50%, and with soy lecithin added. Egg custard has thickening and stabilizing benefits, so its elimination requires a higher concentration of gums. The eggs also act as emulsfiers (see the next post).

The lecithin content of this blend is equal to a large egg yolk. You could theoretically use less—as little as 1/3 this much.

All the notes for manipulating the standard formula apply here. Be careful if increasing the lecithin. You probably don’t have to. If you go too far, it will actually impede the whipping of the ice cream.



Blend 4: Sorbet

Locust Bean Gum : Guar Gum : Iota Carrageenan : Lambda Carrageenan

4: 2: 2: 1

1.33g  0.66g  0.66   0.33g  for 1L  (0.3% total)


This should be blended into the syrup portion of the sorbet, and brought to a simmer. At this point, flavors can be infused into the syrup (sugar syrup is a powerful solvent for both polar and non-polar flavor molecules). Syrup should be chilled for several hours to allow gums to fully hydrate. Then it can be mixed with chilled fruit puree and frozen into sorbet.

This is similar to the standard formula, but with iota carrageenan added, and total gum quantity doubled. Sorbets have no cream, and are low on solids. They have little to no inherent creaminess, and a lot of water to stabliize. The iota carrageenan forms a weak gel in combination with the locust bean gum, adding viscosity and body. The gel breaks easily into a fluid gel under shear and then re-forms. It's freeze-stable and helps give a creamy texture.

Most sorbets have no fat content and so have no need for emulsifiers. If you wish to make a sorbet with chocolate, nut butters, olive oil or other fatty ingredients, you may get smoother results by adding some lecithin (maybe start with 1.5g / Liter).

We'll look at all this in greater depth in a future post on sorbets.


Notes on Using Gums


Three aspects of gums demand attention: measuring, dispersing, and hydrating.

They can be tricky to measure for small batches because the quantities are minute. You should have, in addition to a higher capacity scale, a small scale that reads to 0.01g. There are many available on Amazon and Old Will Knott Scales for under $40. 

I use a small cup or bowl, and use it to weigh all the ingredients that total less than a few grams. This typically includes the stabilizers and the salt. After the ingredients are measured out, I stir them together, and then thoroughly mix them into to the other dry ingredients (sugars, dry milk, etc.). This helps with dispersion:

Dispersion means mixing the dry ingredients into the wet ingredients evenly, without clumping. Gums make this tricky. So does milk powder. The first defense against clumps is to thoroughly stir all the powdered ingredients together. Locust bean gum will only clump with locust bean gum; dry milk will only clump with dry milk, etc.. So if you mix all the powders together, including the sugar (which makes up a lot of bulk and doesn’t clump at all) you can keep the individual powders separate long enough for them to disperse without clumping.

The second defense is proper use of a blender. Adjustable speeds are handy for this: start on the lowest speed that makes a vortex down the center of the blender jar, and pour in the dry ingredients. Once they’re in, crank the speed all the way and blend for a minute or so. Thorough dispersion is required for thorough hydration:

Hydration, of course, means soaking up water. Gums don’t do anything until they’re hydrated, and many of them need time, or heat, or both. Lambda carrageenan hydrates fairly quickly at room temperature. Guar hydrates at room temperature but can take over an hour to reach full viscosity. Locust bean gum needs to be heated, to 74°C–85°C, depending on brand. It may take many minutes at temperature to hydrate fully. 

Some pastry chefs, including Francisco Migoya, save time by mixing a large batch of stabilizer. Then it can be stored and measured out as a single ingredient, like a commercial blend. This approach demands throrough mixing. It makes the most sense if you use the same stabilizer blend most of the time.

If you experiment, pay special attention to the finish—the flavors and textures left behind in your mouth after swallowing. A successful stabilizer blend won't be detectable. The ice cream flavors should linger and continue to develop, but shouldn't be indelible. The feeling of creaminess should gradually dissipate. It should not devolve into pastiness or stickiness. These kinds of textural flaws point to over-stabilization, or to poor choices in stabilizing ingredients. I like the locust-guar-lambda blend as much for its transparency as for its effectiveness.

Note on Gels


Some common stabilizer ingredients form a gel in ice cream. Examples include Sodium Alginate and Kappa Carrageenan (which gel in the presence of the dairy's calcium). Other ingredients form gels in combination with each other. Examples include xanthan gum with locust bean gum, locust bean gum with kappa or iota carrageenan, and carboxymethylcellose with locust bean gum, guar gum, or any carrageenans.

Gels are solids that exhibit properties of a liquid. Technically they are colloidal dispersions in which the solid forms the continuous phase, while the liquid (we're always talking about water in the ice cream world) forms the dispersed phase. The solids create a network, with either physical or chemical bonds, and typically work in very small quantities—often less than 1% the weight of the water.

Gels can be strong or weak, yielding or elastic, brittle or tough, high or low viscosity. Under shear, some gels exhibit brittleness and crumble (like flan), others stretch and bounce back (like gel-o), others deform (like clay), others form a fluid gel that after sheer reforms into a gel (like iota carrageenan), others form a fluid gel that after sheer stays fluid (like agar).

To gel or no to gel? For most ice creams, I prefer  non-gelling stabilizers. They tend to have a less intrusive texture, and to work more predictably, and to be easier to handle. Often with gelling stabilizers, the mix will be too thick after aging to spin efficiently in the ice cream machine. It will have to be thinned with a blender first, turning it into a fluid gel. If possible, I like to avoid this added step.

If you're making low-fat or fat-free ice creams, or sorbets, gelling stabilizers become useful. They can add body and creaminess that's often lacking in these recipes. 

Closing Thoughts


I hope this post has made a case for the usefulness of stabilizers—of custard, at least, but preferably something with a bit more effectiveness and flexibility. The questions should be about how deeply involved you want to get.

Commercial blends are easy to find and easy to use. They go into many of the world’s best ice creams every day. Pastry chefs who know more than i do—about basically everything—rarely have a clue about the level of hydrocolloid micromanagement we’re discussing here. So why bother rolling your ownI?

Well, you’ve read this far, so you’re probably a geek who likes to tinker under the hood of the world generally. And you may appreciate the level of control afforded by the DIY approach. Blending your own stabilizer is like the next step beyond using curry powder from the supermarket—discovering that there are a dozen spices in there, that they can be varied by proportion and by how they’re added to the dish. 

I have another motive, inspired by my days as a darkroom-obsessed photographer. In any technological medium, your creative process can become dependent on proprietary manufactured products. And when these products are discontinued, or “improved,” you’re screwed, at least until you scramble to figure out an alternative. I learned the hard way the benefits of mixing my own formulas from generic ingredients, after watching some favorite photographic papers and developers vanish. I gradually weened myself from proprietary stuff whenever possible. The kitchen's no different. A company like Cuisine-tech could stop making Cremodan tomorrow—but someone’s always going to be selling plain old locust bean gum.

In the end, stabilizers are just ingredients like any other. If they seem daunting, it’s only because textbooks and cookbooks and culinary websites haven’t addressed the topic adequately. Until they do, I hope the information here proves useful.




Appendix


Ingredient sources

Kalustyans (In NYC ... better to visit than to suffer their web store)


For further reading

Ice Cream, 7th Edition, H. Douglas Goff, Richard. W. Hartel. p. 75–82
Stabilizer Blends and their importance in Ice cream Industry 


Ask the experts

TIC Gum Gurus: (800) 899-3953
CP Kelco support: 1 (800) 535-2687

(The tech support people at both companies, when I've called, have been exceptionally friendly women, completely over-qualified—probably chemistry PhDs,—and have seemed happy to talk ice cream. If you're nice they may send you product samples.)


1"Microscopic investigation revealed that stabilized ice cream (locust bean gum and carrageenan) had significantly smaller mean ice crystal diameters both initially and as a result of heat shock and storage (24 weeks) compared to those of ice cream without stabilizer. However, the differences grew larger over time."
—Caldwell, K. B.; Goff, H. D.; and Stanley, D. W. (1992) "A Low-Temperature Scanning Electron Microscopy Study of Ice Cream. II. Influence of Selected Ingredients and Processes," Food Structure: Vol. 11: No. 1, Article 2.
Available at: digitalcommons.usu.edu/foodmicrostructure/vol11/ iss1/2





Part 1 of this series: Introduction
Part 2 of this series: Components
Part 3 of this series: How to Build a Recipe
Part 4 of this series: Basic Recipe Examples
Part 5 of this series: Techniques
Part 6 of this series: Sugars
Part 7 of this series: Stabilizers
Part 8 of this series: Emulsifiers
Part 9 of this series: Booze
Part 10 of this series: Solids, Water, Ice
Part 11 of this series: Introduction to Flavor
Part 12 of this series: Ice Cream Flavor: Coffee
Part 13 of this series: Coffee Ice Cream Addendum: Origin Notes and Minutiae
Part 14 of this series: Chocolate Ice Cream
Part 15 of this series: Chocolate Ice Cream Addendum