Whipping eggs and sugar for ice cream base

[Morfudd]

When I am making an ice cream, i always 'whip my ice cream until pale yellow and doubled in volume'

Can anyone tell me why I actually have to do this, apart from making sure that the eggs and sugar are thoroughly mixed together? (and apologies in advance if it is obvious and I am a bit thick)

Does it actually mean anything in a structural/chemistry way that the mix should be 'pale and doubled in volume'?

[Morfudd]

sorry, meant 'whip my eggs and sugar until pale yellow etc.

[paulraphael]

You're in luck ... I just exchanged some email with David Lebovitz on incorporating sugar, and have been researching it elsewhere as well.

Short story is that whisking sugar into the yolks won't make any difference to your custard. You can mix the sugar with the eggs, mix it straight into the milk, mix it well, or mix it badly.

The point of whisking it \ into the yolks is just to disolve the sugar. And when the yolks get pale and thick, this is all that it means. You haven't caused any magical physical changes to the egg protein; you've just disolved the sugar in the eggs' water.

The only reason I like to add sugar to the eggs (assuming I'm making a custard with enough yolks to disolve the sugar) is a hunch that the sugar might make the yolks a bit more resistant to curdling when you temper them. Just adding a bit of thermal mass to the yolks would help in this regard. But I have no idea if it's a significant difference.

Most of my ice creams have a low number of yolks (too few to really disolve the sugar) so I just whisk the sugar into the milk.

[Morfudd]

Paul thank you - I am writing a book on ice creams and there are a number of gaps in my research!

So when you say 'pale yellow and doubled in volume' that means in effect that that is the way it will look like when the sugar is fully dissolved in the eggs and it is the only real way of knowing that this process has happened?

On another note, I understood that when you covered the top of an ice cream or sorbet with waxed or greaseproof paper, that it was to prevent the ice cream from shrinkage. If that is true, do you know why the ice cream/sorbet would be likely to shrink in the first place?

Morfudd

[chefpeon]

If that is true, do you know why the ice cream/sorbet would be likely to shrink in the first place?

Freezers suck moisture right out of things. That's why they need to be well wrapped (contained) to maintain food quality if you're going to store for a relatively long period. Ice creams/sorbets shrink because of loss of moisture. Luckily, in my house, ice cream NEVER lasts long enough to shrink anyway.....

[paulraphael]

So when you say 'pale yellow and doubled in volume' that means in effect that that is the way it will look like when the sugar is fully dissolved in the eggs and it is the only real way of knowing that this process has happened?

That's my understanding of it. For some kinds of preparations this is probably important ... like when you're baking something that's leavened by the egg foam, or mixing anything where this is the only opportunity for the sugar to disolve. In an ice cream base (or similar creme anglaise) it's not a big deal because the sugar will have plenty of opportunity to disolve in the hot milk.

If that is true, do you know why the ice cream/sorbet would be likely to shrink in the first place?

Ice cream is a pretty unstable (and improbable) emulsion of frozen and unfrozen water, fat globules, other solids, and air. The only things stopping it from deflating spontaneously are the network of ice crystals, and whatever viscosity the emulsified fats and any stabilizing ingredients give to the liquid. Time, and especially warming and cooling cycles (like the self-defrosting of the freezer, and taking the ice cream out and putting it back) all conspire to deflate the foam. These factors also lead to the ice crystal structure changing, and the ice cream getting grainy.

Commercial ice creams use stabilizers (usually tiny amounts of gums like guar, carob bean, and carageenan) and strong emulsifiers like diglycerides to give them shelf life. They also use mixes of sugars that include things besides sucrose, for their influence on texture and stablilty.

Home made ice creams usually rely on lots of cooked egg yolk (the lecithin and other chemicals are emulsifiers), very high butterfat, and the fact that the stuff rarely sticks around more than a few minutes after you make it.

I'm noticing that pastry chefs often take a middle path ... using some commercial ingredients like powdered glucose, starches and gums, etc... They seem less interested in long shelf life than in being able to get perfect textures without relying on a french custard base and lots of fat in all their recipes.

[djyee100]

I've encountered only one set of ice cream recipes that require serious beating of the egg yolks and sugar before adding them to the base, and those are the gelato recipes in Pamela Sheldon Johns' Gelato! cookbook. Her recipe for Custard Gelato is reprinted here: http://www.epicurious.com/recipes/food/vie...D-GELATO-103830

As you can see, her recipe (typical of other gelato recipes in her book) contains a high proportion of milk to cream. Some of her gelato recipes have no cream at all. I'm guessing that the heavy-duty beating of the egg yolks and sugar, not to mention the whipped cream added later, make for the lightness and creaminess of her gelati. The texture is very fine, creamy but not as heavy as high butterfat ice creams.

I don't know the science whys and wherefores behind beating the egg yolks and sugar, but I'd love to find out (Paul?).

I was introduced to these gelati when I assisted a pastry chef in her prep for a corporate dinner. Even though the recipe says to use a blender, she had me beat those egg yolks and sugar for a good 10 mins or so with a hand mixer (a KitchenAid is OK too), and she was careful that the mixture was light and voluminous when I was done. In her experience, that gave the best results for these gelati.

[Morfudd]

One of the main differences between gelato and ice cream is the amount of butterfat in it, and the temperature at which it is served. Gelato recipes often have little or no cream in them at all (in Italy this varies regionally) and are essentially a creme Anglaise. Because gelato has a lower fat content, it wont have as extensive a fat membrane structure, and so less air will be 'trapped' in the custard as it is being churned. It will therefore be denser than an ice cream with a higher fat content, and less rich.

Gelatos often seem more flavour intense than ice creams. Again this is because they have a lower fat content and diffuse the perception of flavour quicker to the taste receptors than a creamier ice cream where the cream coats the tongue with melting fat globules, slowing down the transfer and perception of flavour to the taste receptors.

Paul thank you for your comments re the whipping and also on the shrinkage. But if an ice cream is put in a sealed container, is that sufficient to prevent loss of moisture, or does it need both the sealed container and the waxed or greasproof paper ? Presumably the water is not migrating onto the existing ice crystals, but being lost in the atmosphere?

[Morfudd]

Actually thanks chefpeon too for your comments on shrinkage. do you know the answer to my last question?

[paulraphael]

But if an ice cream is put in a sealed container, is that sufficient to prevent loss of moisture, or does it need both the sealed container and the waxed or greasproof paper ? Presumably the water is not migrating onto the existing ice crystals, but being lost in the atmosphere?

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My guess is that sealing the surface with plastic wrap is mostly to prevent freezer burn (which is what Chefpeon is talking about). It can help prevent the surface from dehydrating, and ice crystals from growing on it, and also help keep flavors fresh.

I doubt this will do much for shrinkage. Or with changes in overall texture, both of which seem to have more to do with the recipe and with consistency of freezer temps.

Edited June 6, 2008 by paulraphael (log)

[paulraphael]

Because gelato has a lower fat content, it wont have as extensive a fat membrane structure, and so less air will be 'trapped' in the custard as it is being churned. It will therefore be denser than an ice cream with a higher fat content, and less rich.

It might be interesting for your purposes to contrast some typical northern Italian recipes (higher fat, more yolks, more similar to French ice cream) with southern recipes (lower fat, often no cream or yolks, and often stabilized with cornstarch ... sometimes with a lot of it).

[Morfudd]

Paul it would be interesting to do a comparison as you suggested, though so far what I have discovered is that in Northern Italy they do have higher fat content in their recipes by using cream and of course the egg yolk content goes up because these are needed to emulsify the fat and provide the protein casing displaced during the fat destabilisation process of churning. In the south, the fat content is lower but sometimes egg yolks are still used in quite high quantities to make a rich creme anglaise, and also I suppose the egg yolks provide an increase in fat that isnt provided by the cream, but these are still more like what people regard as gelatos, as they are denser than the French style ice creams.

I have looked at loads of Italian recipe books and although it varies regionally, there appears to be a lot of just personal preference as well, regardless of the provenance of the writer.

The cornstarch you mention (I presume you mean corn syrup - in Britain we call it glucose syrup) does have stabilizing effects because it is highly viscous and ties up water in the mix, preventing some of the unfrozen water that always remains in an ice cream from migrating onto the existing crystals and creating a course texture. It also has a different sweetening capacity to sucrose, and gives more length to the sensation of sweetness than sucrose. I always include glucose syrup in both my ice cream recipes as well as my sorbets for this reason.

Egg yolks have a different purpose as they have emulsifying properties and are needed as a sort of liquid casing to prevent the destabilised fat from coagulating. If a recipe calls for little cream but lots of egg yolks, I presume it is because they want to achieve the richness provided by the egg yolks; the yolks are not needed to stabilise the fat as milk is obviously much lower in fat than cream.

Am I making any sense, or rambling on?

Maybe you can answer another question for me.

You have explained to me why the egg/sugar mix is thoroughly whisked in order to dissolve the sugar. But why do we bother with mixing the eggs with the sugar in the first place if the sugar is going to be dissolved in the heated milk/cream mix in the first place?

Why not just stick the sugar in with the milk and cream mix and whip the eggs up separately?

[pastrygirl]

I whisk my yolks and sugar, but just until combined. Even if you do want to whip a lot of air into your ice cream, wouldn't the bubbles pop when heated then strained? Maybe not 100%, but I like a dense ice cream, so whipping until pale seems like a big waste of time to me.

I agree with Paulraphael's thermal mass theory. If you add the sugar to the cream, it will raise the boiling point of the cream, so it will be extra hot and you'll really need to be careful tempering it ino the yolks. With the yolks and sugar combined, I think the sugar acts as a buffer. I dump the entire pot of boiling cream onto my whisked yolks and sugar, whisk, then back in the pot to nape'. The only time I've ever scrambled eggs by pouring hot cream on was making caramel ice cream, where all of the sugar was carmelized and in the liquid and the egg yolks were naked.

And I cook my ice cream on high. why stand there and stir for 15 minutes on low when you can get it done in 2 minutes on high?

[paulraphael]

The cornstarch you mention (I presume you mean corn syrup - in Britain we call it glucose syrup)

actually, I mean cornstarch. it's a common stabilizer in eggless, lowfat ice creams and gelatos. It's not mentioned in any of your books?

You have explained to me why the egg/sugar mix is thoroughly whisked in order to dissolve the sugar. But why do we bother with mixing the eggs with the sugar in the first place if the sugar is going to be dissolved in the heated milk/cream mix in the first place?

Why not just stick the sugar in with the milk and cream mix and whip the eggs up separately?

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That's what Lebovitz was anwering for me. He said in his experience it made no difference at all, just as you suspect.

Personally, I whisk the sugar into the yolks when I'm using enough of them to disolve the sugar. Mostly out of habit, i guess. Otherwise I whisk it into the milk.

[merstar]

The cornstarch you mention (I presume you mean corn syrup - in Britain we call it glucose syrup)

Morfudd, cornstarch in the U.S. is the same as cornflour in the UK.

Edited June 7, 2008 by merstar (log)

[ruthcooks]

The best way to tell if the sugar is truly dissolved is to take a bit and rub it between your forefinger and thumb. If dissolved, it will feel smooth. If not, you will feel the tiny granules and need to beat it more. This is an important techinque to know when making other dishes, but ice cream? Not so much if it's going to be heated anyway.

[Morfudd]

I have just been e mailing a dairy scientist in Canada and he says that the reason for whipping the sugar and eggs together is that the sugar does actually help to stabilize the foam. So Paul you were right.

Lebovitz does mention corn starch in his recipes but does not mention it in his ingredients list, although he does mention corn syrup.

[paulraphael]

I have just been e mailing a dairy scientist in Canada and he says that  the reason for whipping the sugar and eggs together is that the sugar does actually help to stabilize the foam.

Does he mention this in the context of ice cream? Stable foam is important for some things, like flourless chocolate cakes, but I'd think that any foam you make would vanish when you incorporate it into the crem anglaise for ice cream. Which I think is why you can incorporate the sugar any way you like with ice cream (but not everything).

Lebovitz does mention corn starch in his recipes but does not mention it in his ingredients list, although he does mention corn syrup.

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here's Lebovitz's short essay on gelato, where he mentions cornstarch: http://www.davidlebovitz.com/archives/2007...ats_gelato.html

[PassionateChefsDie]

I have to admit I agree with the earlier post the only reason to do it.. Is to stop scalding the eggs I presume the addition of sugar and air create enough of a buffer that you don't scald them.

Makes sense Mcgee has Yolks starting to set at 66°c taking that milk is close on 100°c scalding could/should occur.

Edited June 9, 2008 by PassionateChefsDie (log)

[Morfudd]

Yes Professor Goff does talk about the stabilization in an ice cream context. He says that whipping the eggs and sugar together helps stabilize the foam and creates a better foam structure once it is tempered with the milk and cream and returned to the saucepan for cooking. Whether actual experiments have been carried out to compare the structure of an ice cream with eggs whipped alone versus eggs whipped with sugar I dont know.

[pastrygirl]

Yes Professor Goff does talk about the stabilization in an ice cream context.  He says that whipping the eggs and sugar together helps stabilize the foam and creates a better foam structure once it is tempered with the milk and cream and returned to the saucepan for cooking. Whether actual experiments have been carried out to compare the structure of an ice cream with eggs whipped alone versus eggs whipped with sugar I dont know.

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But why would you want foamy ice cream? I 'm pretty sure I don't.

[abooja]

One additional reason for beating egg yolks until they are pale, at least in vanilla ice cream, is to make them appear less shockingly yellow in the finished product.

[tim]

But why would you want foamy ice cream?  I 'm pretty sure I don't.

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He (Professor Goff)  says that whipping the eggs and sugar together helps stabilize the foam and creates a better foam structure ... for cooking.

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[pastrygirl]

But why would you want foamy ice cream?  I 'm pretty sure I don't.

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He (Professor Goff)  says that whipping the eggs and sugar together helps stabilize the foam and creates a better foam structure ... for cooking.

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Thank you Tim, but I did actually read Morfudd's post before I replied with quote.

I find foaminess undesireable in ice cream. I like a dense ice cream, therefore I am interested neither in creating a foam nor stabilizing it. I find that my gelato maker incorporates enough air that I don't want to whip more into the eggs. It just seems to me like a pointless waste of time to beat your yolks and sugar until light and fluffy. Those gelato shops where everything has the consisitency of meringue are extremely displeasing to me, no matter how authentic they may be. I want superpremium, low-overrun, dense and almost chewy ice cream, not a mouthful of foam. Oddly enough, I do enjoy putting various semi-liquids in my ISI canisters and making foams, and I find a savory foam on a restaurant menu a selling point more often than a deterrent, yet I do not aspire to make foamy ice creams. (I did enjoy the frozen foam on the anti-griddle at el Bulli, but that is the exception to the rule). See?

Am I really strange and everyone else likes fluffy ice cream? Now I need to know.

Edited June 11, 2008 by pastrygirl (log)

[paulraphael]

One additional reason for beating egg yolks until they are pale, at least in vanilla ice cream, is to make them appear less shockingly yellow in the finished product.

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Hmmm, I never thought of that one. This should work even without sugar, right?