The Art and Science of Ice Cream
Jan. 28th, 2012 02:55 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
kerravonsenPeople have upon occasion asked about the strange chemical-sounding things I put in my ice cream recipes. Now, part of that is because for some things I prefer using the chemical name because it has many different brand-names depending on who is selling it, so for those things I think it will be less confusing if I use the chemical name. But that begs the question of why I'm using those substances in the first place.
So bear with me while I discuss ice-cream making, and the reasons behind my choices of ingredients.
Now, most people who make ice cream just find recipes that they like, and stick to that. But me, I was looking for the Holy Grail: an ice-cream that was both low-calorie and tasted good. Which means that I was trying to make my own recipes, as well as adapt existing recipes. And if one makes one's own recipes, one has to understand the process much more.
Most ice-cream recipes use cream and/or eggs, plus sugar and flavouring. Most sorbet recipes use fruit (or some other flavour base) and lots of sugar. Some sorbet recipes use alcohol. Which ingredients are essential? What parts do they play in the mixture?
I did lots of googling, looking for both low-calorie recipes, and for more about ice-cream making itself. I'm afraid I can't recall the URL of the site which gave me the first insight into the science behind ice-cream, but it was a revelation.
In order for ice-cream to work, the mixture must have a lower freezing temperature than water, but not too much lower.
Why? Because if the mixture is too like water, then one won't get ice-cream, one will get ice. So the freezing temperature has to be lower than water, so that the mixture won't freeze solid. On the other hand, it can't be too much lower, or the mixture won't freeze sufficiently, and you'll get a kind of slush. Believe me, I've had both things happen in the course of my experiments. The ideal mixture is one that will create tiny ice-crystals and bubbles of air all bound together; not too soft and not too hard.
One of the things that gets confusing in ice-cream making is that a number of the ingredients have multiple roles, such as sugar. People assume that the sugar is just for sweetening, so they substitute the sugar with some other sweetener, and are surprised when it doesn't work. That's because the sugar isn't just for sweetening. Likewise with the cream; it isn't there just to be creamy.
They both lower the freezing temperature of the mixture.
On the site where I got my revelation, the writer said that there were three ingredients that lowered the freezing temperature of the mixture:
Alcohol is the most effective at this, so recipes which use alcohol generally have 3-5 tablespoons of it. Sugar is the least effective, which is why sorbet recipes (which don't have cream and thus don't have the fat from the cream) generally use two cups of sugar, and therefore often add lemon juice to the mixture in order to cut down the sweetness of the sugar.
Non-sugar sweeteners may be just as sweet as sugar, but they don't have the same chemical properties as sugar, or as each other, either.
The following are the major non-sugar sweeteners I know of:
It was when I was looking into non-sugar sweeteners (I love Wikipedia!) that I had my second Eureka moment.
If Xylitol and Erythritol are chemically "sugar alcohols", then might they have a similar effect in ice cream as sugar and/or alcohol?
And I was right. They do. Their effect on the freezing temperature of the mixture is closer to that of alcohol than that of sugar, which means that one can think in terms of tablespoons rather than cups, which makes them brilliant for making sorbets even if one wasn't trying to reduce calories.
Which ones I use and how much of each depends on what I'm trying to do. If I have a mixture which is already as sweet as it needs to be, I use straight Erythritol, because of its lower sweetness. For other things I'm still figuring out the ideal mix. Xylitol has the advantage of being cheaper than Erythritol, but I don't want to use too much or I will be sitting on the loo after my lovely ice cream. Erythritol has the advantage of not affecting the digestion like that, but being more expensive and not as sweet, so sometimes I'll add Splenda purely for the sweetness. I also don't want to add only Xylitol or Erythritol because of their aftertaste; having a blend of different sweeteners helps mitigate that. Natvia is a blend of Stevia and Erythritol, which means it has the sweetness plus the properties of Erythritol. Natvia also has the advantage that I can buy it in the supermarket, while Erythritol and Xylitol I can only get from health food stores. And of course all of them are more expensive than plain ol' sugar. But for me, it is worth it.
Okay, so that answers the questions about Xylitol, Erythritol and Natvia. What about "Xanthan Gum" and "Guar Gum"? They are an attempt to solve another problem: ice cream that becomes rock-hard after it's been left in the freezer. Home-made ice creams have this problem while commercial ice creams don't, precisely because they add such things. Look at the fine print of the ingredients list on a commercial ice cream. You'll find "vegetable gums" and/or "thickeners" and/or "gelatine" in the list. The purpose of these isn't just to thicken the mixture, it's to help stabilize it and keep the air bubbles in it when the ice cream is in the freezer for a long time. I haven't mastered the ideal mix and amount of vegetable gums yet, but I do find that they help prevent the ice cream from becoming un-scoopable when it's been frozen after being freshly made. But if I add too much, then the ice cream tastes gummy and sometimes even like a kind of frozen marshmallow, not like ice cream at all.
Home-made ice cream is always nicest when it's freshly made, but with a household of one, it would be foolish to try to eat a litre of ice cream as soon as it's made. (My ice cream machine has a capacity of about a litre).
The "scoopability" problem is more pronounced with sorbet than with ice cream, because the dairy (even if it's yoghurt or milk rather than cream) does help with the texture and creaminess and scoobability. The trade-off between ice cream and sorbet is usually that ice cream has a creamier texture, and sorbet has a more intense flavour. I've found that mangos and bananas make the best sorbet, because those fruits have a natural "creaminess" to their texture, so one gets the best of both worlds.
Another ingredient you might see me adding to sorbet is Inulin, which is sugar-polymer, a soluble fibre; it is low-calorie and adds bulk. Its purpose in the mix is to give the sorbet a creamier texture (like the fibre in mangos and bananas do) but one needs to be careful in how much one uses, because too much can give one painful gas in the gut, as I discovered for myself with one particular sorbet experiment. I suppose that makes me one of those scientists who experiments on themselves. ;-)
Onward! Upward! The quest continues!
So bear with me while I discuss ice-cream making, and the reasons behind my choices of ingredients.
Now, most people who make ice cream just find recipes that they like, and stick to that. But me, I was looking for the Holy Grail: an ice-cream that was both low-calorie and tasted good. Which means that I was trying to make my own recipes, as well as adapt existing recipes. And if one makes one's own recipes, one has to understand the process much more.
Most ice-cream recipes use cream and/or eggs, plus sugar and flavouring. Most sorbet recipes use fruit (or some other flavour base) and lots of sugar. Some sorbet recipes use alcohol. Which ingredients are essential? What parts do they play in the mixture?
I did lots of googling, looking for both low-calorie recipes, and for more about ice-cream making itself. I'm afraid I can't recall the URL of the site which gave me the first insight into the science behind ice-cream, but it was a revelation.
In order for ice-cream to work, the mixture must have a lower freezing temperature than water, but not too much lower.
Why? Because if the mixture is too like water, then one won't get ice-cream, one will get ice. So the freezing temperature has to be lower than water, so that the mixture won't freeze solid. On the other hand, it can't be too much lower, or the mixture won't freeze sufficiently, and you'll get a kind of slush. Believe me, I've had both things happen in the course of my experiments. The ideal mixture is one that will create tiny ice-crystals and bubbles of air all bound together; not too soft and not too hard.
One of the things that gets confusing in ice-cream making is that a number of the ingredients have multiple roles, such as sugar. People assume that the sugar is just for sweetening, so they substitute the sugar with some other sweetener, and are surprised when it doesn't work. That's because the sugar isn't just for sweetening. Likewise with the cream; it isn't there just to be creamy.
They both lower the freezing temperature of the mixture.
On the site where I got my revelation, the writer said that there were three ingredients that lowered the freezing temperature of the mixture:
- sugar
- fats/oils
- alcohol
Alcohol is the most effective at this, so recipes which use alcohol generally have 3-5 tablespoons of it. Sugar is the least effective, which is why sorbet recipes (which don't have cream and thus don't have the fat from the cream) generally use two cups of sugar, and therefore often add lemon juice to the mixture in order to cut down the sweetness of the sugar.
Non-sugar sweeteners may be just as sweet as sugar, but they don't have the same chemical properties as sugar, or as each other, either.
The following are the major non-sugar sweeteners I know of:
- Saccharine: the oldest modern sugar substitute, it has a bitter aftertaste. (various brands)
- Aspartame: negligible calories, breaks down, short shelf-life (brands: NutraSweet, Equal)
- Sucralose: negligible calories, derived from Sucrose (sugar), has the closest taste to sugar, is usually sold as a mix of Sucralose and Maltodextrin, the Maltodextrin is used for bulk (brand name: Splenda)
- Stevia: negligible calories, derived from the leaves of the Stevia plant, has a slight aniseed aftertaste, the bulking agent varies depending on the brand, often Maltodextrin, sometimes Erythritol (brands: Nirvana Stevia, Equal Stevia, SweetLeaf, Wonder Foods Stevia, Sandra Cabot Stevia, Natvia, NuStevia...)
- Xylitol: a sugar-alcohol, has a menthol aftertaste, 2/3 the calories of sugar, but spoon for spoon as sweet, so no need for a bulking agent, usually extracted from corn husks (USA) or birch (Europe), excessive usage can have an uncomfortable effect on the digestive system (bloating, flatulence, or diarrhoea) (brands: Perfect Sweet, Health Reflections Xylitol, Naturally Sweet, Nusweet, Xylo Sweet, Ultimate Sweetness...)
- Erythritol: another sugar-alcohol, negligible calories, 2/3 as sweet as sugar, menthol aftertaste, does not have the side-effects of other sugar-alcohols (brands: NoCal, Natvia, VitaSweet, Ausweet Erythritol...)
It was when I was looking into non-sugar sweeteners (I love Wikipedia!) that I had my second Eureka moment.
If Xylitol and Erythritol are chemically "sugar alcohols", then might they have a similar effect in ice cream as sugar and/or alcohol?
And I was right. They do. Their effect on the freezing temperature of the mixture is closer to that of alcohol than that of sugar, which means that one can think in terms of tablespoons rather than cups, which makes them brilliant for making sorbets even if one wasn't trying to reduce calories.
Which ones I use and how much of each depends on what I'm trying to do. If I have a mixture which is already as sweet as it needs to be, I use straight Erythritol, because of its lower sweetness. For other things I'm still figuring out the ideal mix. Xylitol has the advantage of being cheaper than Erythritol, but I don't want to use too much or I will be sitting on the loo after my lovely ice cream. Erythritol has the advantage of not affecting the digestion like that, but being more expensive and not as sweet, so sometimes I'll add Splenda purely for the sweetness. I also don't want to add only Xylitol or Erythritol because of their aftertaste; having a blend of different sweeteners helps mitigate that. Natvia is a blend of Stevia and Erythritol, which means it has the sweetness plus the properties of Erythritol. Natvia also has the advantage that I can buy it in the supermarket, while Erythritol and Xylitol I can only get from health food stores. And of course all of them are more expensive than plain ol' sugar. But for me, it is worth it.
Okay, so that answers the questions about Xylitol, Erythritol and Natvia. What about "Xanthan Gum" and "Guar Gum"? They are an attempt to solve another problem: ice cream that becomes rock-hard after it's been left in the freezer. Home-made ice creams have this problem while commercial ice creams don't, precisely because they add such things. Look at the fine print of the ingredients list on a commercial ice cream. You'll find "vegetable gums" and/or "thickeners" and/or "gelatine" in the list. The purpose of these isn't just to thicken the mixture, it's to help stabilize it and keep the air bubbles in it when the ice cream is in the freezer for a long time. I haven't mastered the ideal mix and amount of vegetable gums yet, but I do find that they help prevent the ice cream from becoming un-scoopable when it's been frozen after being freshly made. But if I add too much, then the ice cream tastes gummy and sometimes even like a kind of frozen marshmallow, not like ice cream at all.
Home-made ice cream is always nicest when it's freshly made, but with a household of one, it would be foolish to try to eat a litre of ice cream as soon as it's made. (My ice cream machine has a capacity of about a litre).
The "scoopability" problem is more pronounced with sorbet than with ice cream, because the dairy (even if it's yoghurt or milk rather than cream) does help with the texture and creaminess and scoobability. The trade-off between ice cream and sorbet is usually that ice cream has a creamier texture, and sorbet has a more intense flavour. I've found that mangos and bananas make the best sorbet, because those fruits have a natural "creaminess" to their texture, so one gets the best of both worlds.
Another ingredient you might see me adding to sorbet is Inulin, which is sugar-polymer, a soluble fibre; it is low-calorie and adds bulk. Its purpose in the mix is to give the sorbet a creamier texture (like the fibre in mangos and bananas do) but one needs to be careful in how much one uses, because too much can give one painful gas in the gut, as I discovered for myself with one particular sorbet experiment. I suppose that makes me one of those scientists who experiments on themselves. ;-)
Onward! Upward! The quest continues!
