I've been working on improving my home made ice-cream and was wondering if anyone knew how to get more air into the mix. The ice-cream is great right out of the maker, but once I put it in the freezer to firm up a bit it becomes very dense.
Is it a matter of running the maker longer? making smaller batches?
Thanks for the suggestions
I'm seeing several answers that seem to be tiptoeing around the problem but not quite hitting it head-on...
If you have time, have a look at this Serious Eats article, The Food Lab: Real Ice Cream Without an Ice Cream Machine. Although it's about making ice cream without a machine, many of the principles apply to machines as well, because the problem you're experiencing is the same as those experienced by those without ice-cream makers: Ice crystal formation.
Contrary to what Chef's answer says, you do not need to keep ice cream at above-freezing temperatures in order to prevent crystals. As Mollie has correctly pointed out, that is precisely the purpose of overrun; the airier the ice cream, the less opportunity there is for ice crystals to form. But that's not the whole story. You don't just need to incorporate air, you need to keep it dispersed so that that the liquid never gets too dense in one place.
Ice-cream makers are supposed to do both of these things. By churning the cream while it freezes, it keeps the mixture dispersed and introduces more air (overrun).
It sounds to me like what's happening is that your ice-cream maker is simply not getting cold enough. If it actually brought the temperature of the ice cream to zero or below, then the consistency would not change after putting it into an actual freezer. So you're getting not-quite-freezing ice cream out of the ice-cream maker which is great, but then you're putting it in a freezer where that not-quite-frozen liquid is forming large ice crystals as it freezes for real.
So your solutions to this problem are:
Invest in a higher-end ice cream maker that chills better (this may or may not be practical).
Introduce extra overrun by pre-whipping the cream before putting it into the machine. Whip it until soft peaks form, then fold it into the mixture (don't stir!). You can do the same with the egg whites as well. This may give you an undesirable amount of overrun, like the 94% that's in Breyer's, but it will make it almost impossible for crystals to form.
Flash-freeze it with dry ice or liquid nitrogen. This may not be practical either but is the surest way to prevent ice crystals from forming, since the main thing crystal formation requires is time.
If you can't flash-freeze, then try packing the churned ice cream into ice trays as Kenji (Serious Eats) does with the "raw" ice cream, then give it a whirl in a food processor once it's frozen.
Finally, one thing that even Serious Eats neglected to mention is to use a stabilizer. Xanthan gum is great for ice cream and will help keep it at "whipped" consistency while it's in the freezer. You don't need a lot - use about 0.5% of the total weight at most. Stabilizers in particular are what will allow you to freeze the ice cream for longer, and prevent that 1-2 day "expiration date" that was mentioned by an earlier answer.
Any or all of these things will improve the smoothness of the ice cream and help it to survive the freezing process.
Fat, fat, fat! You need something to keep the water content of the ice cream from forming a big block when it freezes. Commercial ice cream is made in freezers that inject air, thus making them fluffy--the amount of air injected is called overrun.
Since you don't have an air-injection system, your best bet to separate those little ice crystals is to have more fat in the ice cream. It will incorporate more air as it churns, but the fat itself will also make it softer by separating the water droplets. Not too friendly on the hips, but oh, such a wonderful mouthfeel. Try using heavy cream in the mixture.
One other factor may actually be fiber. I have a recipe for a pineapple sorbet that stays scoopable after freezing completely in the freezer. The recipe is simple--1 medium fresh pineapple cut up, 1 1/8 cups sugar and 2 Tbsp. lemon juice. All are pureed in a food processor, then put into the ice cream maker (the small 1 1/2 qt. kind). There is no fat, but it stays easy to scoop and eat. My conclusion is that it must be the fiber in the fresh pineapple.
what about beating it in a mixer before putting in in the ice cream maker? you just want to introduce air into the mixture.
the best ice cream makers agitate the mixture and scrape frequently, thus air gets incorporated into the mixture as it freezes.
I make icecream using one of those frozen bowl systems in my home freezer (-18deg) and it comes out scoopable. I've found the biggest difference is the whipped eggwhites. If you whip them to fine firm whites and base your icecream on that then it should be quite scoopable.
The longer you leave it frozen the harder it will get though. 24-48 hours is ok. After a week it solidifies - which is where the higher fat content would help.
Ian
the big problem is that your home freezer is too cold. natural ice creams are a combination of small frozen ice crystals, fat, sugar and water. the sugar and fat lower the freezing point of the water, but it's still a semi-liquid mixture.
When you stick the mixture in the freezer, you lower the freezing point and freeze the whole thing solid.
you'll notice that ice cream shops serving freezers' aren't bone chilling cold...there's a reason for that.
you can try raising the temp of your freezer.
you'll notice if you let the ice cream thaw a little and then mix it up, it'll be a more palatable texture.
Comercial ice cream machines have a pump to force the air into the mix as it freezes, unfortunately, although not impossible, I cant find any manufacturer who makes one. That leaves using a Magimix or equivalent hand beater. When you heat your mix use the beater in the saucepan as it heats, (the Magimix is made for this purpose I don't know about other makes) After the mix is cool beat it again before churning, using a long thin jug, so it doesn't splash,keep pulling from the bottom to the top and lay to one side as much as you can to allow the air to go in, for a good 5 mins. I stop the machine 3 or 4 times while churning and beat again while in the machine. You must remember that commercial machines cost thousands of pounds so you can only improve and not get 100% results.
Tips. To make your ice cream serve softer, you need to use products in the mix that do not freeze, try using one or some of these. (per litter of mix) a generous pinch of sea salt, 2 tea spoonfuls of Gelatine,or 1 shot or two of alcohol or some good virgin olive oil. Flavouring your ice cream with liquors is good as it flavours and stops freezing at the same time.If you put fruit into your ice cream always soak it in alcohol, if you don't want a flavour use Vodka. This is an adult guide not for kids. Keith Tunkin.
Air will give you volume and some different texture. But for really improving the texture I do that for one litter of cream (i.e., the mix you want to freeze) that varies between 8% and 15% of fat (I tend to put 11%, 14% for vanilla or chocolate flavors). Oh yes, always use pure cream which is usually the case with organic cream. Creams that are sold at the general grocery have often texture agent that will make your ice cream snowy, flaky with large crystals:
Beat 1 to 2 egg yolk with some sugar to make ribbon (yolk become white and thick). Heat your mix to 149°F (but not much, otherwise it will cook the egg yolk) then add the "ribboned" yolk stirring very gently. Water molecules will bind with the egg yolk between 140 and 149°F. It will change your ice cream with a smoother and creamier texture. (P.S. I simplified the explanation as this is a little bit more complex chemistry reaction)
The airiness of ice cream (overrun) depends on the churning speed. The quicker your machine's paddle turns, the more overrun you get, it's that simple.
Unfortunately, I haven't seen machines which allow you to adjust the speed. In general, standalone machines are rather slow turning, and attachments for stand mixers are supposed to turn much faster and produce more overrun. So see if you can get it fluffy with another machine (maybe try your base in a friend's home who has the attachment, before spending money on it).
