Perhaps the most rewarding thing about homemade ice cream, aside from the sheer delight of churning up something even more delicious than the store-bought stuff, is its potential for customization. Once you've got the flavor of the base locked down, whether through extracts or infusions, the freshly churned ice cream can be rippled with all kinds of fruity swirls.
Commercial jams and jellies are a perfectly legitimate option for swirling, as are homemade preserves, since most have been cooked to a temperature of about 220°F, resulting in a relatively high sugar/low moisture product, which means that it will freeze quite well. But if you plan on taking advantage of the market's seasonal bounty, it pays to have a game plan for transforming fresh fruit into something that will freeze just as well as the jams, jellies, and preserves you might find on a supermarket shelf.
While most folks will never be challenged to whip up a fresh raspberry ripple gelato on the fly, as was the case during my farmers market adventure with Sohla, anyone who enjoys homemade ice cream will appreciate having a go-to technique for dealing with fresh fruit.
Thanks to its high water content and its penchant for freezing solid, plain fruit needs a bit of help before it can be swirled into ice cream. This helps comes in the form of sugar and heat: The addition of sugar will lower the freezing point of any fruit purée, and the application of heat will reduce the amount of water in the purée that's available to freeze in the first place.
Not only will this ensure the ribbon in your ice cream is saucy and smooth when frozen, it also gives it a thick-bodied consistency that makes it easier to swirl in the first place. Fresh fruit purée is inclined to run, drip, or pool in the bottom of the pan, or else simply homogenize into the ice cream when stirred. A thick, syrupy ribbon, on the other hand, will stay put and remain distinct, even after a bit of stirring, for beautiful scoops with a fruity ripple.
How to Make a Fresh Fruit Syrup for Ice Cream
Start by preparing those juicy fruits; peel peaches, remove the leafy caps from strawberries, pit cherries, core a pineapple, you get the idea*.
For fruits with a thick skin like cherries, or fibrous flesh like mango, purée with an immersion blender before getting started.
*For this style of syrup, avoid fruits with a moisture content below 80%, such as bananas and figs (when in doubt, ask Google or check a reference guide such as How to Dry Fruits). It's not that they can't be used in a ripple, only that they require a different technique, which I won't be touching on here.
Tender fruits like peaches, blueberries, and blackberries can simply be mashed into a purée with the other ingredients (I prefer the sharp edge of a metal spatula over a potato masher, which tends to encourage splattering as the plump fruits burst).
To minimize the sweetness of the syrup, it helps to start with lightly toasted sugar, since it tastes less sweet than plain. Of course, a generous pinch of salt will go a long way as well.
Otherwise, raw and semi-refined sugar styles can be a great way to reduce perceived sweetness if you have something that sounds like it will pair nicely with the fruit, such as jaggery and pineapple. For more info, consult our guide to raw sugars.
I also recommend adding a splash of something acidic to brighten the fruit's profile, which will seem duller once frozen. Lemon juice is a near universal complement, but this is a fantastic occasion to play with funky vinegars to create more depth of flavor; the Serious Eats Guide to Vinegar will get you started if you need some ideas.
Before cooking the syrup, tare a digital scale and make note of the total starting weight (including the pot itself). This info makes it a snap to track the reduction without a thermometer, as you can check to see exactly how much water has been cooked off.
Using a scale is an especially useful trick for making small batches that don't have enough depth to accommodate a probe. (Surprise: tipping the pan to the side to create more depth for a thermometer will always produce artificially low readings.)
For a thick and gooey swirl that won't drip when scooped up with the ice cream, I like to cook off about five ounces of water from a batch this size (to about 224°F). For a slightly thinner swirl that gets a little saucy as it melts, I'll cook off just four ounces, instead (to about 220°F). Given the small amount of syrup, I find weight to be the quickest, most reliable way to monitor the reduction, but if you have enough depth to achieve an accurate read on a digital thermometer without tipping the pan, that certainly works too.
However you go about the reduction, the finished syrup can be strained for a smoother consistency, or left as-is for those who enjoy the natural texture of seeds and pulp in the fruit.
Amplify the Aroma
As a final step, I like to doctor the syrup with an aromatic to complement and amplify the fruit's natural flavor. The goal isn't to taste the additive itself, but to coax out a stronger aroma to overcome the muting effect that freezing temperatures can have on our palate. A little like adding a pinch of nutmeg to make béchamel seem even more buttery.
Some examples would include a bit of rose water for strawberry, orange blossom water for blueberry, elderflower cordial for raspberry, a few drops of almond extract for cherry or peach, and a hint of vanilla with pineapple.
I've sussed out most of these pairings through trial and error (I've been at this for a while), but if you're not sure where to start, The Flavor Thesaurus can be an invaluable guide.
How to Incorporate a Fruit Swirl
Sure, frozen ice cream (whether homemade or store-bought) can be softened to swirl with fruit, but semi-melting and refreezing ice cream doesn't do it any textural favors. If frozen ice cream is all you've got, it's far better to use the fruit syrup as a sauce instead.
For the the most striking ripple, layer the cooled syrup and freshly churned ice cream into a heavy glass or ceramic dish that's been chilled down to 0°F. I like to use a 2-quart baking dish, as this makes it easier to drizzle the syrup over the wide, flat swaths of ice cream.
You can drizzle the thick syrup over the ice cream with a fork or spoon to produce a ribbon with random variations in thickness. Or, if you'd prefer to have a bit more control, the syrup can be transferred to a disposable pastry bag to create a perfectly uniform ribbon.
After you've layered all of the ice cream into the pan, along with as much or as little of the syrup as you prefer, you can gently stir the whole thing a spatula.
This is nice for creating zones of plain and marbled ice cream, in addition to the bands of gooey syrup. However, if you prefer to keep the ice cream pure, with a distinct ribbon of syrup running throughout, don't bother to fold or stir the layered ice cream.
Can I Use Less Sugar?
In a word, no.
With any syrup cooked above 212°F, the final cooking temperature is a direct reflection of the water content/sugar concentration. Even though this particular technique involves monitoring the syrup's water loss by weight rather than temperature, it's just the other side of the same coin.
When using less sugar, the syrup will simply take longer to reduce, because its water content will be relatively higher to start. By the time the same amount of water has boiled away, it will have an identical sugar concentration compared to a recipe that started with more sugar. In short, using less sugar won't make a syrup less sweet, it will only make less syrup.
Starting with lightly toasted sugar is the easiest way to reduce sweetness, but the judicious use of salt, acid, and aromatics will go a long way toward creating a greater depth of flavor that will, in turn, make the syrup seem less sweet. It can also be helpful to add an extra pinch of salt to the ice cream itself, since the base recipe was likely not formulated with the inclusion of syrup in mind.
With a few minor adjustments, a basket of fresh fruit can be quickly transformed into a thick, saucy ribbon for swirling into your favorite ice cream.