Homemade Raspberry and Watermelon Ice Cream That Won’t Freeze Solid

So, you want to make fruit ice cream at home but it always turns into a solid block of ice? The trick is to think about the fruit like you would a custard base. You need to get rid of some of that water and let fat and sugar do their thing. If you just blend fresh fruit and freeze it, you end up with something like a rock-hard sorbet. What we're doing here is roasting the watermelon first, using frozen raspberries, and blending it all with a ripe banana and some full-fat Greek yoghurt with a bit of lime. You get this no-churn, low-sugar ice cream you can actually scoop out after a couple of hours. It's brighter and cheaper than the stuff from the shop, and honestly, once you see why it works, you'll get it.

Why fruit ice cream always freezes into an ice block (unless you intervene)

Right, so the problem is water. Ripe watermelon is over 91 per cent water, raspberries are nearly 86 per cent. When you put that much free water into a home freezer set to minus eighteen degrees celsius, you get massive ice crystals you can crunch on. I read on the Creamerie blog that it's the crystal size that decides if it feels smooth or rough. Big crystals mean icy, small ones mean creamy. Big manufacturers use all sorts of stabilisers and fast churners to keep those crystals tiny. We're not doing that.

What we're doing instead is borrowing a couple of ideas from ice cream science. First up, fat. It physically gets in between the water molecules and slows down crystal growth. That's why a fattier mix feels creamier – the CourseHorse guide on ice cream texture makes this point well. Then there's sugar. It's what's called a colligative solute, which is a fancy way of saying it messes with ice crystal formation based on how many dissolved bits are floating around. A sugar-free fruit purée freezes like a rock. In our recipe, the full-fat Greek yoghurt, that frozen banana, and a little bit of honey are doing the work that stabilisers and condensed milk do in a lot of no-churn recipes.

There's another, simpler trick too: cook some of the water out. Saveur has this method for fruit ice cream where you roast the fruit at around 160 degrees for thirty to forty minutes until about half the water's gone. You get a more concentrated flavour at the same time, so the ice cream tastes even more like watermelon, funnily enough.

The nutrition case for making your own

Look at a typical shop-bought ice cream. Foodstruct's comparison says it's got about 21 grams of sugar per 100g. Sorbet, which people think is the healthy option? Often more, around 26g per 100g. The NHS Eatwell Guide says adults should stick to 30g of free sugars a day. Two 100g scoops of normal ice cream gives you 42 grams. That's over the limit just from dessert.

This recipe doesn't use any refined sugar. The sweetness is from a really ripe banana and, if your watermelon isn't sweet enough, a tablespoon or two of honey. You're getting fibre and vitamin C from whole fruit too. USDA data shows raspberries have 6.5g of dietary fibre per 100g and are a great source of vitamin C. Watermelon gives you potassium and, according to the National Watermelon Promotion Board, more lycopene than any other fresh fruit or veg – 4,532 micrograms per 100g, beating raw tomato.

There's a blood sugar angle as well. Dr Maya Rosman, who was quoted in The Jerusalem Post, makes the point that because sorbet has almost no fat, your blood sugar spikes faster after eating it than it does after ice cream, where the fat slows things down. This recipe has fat from the Greek yoghurt and fibre from the raspberries, so it's a gentler ride.

Choosing and preparing the fruit

Watermelon is honestly a nightmare for ice cream. It's 91.5 per cent water and has barely any fibre or pectin. It needs more help than most other fruits. Raspberries are a much better partner. They've got over 16 times the fibre of watermelon per 100g – I saw that on SouperSage's nutrition comparison – and that fibre really helps give the finished ice cream some structure. I use twice as much watermelon as raspberry by weight. That keeps the flavour summery and light without letting the watermelon mess up the texture too much.

Get a seedless watermelon if you can find one. Cube up the flesh, spread it on a lined tray, and freeze it solid – takes about four hours. Frozen raspberries from the supermarket are picked ripe and work perfectly here, so no need to hunt for fresh. One large, ripe banana, sliced and frozen, is an absolute must. It's the emulsifier. Helena Laura explains this in her blueberry-banana ice cream recipe; frozen banana gives you creaminess without needing condensed milk.

Taste a cube of your watermelon before you freeze it. If it's a bit bland and not very sweet, you'll need the honey. Plan on two tablespoons. If it's properly ripe and sweet, you can probably leave the honey out altogether.

How to roast watermelon (and why you should bother)

Roasting watermelon might sound a bit weird, but it's honestly the best thing you can do to stop this ice cream from becoming a granita. Saveur says about 160 degrees for thirty to forty minutes, and that's what I do. Spread your cubed watermelon on a tray with some parchment paper and roast it until the edges have gone a bit collapsed and the pieces look smaller. You're getting rid of roughly half the water, which means fewer ice crystals later on.

Let the roasted watermelon cool down completely, then freeze it in a single layer. If you skip this step, the ice cream will still be nice, but it'll be much harder and you'll need to leave it out on the counter for twenty minutes before you can get a scoop in. Roasted watermelon also tastes deeper and more concentrated – less watery, more like watermelon cordial.

This bit takes forty minutes, but it's mostly unattended. You could roast the watermelon the day before and just keep it in the fridge overnight before you freeze it.

Making the ice cream

You'll need a food processor for this. No ice cream machine required, and you don't have to churn it by hand.

What you need:

• 400g watermelon flesh, roasted and frozen (see above)
• 200g raspberries, frozen
• 1 large ripe banana, sliced and frozen
• 150g full-fat Greek yoghurt
• Juice of half a lime
• 1–2 tbsp honey, to taste (optional)

Method:

Chuck the frozen watermelon, raspberries, and banana into the food processor. Pulse it a few times to break things up, then scrape down the sides. Add the yoghurt, lime juice, and honey if you're using it. Blend it all until it's smooth and looks like soft-serve. That usually takes about two to three minutes. You'll probably have to stop and scrape the sides a couple of times.

You can eat it straight away for a soft, spoonable texture. For proper scoopable ice cream, scrape it into a shallow tub with a lid, press a bit of baking paper right onto the surface, and freeze for two hours. Leave it overnight if you want it firmer.

Storage and serving

Home freezers are usually set to about minus eighteen degrees celsius. Without commercial stabilisers, homemade ice cream is at its best within two weeks. After that, you'll get ice crystals forming from the little temperature changes every time you open the door. Keep the tub at the back of the freezer where it's coldest and most stable.

If you've frozen it overnight, let it sit at room temperature for ten minutes before you try to scoop. The banana and yoghurt mean it won't need as long as a sorbet, but it still helps. A scoop dipped in hot water gives you nice clean rounds.

Never, ever refreeze ice cream that's completely melted. Once it's liquid, the texture's gone and you could risk making yourself ill if it's been out too long.

Troubleshooting texture

If it's too hard, either you didn't use enough banana or the watermelon wasn't roasted for long enough. A tablespoon of vodka mixed in can help – alcohol lowers the freezing point – but it's not really needed if you follow the recipe. If it's too soft and slushy, maybe your fruit wasn't frozen solid before you blended it, or you used low-fat yoghurt. The fat is genuinely important here; it gets between water molecules and slows crystal growth. CourseHorse explains this bit well.

If the flavour is a bit flat, just add more lime juice. Acid brightens up fruit and makes the sweetness pop without adding any extra sugar.

What to serve it with

This ice cream is quite bright and light, so it goes well with things that are rich or have a bit of crunch. Crush a digestive biscuit over the top, or have it next to a warm brownie. It's also lovely in a bowl with some fresh raspberries and a drizzle of honey if you want to double down on the fruit. For a summer dessert that looks pretty fancy without much work, scoop it into chilled bowls and stick a few fresh mint leaves on top.

Frequently asked questions

Can I make this without a food processor?

A high-powered blender will do the job, but you'll need to put the yoghurt in first and use the tamper to push the frozen fruit down. A standard blender will struggle with this much frozen fruit and not enough liquid.

Can I use other fruit instead of watermelon?

You can, but watermelon has the highest water content of pretty much any fruit, so swapping it for mango or peach will give you something naturally creamier. You probably won't need to roast those fruits first.

Is this suitable for children?

Definitely. It has no refined sugar and the sweetness is all from fruit. Just watch out for raspberry seeds if you're serving it to very small children.

Can I use low-fat yoghurt?

It's possible, but the ice cream will freeze harder and won't taste as creamy. The fat in the full-fat Greek yoghurt is doing the same thing it does in a custard ice cream: it slows down ice crystal formation.

How long does it keep in the freezer?

Best eaten within two weeks. After that, you'll notice the texture getting grainier as ice crystals develop. Always press baking paper onto the surface before you put the lid on to stop freezer burn.

Can I skip the banana?

The banana is the emulsifier here. Leave it out and you'll need condensed milk or something similar with fat and sugar, which changes the nutrition and the whole character. If you don't like banana flavour, use one that's just ripe, not overripe – the taste will be much milder.

The bottom line

Most homemade fruit ice cream freezes solid because fruit is mostly water, and water turns into big, crunchy crystals. You fix that with three things: roast the watermelon to drive off water, use frozen banana and full-fat Greek yoghurt as your emulsifiers, and let the sugar and acid do their small but important jobs. This gives you a no-churn ice cream you can scoop after two hours, it tastes of real fruit, and it fits comfortably under the NHS's 30g daily free sugar limit.

So tonight, roast a watermelon. Cube it, spread it on a tray, and put it in a 160 degree oven for forty minutes. Once it's cool, freeze it, and by tomorrow you'll have everything ready to blend.