My primer for this article, and the foundation of my work here, is the introductory section of the Gelato Messina recipe book by Nick Palumbo. If you’re interested in dairy-based gelato I recommend it wholeheartedly, but if not, there aren’t many recipes in there for you, sadly. Palumbo doesn’t even consider non-dairy gelato to be gelato, and instead classifies even recipes designed to mimic dairy-based gelato as being sorbets.

Now I’m a good descriptivist, and I’m not going to tell someone their use of language is wrong, but if I was to come up with a distinction between a gelato (or an ice-cream) and a sorbet, it’d be based on texture. Sorbets are mostly water and are very low in  fat, so while a good sorbet can be smooth, it’ll never be creamy – the creaminess of an ice-cream comes from its fat content.

So, to me, what makes an ice-cream an ice-cream is that fat content. Indeed, Nick Palumbo does differentiate between dairy-based gelato and ice-cream by reference to their fat (and sugar) contents – ice-cream has a higher fat content then gelato. Still, despite this perfectly functional and fairly scientific (he has specific values!) definition, he still considers dairy to be required for something to be named ice cream or gelato.

This is, obviously, something I disagree with – but maybe I can change some minds. However, it is worth noting that in several countries ice creams are legally defined by their milk fat content (10% in the US). You’ll see companies get around this requirement through use of terms like ‘frozen dessert’.

As for the science, there are three main elements to the structure of our ‘dairy-free frozen dessert product’. Note: this section won’t go into the actual ingredients we’ll be using here in depth. See my article on ingredients for more detail.

Sugar

Despite the importance of fat to the definition of ice cream, sugar is honestly the most important part of anything frozen and tasty. Noted baker Stella Parks describes sweetness as being sugar’s least important function, and while I as a sweet tooth am quite a fan of sweetness, the key take-away here is that sugar also performs chemical functions in food. In baked goods, the caramelisation of sugars assists with browning, but in sorbets and ice creams, the key structural role of sugar is binding water.

This is why I highly recommend avoiding reduction of the sugar content in my recipes to try and make them healthier. If you want to modify them a bit, you can lower the fat content, but we need sugar’s ability to absorb the water in the mixture. This is important because free-flowing water will freeze into crystals of ice. Cutting down on sugar will thus result in an icy, hard ice cream.

So far I’ve been using ‘sugar’ as a generic term for one thing, but really sugar is a class of things, consisting of small, sweet-tasting carbohydrates. This may seem like pedantry, but it’s an important distinction: different sugars have different effects on our ice cream. Some have a stronger effect on the flavour (by increasing sweetness) while others affect the texture more (by dealing with more water). The technical term for the latter is ‘freezing point depression’, which is typically expressed relative to sucrose (plain table sugar).

Let’s talk a bit about the various sugars we can use.

Sucrose is probably what comes to mind when you think of ‘sugar’. It forms the bulk of most packaged sugar products you’ll see, including white, raw, demerara, turbinado and brown sugars. It also makes up about half of maple syrup and a third of molasses (which is itself present in the darker variants of sucrose mentioned above).

On a chemical level, sucrose is a disaccharide – that is to say, it’s made up of two monosaccharides, namely glucose and fructose. What’s important to note here is that the size of a sugar molecule is related to its effect on freezing point. Smaller monosaccharide molecules disperse through a solution better and depress the freezing point more than sucrose, while longer polysaccharide chains, like maltodextrin, have a weaker effect.

Sucrose, due to its widespread use, is taken as the base point for both sweetness and freezing point suppression. You can make ice creams perfectly fine with just sucrose, but we can experiment with a wider range of flavours better by incorporating other sugars as well.

Glucose is the non-sucrose sugar I use most frequently. You will also frequently see it referred to as dextrose, though this technically refers to only one form of glucose (albeit the vastly more common form in nature). The only thing that matters name-wise is not getting glucose confused with glucose syrup, which is actually a mixture of various forms of sugars and is not even necessarily majority glucose!

In terms of its effects on our recipes, glucose, as a monosaccharide, is mostly used as a way of lowering the freezing point of ice cream without increasing its sweetness as much as sucrose would do. More precisely, glucose is 1.9x more effective than sucrose at lowering the freezing point while being 0.7x as sweet.

Maltodextrin is a long-chain sugar mostly used to bulk out sorbets. I won’t be mentioning it much unless I get into sorbet recipes, but the crucial point about maltodextrin is that it is neither very sweet nor very good at depressing the freezing point. Its main function is increasing the solid content in what are otherwise very watery sorbets, like lemon or lime.

Fat

While milk fat does have a flavour associated with it, the main purpose of the fats added into my recipes will be textural (to an extent, anyway – I do like including cocoa butter into chocolatey ice creams to help increase the depth of flavour).

Creams (dairy or otherwise) are thicker than milk and, well, creamier, because of their higher fat content. Much like different sugars, different fats vary in their physical properties. This is more obvious for fats than sugars; it’s pretty easy to see the difference between vegetable oil and beef tallow (and that the latter is not desirable for any ice cream, vegan or otherwise, goes without saying).

The key property we want from our fat sources is a melting point at about body temperature. When the fats in the ice cream melt at body temperature, this means that they are melting while you are eating the ice cream. They then coat your mouth, holding the flavourful compounds in place and helping make the flavour of the ice cream last.

Fat also contributes to the texture in other ways. It helps incorporate air into the mixture, adding to the body of the ice cream, as well as preventing the formation of ice during long-term storage – meaning your ice cream will keep better. Finally, it also slows melting during consumption.

Emulsifying these fats, which means creating a stable mixture of liquid and fat in a way that doesn’t ‘break’ (i.e. have the fat separate from the liquid) is one of the difficulties of dairy-free ice cream. Breaking occurs because the fats in the liquid are hydrophobic – their non-polar structures don’t mix with the polar water molecules, so the fats start clumping together into globules rather than incorporating evenly throughout the mixture. Emulsifiers address this problem by acting as barriers between the water and the fat, keeping them separate from each other and preventing clumping.

In dairy-based ice creams, the emulsification comes from animal proteins, primarily casein, in the milk. Proteins are great emulsifiers, as their long chains contain both hydrophobic and hydrophilic elements. The hydrophobic parts face the fats, while the hydrophilic regions interact with the water.

Proteins

Speaking of proteins, we’ll want to substitute some of these animal proteins in our ice cream with plant-based ones.

Even setting aside its role in emulsification, adding some extra protein to our ice cream will have several beneficial effects. Protein chains are excellent at helping our ice cream to aerate during the churning process, much like in whipping a meringue. Furthermore, much like the fat, they help maintain the storage stability of ice cream, further inhibiting the formation of ice.

As for which proteins to add, I’ll discuss that in an article more specifically on ingredients.

Stabilisers

The final point to note specifically is the addition of stabilisers. Stabilisers increase the viscosity of the ice cream mixture, which in turn increases the creaminess of the final product. Do note, however, to be careful with these –  overly viscous ice creams end up with a dense, chewy texture, and the effect of a given quantity of stabilise on viscosity can vary greatly depending on the stabiliser in question. For example, I find guar gum should be used in smaller quantities than other stabilisers, as it is very powerful.

Stabilisers are also the best tool for increasing the freezer life of your ice cream. They provide resistance to temperature fluctuation and slow melting times, and are the primary way of stopping those ice crystals I’ve come back to several times now.