I rediscovered my passion for obsession with making ice cream when I co-hosted a dinner party with my lovely and talented friend Nicola last month. Nicola is the owner and founder of http://www.souschef.co.uk, a specialty food export company that sells hard-to-find cheffy ingredients and equipment to home cooks. (Sorry American friends, Sous Chef only ships to the EU for now.) Nicola had a surfeit of pistachio paste (what a wonderful thing to have too much of!) so we decided to make Orangette’s chocolate tart with salted pistachio ice cream for dessert. I took charge of the ice cream and I did not stint with the pistachio paste. The result was wonderful. (Nicola has since blogged a recipe for salted pistachio ice cream using the very same pistachio paste.) Ice creams and sorbets are a fun challenge for home cooks, involving in equal measure the palate and food science. Flavor is key, of course, and limited only by your imagination, but mouth feel is of equal importance.
The basic ice cream consists of a custard base which is then flavored. Sorbets are made from a sweetened, usually fruit-based purée. An ice cream maker freezes this liquid base while whipping air into it. Gelatos are churned more slowly than ice creams, which means they have greater density. When I first started making ice creams at home, I did not fully understand the science, and I was plagued by a chalky mouth feel, the result of crystallization during the freezing process. Now I use ice cream stabilizers. Invert sugars such as glucose help prevent crystallization. Thickeners, such as xanthan gum (a polysaccharide that is a natural by-product of a fermentation process of sugars such as lactose, sucrose, or glucose – explained in detail in this Wikipedia post), guar gum, and carrageenan, both enhance the mouth feel and retard melting. With stabilizers, it is even possible to make ice cream without an ice cream maker. Most professional kitchens and commercial ice creams use stabilizers.
In Seattle, daydreaming about Nicola and our glorious pistachio ice cream, I gifted myself with a brand new ice cream maker. Glucose is difficult to find in the United States, although it is widely available in English supermarkets. High-fructose corn syrup is also an invert sugar syrup, but for a variety of reasons, most of them political, it’s not an ingredient I favor. At Big John’s PFI, a bulk food importer – my favorite import store in the world – I found golden syrup, a partially inverted sugar syrup, made in the process of refining sugar cane or sugar beet juice into sugar.
This sorbet was my first venture with my new ice cream maker. I like intensely flavored, acidic sorbets, the kind that you eat in small nibbles off a spoon and that makes your cheeks pucker and your eyes sparkle. Rhubarb – aromatic and aggressively tangy – is one of my favorite early spring ingredients. The addition of a substantial amount of lime juice adds another dimension of acidity which is softened and tempered by the vanilla. The purée may taste sweet, but freezing foods dulls our taste buds. Frozen, this tastes just right. Do use vanilla beans instead of vanilla extract. And remember, the more ruby red your rhubarb stalks, the more wonderfully pink your sorbet will be.
You will need:
A heavy bottomed saucepan
A food processor, blender, or immersion blender
A wire mesh sieve or chinois
An ice cream maker (you can try this without, but I haven’t road-tested it)
** Conversions are to US cups and measurements
125 ml water (1/2 cup)
240 g sugar (1 cup + 1.5 tablespoons)
450 g rhubarb stalks (about a pound), diced
90 ml lime juice (6 tablespoons or 1/3 cup)
½ vanilla bean
¼ teaspoon salt
1 tablespoon golden syrup or glucose (optional)
Combine the sugar and water in a heavy-bottomed saucepan and heat over medium heat until the sugar has dissolved and the resulting syrup has started to bubble. Split the vanilla bean in half lengthwise with a sharp paring knife and scrape the seeds off each half. Add both the bean and seeds to the pot, along with the rhubarb and salt. Simmer, covered, over medium-low heat, until the rhubarb is completely tender (about 15 minutes). Remove and discard the vanilla bean. Stir in the lime juice and transfer this mixture to your food processor or blender, and blend until thoroughly puréed.
If you wish you can omit the next stage, but if you want a beautifully smooth sorbet, pass the purée through a wire mesh sieve, scraping vigorously with a rubber spatula or wooden spoon to get every last bit, so as to strain out any tough fibers. Stir in the golden syrup or glucose if using, taste, and add additional sugar or lime juice as needed.
Cover and put in the refrigerator to chill. When the purée is cold, freeze in an ice cream maker according to manufacturer instructions. Transfer to a container and store in your freezer until ready to serve. Makes about 500 ml, or a quart of sorbet.