Green Tea Ice Cream, and How to Keep It Green

Almost everything that goes wrong with green tea ice cream comes down to heat, and the ingredients disagree about how much of it they want. Egg yolks need it to thicken the base into custard. Matcha does best with as little as the recipe can manage, since heat is part of what drags chlorophyll's bright green toward khaki. Heat also affects the cook's palate: a spoonful of warm base tastes sweeter and more bitter than the same mixture will once frozen, so tasting it at the stove is misleading. This recipe is arranged around those facts. The custard is cooked on its own to 175 to 180°F. The matcha goes in afterward, sifted and loosened in cold milk, once the base has been pulled off the heat and cooled over ice. Made that way, the scoop comes out the color of new leaves, with a bitter edge that the cream softens without hiding.

The powder

Matcha starts as tencha. The bushes are shaded before picking, and the leaf is steamed and then dried flat, skipping the rolling that turns steamed leaf into sencha. Ito En, the Japanese tea company, describes the shading as lasting longer than the roughly 20 days given to gyokuro, and says tencha is stone-ground into matcha immediately before shipping. In 2022 the International Organization for Standardization published a technical report on matcha, ISO/TR 21380. Japan's National Agriculture and Food Research Organization led the work, and its summary of the report names shade-grown new shoots and specialized processing for the bright green color. The green tea guide sets matcha beside sencha, gyokuro and hojicha.

What sets matcha apart in a dessert is that it is eaten whole. A pot of sencha gives up whatever hot water can dissolve, and the leaves are thrown away. A scoop of matcha ice cream contains the ground leaf itself, suspended in the cream, and that is where its color comes from. An analysis of chlorophylls in green teas, published in Molecules, measured roughly 12,000 to 17,000 mg of chlorophyll per kilogram of dry weight in matcha samples against about 1,060 in a standard green tea, with more of it still intact. The same paper notes that chlorophyll converts readily to pheophytins, which are brownish, under acidic conditions. Harold McGee describes the same slide in On Food and Cooking, where cooked green vegetables go from bright green to olive as heat and the plant's own acids work on the pigment. Keeping the powder out of the saucepan is the cheapest protection a cook has.

Mariage Frères Matcha Midori (shop Matcha Midori) comes in a 40 g tin, and its product listing gives the origin as Miyazaki. At 12 g a batch, one tin makes three quarts with a spoonful left over for a bowl of tea. The Mariage Frères producer guide covers the Paris tea house behind it.

Why a custard base

Douglas Goff, a food scientist at the University of Guelph, points out that egg yolk was the original ice cream emulsifier and appears in most early recipes. A factory mix gets its smoothness from stabilizers and emulsifiers that make up less than half a percent of its weight. A home batch has none of those additives, so here the yolks do the emulsifying, which is why this base uses five.

The proportions follow Goff's numbers loosely. He gives ice cream at 10 percent milkfat and up to 16 percent in some premium brands, with 12 to 16 percent sweeteners. This base comes out around 17 percent fat and a little over 13 percent sugar. The fat runs slightly high on purpose, because matcha's bitterness is easier to enjoy against a rich cream. The sugar is harder to adjust, since it also sets how the ice cream freezes. Sugars lower the freezing point, so even at a serving temperature of about 3°F (-16°C) Goff puts the frozen share of the water at roughly 72 percent. The rest stays liquid as concentrated syrup, and that liquid, along with the air churned in, is what lets a scoop go in. Cutting the sugar gives a harder ice cream, not just a less sweet one. Swapping a spoonful of the sugar for honey goes the other way. Goff notes that smaller sugar molecules such as glucose and fructose depress the freezing point more than sucrose and make a softer ice cream.

Tasting a base that will be eaten frozen

Warm food tastes sweeter and more bitter than cold food. A 2005 paper in Nature by Karel Talavera and colleagues traced part of the reason to TRPM5, an ion channel in taste cells that opens when sweet, bitter or umami receptors fire and that heat activates on its own. Work on human tasters by Barry Green and Danielle Nachtigal in Chemical Senses found a more complicated picture for sweetness: mild cooling did not dull it, but cooling to 5 to 12°C did. For this recipe, that means the base should taste a little too sweet and a little too bitter when warm. If it tastes balanced at the stove, it is likely to taste fainter once frozen. Taste it again cold from the refrigerator before churning, which is the closer guide.

Ingredients

For about 1 quart (1 liter), six servings.

• 360 ml (1 1/2 cups) heavy cream
• 360 ml (1 1/2 cups) whole milk, with 60 ml (1/4 cup) of it kept cold for the matcha
• 5 large egg yolks, about 90 g
• 130 g (2/3 cup) granulated sugar, divided in half
• A pinch of fine salt
• 12 g matcha, about 2 level tablespoons, such as Matcha Midori (shop Matcha Midori). Use 8 g for a gentle flavor and 15 g for a pronounced one.

Equipment: an ice cream machine, a heavy saucepan, a heatproof spatula, an instant-read thermometer, a fine sieve and a bowl of ice water.

Method

1. Set up before any heat

Freeze the machine's bowl according to its manual; a bowl that is only nearly frozen churns a soft, icy batch. Set a medium bowl inside a larger one filled with ice and water, and rest a fine sieve on top. The finished custard has to go somewhere cold at once, so this setup comes first.

2. Sift the matcha and make a paste

Matcha clumps. Ippodo, the Kyoto tea house, blames static electricity, moisture and the powder's own weight, and Hibiki-an, a tea shop in Ujitawara, Kyoto, tells drinkers to sift it to remove lumps. Press the 12 g through a fine strainer with the back of a spoon, the way Ippodo pushes it across the mesh with a spatula. Whisk the sifted powder with the 60 ml of cold milk until the paste is smooth and glossy with no dry pockets, cover it, and leave it aside. A lump that survives this step can show up later as a bitter green speck in the frozen ice cream.

3. Warm the dairy

Put the cream, the remaining 300 ml of milk, half the sugar and the salt in the saucepan over medium heat. Stir now and then until the surface steams and tiny bubbles form at the edge. Do not let it boil. Nothing here is fragile yet, so this step does not need exact timing.

4. Temper the yolks

While the dairy heats, whisk the yolks with the rest of the sugar for about a minute, until the mixture turns paler and falls from the whisk in a thick ribbon. Ladle in about a third of the hot dairy slowly, whisking the whole time, so the yolks warm gradually and do not scramble. Then pour the yolk mixture back into the saucepan.

5. Cook the custard

This is the step that decides the texture. Over medium-low heat, stir constantly with the spatula, sweeping the bottom and the corners where the custard sets first. Over five to eight minutes the foam on top disappears and the liquid thickens slightly and turns silky. Take it to 175 to 180°F (79 to 82°C). A finger drawn across the coated spatula should leave a clean track that holds. Iowa State's food preparation lab manual shows how egg content moves the finish line: a custard with more eggs sets lower, around 77 to 79°C, and one with fewer sets closer to 82 to 84°C. This base is rich in yolk, so watch closely from about 170°F. Taken much past 180°F, the yolk proteins can overset into tiny curds. The whole cook also passes 160°F, the temperature the FDA says will kill Salmonella in a cooked egg base for homemade ice cream.

6. Strain and cool it fast

As soon as it reaches temperature, pour the custard through the sieve into the bowl over ice. The pan keeps cooking whatever stays in it. Stir for three or four minutes, until the custard stops steaming and feels warm rather than hot to a fingertip. The sieve catches any threads of cooked egg and the chalaza.

7. Add the matcha, off the heat

Whisk the matcha paste into the cooled custard until the color is even, scraping the paste bowl clean. For the smoothest texture, run an immersion blender through it for 15 to 20 seconds. Taste it now, remembering that warmth exaggerates both sweetness and bitterness. It should seem slightly too much of each.

8. Chill thoroughly

Press plastic wrap onto the surface so no skin forms, and refrigerate for at least 4 hours; overnight is better. Goff describes the same rest in commercial production as ageing: at least four hours, usually overnight, so the fat can cool and crystallize and the proteins can fully hydrate. The base should be 40°F (4°C) or colder before it goes into the machine. A lukewarm base churns more slowly and can freeze into larger ice crystals.

9. Churn to soft-serve

Matcha stays suspended in the base rather than dissolving, and a little of it settles on the bottom overnight, so whisk the base briefly before pouring it into the machine. Churn according to the manufacturer's instructions, usually 20 to 30 minutes, until the ice cream mounds on the dasher with the texture of soft-serve. Goff notes that ice cream leaves a commercial batch freezer at about this point, with around half its water frozen. Stop churning here. Churned too long, the fat begins to turn to butter, the same way over-whipped cream does.

10. Harden

Scrape the ice cream into a container chilled in the freezer, press parchment onto the surface, and freeze for at least 4 hours. Straight from a home freezer it will be firm. Leave it on the counter for 5 to 10 minutes and the scoop will curl cleanly.

In Denver

The custard targets do not change at altitude. They sit well below the boiling point, which is about 202°F in Denver; Colorado State University Extension lists 203°F at 5,000 feet, and the USDA's rule is just under one degree lower for every 500 feet. Altitude does make a useful check on the thermometer. In boiling water, an accurate instant-read thermometer should read about 202°F in Denver, not 212°F. One that reads 212°F there is running ten degrees high and would call the custard done at a true 170°F, before it thickens. One that reads low could carry the custard past the curdling point. Check it before starting. The Denver altitude cooking guide has the elevation numbers for the rest of the kitchen.

When it goes wrong

Homemade ice cream is at its best soon after it hardens. Goff notes that ice crystals stop growing only below about -25°C (-13°F), colder than a home freezer keeps ice cream. Above that, the crystals can keep growing, and every partial thaw and refreeze, which the trade calls heat shock, makes the ice cream icier. A factory batch has stabilizers to slow that down. This one does not.

The same base with roasted tea

Hojicha, green tea roasted at about 200°C (392°F), is brewed hot. Ito En brews it at 200°F, while sencha gets 180°F. That tolerance for heat lets it go into the dairy itself. Steep about 15 g of hojicha leaf in the cream and milk in step 3 for ten minutes off the heat, strain, and press the leaves to get all the liquid out. Then rewarm the dairy and continue without the matcha. The ice cream comes out tan, with a toasted, almost caramel flavor, and it is the version to make for anyone who prefers a roasted tea to a fresh, vegetal one. Genmaicha, green tea mixed with roasted brown rice, is another roasted-flavor option. The Mariage Frères Genmaïcha Matcha Émeraude (shop Genmaïcha Matcha Émeraude) blends green tea, roasted puffed rice and matcha, and its listing describes a toasty roasted-rice flavor.

At the table

Japan's ice cream began as a custard, sold in Yokohama. According to the Japan Ice Cream Association, in 1869, the second year of the Meiji era, Machida Fusazō began making and selling aisukurin on Bashamichi street, freezing it with ice and salt. The association believes it was made from milk, eggs and sugar, which puts it close to the base in this recipe. The association donated a monument to the spot in 1976, a sculpture called Mother and Child of the Sun, which Kanagawa's tourism office still lists as marking the origin of ice cream in Japan.

The famous green tea scoop is a Japanese flavor from an American brand. Häagen-Dazs Japan launched Green Tea in 1996 and calls it the first flavor developed in Japan. According to a staff member interviewed about its development, the idea dates to 1989, and it took more than a hundred trial batches, blending first and second-picking matcha, over seven years to reach the recipe. The interview says it was first sold at the Aoyama shop in Tokyo in June 1996 and then in stores limited to the Kanto region, until shoppers elsewhere in Japan asked why they could not buy it. The company now counts it among the flavors that represent Häagen-Dazs Japan, and the interview says its popularity has spread abroad, mainly in China and elsewhere in Asia.

The last spoonful tastes different from the first. As a scoop melts and warms in the bowl, it tastes sweeter and more bitter, for the same reason the warm base did at the stove. Anyone at the table who says the end of the bowl tastes stronger is right.

Serving

Scoop into bowls chilled in the freezer, and serve with something crisp and buttery. A plate from the brown butter shortbread recipe works, and so do Makabi & Sons Matcha Toasted Black Sesame Cookies (shop Makabi & Sons Matcha Toasted Black Sesame Cookies). For anyone who wants the tea as a drink afterward, the sencha brewing recipe covers a first pot, with the water temperatures that keep it from turning harsh.

The shop is at 263 Josephine Street in Cherry Creek, Denver, and products ship across the continental U.S. from theambrosianpantry.com.

Sources & Further Reading

• H. Douglas Goff, University of Guelph Department of Food Science: Finding Science in Ice Cream
• Harold McGee, On Food and Cooking: The Science and Lore of the Kitchen (Scribner, 2004): chlorophyll in cooked green vegetables
• Talavera et al., Nature 438 (2005): Heat activation of TRPM5 underlies thermal sensitivity of sweet taste
• Green and Nachtigal, Chemical Senses (2015): Temperature affects human sweet taste via at least two mechanisms
• Molecules (PMC): HPLC-MS2 analysis of chlorophylls in green teas
• Ito En: Types of Japanese green tea
• Ito En: How to brew at the right temperature
• National Agriculture and Food Research Organization, Japan: ISO technical report on matcha
• Ippodo Tea: Matcha sieve
• Hibiki-an: Matcha preparation
• Basic Scientific Food Preparation Lab Manual (Iowa State University, via LibreTexts): Eggs, Custard
• USDA Food Safety and Inspection Service: Safe internal temperature for food made with eggs
• U.S. Food and Drug Administration: Enjoying Homemade Ice Cream without the Risk of Salmonella Infection
• Colorado State University Extension: High Elevation Food Preparation
• USDA Food Safety and Inspection Service: High Altitude Cooking
• Japan Ice Cream Association: The birth of aisukurin
• Bashamichi Shopping Street Association: The birthplace of ice cream in Japan
• Visit Kanagawa: Monument to the Origin of Ice Cream in Japan
• Häagen-Dazs Japan press release (PR TIMES, 2019): Green Tea, the first flavor developed in Japan
• Walkerplus: interview on the seven-year development of Häagen-Dazs Green Tea