The short answer
Choose Philadelphia style when you want fewer steps and no cooking. Choose a custard base when you want egg yolk working as an emulsifier in your mix and you are ready to heat it to a safe temperature and cool it fast.
Our two base formulas use the same targets for both styles: 14% fat, 10% milk solids-not-fat and 16% sweetener. The custard formula adds 6% egg yolk. The Philadelphia formula has no yolk. These are base formulas built on standard food-science ranges, not recipes we have churned.
The buttons under this intro, Open the custard base and Open the Philadelphia base, load each formula in the Base Builder. The calculators run in your browser, and the numbers you type are not sent to our server.
What Philadelphia-style means
“Philadelphia-style” is a cooks’ term. No standard or regulation defines it. In practice it means a base with no eggs that is never cooked.
Cuisinart’s “Simple Vanilla Ice Cream” is a clear example. It uses whole milk, sugar, salt, heavy cream and vanilla. You whisk until the sugar dissolves. The ICE-21 booklet then has you chill the mix for 1 to 2 hours or overnight, and the ICE-30BC booklet has you churn it straight away.
Under the U.S. rule, an eggless base like this falls on the ice cream side of the line, because it has no egg yolk at all.
What the egg yolk does
The University of Guelph Ice Cream Technology e-Book says egg yolk was the original ice cream emulsifier. Commercial makers now lean mostly on mono- and diglycerides and polysorbate 80 instead.
According to the same e-Book, emulsifiers lower the tension between fat and water. That pulls some protein off the fat droplets, so the fat emulsion breaks down in a controlled way during freezing. The e-Book links this to a smooth, dry product with good meltdown.
A home-freezer guide from 1980, hosted in the Guelph e-Book, puts it in kitchen terms. It says eggs help fat and water mix, and they improve whipping, which gives the ice cream resistance to melting. Its home recipes use one medium or large egg for roughly 2 liters of mix, along with gelatin.
You will hear cooks describe custard as richer or denser. That is the cooks’ tradition talking. The sources we use do not compare the texture of custard and eggless ice cream in numbers.
The U.S. 1.4% rule
The federal standard for ice cream and frozen custard (21 CFR 135.110) draws the line at egg yolk solids:
- Ice cream has less than 1.4% egg yolk solids by weight.
- Frozen custard must have 1.4% egg yolk solids by weight of the finished food.
- With bulky flavors like fruit, nuts or chocolate, frozen custard’s yolk solids can drop in proportion to the flavor, but not below 1.12%.
- A product above 1.4% yolk solids is named “frozen custard”, “french ice cream” or “French custard ice cream”. The rule also allows other names if the label follows the regulation.
The line is about yolk, not fat. Both products still need at least 10% milkfat, plus the same milk solids and weight minimums. So custard vs Philadelphia ice cream is not a question of which one has more cream.
What that means in raw yolk
By our arithmetic, raw yolk is about 47.7% solids, based on USDA data showing it is 52.31% water. So 1.4% yolk solids works out to about 2.9% raw yolk by weight of the mix.
Our custard formula, at 6% yolk, sits well above that line. The Guelph e-Book’s example ice cream mix uses 1% yolk, which by our reading falls below it.
Cooking a custard base safely
Raw yolk is the reason a custard base gets cooked. Here is what the sources say, and who says it:
- FDA Food Code 2022 (a rule for restaurants and stores): raw eggs not served right away must reach 155°F (68°C) for 17 seconds. The same table lists 145°F for 3 minutes, 150°F for 1 minute, or 158°F with no hold.
- FDA Food Code, on recipes like ice cream: retail kitchens must use pasteurized eggs or egg products instead of raw eggs, unless the dish is cooked to those temperatures.
- FoodSafety.gov: egg dishes should reach 160°F (71°C).
- The 1980 Guelph home guide: heat the mix to about 158°F (70°C), then cool it quickly to below 18°C (about 64°F).
For scale, commercial ice cream mix is pasteurized by holding it at 155°F for 30 minutes or 175°F for 25 seconds, or an equivalent combination (21 CFR 135.3).
The sources we use do not cover pasteurized shell eggs for home cooks, so we cannot tell you whether they let you skip cooking.
A suggestion from us: use an instant-read thermometer and stir the base constantly over gentle heat, so you can see the number rather than guess.
Cooling either base
A cooked base has to come down fast before it goes in the machine.
- Cuisinart tells cooks to chill precooked mixtures overnight, or over an ice bath until completely cool.
- Ninja says to cool a cooked base in an ice bath to below 40°F before freezing.
- The Food Code’s retail cooling rule asks food to drop from 135°F to 70°F within 2 hours, and to 41°F within 6 hours total.
A Philadelphia base starts cold, so it skips this step. You only chill it as long as your machine’s booklet asks.
How to choose
These are our suggestions, not rules from a source:
- Short on time or making ice cream with kids: start with Philadelphia style. No stove and no eggs.
- Want yolk as your emulsifier, or want to call it frozen custard: go custard, and keep the yolk above the 2.9% mark worked out above.
- Adding chunky mix-ins to a custard: remember the rule lets yolk solids drop toward 1.12% in proportion to bulky flavors.
- Comparing the two: run both formulas in the Base Builder. Fat, milk solids and sugar match, so the yolk is the only change.
FAQ
Is French custard ice cream the same as frozen custard?
Under 21 CFR 135.110, yes. A product above 1.4% egg yolk solids can be named frozen custard, french ice cream or French custard ice cream.
Does Philadelphia-style ice cream have less fat than custard?
Not by definition. The U.S. rule sets the same 10% milkfat minimum for both, and our two formulas use the same 14% fat target.
Can I skip cooking a custard base?
The sources we use do not support skipping it. The FDA Food Code has retail kitchens either cook raw eggs to set temperatures or use pasteurized eggs, and FoodSafety.gov gives 160°F for egg dishes.
How much yolk makes a base count as custard?
The rule says 1.4% egg yolk solids. By our arithmetic that is about 2.9% raw yolk by weight of the mix.
Is egg yolk the only emulsifier I can use?
No. The Guelph e-Book says commercial makers now mostly use mono- and diglycerides and polysorbate 80 in place of yolk.