Reading the Kansas State frostings and fillings data as a cottage baker

In Virginia cottage-baker circles, one link comes up every time someone asks about frosting: a Kansas State University PDF full of frosting and filling recipes sorted into "TCS" and "non-TCS." People share it as a list of shelf-stable recipes. It is useful. It is also easy to read more into it than it says.

Here is what the resource is, how to read it, and when to pick up the phone.

Why shelf-stable matters on the cottage path

Many cottage food laws are built around foods that are safe at room temperature. Virginia's home-kitchen exemption, Va. Code § 3.2-5130, only covers baked goods and other listed foods that "do not require time or temperature control after preparation."

The VDACS Home Food Exemptions FAQ (REV JUL 2026) explains the term. A time/temperature control for safety (TCS) food "requires controls like refrigerated or frozen storage to limit the growth of microorganisms or formation of toxins that can cause illness." Non-TCS foods "are safe when held at ambient temperatures after preparation."

For bakers, the frosting or filling is often where a product slips into TCS territory. Many of the FAQ's "may not qualify" examples are breads or cakes filled or topped with fresh fruit, fruit curd, custard, whipped cream, mousse, or cream cheese.

What the Kansas State resource is

The link bakers share lives on the Fair Judging page of the K-State Extension Rapid Response Center, based in Kansas State University's Department of Grain and Food Science. The page is built for people who judge foods at Kansas county fairs and the State Fair. Its frosting section includes:

• Food Safety of Frostings and Fillings (MF3544), a six-page fact sheet from December 2020
• A Review of Recipes for Kansas Fairs and Exhibitions, the testing data behind that fact sheet (July 2020, Kansas State University Food Science Institute). This is the PDF most people pass around.
• Calculating Frostings and Fillings, slides on working out percent sugar by weight
• A Frostings and Fillings Worksheet (4H1171) and an August 2020 presentation

The study behind it is simple. K-State Research and Extension agents and specialists submitted 49 frosting and filling recipes, some with variations. The recipes were made in a home kitchen, then tested in duplicate at the Kansas Value Added Foods Lab for acidity (pH), water activity (Aw), and percent soluble solids (% Brix). The goal was to sort out which recipes can be displayed safely at room temperature at a fair and which need refrigeration.

So it is lab test data from a fair-safety study. Kansas State does not call these certified recipes, and the fact sheet says plainly that "the recipe examples give information about the ingredients included and are not recipes to be followed."

How to read the headings

The data PDF sorts recipes under three headings:

• TCS Foods: DO NOT LEAVE AT ROOM TEMPERATURE
• Non-TCS Foods: CAN BE LEFT AT ROOM TEMPERATURE
• Non-TCS with Conditions

Each entry lists the ingredients, notes whether the recipe was cooked or microwaved, and gives the measured pH and water activity.

The sorting follows a table from the 2017 FDA Food Code that crosses pH with water activity. In that table, anything with a water activity below 0.88 counts as non-TCS at any pH. Above that line, a recipe has to be more acidic to stay non-TCS, or it needs a product assessment.

The third heading is easy to miss. MF3544 explains that these recipes technically qualify as non-TCS, but their water activity is above 0.85. At that level, Staphylococcus aureus carried in from hands can still grow and make toxins at room temperature. Lemon curd, a microwaved ganache, and a basic milk-and-sugar glaze sit there. So does a basic buttercream made with 2 to 4 tablespoons of heavy cream (water activity 0.86). A similar "simple buttercream" with a quarter cup of cream tested at 0.83 and landed in the plain non-TCS group. Two recipes that look nearly the same ended up in different groups.

One more caution. The non-TCS heading includes several cream cheese frostings. Even so, the same fact sheet says that, as a general rule, "no cream cheese based frostings or fillings will be allowed at Kansas fairs and exhibitions," because in their testing some cream cheese recipes needed refrigeration and some did not. The VDACS FAQ also lists cream cheese-based frostings among foods that may be TCS. Treat the non-TCS heading as a first screen and keep checking.

Make it exactly as written

The advice bakers repeat most is this: if you use a recipe from the data, make it as written. Don't change the ratios. Don't swap ingredients. If it calls for 1 teaspoon of vanilla, use 1 teaspoon, not half, and not a different extract.

Kansas State says the same thing in its own words. Changes to a recipe "will affect the pH, Aw, and % Brix values of products, and could change the way some recipes are categorized." Water is the big one. Sugar binds free water and pulls water activity down. Dairy ingredients generally carry more water, and adding water as an ingredient raises water activity. Even a little more liquid to loosen a frosting can move it.

For recipes that are not in the data, Kansas State offers a screen that needs no lab: use a frosting or filling with at least 65% sugar by weight. Their calculation slides walk through it with a kitchen scale. Weigh every ingredient in grams, add up the sugar, divide by the total weight, and multiply by 100. Their worked example is the simple buttercream: 960 grams of powdered sugar in a 1,484-gram batch comes to 65%. Corn syrup only counts as 70% sugar, and the calculation leaves out sugar already inside ingredients like chocolate chips or sweetened coconut. Starting in 2023, K-State says the 65% rule is recommended at Kansas county fairs and required at the State Fair.

Butter in frosting

A common worry is that butter is off-limits on the cottage path. Some bakers say no butter in icing at all.

That is not what Virginia's FAQ says. It lists buttercream as a food that "may be TCS or non-TCS depending on the recipe." The Kansas data backs that up. Butter-heavy recipes like the simple buttercream and an oatmeal cream pie filling tested non-TCS. Several cooked frostings built on milk and flour tested TCS.

The fact sheet explains why. Fat does not raise water activity. Most of the TCS recipes in the study used dairy like milk, cream cheese, butter, or cream as main ingredients without enough sugar to bring water activity down. So look at the whole recipe: the sugar, the liquid, and whether it was cooked.

Rules differ by state, and some states treat butter frostings differently. Check how your state handles it on Crosodo's buttercream icing and cream cheese icing pages.

What this means in Virginia

VDACS does point bakers to this research. Section IV of the Home Food Exemptions FAQ, under "Frostings and Fillings Research," links both A Review of Recipes for Kansas Fairs and Exhibitions and Food Safety of Frostings and Fillings. The FAQ presents them as research for judging your own recipe. It does not adopt them as an approved recipe list.

The FAQ is also clear that the call depends on your recipe: "the determination of whether a product meets the exemption ultimately depends on the recipe of that specific product." It gives examples that may be allowed, such as breads or cakes that are not filled or topped with fresh fruit, fruit curd, custard, whipped cream, mousse, or cream cheese. Cheesecakes, cream pies, custards, and meringues are examples that may not be. When a recipe is borderline, the FAQ says laboratory testing by a food processing authority may be needed. It links the AFDO Food Processing Authorities Directory and Virginia Tech's Food Producer Technical Assistance Network.

The exemption is state law, so the frosting rules don't change from county to county. Your locality can still require zoning approval and a business license.

Cinnamon rolls are the most common frosting question in Virginia. Our shelf-stable cinnamon roll frosting note covers the glazes bakers use instead of cream cheese.

When to ask VDACS or your state agency

Reach out before you sell if:

• you changed anything in a tested recipe, even a small swap
• your recipe is not in the data and you haven't checked it against the 65% sugar screen
• the frosting or filling uses cream cheese, fresh fruit, curd, custard, whipped cream, or a lot of milk or cream
• the recipe sits under "Non-TCS with Conditions"
• you sell outside Virginia, where another state's rules apply

In Virginia, the VDACS Food Safety Program takes questions at (804) 786-3520 or [email protected]. In other states, start with the agency that runs your cottage food program, and ask about lab testing if the answer depends on the recipe.

Get the paperwork side in one place

Frosting is one piece. Zoning, business licenses, and labels are the rest. Start with the permit picker. The full state PDF and every county guide are included in the Library Pass ($15/mo or $99/yr).

• Permit picker: county zoning, health, and business-license steps
• Library Pass: every county Permit Guide plus the state books, $15/mo

Not legal advice. Confirm your recipe and your setup with VDACS or your state agency before you sell.