Originally Posted by FromScratchSF
Simple - whatever they are making is shelf stable. The American National Standards Institute (guidelines used by most health departments) says something is shelf stable if it has a water activity of .85 or below, or a pH of 4.6 and above. Science proves that under these conditions, the bacteria that causes food born illness cannot grow and thrive. When you add pounds of powdered sugar to cream cheese, you are drastically lowering the water activity level way under .85 (sugar eats water by osmosis). That's why, even with a little cream or sour cream added, ABC icing is shelf stable.
So is ganache - I don't know why people here even question this! There is so much sugar in chocolate and the pH is so high that its' completely shelf stable.
Well I have to correct some of the above. My education taught me that bacteria like pH to be higher than 4--the closer it is to 7, the happier the little buggers are to eat and reproduce. So I went to the link at Earlene's recipe in this thread. Thanks for posting it.
First of all, what is permitted to a cottage food operator varies from state to state. The recipe link is ONLY good for the State of Texas.
Second: here is a link to the link to TX regulations http://www.texascottagefoodlaw.com/Resources/FoodTesting.aspx and the regs themselves
I downloaded the rules and read pages 11-13 carefully: correct info is that a LOW pH is what protects against bacterial growth. The pH and water activity must both be LOWER than set limits, as you can see from the two tables on page 13. That is, FOR THE STATE OF TEXAS.
FYI a partial answer to the original question: I have read the ingredients lists of commercial icings, and they contain potassium sorbate and other chemical preservatives.
Commercial sour cream naturally contains a fair bit of acid, and when you load it with sugar, it may comply with safe rules for commercial restaurants and bakeries but NOT some state cottage food regs.
I will finally say that food establishments usually replenish room-temperature products every few hours from chilled products stored in production fridges. Food put out for sale must be covered if not packaged, and must comply with holding temperature times in some local jurisdictions.