The most common marijuana infused food products are typically baked goods-items like cookies, brownies and cakes. These are considered to be fairly safe items because they are baked to a very dry state and usually have high amounts of sugar. A dry high sugar environment is not ideal for yeast and mold growth.
If your baked good is not dry enough, or it doesn’t have enough sugar—or it has some high moisture inclusions like fruit or jam, your product may all of a sudden be a happy growth medium for spoilage bacteria.
In food science, the term “moisture” refers to how much water is in a food product, but “water activity” (aw) is used to describe the amount of available or “free” water in a food product or its environment. The free water is what microorganisms can access to grow and thrive in a food system. The aw of pure water is 1.00; the aw of a completely dehydrated food is 0.00. The aw can be manipulated and lowered in foods by adding solutes such as salt or sugar, physically removing water through drying or baking, or binding water to various components in the food like fiber, sugar or starch.
It is difficult to know exactly which combination of ingredients will give you a finished food product that does not support spoilage bacteria growth. You could just take a chance- make your baked good, wrap it up and sell it around town but a better way to ensure a clean mold free product is to have a simple water activity (aw) test performed on your product. Any food-testing lab can do this. You want your aw to be around the 0.65 to 0.7 range—the lower the aw the longer your product will remain yeast and mold free.
Follow this path to ensure shelf stability of your baked good product:
Create and document your recipe in grams, keep track of your oven time and temperature, this will ensure consistency in the long run.
Take your finished good to a local food lab and ask them to test the aw. It should be less than 0.70.
Test every baked good batch for a few months till you feel secure that your process and cook time are giving you consistent results.
The aw of your baked good can be used as a quality control measure to help ensure that your baked good will last longer on the shelf. You should package it in a sealed foil package that will keep out moisture, air and light. A shelf life study should be done on your product before selling it to the masses. The aw unit can be purchased from Decagon (aqualab.com), the only U.S. manufacturer of Water Activity equipment. A handheld unit will cost about $2,000.