Science Buddies: "Ask an Expert"

I am testing the digestibility of different types of cat food. First I add 300ml of HCl at pH level 2 to 150g of dry cat food to denature the proteins. Then I must add 300ml of meat tenderizer to mimic the acid in a cat's stomach. This will break down the proteins to amino acids. The procedure says to pour the meat tenderizer. Does that mean I need liquid meat tenderizer? Can I use powder meat tenderizer? Will the sodium in powder meat tenderizer affect the protein breakdown? Can I substitute pineapple juice (I saw that recommendation in the fruit dessert project question) for liquid meat tenderizer instead? I appreciate your response.

The type of meat tenderizer matters.

Before you do any substitutions, you need to understand what the procedure writer meant by "meat tenderizer". If you have something specific, you can try to make an equivalent (eg, add water to powdered and get the same result because you essentially cooked up the same kind of meat tenderizer as the original recipe).

It's the same idea as saying "can I substitute powdered milk for milk in a baking recipe". The answer is "probably not, unless the recipe called for skim milk, and even then you need to add just the right amount of water" (powdered milk usually has no milkfat). You can get a box of Mac & Cheese to work without whole milk and butter, but a meal just has a goal of "edible calories" not the kind of precision you're trying to duplicate.

From a scientific standpoint, I'm a bit puzzled by the procedure. It's been a long time since I looked at stomach biology, but hydrochloric acid is the primary component of "gastric acid" Maybe the point of the tenderizer is that it is providing the salt? (NaCL and/or KCl). If that was the case, you'd just need to know the salt content of 300ml of meat tenderizer and maybe just do it with 300ml of water and whatever amount of salt is wanted.