Are the oats in overnight oats processed differently by milk than by milk substitutes?

Question

I've read some recipes/blogs that say that overnight oats can be made with milk substitutes such as almond milk. Other recipes/blogs I've read say that enzymes found in milk help to break down the oats, which allows for the long soaking process to serve as an alternative to cooking them with high heat.

Clearly many people make overnight oats using milk substitutes, so it works to some extent, but does using actual milk make a notable difference in how the oats end up? Does the choice between milk versus milk substitute affect their nutritional profiles (as one can break down more/different substances in them than the other)? Does the choice between milk versus milk substitute affect their texture?

Perhaps the claims about enzymes in milk being important for the oats are simply incorrect. After all, processing techniques commonly used for milk (e.g. heat treatment) destroys/deactivates many of the enzymes in milk.

Answer 1

The main enzymes found in milk are: alkaline phosphatase, lactoperoxidase, lysozyme, lipase, proteinase, cathepsin D. (Jimenez-Flores, 2013). These enzymes appear in very low concentrations in pasteurized milk. Most of them have to do with protein digestion for the calf (to make proteins in the milk itself more accessible to the calf) and some antibacterial action. I did not see any carbohydrate enzymes - which would soften or otherwise digest the oats in question.

The real impacts on your overnight oats will come from the type of oats. Rolled oats will soften much more than steel cut oats as they have more surface area exposed to the liquid. Instant oats have less of the germ left so may be less nutritious. Also anecdotally the rolled oats taste chewier for a better mouth feel than moist instant oats.

My family has made overnight oats both ways, and the verdict among us seems to be that the oiliness is what gives a smoother overnight oats. Therefore oilier milk or milk substitutes tended to get a better reaction than more watery substitutes; think soy milk (generally more oily) vs. Oat milk (generally more watery).

There is a way to have the best of both worlds: use 1/8 cup chia seeds for every cup of oats. They release a gel that really helps the mouthfeel of the meal, especially if using a waterier milk substitute like almond milk.

A lot of this is necessarily anecdotal, but it seems at least agreed upon among my close ones after about two years of trial and error.