I was browsing through the USDA Food Search system for data on various foods, when I noticed they include how much of a food is water. What really perplexed me is how 81.1 grams out of 100g of russet potato is water… when 88.1g of 100g of milk is also stated as water.
Obviously a potato isn’t liquid like milk, and my intuition would say that 100g of potatoes seem far denser and “drier” than 100g of milk. I mean can you imagine sating your thirst with just solid potatoes, as opposed to say a glass of milk?
But yet I can’t make sense of why one is solid and the other is liquid when they’re nearly the same in water content, or why one would seem to sate thirst more.
​
Bonus question: does this mean you poop about as much from 100g of milk as you would from 100g of, potatoes? I guess you could blend the potatoes…
In: 7
Milk, real cows’ milk, directly from the source, is very different than what you are buying from the store. Milk has cream and liquids. It’s cream is sweet, light, and fatty.
The stuff you buy from the store has gone through a process called “homogenization”, where they force all of the fatty cream through a fine mesh to make one uniform liquid. The fats are mixed so small that you can’t see them or feel them in your mouth. And if you buy skim milk or reduced fat milk, you are losing a lot of those non-water parts. Watch a video about churning butter to get a good idea about how much solid you can get; it can be surprising if you have not seen it before.
The other major components of milk are proteins and sugars. Unlike the fats, the proteins and sugars are soluble. They mix well into the water and it stays liquid. Imagine stirring in sugar into a cup of water – the water can dissolve a lot of sugar while still looking just like water.
Store bought milk is basically a natural protein shake with microscopic drops of oil blended into a super smooth liquid.
Potatoes on the other hand are cellular organisms. From the store, a potato has almost no “free” liquid. That means all of the liquid is trapped inside of cells (while milk has almost zero cells mixed in). Cell walls are very thin protein sacs. The cell walls have very high surface area per volume. This means that even if you break open a cell, there is still a mostly in tact sac of protein.
The last major piece of the puzzle is what plants use as sugar: starch. Inside the cells of potatoes is a good bit of starch, and it doesn’t take much starch to make water become viscous. For instance, corn starch is used in cooking to thicken sauces, and a little bit goes a LONG way. The difference between sugar and starch in water is pretty crazy. A tablespoon of starch can turn a sauce from soup to goop, where a tablespoon of sugar will not change the texture at all.
Latest Answers