Expert: Florence M Rollwagen - 3/30/2009

Question
Hi:

I've heard that bacteria can easily digest and metabolize carbohydrates and proteins but cannot metabolize lipids. If this is true, then can bacteria be used to breakdown all the carbs and proteins in the milk [which pretty much constitute most of the non-fat milk solids] to make the butter? Once the proteins and carbs are metabolized by the bacteria, they will no longer be in the hard solid form the originally were in. For example, casein [the chief milk protein] is solid, however, once bacteria break it down, they will convert it to amines, ammonia, propionic acids and other volatile compounds -- some maybe solid but very soft and not take up as much space as the original casein.

I'm guessing if all of the above happens, then the end result will resemble butter. Right?


Thanks,

Green

Answer
Hi Green:  An interesting question, but based on a false premise.  Bacteria can indeed metabolize (synthesize and digest) lipids.

When butter is made, the cream is vigorously mixed and the fat coalesces out from the milk solids (sugars and proteins).  The fat globules are scooped out and kneaded to release trapped water and you are left with butter.

Here's a link on butter making:

http://goldenrodfarm.tripod.com/BUTTER.HTM

Hope this helps!

FM Rollwagen, PhD