Monday, January 9, 2012

Easy Enzyme Experiment: Protease and Gelatin

In the two beakers of gelatin above, fresh pineapple was added to the one on the left and canned pineapple to the one on the right.  The enzyme protease, present in the fresh pineapple on the left, broke down the structure of the gelatin liquefying it.  The canning process breaks down the protease enzyme so it no longer works so the beaker on the right has solidified gelatin in it

Being that enzymes breakdown molecules or digest them, enzymes are extremely important to our own food digestion.  Every living organism has enzymes within their body in order to do molecular work and we are no exception.  Plants and animals alike have enzymes, and interestingly they often have similar enzymes.  When animals eat protein, in order for them to breakdown the protein so it can be absorbed by the body it must be digested into amino acids.  Amino acids are the individual molecules that when strung together make proteins.  The group of enzymes called proteases are responsible for the breakdown and digestion of protein in the body.  Some plants, such as pineapple also have high levels of protease enzyme.  Specifically, pineapple has a protease called bromelain.  Pineapple bromelain has been utilized for all kinds of medical purposes some of which work and others of which do not.  At least to some degree, it does aid the digestion of proteins if we consume it with meat.  Bromelain also is commonly used as a meat tenderizer, in effect, it is digesting the meat before we eat it.  I have done quite a bit of reading on the internet as to why pineapple would need bromelain in it, but couldn’t come up with anything.  The only thing I can think of is that protease would probably help pineapple fight off infectious organisms.  By using fresh pineapple we can carry out a very simple enzyme experiment demonstrating the action of protease.

As mentioned before, protease digests protein helping to tenderize meat.  This is helpful in some circumstances but not in others.  For example, if you make Jello or any other type of gelatin food, adding pineapple will ruin the dish.  Gelatin makes a liquid into a solid by the action of a protein called collagen.  This is the most abundant protein in humans, composing as much as 25 to 35 percent of all our bodies protein.  It is utilized in connecting and holding things together in the body.  It is also abundant in other animals of course, and almost all collagen protein for gelatin is extracted from pork and beef skin and bone after the butchering process.  Contrary to popular belief, animal hooves are typically not used.  On the side of the Jello box it says to not add raw ginger, pineapple, kiwi, or papaya.  All of these foods naturally contain protease enzymes that would digest collagen and prevent the gelatin from solidifying.  

A basic experiment can demonstrate this:

Fresh pineapple
Jello or gelatin and supplies for making it

1.  Make your gelatin as directed on box.

2. Pour liquid gelatin into multiple containers for different treatments.  For example: 1 container as a control where nothing will be added, a second container where chunks of fresh pineapple will be added, and a third or more where other test items might be added.  Other test items might be canned pineapple, the other fruits mentioned above, or anything else you want to test.

3. Add the fruit to the different containers and let the gelatin solidify.

After the gelatin is supposed to solidify you should find that the gelatin container where nothing was added has solidified.  The container where fresh pineapple was added should still be liquid.  The liquid indicates that protease from the pineapple digested the collagen protein preventing the gelatin from solidifying.  If you add canned pineapple to another container the gelatin should solidify.  This is because heating in the canning process breaks down, or denatures, the protease enzyme in pineapple.  Try other fruits and see what happens or see if cooking fresh pineapple has the same results as canned pineapple.

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