Abstract: The purpose of this experiment is to determine whether 5 ml of 0.1M HCl in a 40 gram sample of gelatin with pineapple chunks is enough to denature the enzyme bromelin found in fresh pineapple and prevent it from breaking down the collagen in gelatin.
Introduction:
On Jello boxes, there is often the direction: Do not add uncooked pineapple. The reason behind this seemingly random warning lies in the fact that Jello is mostly gelatin, which is hydrolyzed collagen (http://www.greatlakesgelatin.com/consumer/CollagenFAQ.php), which in turn consists of long strands of protein. Pineapple contains an enzyme, Bromelin, which breaks down many different types of proteins (http://science.howstuffworks.com/innovation/edible-innovations/pineapple-enzyme-tenderize-steak1.htm). Pineapples probably contain Bromelin to speed up the digestive process in its consumers and thus encourage less deterioration of the seeds in the digestive tract.
Usually the digestive system breaks down food, but if Bromelin breaks down the proteins that make up cellular structure, the digestive system* will expel the pineapple containing Bromelin.
Enzymes only work in a certain ph and temperature range. If their environment is unsuitable, enzymes become denatured and their active sites change shape. they can no longer accept substrates and preform their duties as catalysts. By changing the pH of the jello, we hope to denature bromeliad and prevent it from breaking down the collagen in our Jello so that the jello will harden.
*the digestive system works like this:
in the MOUTH,
salivary amylase from the salivary glands breaks down polysaccharides into smaller polysacchs like maltose.
the tongue and teeth mash up the food, which goes down the pharynx and esophagus into the stomach.
The STOMACH contains HCl acid and pepsin (which digests proteins into small polypeptides).
In the first part of the small intestine, the LUMEN, there is
pancreatic amylase (from the pancreas) which breaks polysaccharides into DIsacchs like maltose, sucrose, lactose. there is also
pancreatic trypsin and chymotrypsin which break polypeptides into down further so that
pancreatic carboxypeptidase can break these smaller polypeptides into amino acids.
Pancreatic nucleases break down DNA into nucleotides.
Bile from the liver/gallbladder break fat into smaller droplets so that
pancreatic lipase (from the pancreas) can dissolve the droplets into glycerols, glycerides, and fatty acids.
in the EPITHELIUM of the small intestine,
disaccharidases break any remaining saccharides into monosacchs like glucose, galactose, and fructose.
dipeptidases, carboxypeptidases, and
amino peptidases brake down amino acids into really basic amino acids.
Nucleotidases turn nucleotides into nucleosides, which then turn into nitrogen bases, sugars, and phosphates after being processed by
nucleosidases and phosphatases.
and then everything moves to the duodenum(the large intestine) to process and to the jejunum and ileum for absorption into the bloodstream, then to the large intestine where water is sucked out, and to the cecum where mucus is added, then to the colon and rectum where food ends its journey through the digestive system.
Hypothesis: 5 ml of 0.1M HCl
will denature the enzyme and allow the jello to set in the presence of (technically) uncooked pineapple.
Materials:
1. pack of Green Jell-O powder
2. 3xPetri Dishes
3. 100 ml Boiling water
4. 100ml Cold Water
5. some Fresh Pineapple chunks
6. 0.1 M HCl acid
7. 15 ml or 25ml graduated cylinders
8. ph paper
9. 3x50 ml beakers
Procedure:
1. Measure out 6.67 grams out green jell-o powder into each 50 ml beaker.
2. Add 20 ml of boiling water to each beaker. stir
3. Add 19 ml of cold water to the first TWO beakers. stir.
4. Add 14 ml of cold water and 5ml of 0.1M HCl to the third and last beaker. stir.
5. Use pH paper to take the pH of the contents of each beaker. record.
6. Pour solution of each beaker into its own dedicated petri dish. label each.
7. place 2 grams worth of fresh pineapple chunks into ONE HCl-free jello sample.
8. place 2 grams worth of fresh pineapple chunks into the HCl laced jello sample.
9. wait for the pineapple-free jello to set. record whether the other two samples have set.
Data:
pH no HCl: 4 for both samples
pH yes HCl: 3
no HCl/ no pineapple: Set
no HCl/ yes pineapple: no set
yes HCl/ yes pineapple: no set
Conclusion: No, 5 ml is not sufficient for our purposes. We can verify that our control sample did set, meaning we mixed the jello correctly, and in future experiments more drastic change in pH should have the desired effect of denaturing the enzyme Bromelin.
Errors could include diluting the acid with water in the measuring graduated cylinder, which would have slightly lowered the amount of pH change we could cause in our jello samples. We could have mixed the non-control samples of jello incorrectly: adding too little gelatin mix or too much water.
