Introduction – For some strange reason, gelatin and fresh pineapple do not get along. When juice of the fresh pineapple, unchanged from its natural form, comes into contact with the gelatin, it changes the gelatin from a solid into a liquid that cannot be reformed into gelatin. A very interesting occurrence in life, and we want to why this is. We have a hypothesis, and it is that the juice from the pineapple contains enzymes, which break down protein. So to prove this we have to do multiple experiments that test the qualities of enzymes so it can be narrowed down to be one thing, which we believe is enzymes.
All our experiments have to be controlled experiments, or experiments that only have one variable factor and a control group to compare the results to. We will use Petri dishes, or sterile circular plates where I can observe the experiments as they take place.
Hypothesis – The colder pineapple juice will break down the gelatin slower than the room temperature pineapple juice.
Also, the warmer pineapple juice will break down the gelatin faster than the room temperature pineapple juice. I think this because when molecules heat up they vibrate faster and therefor the enzyme will touch more substrates, which will get more gelatin broken down. However, the boiled pineapple juice will not work because the enzyme will be denatured because of the heat
Procedure- Take four even amounts of pineapple juice and put it in different test tubes.
Put one test tube in a tube full of ice water, another in hot water, and leave them in for fifteen minutes. Also, put one test tube over a flame until it boils for a short amount of time, and leave one at room temperature. Put the juice from each test tube onto different piece of gelatin after waiting for the boiled pineapple juice to cool so it won t melt the gelatin. and wait for 25 minutes. Then put the Petri dish in the refrigerator to see if the liquid around the gelatin reforms into gelatin again. Our experimental groups are the juices that the temperature is changed and the control group is the room temperature juice.
Results – The boiled pineapple juice made no indent in the gelatin, the colder juice made a small indent, the room temperature made a medium sized indent, and the warm juice made a larger indent. Also, none of the liquid around any of the gelatin
Indent Yes Yes Yes No
Size Medium Smaller Larger None
Reformation of liquid No No No Not applicable
Conclusion- As we hypothesized, the warmer the pineapple juice was the faster the gelatin was broken down, until it got to the point where the enzyme was denatured (boiling).
Hypothesis- We think that the more the acidic the solution is, the faster the enzyme will work, and the more basic the solution the slower it will work.
Procedure – Take 6 test tubes, fill with same amount of pineapple juice and add hydrochloric acid to it to create a solution with a pH of one and three in. Leave one test tube without anything added. Then take sodium hydroxide and add it to the pineapple juice to get a neutral pH, a pH of nine, and a pH of eleven. Mix well and then add onto gelatin. Leave for 24 hours and then observe.
Results – The pH of one did not have an indent, the pH of three worked very well, the unchanged pineapple juice worked like regular, the neutral pH did not work as well as the unchanged, the pH of nine worked even worse, and the pH eleven did not work at all.
pH 1 pH3 pH 5 pH 7 pH 9 pH 11
Indent No Yes Yes Yes Yes No
Size None Biggest 2nd Biggest 3rd Biggest 4th Biggest None
Conclusion- We realize now that enzymes only work in a narrow range of pH, this one being from three to nine. So if we had looked over our notes more carefully we would have understood and had a better hypothesis. Still, the results describe the characteristics of enzymes.
Hypothesis- I think when I put only a small amount of pineapple juice on the gelatin that, if I give it enough time, it will break down the entire gelatin. I think this because enzymes are unchanged after they break up a substrate, so the enzyme can keep on working over and over again and ultimately break down all the gelatin if untouched.
Procedure – Take a piece of gelatin and put one small drop of pineapple juice on the top. Observe for four days. Our experimental group is gelatin with the pineapple juice on it for multiple days and the control group is the gelatin after only one or two days.
Results- The gelatin got progressively smaller each day that the pineapple juice was on it until there was only a ring of gelatin where the juice did not touch and liquid at the bottom of the Petri dish.
Conclusion- Our hypothesis was correct, the piece of gelatin continually got smaller.
Hypothesis- We think that pineapple juice will have protein in it because enzymes are made of protein and I believe that pineapple juice has enzymes in it.
Procedure- Take 4 milliliters of pineapple juice and add three drops of Millon s reagent, which tests for protein, to it in a beaker. Compare color to that of 4 milliliters of water (which has no protein in it) when it has three drops of Millon s reagent in it.
Results- The color of the pineapple juice was much darker than that of the water, meaning that there was protein in the pineapple juice.
Pineapple Juice Water
Color Dark Light
Protein Yes No
Conclusion- There was protein in the pineapple juice, and if there wasn t then our hypothesis about enzymes would be incorrect. So this is was way to prove that enzymes might be a part of the juice.
Hypothesis- We think that if we make twice the amount of substrate accessible for the enzyme, it will break it down twice as fast.
Procedure- Take one square of gelatin, put pineapple juice on it, and then put another piece of gelatin on top of it. Let sit for a day. My control group is one piece of gelatin with the same amount of juice on it. Compare the amount of liquid in the bottom of the dish and the extent that the gelatin is broken down.
Results – The Petri Dish with twice as much gelatin had more liquid at the bottom and there was about the same amount of solid gelatin as one whole square, while the Petri dish with only one square of gelatin had about half of one whole piece of gelatin.
Two Pieces of Gelatin One Piece
Liquid in bottom Quite a bit About half of Quite a bit
Amount of gelatin left in Petri dish About one piece of Gelatin About half a piece of Gelatin
Conclusion- Seems that our hypothesis was correct, the pineapple juice broke down twice as fast when it had twice as much substrate available to it. Remember, when you do this experiment, make sure to put the juice in between the two pieces of gelatin, because if you don t and just put it on top, the extra substrate isn t available for the catalyst, which will alter the results.
Hypothesis- I think it is not weight that makes the impression in the gelatin, so the water the same weight as the pineapple juice will make no impression
Procedure. Put one drop of pineapple juice on a piece of gelatin, and one drop of water on another. Observe after 24 hours. The control group is the gelatin with the pineapple juice on it and the
experimental group is the gelatin with the water on it.
Results – The water made no impression, and the pineapple juice did.
Pineapple juice Water
Impression Yes No
Conclusion- Weight is not the reason that the impression is made.
Hypothesis – The enzyme will not break down starch because it breaks down protein and we dont think that it will break down two things.
Procedure-mix starch solution with two milliliters of pineapple juice and let sit for one hour. Add a drop of Lugol s lodine in with solution. Compare color to that of starch solution mixed with two milliliters of water and one drop of Lugol s lodine. My control group is the starch with the water and my experimental group is the starch with the pineapple juice.
Results – The color of the water and starch was darker than the pineapple juice and starch, which means that the pineapple juice broke down starch as well as protein.
Starch with Pineapple Juice Starch with Water
Color Medium brown Dark brown
Break down starch No Yes
Conclusion-Seems that we were wrong, that the enzyme does break down starch. That s OK, because I looked back in my notes and saw that the intestine breaks down starch and protein, so there are enzymes that break down two substrates.
Hypothesis- We think that the stomach extract and the intestine extract will break down gelatin because in our notes it says that they both break down protein. The spit will not work.
Procedure- Take four drops of spit, stomach extract, and intestine extract put them on separate squares of gelatin. Let sit for 24 hours. The control group is fresh pineapple juice on gelatin and the experimental groups are the different bodily fluids on the gelatin.
Results – The spit and stomach extract made no indentation in the gelatin, but the intestine extract did.
Spit Stomach Extract Intestine Extract
Impression No No Yes
Conclusion. The stomach acid didn t work, very unexpectedly. However, the Intestine extract did which also breaks down starch, very much like pineapple juice. So pineapple juice is a lot like intestine extract.
Hypothesis- We think that canned pineapple juice will not break down gelatin because it has been pasteurized, which will denature the enzyme.
Procedure- Take six drops of canned pineapple juice and put it on gelatin. Leave for 24 hours and then observe. The control group is the regular pineapple juice on gelatin and the experimental group is the canned pineapple juice on the gelatin.
Results- The canned pineapple juice did not leave an impression.
Fresh pineapple juice Canned pineapple juice
Impression Yes no
Conclusion- My hypothesis was correct, the canned pineapple juice was denatured and unable to make an indent in the gelatin.
Room Medium No
Cold Smaller No
Warm Larger No
Boiled none Not applicable
pH 1 None
pH 3 Biggest
pH 5 Second biggest
pH 7 Third biggest
pH 9 Fourth biggest
pH 11 None
First day None
Second day Small
Third day Big indent
Fourth day All the way through
Pineapple Juice Dark Yes
Two pieces more than usual About one whole piece( missing one piece)
One piece Regular amount One half( missing only one half a piece)
Pineapple juice Yes
Starch with pineapple Medium Brown Yes
Starch with water Dark brown No
Stomach Extract No
Intestine Extract Yes
Canned pineapple juice no
From the beginning of the lab we thought it was enzymes. A hint from our teacher was that everyday before class he would tell us to read our enzyme notes. The answers will pop out at you, he said. That should be proof in itself. Yet I doubt that we would get a good grade if that s all I said so I will continue. We knew it was enzymes, so then it was all a matter of testing the qualities of enzymes. Enzymes have certain qualities that are not very common throughout the physics of the world. One of these being that they are unchanged when they finish their job of joining or breaking up two elements. We tried to test for this by putting a very little amount of pineapple juice on the gelatin and letting it have time to keep on breaking it down. If we had had time, we would have taken it to a further extent and taken the liquid from the bottom of Petri dish and put it on a piece of gelatin.
A similar experiment but testing for a completely different concept was doubling the available substrate by placing a second piece of gelatin on top of the piece of gelatin with the pineapple juice on it. This was testing that the more substrate available, the faster the catalyst works because it spends less time looking for something to do. This experiment went as planed, the two pieces of gelatin were broken down by the same amount of juice in half the time as the standard juice on top of the gelatin experiment.
Another thing related to this experiment is the kinetic Molecular Theory. This states that if you heat up something, the molecules start vibrating faster and touch more things. So instead of touching more substrate because it was crowding the catalysts like the last experiment, the catalyst touch more substrates because they re moving around faster or are not touching as many substrates because they re moving slower. Depends whether you are heating them up or cooling them down. However, if you heat them up too much, they become denatured and stop working. This happens when you boil or pasteurize it.
Which brings us to our next experiment, whether or not the canned pineapple juice would break the protein down. Well, everyone knows that canned stuff is pasteurized, so of course the canned pineapple juice wouldn t break it down.
Which leads me to another no brainer experiment. Whether or not the weight of the juice was causing the indentation. It was a possibility, so we had to test for it. We put the same weight of water as
pineapple juice on separate pieces of gelatin, and, as expected, there was no indentation under the water. So much for that hypothesis.
Which leads me to my other experiments that have to do with water. We tested whether the pineapple juice had protein in it (which it did) and used water to compare the color to. We had to see what water looked like because we knew that water had no protein in it if the pineapple changed to a different color than the water than it had protein in it. Also, we used water when we tested whether or not the enzyme broke up starch, because if we used straight starch than of course it would be darker, the concentration of starch wouldn t be as great. The pineapple juice ended up breaking down starch, which leads into another experiment.
What type of bodily fluid breaks down both protein and starch? Well, that would be the fluid that is located in the intestine. We just happened to have some in class (I don t want to know who it was extracted from) so we tested that as well as spit and gastric juices. The last two didn t break down the gelatin, but good old intestine juices did. So the enzyme in pineapple juice is a lot like the enzyme in the intestine. And the intestine has a pH, which leads us to our final experiment.
Enzymes only work in a narrow range of pH, and there is a pH where a certain enzyme works best. The pH for this enzyme where it worked best was three. If it got to a higher concentration of hydrogen ions than that the performance went down rapidly, and if it became more basic, it declined slowly until at eleven it worked no more. The normal pH was five.
Well, that concludes the infamous pineapple lab, which I, must say, takes a very long time to write up. But, by golly, it was so much fun mashing fruit with the mortar and pestiles, and boiling pineapple juice smells 336.78 times better than boiling spit.