You have surely also found the following results after 10 minutes of your experiments:
| Experiment | Result |
|---|---|
| Experiment 1: green kiwi with milk | bitter, not homogeneous |
| Experiment 2: cooked green kiwi with milk | not bitter |
| Experiment 3: green kiwi heated to 60 °C with milk | bitter, relatively homogeneous |
| Experiment 4: green kiwi with oat milk | not bitter, not homogeneous |
| Experiment 5: pineapple with milk | very bitter! not homogeneous |
| Experiment 6: cooked pineapple with milk | not bitter |
| Experiment 7: pineapple heated to 60 °C with milk | bitter, relatively homogeneous |
| Experiment 8: pineapple with oat milk | not bitter, not homogeneous |
| Experiment 9: canned pineapple with milk | not bitter |
It thus becomes apparent that dairy products become bitter after a short time when combined with fresh green kiwis or fresh pineapple. The enzymes in the green kiwi or pineapple react with components of dairy products, and one of the reaction products tastes bitter.
If these fruits are cooked for 5 minutes, the enzymes are destroyed, and the dairy products continue to taste delicious. If these fruits are only heated with 60 °C hot water, this is not sufficient to destroy the enzymes. In fact, the enzyme bromelain, which is responsible for the reaction with dairy products in pineapple, is relatively temperature-stable compared to other enzymes in fruit and even has its highest activity at 50 °C. However, at temperatures above 50 °C, bromelain slowly begins to denature. Canned pineapple is pasteurized during processing, meaning it is heated to such a high temperature that the enzymes are denatured and no longer pose a risk of making dairy products taste bitter. No reaction occurs with oat milk either, but the mixture did not remain homogeneous for us.
Why do we repeatedly emphasize that these experiments should be done with green kiwis? Try it out or take a look at the experiment “How can kiwis cause trouble in a milkshake?” here at Kniffelix!
And what does this have to do with biotechnology?
Bromelain is not only an enzyme that can be annoying in the kitchen, but it is also obtained as an important raw material and used in the food industry, cosmetics, dietary supplements, and as an active ingredient in medications. The extraction and use of enzymes is a subfield of biotechnology.
Specifically, bromelain is used for tenderizing meat, in brewing and baking, and for the production of protein hydrolysates, which serve as a protein source for athletes, for example. Further applications are found in the leather and textile industries, in wool production, for skin care, and in detergents.