Development of the laboratory experiments for the digestion of protein at secondary school

Abstract

We have developed a laboratory experiment for the digestion of protein at secondary school. We used trypsin and papain as the protease, and the protein rich substrates ; egg white, milk, powdered skimmed milk, and tofu cake. We stuffed 10g of the substrate suspension into a dialysis membrane bag with 5ml of 1% enzyme solution, and soaked it in 30ml-buffer solution at 37°C. Then we sampled 2ml of the buffer solution every 5 minutes, and the Ninhydrin Reaction of each sample was examined and wes measured using the colorimerty of 570 nm wave length. As a result, we could detect the increase of digested products within 30 minutes not only quantitatively but also visually. We examined further experiments to test the optimum pH and temperature of these enzyme reaction. The optimum pH of each enzyme could be found out, but the optimum temperature could not be measured distinctly. The best result was obtained using the powdered skimmed milk as substrate. Using this substrate we could detect the decreasing step of the substrate as a visual color change from the original white to colorless.