Experimental Teaching Material Development for Understanding the Digestion of Protein

Abstract

A method using an experimental teaching material to illustrate enzymatic digestion of protein to amino acids was verified. Experimental teaching materials and a method were developed to explain digestion of protein to students. Dried bonito shavings (no-processing, powdered and extracted once), boiled egg albumen, tofu and confectionery gelatin were chosen as substrates. A pack of "Balancer-Ichoyaku granules" was dissolved in 100 mL of purified water and used as a digestive fluid. (1) Ninhydrin reactions were positive and amino acids were detected in 24-h incubated samples of dried bonito shavings (no-processing and extracted once}. egg albumen, tofu and gelatin. (2) Visible changes of protein were confirmed only in the tofu and gelatin. (3) In the gelatin only, the biuret reaction became negative with digestion. According to these results. gelatin is the best protein for use as a substrate. Comparable results to those of Balancer-Ichoyaku were obtained by substituting other digestive agents. In addition, results were confirmed in which an inactivated digestive solution was incapable of digesting gelatin. Students can thereby understand protein digestion using the following series of experimental methods. (1) Weigh 2.0 g of confectionery gelatin and then was dissolved in 50 mL of running 80 ℃ water. A test tube containing 2.0 mL of this gelatin solution was refrigerated. (2) Into the test tube 10.0 mL of artificial digestive solution prepared from the digestive agents was poured, and kept for 24-h at 40 ℃. After incubation, it was refrigerated for at least 1-h. (3) In the refrigerated samples, in which gelatin gel had not solidified, the biuret reaction was negative and the ninhydrin reaction was positive, confirming that the protein has been digested and changed to amino acids. (4) By using an inactivated digestive solution, it was confirmed that the gelatin gel had solidified and was not digested.