In the absence of calcium ions, the rennin is not activated and cannot
    catalyze the reaction to convert caseinogen into paracasein; thus, the milk
    does not coagulate.

Reference
    Borgford, C., and Summerlin, L. (1988). Chemical activities. Washington, DC:
        American Chemical Society.

Demonstration 2: Pectinase and Apple Juice Production

Purpose
    The activity of a typical enzyme, pectinase, is illustrated in this demonstration.
    Pectinase breaks the cell wall of fruit, producing more “juice.”

Safety
    Students should not eat or drink any of the material from this demonstration.

Materials
    Applesauce
    Pectinase enzyme (available from chemical or biological supply companies)
    Beakers
    Droppers
    Graduated cylinder
    Filter paper

Procedure
    Measure about 50 mL applesauce into each of two small beakers. Add 1-mL
    pectinase to the applesauce in one beaker; add nothing to the other beaker.
    Stir the applesauce in both beakers, and allow to stand for 10 min. Filter
    each, and measure the amount of juice produced from the applesauce with
    and without the enzyme.

Remarks
    Pectin is a large polysaccharide that is present in fruit cells. It prevents
    material, including the juice of the fruit, from settling out in the cells. When
    this large molecule is acted on by the enzyme pectinase, the juice can be
    easily separated. The pectinase enzyme ruptures the cells of the apple,
    allowing the juice to settle and to be easily separated from the other material
    in the cell.

Extensions
    Students should be encouraged to devise activities to answer the following
    questions:
        1.   What is the relationship between the amount of enzyme added and the
              amount of juice produced? [The greater amounts of enzyme will lead to
              production of more juice.]
        2.   What is the relationship between time of standing and the amount of
              juice? [Typically more juice will be produced.]
        3.   What is the relationship between the temperature and the amount of
              juice produced? [Enzyme activity is dependent on the temperature.]

Reference
    Borgford, C., and Summerlin, L. (1988). Chemical activities. Washington, DC:
        American Chemical Society.
 

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