Enzymatic Browning Lab

Enzymatic Browning Lab

Purpose

To determine what does and doesn’t prevent enzymatic browning.

Hypothesis

What do you think will happen with the apple in each substance?

Materials

Lemon Juice

Water

Sugar

Cups

Apple slices

Procedure

1.  Predict the relative amount of discoloration each of these apple wedges will show when exposed to air. Justify your prediction.

Sample 1: Untreated apple wedge

Sample 2: Apple wedge submerged in boiling water

Sample 3: Apple wedge submerged in lemon juice

Sample 4: Apple wedge submerged in sugar solution

2.  Prepare 75 mL of each of the following: boiling water, lemon juice, and sugar solution in three 250 mL beakers.

3.  Slice an apple into 6 wedges. Immediately use tongs to submerge each wedge in a different liquid. Put one wedge aside.

4.  Submerge the wedges for three minutes, then place on a paper towel, skin side down. Observe for 10 min, then record the relative amount of discoloration of each apple wedge.

Data and Observation

Treatment / Lemon / Sugar Water / Boiling Water / Control
Prediction& Why
(I predict__because__)
Observation
(I observe___)
*make observations every two (2) minutes*
Result
(The effect of___ on polyphenol oxidase is____)

*Observation comments*

Completely dark brown

Fully covered light brown

Half-covered light brown

Slight or scant brown patches

No browning present

Discussion Questions:

1.  What causes browning when fresh fruits and some vegetables are peeled or cut?

2.  What conditions enhance the browning process? Why?

3.  How do food additives or treatment processes in use today prevent or slow browning fruits or vegetables?

4.  Why do citrus juices slow browning in fresh fruits?

Conclusion: (Refer to your hypothesis: Were you correct? What were sources of experimental error? What happened?)