Assuming that a solution of ascorbic acid and vinegar both have the same pH, which would be more ...

Answer to #1

Ascorbic acid because it is also an antioxidant.

Answer to #2

Techniques to prevent browning include the following: add an acid like cream of tartar (acts as a redox reagent to prevent oxidation from occurring) to reduce pH; add an antioxidant; immerse fruit or vegetable into a dilute sodium chloride or a sugar syrup; or blanch it. Browning occurs because polyphenolic compounds in fruits and vegetables are exposed to oxygen and catalyzed by polyphenolases resulting in browning. Individual student responses.

Answer to #3

Using a lid when cooking does influence the pH of the cooking liquid. When the product is heated, the natural acids are released; a lid prevents the acids from escaping out of the saucepan, which promotes an acidic environment. This will discolor the final product. Keeping the lid off of the pan during the first three minutes of heating will reduce acid accumulation.

Answer to #4

When heat is applied to products that contain green chlorophyll, the product will change to a bright green color; however, prolonged heating will result in the formation of pheophytins, causing the vegetable to turn an olive-green/brown. The release of natural organic acids when cooking or the addition of acids will also result in pheophytin formation and a brownish color.

Answer to #5

Vegetables that contain anthocyanin pigments include red cabbage, eggplant, radish, and red potatoes. Fruits that contain anthocyanin pigments include cherries, blueberries, strawberries, plums, and purple grapes.

Answer to #6

Four ways to minimize enzymatic browning include adding an acid to decrease the pH below 4; decreasing the oxygen exposure by coating with sugar or immersing in sugar solutions; applying an antioxidant, such as ascorbic acid or sulfur solutions; and blanching the fruit or vegetable, which denatures the polyphenolic oxidase enzymes.

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