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Antioxidants (May 2009-1)

Antioxidants (May 2009-1)

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Antioxidants (May 2009-1)

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  1. Antioxidants (May 2009-1) • Antioxidants occur naturally and are often added to extend the shelf life of our food. • Define the term antioxidant (1) • State two naturally occurring antioxidants and one source of each (2) • State two other traditional methods of extending shelf life of food (2) • Table 22 in the Data Booklet shows the structures of some antioxidants. Determine the two functional groups that are found in all of these synthetic antioxidants: 2-tert-butyl-4-hydroxyanisole (2-BHA), 3-tert-butyl-4-hydroxyanisole (3-BHA), and 3,5-di-tert-butyl-4-hydroxytoluene (BHT) (2) • Discuss one advantage and one disadvantage of using natural antioxidants (2)

  2. Antioxidants (May 2009-1) • A substance that delays the onset or slows the rate of oxidation • Vitamin C= citrus fruits/green leafy vegetables/broccoli/peppers/strawberries/potatoes… • Vitamin E= wheat germ/nuts/whole grains/green leafy vegetables/vegetable oils • Beta-carotene: carrots/squash/broccoli/sweet potatoes/tomatoes/kale/cantaloupe/peaches/apricots • Selenium: fish/shellfish/red meat/eggs/grains/chicken/garlic • Fermentation/canning/pickling/smoking/salting/drying/cooling/reduced exposure to light • Alcohol/hydroxyl and alkene/benzene/aromatic • Advantages: Vitamin C/E and carotenoids reduce the risk of cancer and heart disease; Vitamin C prevents scurvy; beta-carotene is used to give color to margarine • Disadvantages: Add color, aftertaste, less effective at slowing the rate of oxidation/rancidity than synthetic antioxidants Antioxidants occur naturally and are often added to extend the shelf life of our food. • Define the term antioxidant (1) • State two naturally occurring antioxidants and one source of each (2) • State two other traditional methods of extending shelf life of food (2) • Table 22 in the Data Booklet shows the structures of some antioxidants. Determine the two functional groups that are found in all of these synthetic antioxidants: 2-tert-butyl-4-hydroxyanisole (2-BHA), 3-tert-butyl-4-hydroxyanisole (3-BHA), and 3,5-di-tert-butyl-4-hydroxytoluene (BHT) (2) • Discuss one advantage and one disadvantage of using natural antioxidants (2)

  3. Color (Nov 2010) • Distinguish between a food dye and a pigment (2) • The pigment in blueberries is anthocyanin • With reference to the color wheel above, explain how the pigment in blueberries causes them to be blue (2) • List 2 other fruits that contain significant amounts of anthocyanin(s) (2) • State the combination of pH and temperature that produces the strongest color in anthocyanins (1)

  4. Color (Nov 2010) • Dye: synthetic (water-soluble) colourant; Pigment: naturally occurring colourant; [2] • (a) red/orange/yellow absorbed; blue/complementary colour reflected/transmitted; [2] (Note: Award [1 max] for all colours other than blue absorbed.) • (b) strawberries; raspberries; cranberries; blackberries; blackcurrants; cherries; (red) plums; (red) grapes; [2 max] (note: Accept other correct answers, but do not accept answers which are not fruits e.g. beets, flowers…) • (c) low pH and low temperature; • Distinguish between a food dye and a pigment (2) • The pigment in blueberries is anthocyanin • With reference to the color wheel above, explain how the pigment in blueberries causes them to be blue (2) • List 2 other fruits that contain significant amounts of anthocyanin(s) (2) • State the combination of pH and temperature that produces the strongest color in anthocyanins (1)