Traditional Food
Preservation
Pemmican and Vitamin C
Food Preservation
Food Preservation
Ways to preserve food:
Pemmican
•
Dried meat
- pounded into coarse powder
•
Melted fat
•
Dried berries
Drying Berries
• Preservation method
- prevents spoiling of berries
- can eat berries all year long
• Preserves vitamins and minerals
Example: vitamin C (ascorbic acid)
Vitamin C Titration
Detecting Vitamin C in fruit
Vitamin C titration
No colour change!
Colour change!
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=
Step 1: Gather supplies
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Berries
Diluted tincture of iodine
1% (w/v) starch solution
2 cups
Fork
2 eye droppers
2 small clear cups or test tubes
Stir stick (e.g. straw or popsicle stick)
Step 2:Mash berries
• Add berries to cup
• Mash berries up with fork
Step 3: Mash berries (cont.)
• Add an equivalent amount of water to the
cup and continue to mash
• Remove the pieces of skin and other large
chunks
Step 4: Aliquot berry juice
• Separate the berry juice into two containers
Step 5: Add starch solution
• Add 10 drops of 1% starch solution per
0.5mL of berry juice and stir sample
• Be sure to stir starch solution before use
Step 6: Begin titration
• Add one drop of the iodine solution to the
sample you added the starch to.
• Stir solution if colour change observed
• If colour disappears continue to step 5
Step 7: Continue titration
• Continue to add iodine one drop at a time
• Stir solution after each drop is added
• The titration is done when the colour
change remains after stirring
Step 8: Determine
approximate Vitamin C
concentration
• Can you determine the concentration of
Vitamin C in the berry juice?
Step 9: Repeat Steps 2-8
• Repeat steps 2-8 using berries preserved
using a different method (fresh, frozen,
boiled, dried, juice)
• Compare results between preservation
methods
- which berries require more drops of
iodine?
- what does this tell us about the
different preservation methods?