Abstract

1
Abstract

• In order to determine the time and method of
  cooking a vegetable so that it maintains the most
  Vitamin C, an oxidation-reduction titration was
  performed to find the concentration of ascorbic
  acid within six different broccoli juice
  solutions.
• The juice from the broccoli soaked for five and
  ten minutes maintained the lowest concentration
  of ascorbic acid (2.94 x 10-7 M 2.83 x 10-9 and
  4.68 x 10-7 2.12 x 10-8, respectively). Cooking
  the broccoli on the stove for five and ten
  minutes released the most Vitamin C into the
  water (7.58 x 10-5 1.06 x 10-6 and 1.37 x 10-4
  0, respectively). Microwaving caused the
  five-minute sample to release 8.10 x 10-7 8.49 x
  10-9 and the ten-minute sample to release 9.51 x
  10-7 2.89 x 10-8. The healthiest preparation
  for broccoli would be to leave it uncooked or
  cooked for a minimum amount of time.

2
Introduction

• The objectives
• To find the concentration of Vitamin C within
  broccoli juice solution samples.
  
• To determine the time and method of cooking
  broccoli so that the vegetable maintains the most
  ascorbic acid.

• The assumptions
• The broccoli juice contained the ascorbic acid
  released during cooking therefore, the solutions
  with lower concentrations of Vitamin C maintained
  more ascorbic acid in the vegetable.
• Soaked broccoli and broccoli sitting in the water
  the least amount of time should retain the most
  ascorbic acid.

3
Materials and Methods
125 mL Erlenmeyer flask Beakers Broccoli Buret
Dichlorophenol-indophenol Distilled
water Microwave Pure ascorbic acid Solid meta-p
hosphoric acid Stove Tap water Volumetric glass
kit Ziploc bags
Using parallel dilutions dilute the 5 x 10-3 M
DCIP solution to 4 x 10-5 M. Titrate the 20 mL
solution (10 mL broccoli juice and 10 mL
metaphosphoric acid) with the 4 x 10-5 M DCIP
solution until the solution turns a light pink.
4
Broccoli Juice Samples
Bought a head of broccoli from Frys grocery
store. Stored it in an airtight Ziploc bag in a r
efrigerator. Head of broccoli cut into six pieces
of similar weight (approximately 26.0000
grams). Pieces of broccoli cooked in 330 mL of ta
p water Boiled two pieces of broccoli on the sto
ve in an aluminum pot for 5 and 10 minutes.
Microwaved two pieces of broccoli for 5 and 10
minutes in a ceramic bowl. Soaked two pieces of b
roccoli in room-temperature water for 5 and 10
minutes in a glass jar. Broccoli removed from jui
ce and juice stored in clean plastic soda bottles
in a refrigerator until needed.
5
Observations

• Color of solutions ranged from lightly tinted
  green to dark green.
  
• When metaphosphoric acid was added, the broccoli
  samples went colorless.
  
• When the titrated solutions were allowed to sit
  for 30 minutes or more, the color pink had
  disappeared.
  
• Water was lost during the cooking of the broccoli
  in the stove and microwave.

6
Results
7
Further Work

• Other tests using broccoli juice solutions
• Titrating a solution of digested pieces of
  broccoli instead of just the solutions in which
  the broccoli was cooked.
  
• Differing the amount of water used to see if the
  amount of water used in cooking affects the
  amount of ascorbic acid released into the water.
  
• Titrating other vegetables using the methods
  prescribed earlier in order to see whether they
  lose ascorbic acid in relatively the same way as
  broccoli.

• Recommendation for the previously specified
  methods
  
• Boiling/microwaving/ soaking broccoli for a
  larger variety of times (such as samples cooked
  for 5 minutes, 10 minutes, 15 minutes, and 20
  minutes).
• Allowing titrated solution to be a darker rose
  color instead of a light pink.