Lab 4. EFFECT OF HEAT & pH ON COLOR & TEXTURE OF GREEN VEGETABLES
Part 1
pH (acidic, neutral,
basic)
Drained solution
Color
Peas
Color intensity
Color
(scale 0-10)
Color
Firmness
intensity
(0-10)
(0-10)
Cold
neutral
No color
0
Bright green
10
10
neutral
Pale green
1
Yellow-green
5
5
Vinegar acidic
Pale green
1
Olive green
2
8
Baking
Yellow-
5-6
Dull green
7
1
water
Heated
water
basic
soda
brown
1.1 What is the temperature of water used for heating the beans in your experiment? How
does this temperature compare with that used for commercial processing of vegetables?
The temperature of boiling solutions is ~100 °C. This is lower than the temperature used by
commercial food processors, which is ~116-121 °C.
1.2 Which of your solutions were near neutral? Acidic? Alkaline?
The distilled solution will be neutral, the vinegar one will be acid and baking soda alkaline.
1.3 Which pH solution provided the best color and texture retention in the heated peas?
The best color retention is provided by the baking soda solution, but produces the poorest
texture, soft and mushy.
1.4 Which pH solution provided the poorest color retention in the heated beans?
The vinegar solution provided the poorest color retention
1.5 What pigment is responsible for the observed changes in color of the cooked vegetables?
Chlorophyll is the pigment responsible for the green color of vegetables.
1.6 What reaction is responsible for loss of texture (firmness) in cooked green beans?
The loss of firmness is due to the destruction of hemicellulose.
Part 2
pH (acidic, neutral,
Tea solution
basic)
Color
Color intensity (scale 0-10)
Cold water
neutral
Slightly dark
2
Heated water
neutral
Dark
10
Vinegar
acidic
Lighter
5
Baking soda
basic
Darker
10
2.1 What is the temperature of water used for heating the beans in your experiment? How
does this temperature compare with that used for commercial processing of vegetables?
I am guessing the question is referring to tea. Generally all the tea already prepared in coffee
shops is done with boiling water as the one used in this experiment.
2.2 Which pH solution provided the best color development in the heated tea?
The best color was obtained in the baking soda solution.
2.3 Which pH solution provided the poorest color development in the heated tea?
The poorest color was obtained in the vinegar solution.
2.4 How does the intensity of the cold-steeped tea color compares to hot-steep tea color?
Why is there a difference?
The hot-steep tea color has a more intense color than the cold one.