The Effects of Heat on the pH levels of Vegetables and Their Pigments

Topics: Cooking, PH, Water Pages: 14 (3845 words) Published: June 23, 2014
The Effects of Heat on the pH of the Vegetable and Their Pigment PURPOSE
The purpose of this experiment is to see how pH levels of certain vegetables change while being cooked in four different mediums (frying, boiling, steaming, roasting), and how the varying pH levels change the coloring of the vegetables. We will analyze how the different method of cooking/heating changes the levels of pH. 

This experiment is based around the different pigments in vegetables, of which we researched and encountered 3. We were looking at the effects of four different types of heating or cooking methods to see their effects on the pH of vegetable and their pigments. Cooking Methods:

Boiling relies on currents of heat and doesn’t trigger browning reactions. The temperature of the wateraises to around 212 degrees, and it is the heat of the water that cooks the food.  Steaming is a less dense medium. Vapors in steaming provide more energy, and like boiling, the water used is around 212 degrees and provides steam which is hot enough to cook food in a similar fashion to boiling.  Frying uses a small amount of cooking medium, which is oil. It provides higher heats than boiling and steaming, though not as high as roasting. pH pH is the standard measure of proton activity, or measure of acid or base character of a liquid solution. The measure is based on the hydrogen ion concentration of the liquid or solution. The measure is expressed in a number from 0 - 14, and the measure of water is neutral pH 7, the liquids going from pH 0 to pH 6 are acidic, and the liquids going from ph 8 to pH 14 are basic. 

Pigment Any coloring matter in plant or animal cells that reflects light of certain wavelengths while also bringing light of other wavelengths without producing appreciable luminessence used to impart color to other material. Chlorophyll is a green pigment with a ring structure similar to HEME molecule in animal blood. It is the most common and familiar pigment family. Chlorophyll a is bright blue-green and is twice as common as chlorophyll b, which is olive. Chlorophyll traps solar energy and makes it available to form sugar out of water and carbon dioxide in photosynthesis. Clorophyll is concentrated in discrete cell bodies and is never found in cytoplasm. Cartenoids are named for carrots, which they are found in. They are the pigments responsible for yellow and orange color. They are always found in mixtures, never alone. Cartenoids play an indirect role in photosynthesis by trapping certain wavelengths of light and funneling them. Anthocyanins are the third major class of plant pigments and are a subgroup of phenolic compounds. Their only functionis to give color to plants. They are water soluable and stored in cell vacuoles. 


The methods of cooking which are performed at a higher temperature will change the level of pH more drastically, because the denaturization of the proteins will be increased. Most likely, as the temperature rises, the pH will lower, and the lower the level of pH, or the higher the acidity, the more the pigment will lose its natural color. MATERIALS

 Vegetables 
a. carrots 
b. broccoli 
c. beets 
 Cooking Materials 
a. A frying pan 
b. grapeseed oil 
c. A stove top 
d. a pot for boiling 
e. a spatula 
f. a steamer 
g. a strainer 
h. a knife 
i. a cutting board 
j. a measuring spoon 
k. multiple bowls
 Others 
a. pH measuring tape 
b. a camera 
c. Thermometer 



1. Rinse and peel the vegetables
2. Cut each vegetable into slices (2 cups of slices 2 cm thick) 3. Take a photograph of the raw vegetable for color.
4. Blend 1/2 cups of sliced vegetables in the blender on the lowest level of power, along with 1/4 cups of water. 5. Put the pureed vegetables into a strainer, and mash it into the netting until there is enough liquid to measure the pH.   6. Take the blended vegetables and measure the pH...
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