Lesson 2 Activity This activity entitled: 'Effects of roasting upon color, flavor and texture of peanut butter' is taken from Experiments in Food Science, developed by the Institute of Food Technologists.

Experiment

In this experiment you will roast whole or shelled peanuts at 350º F for 20, 30 or 40 minutes to produce variable degrees of color and flavor intensity. Each lot of heated peanuts will be used for producing peanut butter. You will then evaluate the peanut butter products for color, flavor and texture. You will also be given an opportunity to compare your experimental peanut butter products with those produced commercially and available in your local grocery or supermarket.

 

Materials

Peanuts

Peanut Oil

Lecithin (emulsifier)

Soda crackers

 

Equipment and Supplies

200 gram capacity balance

Oven with thermostat to 350º F

Mortar and pestle

Timer or wall clock

Heavy duty aluminum foil

100 to 250 ml beakers or small plastic cups

Spatulas

1/4, 1/2 and 1 teaspoon (tsp) measures

 

Procedure

  1. Cut 12 x 12 inch sheets of aluminum foil and bend the edges up to form a flat pan.
  2. Label the pans 20, 30 or 40 minutes.
  3. Spread about 250 grams of unroasted peanuts over the bottom of each pan.
  4. Preheat the oven to 350º F.
  5. Roast the peanuts in the oven for the prescribed time, stirring them occasionally to provide uniform roasting.
  6. Remove the shells and skins from the peanuts and discard them.
  7. Students will be assigned to one or more groups - A, B, C or D and will work with one or more of the roasted peanut conditions -- 20, 30 or 40 minutes.
  8. Grind enough peanuts for each condition and group to provide 45 grams of ground peanuts.
  9. The peanuts are ground in the mortar. Add only 6 or 8 peanuts at a time and grind them thoroughly using pressure and a circular motion. It is very important to do a thorough job at this stage in order to produce a smooth final product.
  10. You will note that the peanuts take on a dark and moist appearance as the grinding proceeds. This change is due to melting and release of the peanut oil by the grinding. This oil then coats the solid fiber, protein and carbohydrate components to provide a smooth, sticky mass.
  11. Suggestion: Place the mortar on a moist, flat sponge to keep it from slipping when you are grinding the peanuts and blending.
  12. Weigh or measure out the following ingredients and combine them according to the following schedule:

    Material
    Group A
    Group B
    Group C
    Group D
    Ground peanuts
    45 grams
    45 grams
    45 grams
    45 grams
    Peanut oil
    5 grams or 1-1/4 tsp
    10 grams or 2-1/2 tsp
    4 grams or 1 tsp
    8 grams or 2 tsp
    Lecithin
    -
    -
    1 gram or 1/4 tsp
    2 grams or 1/2 tsp
    Salt

    Add salt to taste

    Add salt to taste
    Add salt to taste
    Add salt to taste
  13. For those products containing added lecithin, combine the peanut oil and lecithin in the mortar and mix them before adding the other ingredients.
  14. Add all remaining ingredients to the mortar and thoroughly blend them by using pressure and a rotary motion of the pestle.
  15. Spread a small amount of each peanut butter on separate crackers and evaluate them for color, flavor and texture (smoothness).
  16. Cover the remaining peanut butter in beakers or small plastic cups and store at room temperature overnight. Examine them the next day for degree of oil separation.
  17. Record all data and observations in the table on the next page.

Calculations

1. Assume that your peanuts contain 50% oil (fat) and calculate the expected total fat content. For this exercise, assume also that the total fat added is equivalent to the weight of peanut oil plus emulsifier.

2. Which of your peanut butter products were within the legal standards of the Food and Drug Administration?

Optional Project

  1. There are many different kinds of peanut butter. Make a list of the various ingredients listed on the labels and group these into: peanuts, oil, emulsifier, carbohydrate or sugar, and salt.
  2. Compare a commercially available peanut butter with those that you prepared in the laboratory in terms of color, flavor and texture, as well as oil separation upon standing overnight.
  3. Record your observations and discuss possible reasons for the observed differences between commercial and experimental peanut butter products.

Table 1

Comparison of Commercially Available Peanut Butter (Circle the appropriate #)

 

Peanut Butter Type

 

Chunky
Creamy

 

 

 

 

 

Color

Light
Dark
Light
Dark

(0=light,5=dark)

0 1 2 3 4 5
0 1 2 3 4 5

 

 

 

 

 

Flavor

Mild
Strong
Mild
Strong

(0=mild,5=strong)

0 1 2 3 4 5
0 1 2 3 4 5

 

 

 

 

 

Texture

Smooth
Coarse
Smooth
Coarse

(0=smooth,5=coarse)

0 1 2 3 4 5
0 1 2 3 4 5

 

 

 

 

 

Oil Separation

None
Large
None
Large

(0=none to slight,5=large amount)

0 1 2 3 4 5
0 1 2 3 4 5

 

Table 2

Comparison of Experimental Peanut Butter (Circle the appropriate #)

 

Roasting Time

 

20 minutes
30 minutes
40 minutes

Color

Light
Dark
Light
Dark
Light
Dark

(0=light,5=dark)

0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5

 

 

 

 

 

 

 

Flavor

Mild
Strong
Mild
Strong
Mild
Strong

(0=mild,5=strong)

0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5

 

 

 

 

 

 

 

Texture

Smooth
Coarse
Smooth
Coarse
Smooth
Coarse

(0=smooth,5=coarse)

0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5

 

 

 

 

 

 

 

Oil Separation

None
Large
None
Large
None
Large

(0=none to slight,5=large amount)

0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5

 

Additional Comments:

 

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