Your mom was at home canning beans when she noticed that some of the beans she was canning seemed to be too mushy. They were almost like refried beans. Since you have a degree in food science, she called to ask you if you could help her figure out why her beans were not canned correctly.

BACKGROUND INFORMATION:

Dry beans have been an important food for many centuries. Together with other legume seeds, they are an excellent source of protein, calories and dietary fiber. However, dried beans require prolonged soaking, followed by a long cooking time to achieve desirable palatability. Calcium ion is one of the major factors affecting preparation time and quality attributes of thermally processed beans. Since calcium ions can cross-link the galacturonic acid chains and peptic substance present in the middle lamella of bean tissues, it results in restriction of water uptake and improvement of seed integrity. In modern vegetable canning, the use of calcium ions has been employed to control the texture and integrity of cooked products.

OBJECTIVE:

The student will determine the effects of calcium ions in soaking and cooking on bean quality characteristics including; color, seed integrity and texture.

MATERIALS:

Dry beans (Navy, pinto, or kidney)

Pressure cooker

Sodium bicarbonate (NaHCO ₃ )

Canning jars- 6 per group (half pint with lids and rings)

Paper plates

Balance beam

CaCl ₂

SAFETY AND DISPOSAL:

Care should be taken when handling a pressure cooker. When blanching the beans the steam is very hot and caution should be exercised.

TIME:

Beans must soak overnight. One class period for the experiment.

PROCEDURE :

To be done by the teacher:

1. Divide beans into two lots. Soak one lot overnight covered in plain tap water. Soak the other lot overnight covered in 0.75 % NaHCO ₃ solution. (Add 7.5 g of NaHCO ₃ per liter of tap water.)

To be done by students:

1. Obtain 6 half -pint canning jars with lids and rings. Number the jars and lids with a permanent marker such as a Sharpie. Scald the lids in boiling water to prepare the sealing surface.

2. Blanch each batch of beans at 190C for 4 minutes to soften the beans and remove air.

3. Prepare CaCl ₂ solutions. Add 0.1 g CaCl ₂ per liter to make 100 ppm and 0.2 g CaCl ₂ per liter to make 200 ppm.

4. Fill jars according to Table 1.:

   Table 1. Jar fill schedule
   Jar Number	Soaking Agent	Amount of Beans	Brine*
   1	Tap water	120 g	Boiling tap water
   2	Tap water	120 g	Boiling with
   3	Tap water	120 g	Boiling with
   4	0.75 % NaHCO 3	120 g	Boiling tap water
   5	0.75 % NaHCO 3	120 g	Boiling with
   6	0.75 % NaHCO 3	120 g	Boiling with

   * Leave headspace in jar of 1.2 cm

5. Place a scalded lid on each jar and tighten ring hand tight. (Do not over tighten!)

6. Place 3 cm of water in the bottom of the pressure canner. Place jars in canner, attach lid and place on high heat.

7. Allow steam to exhaust for 2 minutes; then close the pressure control on cooker. Process at 10 psi for 60 minutes.

8. When 60 minutes has expired turn off the burner and allow canner to cool. (Do not open pressure control or remove lid until pressure in canner has reduced to zero!!)

9. Allow jars to cool until vacuum pulls the lids down; then place jars in cool water

   until the temperature is lower than 35 C.

10. Label one paper/plastic plate each with Numbers 1 through 6. Open the jars of beans and pour each jar into the corresponding plate.

11. Observe beans in each lot and note their texture (firm to soft), color (light to dark) and seed integrity (whole or broken).

QUESTIONS:

1. What is the effect of soaking beans in NaHCO ₃ solutions on bean texture?
   
   
   

2. On a molecular basis how do NaHCO ₃ solutions create the effect in question 1?
   
   
   

3. What effect did added CaCl ₂ have on the beans?
   
   
   

4. Which treatment gave the hardest bean? Why?
   
   
   

5. Which treatment gave the softest bean? Why?
   
   
   

FOR ADDITIONAL INFORMATION CONTACT:

Jim Goff, Food Processing, Food Science Department, U of A - Fayetteville,
jgoff@comp.uark.edu

REFERENCES:

Darrow E., Student Research Projects in Food Science, Food Technology, and

Nutrition, College of Agriculture-Ohio State University, 1989.

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