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Biofuels Webquest: Grab Some Pine Meat

Grab Some Pine Meat

The tender tale of beef


How can enzymes be used to make meat easier to chew?  Can pineapple juice contain enzymes that digest protein?

One of the problems that the meat industry faces is to produce the tenderest meat for consumers. 

However after years of research and animal breeding there still remains great variation in the tenderness of meats.  Even further variation exists among the various cuts of meat.

The person preparing the meat has a few techniques at their disposal to help tenderize meat prior to and during cooking.  Some of these include marinades, commercial meat tenderizers, and physical means such as cubing/slicing and pounding with a meat tenderizing hammer.



Read the following background information:  Then create a mind map of important terms: using the mind meister app on you iPad.



Pineapple’s lush, tropical sweetness is reason enough to enjoy it any way you can, but this fruit also contains vitamin C and manganese. This fruit’s most promising nutritional asset, though, may be bromelain, a natural enzyme found in both the fruit and the stem.

Most of the pineapple consumed in the United States is canned (in the form of juice as well as fruit), but fresh pineapple is much more flavorful, and, despite its tough bristly shell, is easy to prepare.

The fruit probably first grew wild in parts of South America and then spread to the Caribbean, where Columbus encountered it.  By 1600, early European explorers had carried pineapples as far as China and the Philippines. In the 18th century, pineapples were taken to the Hawaiian Islands, eventually becoming the major fruit crop. Hawaiian pineapple producers were the first to can the fruit.



The pineapple plant contains protein-digesting enzymes called, as a group, bromelain. In the health world, these enzymes are regarded as useful in reducing muscle and tissue inflammation (hence the joint pain and wound-healing possibilities), as well as acting as a digestive aid. In the cooking world, on the other hand, bromelain is regarded as the enemy of the gelatin dessert. If you use fresh pineapple in gelatin, the enzyme eats the protein and the gelatin will not gel—in fact bromelain is measured in units called GDU, or gelatin digesting units.  The classic kitchen trick for getting around this pineapple-gelatin incompatibility is to cook the pineapple, thus reducing the power of the bromelain.  Recipes that would highlight the benefits of bromelain start with fresh pineapple (which has two to three times the amount of bromelain as canned pineapple does), and is then subjected to as little heat as possible.  Bromelain is used in meat tenderizers, and in preparation to treat edema and inflammation.



Gelatin, a familiar, ingredient in cooking, is obtained by boiling the skin, tendons, and ligaments of animals. As a result, it contains protein called collagen ( a primary component of joints, cartilage, and nails), and various amino acids. Remember: amino acids are the building blocks of proteins.  Gelatin has long been a key ingredient for providing support for “jelled” deserts, salads, frozen drinks, and soft candies such as Gummi Bears. (In fact, the word gelatin is derived from the Latin “gelatus”, meaning stiff or frozen.  In addition to its famous “jiggly” food uses, gelatin with its flexible, dissolvable structure, is also used to manufacture capsules (both hard and “soft-gel”) to hold medications, vitamins, and other dietary supplements. It also has a range of industrial and medical engineering applications: Gelatin is an ingredient in film coatings, medical devices such as artificial heart valves, and in specialized meshes used to repair wounds, to name a few.



About one quarter of all the protein in your body is collagen.  It is a major structural material that forms molecular cables to strengthen the tendons and resilient sheets that support the skin and internal organs. Bones and teeth are made by adding mineral crystals to collagen. Collagen provides structure to our bodies, protecting and supporting the softer tissues and connecting them with the skeleton. But, in spite of its critical function in the body, collagen is a relatively simple protein.  Collagen from livestock animals is a familiar ingredient in cooking. Collagen is a protein, and like most proteins, when heated, it loses all of its structure. The polymer molecule unwinds. Then, when the denatured mass cools down, it soaks up all of the surrounding water like a sponge, forming gelatin.

Bromelain and Papain are derived from pineapple, and  from papaya, are both protease enzymes, meaning that they digest and tenderize protein. This makes them popular choices as ingredients in meat tenderizers. It is because of the healing properties of bromelain and papain that meat tenderizer has become a popular home remedy for insect bites, jellyfish stings, burns, and minor wounds.  Bromelain and papain appear to work in synergy to accomplish many of the same medicinal tasks.  Bromelain is a powerful anti-inflammatory, so strong that it can replace the use of conventional medicine like ibuprofen for treating painful inflammation. This makes it ideal for combating pain from or arthritis, injury, menstrual cramps, or digestive problems. 



Now that your mind map is finished you will enter the lab with your group.  You will use papain, an enzyme from tropical fruits, to show the how this enzyme tenderizes meat. 

Papain breaks down the protein sheath around meat fibers and make the meat easier to chew. Commercial meat tenderizers such as Adolph’s, contains papain.  Cooks often use fresh pineapple slices on meat as it cooks.  Although most think this is for flavor, the flavor is secondary to the tenderizing effects papain from the pineapple.  Fresh fruit such as pineapple is necessary because canning or other heat processing destroys the enzyme papain.

Gelatin is a protein that comes from the connective tissue of animals such as bones, ligaments and cartilage.  Gelatin is a protein and will break down in the presence of the enzyme papain.  You will use gelatine in this lab to represent meat.


What form of pineapple juice contains enzymes that digest protein?



For every 3 groups                          For each group                   For entire class

1 envelope Knox gelatin                        4 test tubes                                    water

Measuring cup                                    1 test tube rack                        pineapple juices (below)

1 spoon                                                4(1ml)disposable pipettes         hot plate to heat water

100ml graduated cylinder                10ml graduated cylinder

                                                                    Marking pen


  1. Number and label the test tubes “1-4” and use the initials of a group member to identify your group.
  1. Find 2 other groups and prepare 1 package of gelatin in the measuring cup using 90ml of boiling water and 30 ml of cold water. Stir well with a spoon until the gelatin is dissolved.
  1. Place 3 ml of the designated pineapple juice into each test tube. Use a separate pipette for each type of juice. Failure to do so may result in mixing of the juice types and inaccurate results.
    • Tube 1: water only
    • Tube 2: fresh pineapple juice
    • Tube 3: Canned pineapple juice
    • Tube 4: Concentrated pineapple juice (thawed)
  1. Add 10 ml of gelatin mixture to each test tube. Shake well to ensure proper mixing and place your samples in the refrigerator overnight using a test tube rack.
  2. On Day 2, check the contents of each test tube for solidification of the contents and record your observations.


What effect does temperature have on an enzyme?



For every 2 groups                    For each group                 For entire class

1 envelope Knox gelatin                        6 test tubes                                    water

Measuring cup                                    1 test tube rack                        pineapple juices (below)

1 spoon                                                1 (1ml) disposable pipette           

100 ml graduated cylinder            10ml graduated cylinder           

                                                                 Marking Pen

                                                                     Hot plate


  1. Prepare the Knox gelatin by mixing 1 package of gelatin in the measuring cup using 90ml of boiling water and 30 ml of cold water. Stir well with a spoon until the gelatin is dissolve.
  2. Number the test tubes from 1-5. Label the remaining test tube as “RT” (room temperature).
  3. Each group will be assigned their own temperature gradient ranging from 40C – 100 C. Each group must record the test tube numbers and the corresponding test temperatures for each test tube. Record the temperature of the room for the temperature for the “RT” test tube.
  4. Next, add 3 ml of pineapple juice to each test tube.
  5. Then heat each test tube to the appropriate temperature as assigned. Leave the test tube “RT” at room temperature. (HINT: start with all the test tubes in cool water in a glass beaker water bath. Gradually increase the temperature withdrawing the numbered test tubes in 2C increments in order as the appropriate temperature level in the bath is reached.)
  6. After the test tubes have been pulled from the water bath, add 10 ml of Knox gelatin (prepared in step 1) to each test tube and mix well.
  7. Finally, place the test tubes in the refrigerator overnight.
  8. On day 2, check each test tube for solidification or liquidity of the contents and record your observations.

What effect does pH have on enzyme activity?



For every 3 groups                         For each group                      For entire class

1 envelope Knox gelatin                  3 test tubes                                           goggles

Measuring cup                                    1 test tube rack                                    apron

1 spoon                                                4 (1ml) disposable pipettes                 water

100 ml graduated cylinder           10 ml graduated cylinder                        pineapple juice

                                                            Marking pen                                          1M HCl

                                                                                                                               1M NaCl


  1. Prepare the Knox gelatin by mixing 1 package of gelatin in the measuring cup using 90ml of boiling water and 30 ml of cold water. Stir well with a spoon until the gelatin is dissolved.
  2. Label 1 test tube “A” for acid, 1 test tube “B” for base, and the last test tube “C” for control.
  3. Place 3ml of pineapple juice into each of the labeled test tubes. Transfer 1 ml of base, 1 ml acid, and 1ml of water into the appropriate test tubes of pineapple juice. HINT: Use a different pipette for each test tube to avoid contamination.
  4. Add 10 ml of gelatin mixture to each test tube. Mix well, being careful to not get any of the acid or base on your skin.
  5. Refrigerate the test tubes overnight and on day 2 check each test tube for solidification or liquidity of the contents. Record your observations.


After you have completed your experiments and record your data:


Post Lab Homework questions:

1. When Wasps, hornets and jellyfish sting the venom they inject is a type of protein.  One first aid recommendation is to apply Meat Tenderizer.  Why?

2. Some laundry detergents contain enzymes in the same class as papain called proteinase.  These detergents will clean blood and grass stains.  Based on what you know about how papain works, how do these detergents work to remove stains? 

3. Bacteria, including disease causing bacteria, made up of proteins.  In the tropics, fresh tropical fruits are important in the prevention of disease.  How do they help prevent 

Subject Guide

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Jennifer Jourdain
Montachusett Regional Voc Tech School
1050 Westminster Street
Fitchburg, MA 01420
(978) 345-9200 x5125