Question

Fresh pineapple contains the enzyme bromelain that hydrolyzes peptide bonds in proteins. a. The directions for a gelatin dessert say not to add fresh pineapple. However, canned pineapple where pineapple is heated to high temperatures can be added. Why? b. Fresh pineapple is used in a marinade to tenderize tough meat. Why? c. What structural level of a protein does the bromelain enzyme destroy?

Short answer

a. Bromelain in fresh pineapple breaks down gelatin proteins. b. Bromelain tenderizes meat by breaking down proteins. c. Bromelain destroys the primary structure of proteins.

Step-by-step solution

Understanding the effect of bromelain in fresh pineapple on gelatin

Discuss why fresh pineapple cannot be added to gelatin. Fresh pineapple contains bromelain, an enzyme that hydrolyzes peptide bonds, preventing the gelatin from setting because gelatin's structure relies on intact protein molecules.

Explaining the effect of canned pineapple on gelatin

Consider why canned pineapple can be used. Heating during canning denatures bromelain, rendering it inactive. Therefore, canned pineapple does not interfere with gelatin setting.

Understanding the use of fresh pineapple in meat marinades

Explain why fresh pineapple is used in marinades. Bromelain in fresh pineapple breaks down proteins in meat, tenderizing it and making it easier to chew.

Identifying the structural level of proteins affected by bromelain

Determine which level of protein structure is destroyed by bromelain. Bromelain hydrolyzes peptide bonds, affecting the primary structure of proteins, which is the sequence of amino acids.

Key concepts

Bromelain

Bromelain is a powerful enzyme found in fresh pineapple. Enzymes are special proteins that accelerate chemical reactions. Bromelain's main role in food chemistry is breaking down proteins by hydrolyzing peptide bonds. This means it helps split the links between amino acids that form the structure of proteins.
Adding fresh pineapple to gelatin isn't recommended because bromelain will disrupt the setting process. However, using heat-treated or canned pineapple is safe, as heat inactivates the enzyme. This makes bromelain a versatile tool in cooking and food preparation, though care must be taken in how it's used.
Its protein-breaking properties also make it handy for tenderizing meat in marinades, helping to soften tough fibers and improve texture.

Protein Hydrolysis

Protein hydrolysis is the chemical process where peptide bonds in proteins are broken down. This happens through reactions involving water, where enzymes like bromelain play a significant role.
Hydrolyzing proteins affect their structure. For example, in the case of fresh pineapple and gelatin, adding bromelain leads to the breaking down of the gelatin's proteins, preventing it from setting.
In meat marinades, this same breakdown process helps tenderize the meat, making it softer and easier to eat. Hydrolysis changes the meat's texture dramatically and improves its palatability.

Gelatin Setting

Gelatin is a type of protein derived from collagen, often used in desserts. The setting of gelatin involves the formation of a gel-like structure where proteins are bonded in a particular arrangement.
When fresh pineapple is added, the bromelain enzyme disrupts this process by hydrolyzing proteins, making it impossible for the gelatin to set. This is why recipes often caution against using fresh pineapple.
On the other hand, canned pineapple is safe to use. The heat during the canning process denatures bromelain, meaning it loses its protein-breaking ability, allowing the gelatin to set as intended.

Protein Structure

Protein structure is crucial in understanding how enzymes like bromelain affect food. Proteins have four levels of structure: primary, secondary, tertiary, and quaternary. The primary structure is the sequence of amino acids linked by peptide bonds.
Bromelain predominantly affects the primary structure by hydrolyzing these bonds. Disrupting the primary structure changes the protein's overall form and function, impacting its properties drastically.
For example, in tenderizing meat or preventing gelatin from setting, bromelain's action at the primary structure level demonstrates how altering amino acid sequences can change texture and food quality.