Foundation
Enzymes play a key role in the production of various food products, either through their desirable effects during processing (e.g., cheese making, malting) or through the need to inactivate them to prevent or limit adverse reactions in the final products.
One such reaction is enzymatic browning in fruits and vegetables when they are peeled or cut, mainly caused by polyphenol oxidase (PPO). When you cut or peel the raw material (as in Stop 3 of your process), you break the cell membranes, bringing this enzyme into contact with its substrates (phenolic compounds) and oxygen. The result is the formation of melanins (dark spots) that alter the product.
The 56 kg challenge
- Timing
- 00:30
- Students
- 4
Lili knows that in the production of dehydrated and freeze-dried vegetables, controlling enzymes—especially polyphenol oxidase (PPO)—is critical to prevent browning and loss of nutritional value.
Remembering her childhood, Lili smiles thinking about her grandmother Meri’s tricks, who, without being a biochemist, managed to prevent vegetables from darkening when cooking. Meri would always rub artichokes with a piece of lemon before adding them to her delicious chicken and rice, or soak eggplants in salted water before baking them.
Today, after consulting her robotic assistant on food technology, Lili has discovered the science behind her grandmother’s wisdom:
Lili faces her biggest order yet, but she has an existential dilemma. She knows she must prevent browning in the apples, but she hasn’t decided on a method. As the plant’s technical team, your mission is to investigate, propose, and execute.
1. Research Phase (Decision Making)
Lili presents the following treatment options. In groups of four, choose one and justify your choice in the class journal:
Option A: Citric acid 0.5%
Option B: Citric (1%) + Ascorbic acid (2%) (Recommended by Grandma Meri)
Option C: Salt bath (NaCl) 2%
Option D: Sugar solution 10% + Citric acid 3%
Option E: SO₂ solution (consult Regulation 1129/2011)
Question: Which method best preserves color without altering the original taste of a fruit that will be freeze-dried?
2. Calculation Phase (Industrial Scaling)
Once your option is approved by the instructor (Plant Manager), calculate the required quantities for the 56 kg batch:
Water volume: ______ Liters (1:1 ratio)
Additive 1: ______ g
Additive 2 (if applicable): ______ g
(Example: For Option B, calculate grams of citric acid and ascorbic acid for 56 kg fruit in 56 L water.)
3. Plant Phase
Prepare the workstation following the logical order from Stop 3:
Cleaning
Weighing additives
Preparing the bath
Conditioning the fruit: peel and cut. The slices go directly into the bath.
Inactivation: keep submerged for 10 minutes
4. Control and Improvement Phase
After completing the process, each group must complete a report:
Did browning appear at any stage? Why?
What are the advantages and disadvantages of the chosen method compared to the others?
Justify whether the remaining solution can be reused for a second batch or must be discarded.