Question

Pigmented Propioni bacterium causes a color defect in …….

• A. Meat
• B. Cheese
• C. Egg
• D. Juices

Hint:

Propionic acid = Swiss Cheese eyes.
Pigmented strains = Rusty spots defect.
Always associate Propionibacterium with Cheese in food technology exams.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks about the food product where Propionibacterium species cause undesirable color changes. These bacteria are most famously used in the dairy industry but can cause defects if the wrong strains or conditions are present.

Step 2: Detailed Explanation:

• Propionibacterium in Cheese: These bacteria are the "starter" or "adjunct" cultures for Swiss-type cheeses (like Emmental). They ferment lactate into propionic acid, acetic acid, and $CO_2$. The $CO_2$ creates the famous "eyes" (holes) in the cheese.

• Color Defect: Certain species, such as Propionibacterium jensenii or pigmented strains of P. freudenreichii, can produce reddish, brownish, or rusty-colored spots in the cheese body.

• "Rusty Spot" Defect: This is a well-known defect in Emmental and Cheddar cheeses characterized by small, discrete colored colonies. It is usually caused by contaminating pigmented propionic bacteria or certain lactobacilli.

• Context: While these bacteria are not typically associated with spoilage in juices, eggs, or meat in a way that causes specific "pigmented defects," they are a central part of cheese microbiology.

Step 3: Final Answer:
Pigmented propionic bacteria are responsible for color defects (like rusty spots) in cheese.