Step 1: Understanding the Question:
The question asks which food preservation method relies on the active, controlled growth of helpful microorganisms.
Step 2: Key Concepts and Approach:
Most preservation methods focus on killing or inhibiting microorganisms to prevent spoilage (physical/thermal methods).
In contrast, some methods use controlled microbial growth to outcompete spoilage organisms and preserve the food.
Step 3: Detailed Explanation:
• Fermentation as Preservation: Fermentation uses beneficial microbes (like lactic acid bacteria, yeasts, and molds) to preserve food.
These microbes consume available sugars and produce organic acids, alcohol, and antimicrobial compounds (like bacteriocins).
• Inhibition of Spoilage: These metabolic products lower the pH of the food, creating an environment that inhibits the growth of pathogens and spoilage organisms.
Examples include converting milk into yogurt/cheese or cabbage into sauerkraut.
• Physical Preservation Methods: Sterilization, drying, and freezing are physical methods that preserve food by destroying microbes or rendering them inactive, without utilizing biological activity.
Step 4: Final Answer:
Therefore, fermentation is the preservation method that uses beneficial microbes, corresponding to Option (B).