How do pasteurization and storage conditions differentiate spoilage from pathogens in milk?

• A. Spoilage is due to psychrotrophs and enzymes; pathogens are controlled by adequate pasteurization and cold storage.
• B. Spoilage and pathogens are both prevented entirely by pasteurization.
• C. Storage alone determines spoilage.
• D. Pathogens cause spoilage but are not affected by pasteurization.

Answer: (A)

Spoilage in milk is mainly about organisms that can grow at refrigeration temperatures and the enzymes they produce, not necessarily about illness-causing pathogens. Psychrotrophic bacteria such as certain Pseudomonas species can thrive in the cold and release enzymes like proteases and lipases that break down milk proteins and fats, leading to off flavors, curdling, or rancidity. Pasteurization is designed to inactivate pathogens and reduce overall microbial load, but it doesn’t eliminate every spoilage organism, nor does it guarantee inactivation of all enzymes. Cold storage then slows the growth of both spoilage organisms and pathogens, helping prevent deterioration and illness risk. So, spoilage is driven by psychrotrophs and their enzymes, while adequate pasteurization and cold storage are what control pathogens.