Food microbiology — Antimicrobial constituents naturally present in a food (for example, lysozyme in egg white or lactoferrin in milk) are classified as which type of factor influencing microbial growth?

Introduction / Context:
Food spoilage and safety depend on multiple hurdles. The classic framework divides determinants of microbial growth into intrinsic factors (properties of the food itself), extrinsic factors (environmental storage conditions), and implicit factors (microbial interactions). Recognizing where antimicrobial constituents fit helps predict which foods have natural protection against microbes.

Given Data / Assumptions:

• Examples of antimicrobial constituents include lysozyme, lactoferrin, and essential oils inherent to the food matrix.
• Intrinsic = inherent to food; extrinsic = outside the food (temperature, atmosphere, humidity).
• We must classify antimicrobial constituents correctly.

Concept / Approach:
Intrinsic factors are built into the food: pH, water activity, redox potential, natural antimicrobial compounds, and nutrient composition. Extrinsic factors are external conditions like refrigeration temperature, packaging gas composition, and relative humidity. Because antimicrobial constituents are inherent components of the food, they are intrinsic. They are not extrinsic, and the category is not “both,” since classification depends on origin, not effect.

Step-by-Step Solution:

Verification / Alternative check:
Food microbiology texts list natural antimicrobial systems (e.g., lactoperoxidase in raw milk) under intrinsic factors. Storage temperature or modified-atmosphere packaging are listed separately as extrinsic factors.

Why Other Options Are Wrong:

• Extrinsic factor: involves outside conditions, not internal constituents.
• Both (a) and (b): incorrect because the origin is exclusively intrinsic.
• None of these: incorrect because “intrinsic factor” precisely matches.

Common Pitfalls:
Equating “effective at storage” with “extrinsic.” Effectiveness does not change their classification as intrinsic if they are native to the food.

Final Answer:
intrinsic factor