ASRB NET: Food Science and Technology

ASRB NET Food Science and Technology covers food chemistry, food microbiology, food processing, dairy and meat technology. The exam tests preservation principles and process calculations.

Core concepts

• Water activity, aw, predicts microbial growth better than moisture content; most bacteria require aw above 0.90, while xerophilic moulds grow at lower values.
• Thermal processing: D-value is the time at a given temperature to reduce the population by 90%, one log; z-value is the temperature change for a tenfold change in D.
• HACCP identifies biological, chemical and physical hazards and sets critical control points; it is preventive, not end-product testing.
• Dairy: pasteurisation at 72°C for 15 s or 63°C for 30 min kills pathogens but is not sterilisation; homogenisation reduces fat globule size.
• Meat: post-mortem glycolysis lowers pH; rigor mortis resolves through proteolysis during conditioning.

Worked example

A canned food has a target 12-log reduction of Clostridium botulinum spores. If D at 121°C is 0.2 min, process time at 121°C = 12 × 0.2 = 2.4 min, ignoring come-up and cooling. Reasoning: each D reduces the population by one log; 12D is the classical botulinum cook. In practice, heat penetration and F0 integration are used.

Traps that cost marks

• Confusing D-value, a time, with z-value, a temperature change.
• Assuming pasteurisation sterilises food.
• Using moisture content alone to predict spoilage.
• Ignoring cold-chain abuse after processing.