Question

1) List the food preservation fundamentals and provide advantages and disadvantages of each preservation strategy (15 points] 2) The following temperature-time data has been collected during UHT processing of a liquid food: Time (s) Temperature (°C) 10 69 15 23 20 90 35 90 40 86 Estimate the lethality (Fgo) for a microbial pathogen with z = 8°C. Determine the number of survivors at the end of this process for an initial population of 5.2 x 106 CFU and the D80 = 0.53 min. (15 points] (Show all calculations)

Answer 1

1) Food preservation methods

1. Inhibition

• Low-temperature storage
• Reduction of water activity
• Decrease in oxygen
• Increase of carbon dioxide
• Acidification
• Fermentation
• Adding preservatives
• Adding antioxidants
• Control of pH
• Freezing
• Drying
• Concentration
• Surface coating
• Structural modifications
• Chemical modifications
• Gas removal
• Changes in the phase transition
• Hurdle technology

2. Inactivation

• Sterilization
• Pasteurization
• Irradiation
• Electrifying
• Pressure treatment
• Blanching
• Cooking
• Frying
• Extrusion
• Light
• Sound
• Magnetic field

The advantages of using heat for food preservation are: safe and chemical-free, provides tender cooked flavours and taste, most of spoilage microorganisms are heat-labile, long shelf life

The main disadvantages of using heat are: overcooking, textural disintegration, undesirable cooked flavor, nutritional deterioration

3. Avoid recontamination

• Packaging
• Hygienic processing
• Hygienic storage
• Aseptic processing
• HACCP
• GMP
• ISO 9000
• TQM
• Risk analysis and management

2) Time temperature data = N0 = 5.2 x 106 CFU

D80 = 0.53 min

z = 8°C

Lethality Rate = 10(T-Tr)/Z

T = temp in Celsius at which lethal rate is required; Tr = reference temperature

(i) Since the time step/interval is 5 s:

F80 = 41.212 × 8 = 329.696 s

F80 = 5.494 min

(ii) Number of survivors: N = N0 10-F/D = (5.2 x 106)10-5.494/0.53