Flashcards in 14- Food processing/preservation Deck (7):
What are Food processing/preservation?
– Prevent or delay decomposition by microorganisms (spoilage).
– Destroy pathogens or inhibit their growth
– Prevent or delay self-decomposition by enzymes present in the food.
• Refrigeration and freezing
• Heating (pasteurization)
• Reducing water availability
Explain Refrigeration and freezing
• Aims: slow or inhibit growth of microorganisms.
• At -20°C the aw can reach 0.82. Most microorganisms cannot grow.
• Viable microorganisms will resume growth once the temperature is permissive.
• Freeze/thaw cycles affect the quality of the food (ice crystals).
Explain pasteurization (3 methods for milk)
• Aim: reduce the number of microorganisms to delay spoilage and to eliminate
• Dairy products, liquid egg products, alcoholic beverages, fruit juice.
• Three methods for milk:
– Long temperature long time (LTLT): 30 min, 62.8°C, bad taste (ice cream and cheese)
– High temperature short ?me (HTST): 15 sec, 71.7°C (milk for drinking).
– Ultrahigh temperature (UHT): 2 sec, 141°C (long shelf life at room temperature, virtually sterile).
• LTLT or HTST treated milk is equally safe.
• Time and temperature required are affected by the amount of fat, sugar and protein.
• Aim: seal the food from the outside world and heat the container to kill most, if not all, of the microorganisms. It creates an anaerobic environment.
– 100°C for acidic food
– Up to 121°C for low-acid food.
• 12D process: temperature and time of exposure must be sufficient to kill 10'12 spores of Clostridium botulinum.
• Must have a balance between food safety, nutritional value and taste of the food.
Explain Water availability
• Aim: prevent microorganisms from growing.
• Drying: meat, fish, fruits, milk
– Sun dried
– Hot air drying.
– Freeze-drying (lyophiliza?on) results in lille lost of quality but is expensive.
• Reducing water availability by adding salt or sugar: increases the osmotic strength of the surrounding solution.
• Doesn’t necessarily kill the
microorganisms, inhibits their growth.
• Aim: reduce contamination of fresh product by pathogen and spoilage organism.
• Dosage can be adjusted to:
– Kill all microorganisms (radappertization)
– Kill specific microorganisms (radicidation)
– Reduce overall contamination (radurization)
• Some concerns among consumers of possible radioactive contamination,
production of toxic or carcinogenic compounds, altered nutritional value,
production of off-flavor.