Spoilage
13 important questions on Spoilage
Preservation pitfalls of reduced water activity?
- Non-microbial spoilage (lipid oxidation, nonenzymatic browning)
- Local changes in water activity
- Product reformulation (removal of sugar or salt) that does not reduce water activity
Sources of contamination of raw cow's milk?
- Contamination of teats via feed, feces, bedding and soil (mastitis)
- Contamination via feed (yeasts and moulds)
- Contamination of feces and soil (spores and bacteria)
Measures against contamination of raw cow's milk?
- Keep micro-organisms out
- Kill micro-organisms with heat
- Remove micro-organisms with bactofugation or microfiltration
- Prevent micro-organisms from growing by lower temperature storage, lower water activity and acidification by fermentation
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Post-mortem changes in meat?
Dressing of animal to meat/by-products?
- Remove hair or feathers (outside)
- Evisceration (inside)
- Wash (-1log)
- Chill (cold shock and surface drying)
- Primal cut (10^2-10^4 CFU/cm2)
Short shelf life food products?
- Fish = high pH (no post-mortem acidification), MAP less effective (TMAO)
- Cut vegetables = (re)contamination, ready to eat
Natural preservatives in milk?
- Lactoperoxidase system
- Lysozyme
- Lactoferrin
- Antibodies
Natural preservatives in eggs?
- Lysozyme
- Avidine
- Conalbumine
- Alkalic pH
- Egg shell barrier
Spoilage potential tests?
- Ask the expert
- Challenge test = follow the product fate with spiking (contamination with organism(s) of interest)
- Storage test = follow the product fate without spiking
Advantages and disadvantages of radiation?
- Microwave = quick/readily available, non-uniform heating
- UV light = no taste defects, low penetration depth/energy easily absorbed by solutes
- Gamma rays = deep penetration/instant/uniform, consumer resistance
Advantages and disadvantages of high pressure?
- Advantages = instantly/uniformly/little effect quality
- Disadvantages = enzymes difficult to inactivate, difficult to scale up
Heat inactivation processes?
- Pasteurisation (60-80°C, few minutes)
- Appertisation/Sterilisation
- Blanching (90-100°C, minutes)
- Hot steaming
- Pre-pasteurisation (60°C, few seconds)
- Hot room (50-55°C, days)
- Sous-vide (90°C, ten minutes vacuum)
Comparison of different temperatures?
- Temperature can differ within a food product
- A food product manufactured at multiple production lines/locations, should obtain the same inactivation result using different machinery
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