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Chapter 4: Food Spoilage (Caused by: (Environmental factor, Enzymes, Pest,…
Chapter 4: Food Spoilage
Caused by:
Environmental factor
Enzymes
Pest
Chemical reaction
Microorganisms
Time
Source of microbes
Plant and plant product
Animal hides
Utensil and processing equipment
Gastrointestinal tract of animals and human
Soil and water
Food handlers
Microbes involved in food spoilage:
Yeast
Containing high sugar/salt content
fruits and juices with low pH
surface of meat and cheese
e.g.
Saccharomyces spp, Zygosaccharomyces, Candida
Mold
at low water activity level (0.7 - 0.8)
pH: 3 - 8
e.g.
Mucor, Rhizopus, Botrytis
Bacteria
Spoilage of meat
Aerobic condition
Off flavors and odours
Color change
Rancidity
Surface slime
Anaerobic condition
Putrefaction
Souring
Spoilage of milk
Gas production
Proteolysis
Sweet curdling
Slow proteolysis
Acid proteolysis
Residual proteolysis
Souring
Ropiness
Surface
Throughout
Color changes
Alkali production
Fruits
Black mold:
Aspergillus spp
Green mold:
Cladosporium spp
Blue mold rot:
Penicillium expansum
Bacteria soft rot:
Xanthomonas, Erwinia
Vegetables
Mold spoilage
Sour rot:
Geotricum candidum
Rhizopus soft rot:
Rhizophus nigricans
Grey mold rot:
Botrytis spp
Alternaria rot:
Alternaria spp
Bacterial spoilage
Bacteria soft rot:
Erwinia carotovara
Cereals
Dwarf bunt:
Tilletia conroversa
Blue-eye rot:
Penicillium
Common bunt:
Tilletia tritici
Bread
Mouldy bread:
Aspergillus niger
Ropiness:
Bacillus subtilis
Measuring Bacterial Growth
Direct method
Filtration
MPN
Plate counts
Direct microscopic count
Indirect method
Metabolic activity
Dry weight
Turbidity