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Chapter 3: Microbial Food Spoilage (Spoilage Signs (Sliminess (e.g.…
Chapter 3: Microbial Food Spoilage
Definition:
Undesirable deterioration of food quality that may result in changes in:
taste.
appearance of food.
odour.
Food Spoilage
Microbial Spoilage
Factors that affect spoilage:
pH
Acidic/ alkaline
Water activity
Most bacteria, for example, do not grow at water activities below 0.91, and most molds cease to grow at water activities below 0.80.
Temperature
Serving Temperature
Danger Zone Temperature (5-60 degree celsius)
Humidity
Direct relation to environment.
e.g. environment storage.
Oxygen
e.g. Vapor-proof packaging that keeps oxygen out helps reduce oxidation problems.
Extrinsic Factors
Chemical Reactions (contact with metal)
Microorganism
Growth & multiplication of microorganisms
Mechanical Damages
e.g. improper handlings.
Insects, Rodents, Birds
Non Microbial Spoilage
Foreign Materials
e.g adding spoon or fork during cooking.
Enzymes
e.g. banana matures, the color changes from green to yellow to brown to black. The change is caused by the enzymes (chemicals) in the banana.
ripening, softening, of other fruits such as apples, peaches and tomatoes
Spoilage Signs
Discoloration
e.g. Meat. From red to dark bright green.
Souring
Production of acid.
Meat to souring - rare.
Sour milk - production of lactic acid.
Sliminess
e.g. Cucumber - sliminess.
Throw the sliminess part at above the below part still can consume.
*applicable to fruits and vegetables only.
Milk no sliminess.
Gas Fomation
Meats - spongy.
Swollen / bubbling packaged & cans.
Odour
Breakdown of proteins - putrefaction
e.g. rotten egg smell
