Food spoilage means the original nutritional value, texture,
flavour of the food are damaged and can no longer be consumed by humans.
Food spoil because of:
- poor sanitation
- improper temperature control
- microbial growth
- physical abuse.
- Enzymatic and chemical reaction
General characteristics of food spoilage:
Canned Foods: Swollen
top or bottom, dented area along the side seam. Unusual odour of contents.
Fruits & vegetables:
Sunken, soft areas, browning.
Fish: Gills gray and
greenish. Eyes sunken, flesh is easily pulled away from bones. Fingernail
indention persists in flesh; rigidity not present. Foul odour.
Meat: Beef usually
spoils first on surface while pork spoils at the juncture of bone and meat in
the inner portions. Foul odour is generally detectable and the meat is slimy to
the touch.
Poultry: Stickiness
appears first under the wing, at the juncture of legs and body as well as
darkening of the tips of the wings.
Frozen foods:
Spoilage is promoted by thawing at room temperature, which provides
optimal conditions for the growth of bacteria.
Foods should be thawed in the refrigerator.
This lesson we will be concentrating on food spoilage caused by
micro-organisms (microbial growth). We will concentrate on the others in weeks
to come.
There are three types of microorganisms that cause food
spoilage yeasts, molds and bacteria.
Yeasts growth
causes fermentation which is the result of yeast metabolism. There are two
types of yeasts true yeast and false yeast. True
yeast metabolizes sugar producing alcohol and carbon dioxide gas. This is
known as fermentation. False yeast grows as a dry film on a food
surface, such as on pickle brine. False yeast occurs in foods that have a high
sugar or high acid environment.
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| spoilage in orange caused by yeast and |
Molds grow
in filaments forming a tough mass which is visible as ‘mold growth’. Molds form
spores which, when dry, float through the air to find suitable conditions where
they can start the growth cycle again.
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| spoilage in bread caused by yeast and molds |
Mold can cause illness, especially if the person is allergic
to molds. Usually though, the main symptoms from eating moldy food will be
nausea or vomiting from the bad taste and smell of the moldy food.
 |
| Spoilage in tomatoes cause by yeast and molds |
Both yeasts and molds can thrive in high acid foods like
fruit, tomatoes, jams, jellies and pickles. Both are easily destroyed by heat.
Processing high acid foods at a temperature of 100°C (212°F) in a boiling water
canner for the appropriate length of time destroys yeasts and molds.
 |
| spoilage in meat caused by bacteria |
Bacteria may
grow under a wide variety of conditions. There are many types of bacteria that
cause spoilage. They can be divided into: spore-forming and non-spore-forming. Bacteria generally prefer low acid foods like vegetables and
meat.
Spoilage can also occur in cooked foods that are not stored
at the correct temperatures, or temperatures that are constant for a long
period of time. It is important to monitor hot food temperatures and consume
foods before there expiration date. Microbial growth in cooked foods can lead
to food intoxication or food poisoning.
 |
| characteristics of meat spoiilage |
Follow the link to watch video on food spoilage and other causes of food spoilage http://www.youtube.com/watch?v=63OEbUg_eFs
Activity
Go into the kitchen at home and make notes of foods that can
be spoiled by bacteria, yeast and molds. Make a table and write each food item
in the categories of the micro-organism that can cause spoilage in them.
References
Anonymous. (2009). Food Preservation. Retreieved March 1,
2013 from
http://www.foodfreshly.com/food-preservation/food-preservation.html
Anonymous. (2013). Food safety. Retrieved March 1, 2013 from
http://www.eufic.org/article/en/food-safety-quality/safe-food-handling/expid/basics-food-safety/
Garden-Robinson, J & Hegerfeld-Baker, J. (2012) Food
preservation. Retrieved March 19, 2013 from http://www.ag.ndsu.edu/pubs/yf/foods/fn189.pdf
