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12. There are three types of microorganisms that cause food
spoilage -- yeasts, moulds and bacteria
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

13. •grow in filaments forming a tough mass which is visible as
`mould growth'. Moulds form spores which, when dry, float
through the air to find suitable conditions where they can
start the growth cycle again
•Mould can cause illness, especially if the person is allergic to
molds. Usually though, the main symptoms from eating
mouldy food will be nausea or vomiting from the bad taste
and smell of the mouldy food
•Both yeasts and moulds 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 C( F) in a boiling water canner for
the appropriate length of time destroys yeasts and moulds

14. Fungal Spoilage
Storage rot in grapes caused by Botrytis
cinerea.
Storage rot in strawberry caused by Botrytis
cinerea.
Blue mould rot in tomato caused
by Penicilliumi spp. (also by Fusarium spp.)
Black mummy rot of grapes caused
by Guignardia bidwellii
Watery soft rot in apple caused
by Sclerotinia sclerotiorum.
Blue mould on oranges caused
by Penicillium digitatum.

15. are round, rod or spiral shaped
microorganisms. Bacteria may grow under a
wide variety of conditions. There are many
types of bacteria that cause spoilage. They can
be divided into: sporeforming
and nonspore-forming
Bacteria generally prefer low acid foods like
vegetables and meat. In order to destroy bacteria
spores in a relatively short period of time, low
acid foods must be processed for the appropriate
length of time at C( F) in a pressure
Soft rot in tomato
canner caused by Erwinia
Temperatures higher than C[ F] can be carotovora
obtained only by pressure canning
•Eatting spoiled food caused by bacteria can
cause food poisoning

16. Microorganisms involved in food spoilage(Other than Canned Foods) with some examples of causative organisms
Food Type of Spoilage Microorganisms involved
Rhizopus nigricans
Mouldy Penicillium
Bread
Aspergillus niger
Ropy Bacillus subtilis
Ropy Enterobacter aerogenes
Saccharomyces
Yeasty
Zygosaccharomyces
Maple sap and syrup
Pink Micrococcus roseus
Aspergillus
Mouldy
Penicillium
Rhizopus
Soft rot
Erwinia
Fresh fruits and vegetables
Gray mold rot Botrytis
Black mold rot A. niger
Pickles, sauerkraut Film yeasts, pink yeasts Rhodotorula
Alcaligenes
Clostridium
Fresh meat Putrefaction
Proteus vulgaris
Pseudomonas fluorescens
Aspergillus
Mouldy Rhizopus
Penicillium
Cured meat Pseudomonas
Souring
Micrococcus
Lactobacillus
Greening, slime
Leuconostoc
Discoloration Pseudomonas
Fish Alcaligenes
Putrefaction
Flavobacterium
Green rot P. fluorescens
Pseudomonas
Eggs Colorless rots
Alcaligenes
Black rots Proteus
Lactobacillus
Concentrated orange juice "Off" flavor Leuconostoc
Acetobacter
Pseudomonas
Poultry Slime, odor
Alcaligenes

20. Enzymes are proteins found in all plants and
animals. If uncooked foods are not used while
fresh, enzymes cause undesirable changes in
colour, texture and flavour. Enzymes are
destroyed easily by heat processing
Atmospheric oxygen can react with some food
components which may cause rancidity or
color changes

21. Infestations (invasions) by insects and
rodents, which account for huge losses
in food stocks.
Low temperature injury - the internal
structures of the food are damaged by
very low temperature.

23. Removal of Microorganisms