Microbial Food Spoilage
Basic Types of Food Spoilage
1. Appearance: when a food “looks bad,” what is this referring to?
i. Microbial growth mycelia or colonies visible on surface, development of
cloudiness in liquids
ii. Changes in food colour due to heme or chlorophyll breakdown, colony pigments,
growth of mycelia, etc.
2. Textural changes (feel)
i. Slime formation due primarily to surface accumulation of microbial cells, can also
be a manifestation of tissue degradation
ii. Tissue softening due to enzymatic degradation (e.g. soft rot in veggies)
3. Changes in taste and odour: The reasons for these are the development of
i. nitrogenous compounds (ammonia, amines, etc.)
ii. sulphides
iii. organic acids
Microbial agents associated with the spoilage of certain foods
Food Examples of Microbial Agents
a) Meat and meat products Bacillaceae, Enterobacteriaceae,
Lactobacillus, Pediococcus, and Streptococcus
b) Poultry products Lactic acid bacteria, Enterobacteriaceae,
Pseudomonas,Coliforms, B. thermosphacta,
Aeromonas
c) Milk and dairy products Pseudomonas, Acinetobacter, Psychrotrophic
Bacillus, Coliforms
d) Baked foods and
confectioneries
Rhizopus sp., and Mucor sp., Penicillium sp.,
Eurotium sp., Aspergillus sp. and
Moniliasitophilia, Bacillus species,
Staphylococcus aureus
e) Fruits and vegetables Pseudomonas, Xanthomonasmaltophila,
Enterobacteriaceae, Flavobacterium
spp., Basidiophora, Peronospora,
Phytophthora, Plasmopara
f) Canned foods Bacillus subtilis, Bacillus mycoides, Bacillus
stearothermophilus, Bacillus coagulans,
Bacillus macerans and Bacillus polymyxa,
Clostridium botulinum, C. putrificum, C.
Histalyticum, C. bifermentans and C.
sporogenes Lactobacillus and Leuconostocspp.
g) Dried foods Streptococcus, Staphylococcus, Bacillus,
Xanthomonas, Achromobacter,Pseudomonas,
Micrococcus, and Brevibacterium, Coliforms,
and Staphylococcus aureus Aspergillus flavus,
Aspergillus niger, and Rhizopus spp,
Penicillium spp.
h) Fish and fish products Shewanellaputrefaciens, Pseudomonas spp.,
Photobacteriumphosphoreum, Aeromonas
spp., Psychotolerant Enterobacteriaceae,
Lactobacillus spp. Garnobacterium spp.
i) Cereal and cereal products Bacillus cereus, Clostridium botulinum,
Clostridium perfringens, Escherichia coli,
Salmonella, Staphylococcus aureus, Candida
spp., Pichia spp., Fusarium, Aspergillus and
Penicillium