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Microbiology

Four types of micro-organisms that can be controlled by MAP

Bacteria, yeasts and moulds have different respiratory and metabolic needs and can be grouped into four types, according to their oxygen requirement for metabolic and growth processes.

  • Aerobic Microbes – require oxygen or air for respiration and growth, e.g. Pseudomonas species, some Bacillus species, Acinetobacter/Moraxella species, Micrococcus species, film yeasts and moulds. Therefore some control of these organisms can be obtained by excluding oxygen from a pack.
  • Anaerobic Microbes – do not require oxygen or air to grow and many are inhibited or killed by the presence of small quantities of oxygen, e.g. Clostridium species.
  • Microaerophilic Microbes – require low levels of oxygen for optimum growth. Some also require increased levels of carbon dioxide for optimum growth, e.g. Campylobacter and Lactobacillus species.
  • Facultative Anaerobic Microbes – can respire and grow with and without the presence of air or oxygen, e.g. Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Brochothrix species, Salmonella species, Vibrio species, fermentative yeasts and some Bacillus species.

Minimum growth conditions of selected micro-organisms

This table lists various species and indicates approximate growth and survival limits with the various other factors being optimal, e.g. minimum growth temperatures are for growth in optimal neutral pH, high aw (water activity) microbiological media.

Principal spoilage micro-organisms
 

Micro-organism Minimum
pH for
Growth1		 Minimum Aw2  for Growth1 Anaerobic Growth
(e.g. in vacuum pack)		 Minimum Growth1 Temp 0°C
Aeromonas hydrophila <4.5 (3) 0.97 Yes -0.1
Bacillus cereus 4.4 0.93 Yes 4
Campylobacter species 4.9 0.987 No 4 30.5
Clostridium botulinum
Proteolytic A, B, F
non-proteolytic B, E, F 		4.6
4.7 		0.94
0.97 		Yes
Yes 		10
3.3
Clostridium perfringens 4.5 0.93 Yes 12
Escherichia coli 4.4 0.935 Yes 7-8
Lactic acid bacteria e.g. Lactobacillus 3.5 0.90 Yes 4
Listeria monocytogenes 4.3 0.92 Yes -0.4
Pseudomonas species 5.0 0.97 No 0
Salmonella species 3.8 0.92 Yes 4
Shigella species 4.8 0.96 Yes 6
Staphylococcus aureus 4.0 0.83 Yes 7
Vibrio parahaemolyticus 4.9 0.94 Yes 5
Yersinia enterocolitica 4.4 0.96 Yes -1.3
Yeasts 1.5 0.62 Yes Pink yeast -34
Moulds 1.5 0.61 No Unspecified
moulds -12

Reproduced with kind permission of CCFRA. Taken from CCFRA Guideline No. 46. Evaluation of Product Shelf-life for Chilled Foods (2004).

 

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1 Minimum growth characteristics are given for each factor when other conditions are optimum for growth. If more than one factor is present, it is likely that these minimum characteristics will change. These figures are indicative and not representative of all strains in all foods.

2 Using salt.

3 For Aeromonas species.

4 Micro-aerophylic requiring limited levels of oxygen to grow.

 
 
 
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