| Bacteria - Yeasts - Molds | Bacteria Survival Tables |
Bacteria will multiply when conditions are favorable but will become lethargic when temperatures drop lower. When temperatures are high enough they will die, some of them will not survive in an oxygen absent atmosphere. Keeping them in check is of utmost importance during the manufacture of fermented and air-dried products as these products are normally not heat treated which is the most effective method for killing bacteria. In the following table we have compiled data that indicates the physical parameters which can be regulated in order to control the growth of bacteria.
It should be noted that when the two hurdles (or more) are applied (pH drop, drying, sugar, starter culture etc), their cumulative strength is magnified and bacteria are constrained more effectively. Adding salt and nitrite creates the first hurdle against the growth of bacteria and as the acidity of the sausage increases and moisture continues to evaporate, the sausage becomes more stable and contains less and less bacteria.
The first 24 hours are the most crucial and moisture removal must be slow enough to permit lactic acid bacteria to grow. Lactic bacteria Lactobacillus and Pediococcus like other species need moisture to live and will not produce lactic acid if the Aw - water activity drops below 0.93 which can happen during fast drying.
Accelerated drying will decrease moisture levels in the outside area of the sausage and will inhibit curing and color fixing bacteria Staphylococcus, Kocuria (also known as Micrococcus) from doing their job. The resulting hardened and dried surface area of the meat will not be red, it will be grey which will subsequently show on a sliced sausage.
Factors Affecting the Growth and Control of Pathogenic Bacteria
| Name | Temperature in º C | Min pH | Min Aw | O2 needs | ||
| Minimum | Optimum | Maximum | ||||
| Salmonella | 5 | 37 | 45 | 4.4 | 0.95 | FA* |
| Clostridium botulinum | 3 | 35 - 40 | 50 | 4.7 | 0.94 | OA* |
| Staphylococcus aureus | 7 | 37 | 45 | 4.6 | 0.86 | FA* |
| Campylobacter jejuni | 32 | 42 | 45 | 4.9 | 0.98 | MA* |
| Listeria monocytogenes | 0 | 35 | 42 | 5.0 | 0.92 | FA* |
| Escherichia coli | 7 | 37 | 45 | 4.0 | 0.95 | FA* |
| Shigella | 7 | 35 - 37 | 45 | 4.5 | 0.91 | FA* |
| Bacillus cereus | 4 | 32 | 45 | 4.1 | 0.95 | FA* |
| more on above bacteria at: http://www.wedlinydomowe.com/fermented-sausages/bacteria-yeasts-molds.htm | ||||||
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FA*: Facultative anaerobic feels comfortable in oxygen but can live without it as well
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OA*: Obligate anaerobic cannot grow in presence of oxygen
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MA*: Microaerophile bacteria like very little of oxygen (5%) and low levels of CO2 (carbon dioxide-10%)
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As seen in the table Staphylococcus aureus is quite resistant to drying
Fermentation Temperatures of Commercial Lactic Acid Bacteria
| Name | Temperature range in º C |
| Lactobacillus curvatus | 22 - 37 |
| Lactobacillus farciminis | 22 - 32 |
| Lactobacillus plantarum | 25 - 35 |
| Lactobacillus sakei | 21 - 32 |
| Pediococcus acidilactici | 25 - 45 |
| Pediococcus pentosaceus | 20 - 37 |
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Source: Chr. Hansen |
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Page added on May 2, 2008.
This section will be expanded in time and photos will be added.