By itself, salt can permanently inhibit the growth of dangerous bacteria. But it takes so much salt to do so that the food is rendered inedible. Instead, curing with salt means using a little salt to slow bacteria growth and give time for friendly, acid-producing bacteria to lower the food's pH and inhibit the growth of dangerous bacteria for the long term.
Pediococcus cerevisiae – Responsible for the fermentation that turns sugar into lactic acid. This bacteria is often used in sausage fermentation cultures, but it is also one of the bacteria that ferments vegetables.
Micrococcus – A genus of bacteria that breaks sodium nitrate down to sodium nitrite in long cures.
Leuconostoc – A lactic bacteria responsible for fermentation of sugar into lactic acid.
Staphylococcus – During the fermentation process, this bacteria grows if the curing sausage is above 60F before reaching a pH of 5.3. This is also used to reduce nitrate levels.
Lactobacillus – This genus of bacteria are responsible for fermentation in yogurt, cheese, wine, beer, cider, kimchi, and pickles.
Penicillium nalgiovense – Highly desired in some Italian salamis.
There are numerous species of bacteria that threaten to ruin a good cured meat. Here are some of the more common threats:
Clostridium botulinum – C. botulinum produces a neurotoxin that can cause paralysis and death. The bacteria dies when exposed to atmospheric oxygen, so it needs to grow in an anerobic environment, like the inside of a curing ham. A combination of acid produced by lactic bacteria and dryness will prevent it from growing in a curing food. The toxin can also be denatured at temperatures above 176F. The botulin toxin is extremely poisonous – 1kg would be enough to kill every human on earth. The botulinum toxin is also the active ingredient in Botox.
Clostridium perfringens – Related to C. botulinum, this bacteria is extremely heat resistant. It can survive boiling for more than four hours. It tends to grow in an anaerobic, warm, moist, and protein rich environment. It tends to grow in meat that is heated or prepared and left out for too long before eating. It is one of the leading causes of food poisoning in the United States.
Escherichia coli – Although most strains of E. coli are harmless, there are some virulent strains that can infect food if it is improperly handled. Most common when animals are raised in a dirty environment. Has been found in dry-cured salami and cured game meats.
Listeria monocytogenes – Found in fermented sausages. It is tolerant of low temperatures, acidic environments (as low as 5.0 pH), salt, and dryness. It is, however, easily destroyed by heat. It causes Listeriosis, which is rare in humans. If contracted, it can cause meningitis and death. In pregnant women, who account for approximately 30% of cases in the United States, the disease gives the mother mild flu-like symptoms, but can lead to a miscarriage or life-threatening infection for the fetus.
Lactobacillus viridescens – Commonly associated with greening of meat from hydrogen peroxide.
Salmonella – Occurs in raw or undercooked food. Infection causes food poisoning, and can be prevented by proper handling and heating the food above 167F.
Trichinella spiralis (trichinae) – A parasite found in pork that invades muscles to cause severe pain and edema. In the United States, cases averaged over 400 a year in the late 1940’s, and have dropped to around 11 a year for the period of 2002-2007.
Staphylococcus aureus (staph) – High salt levels inhibit its growth on the outside of dry-cured meats, but it can grow once the meat is sliced.
Mold – Not a bacterium, but worth mentioning, mold doesn’t typically grow inside a piece of meat, but can grow on the surface if drying is too slow and/or humidity in the drying environment is too high. Often harmless, but can sometimes produce mycotoxins. Will typically grow in areas exposed to oxygen, which is why foods pickling are cut off from the atmosphere. Most mold can be washed off with hot water and a stiff scrub brush.