Bacterial hazards

Bacteria are the largest group of hazards in curing, and they behave differently from the parasites and the moulds. A parasite is already present in the meat and does not grow further, and a mould colonises a surface, but a pathogenic bacterium multiplies, and given warmth, moisture and time it can multiply quickly. This is why the craft is built around denying it the conditions to grow. The Safety Triangle and the curing salts are the answer: the salt and the fall in water activity, the drop in pH during fermentation, the nitrite in the cure, and the control of temperature and time are all hurdles stacked against bacterial growth.

For the curesmith the bacterial hazards fall into two groups, and the distinction decides how each is controlled. The first can grow in or on the product, so the cure itself must be designed to stop them. Clostridium botulinum is held out by nitrite and by a low water activity and pH. Listeria monocytogenes grows even in the cold and settles on ready-to-eat surfaces after processing. Staphylococcus aureus tolerates salt and grows in the warm early hours of a ferment, before the pH falls. The second group does not grow in or survive a proper cure, but is dangerous on the raw material and in the workspace. Salmonella, Escherichia coli O157:H7, Campylobacter and Yersinia are carried in on raw meat and controlled either by a validated reduction where the product is raw and fermented, or otherwise by clean handling, thorough cooking and the cold chain. Clostridium perfringens stands a little apart, as a hazard of cooked meat cooled too slowly.

**How it endangers cured meat.** A bacterial hazard threatens a product in one of two ways: by growing in it, or by being present in the raw material and surviving a process that does not remove it. Dry-cured and fermented products carry the sharper form of the problem, because they are eaten without cooking, so the process itself must either prevent growth or achieve a validated reduction. For fermented sausages this is the five-log reduction of Salmonella and E. coli O157:H7 across the whole process; for shelf-stable products it is the combination of low water activity, low pH and nitrite that holds Clostridium botulinum and the rest. Where a product is cooked, heat does most of the work, and the remaining concern is recontamination afterwards, chiefly with Listeria. Each organism has its own article; this entry is the map to them.