Salmonella bacteria are a group of microbes that can cause serious food poisoning. They are killed by heat and so are more of a danger in raw foods. Crunchy beansprouts, alfalfa sprouts, or any other form of sprouts may commonly be served raw instead of cooked. Sprouts and salmonella are associated with issues such as manure from infected animals on the crops or from contaminated machinery used to process the crops.
Sprouts and salmonella are closely related in many countries across the world, wherever sprouts of any plant are consumed raw. Examples of sprouts that have been associated with salmonella food poisoning include alfalfa, mung bean, and radish sprouts. These young plants are grown from seeds in sprouting farms.
In many instances, the seeds themselves are contaminated with the salmonella bacteria. These seeds may have become contaminated through animal or bird droppings. The farm machinery that processes the seeds may also be contaminated. Manure used to fertilize the crops or irrigation water that contains the bacteria can also deposit the salmonella on the seeds.
Processes that kill any contamination on the seeds are available to sprout farmers but may be prohibitively expensive for small sprouting farms. These techniques include bathing the seeds in calcium hypochlorite solution or irradiating the seeds. Organic farms may also reject the techniques as being contrary to the organic ethos.
Sprouting farms generally grow the seeds in indoor environments that are kept at warm temperatures with high humidity. These conditions are highly suitable for sprouts and salmonella bacteria to grow. Salmonella infect humans and other animals and so prefer to grow at body temperature and in conditions of high water availability, such as exist in the human body. Even if the seeds originally have a low contamination of the bacteria, these can grow and multiply to dangerous levels during the sprouting process.
The U.S. Food and Drug Administration recommends that certain groups of people avoid eating raw sprouts because of the risk of infection. Susceptible people include the elderly, pregnant women, kids, and those who have immune system problems. Cooking the sprouts is the only definitive way to remove the risk of infection, although some people may still prefer to eat raw or lightly cooked sprouts for the crunchy texture.
Apart from the connection between sprouts and salmonella, raw sprouts can also harbor the potential food-poisoning bacteria E. coli and Listeria monocytogenes. Although sprouts are one potential source of food poisoning, they are not the only source. Any food that may come into contact with contaminated fecal matter, such as manure, and then does not undergo cooking is a potential source of the illness.