Food Chain Crisis

Background Low-moisture foods, such as nuts, generally have been considered low risk for foodborne illness because they are consumed in a dry state. In low-moisture foods the water activity (available moisture) is too low to support microbial growth. For example, the water activity in tree nuts is generally less than 0.7. This may lead to the common misconception that low levels of pathogenic bacteria in foods such as tree nuts are not a food safety concern. However, it is increasingly recognized that many foodborne pathogens, including Salmonella and EHEC, can cause illness when present at very low levels, i.e. for illness to occur microbial growth does not need to take place. In addition, once ingested, the high fat content in tree nuts may protect pathogens from stomach acids allowing passage of viable organisms to the intestine. While a number of low-moisture foods have been associated with foodborne illness, e.g. spices, chocolate, powdered infant formula, the recognition of tree nuts as a potential source of foodborne pathogens and human illness is relatively recent.