The story of low moisture foods.
Low moisture foods are foods which are naturally low in moisture or where moisture has been purposefully reduced, typically by drying. Historically, not much concern was given to the safety of low moisture foods as microorganisms cannot grow in these conditions. The majority of the food industry was operating under the (incorrect) assumption that because pathogenic microorganisms could not grow these foods would be safe. This is not the case. Pathogens can survive in low moisture foods for extended periods. In the past 10 years there have been 16 outbreaks linked to Salmonella in low moisture foods. These outbreaks have accounted for 20% of the reported Salmonella outbreaks in food during this time period and affected a reported 1,810 individuals, leading to over 350 hospitalizations and 11 deaths.
One of the most notable Salmonella outbreaks involved peanut butter for use in industrial settings and as an ingredient in other products. This outbreak led to over 700 illness and the recall of over 3,600 products. This was troubling as FDA inspectors found numerous issues that may have attributed to this large-scale outbreak.
Not only Salmonella has been noted as a pathogen of concern in these foods; outbreaks have been linked to Escherichia coli in flour, hazelnuts, and cookie dough (flour). Even more troublesome is the list of recalls associated with the potential presence of these pathogens (Salmonella, E. coli, and Listeria monocytogenes) in low moisture foods, which includes; nuts and seeds, spices and botanicals, pet food, cereals, etc.
Traditional thermal technologies, such as baking, extrusion, and roasting, are commonly used to provide the expected taste and texture quality attributes of many low moisture foods. Heat is known to inactivate pathogenic microorganisms, but this may not always the case in these foods. As moisture content decreases, thermal resistance of pathogens increases, making it much more difficult to inactivate them.
Since control with typical processing unit operations may not always control foodborne pathogens in low moisture foods, special emphasis must be placed on good manufacturing practices (including sanitation), proper flow and segregation through the plant, and post process contamination to control the presence of pathogenic microorganisms in low moisture foods.