An official website of the United States government.

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.



An estimated 48 million cases of foodborne illness occur in the United States per year (CDC, 2019). Out of these cases, approximately 1.5 million are attributed to Salmonella, Shiga toxin-producing E. coli (STEC), and Listeria monocytogenes with a combined economic burden of over $6.3 billion (Scallan et al., 2011). The majority of these cases are linked to foods that are known to actively support the growth of microorganisms with high water activity levels and available nutrients, but there have been increased numbers of outbreaks and recalls implicating foods with a reduced water activity (low-water activity foods, LWAF), such as spices, nuts, dried fruits, powders and grains (Beuchat et al., 2013).While there are increased recalls and outbreaks associated with LWAF, they are not generally regarded as high-risk foods due to the lack of available water needed to support growth of foodborne pathogens and are not always suspected as likely carriers of pathogens. However, pathogen contamination should be more critically considered as many LWAF (nuts and dried fruits), are raw agricultural commodities and/or minimally processed. Contamination with foodborne pathogens may occur, and these products might only be shelled, washed, dried, etc., which may not remove pathogen contamination. In these instances, prolonged survival has been observed and could pose great risks to consumers. Furthermore, many LWAF are nonperishable and have longer shelf lives than those of fresh foods, leading to less frequent or extensive cleaning and sanitizing plans within processing plants. If a contamination event occurs, the results are larger product lots that must be recalled and recalls that may last for extended periods due to the long shelf lives. Finally, many LWAF are ingredients and inclusions in other foods, which further complicates and extends the reach of recall procedures and impacts. These factors must be considered when considering the seriousness of pathogen contamination in LWAF that may lead to recalls and outbreaks.To reduce contamination risks, implementation of Good Agricultural Practices (GAPs) and Good Manufacturing Practices (GMPs) is recommended, but consistency and efficacy of practices may vary (Bourdoux et al., 2016; FAO, 2011; Munck et al., 2019). As a proactive approach to potential recalls and outbreaks, the Risk-Based Preventive Controls for Human Foods Rule under the Food Safety Modernization Act places responsibility on food processors to address potential contamination by recognizing risks and implementing preventive measures (US FDA, 2016). To meet these standards, food processors may need to provide data to prove their manufacturing procedures promote food safety by inactivating pathogens or preventing growth on or within a food product. A great deal of work has been done to investigate methodologies to control foodborne pathogens on LWAF (Ban and Kang, 2016; Brar et al., 2015; Farakos et al., 2017; Jeong et al., 2011; Limcharonenchat et al., 2018), but processors still need assistance in optimizing or identifying an intervention that suit their needs. For these reasons, there must be strong collaborative relationships between food processors and academic researchers to investigate and validate interventions that may be necessary for assessing the preventive controls and assist processors with regulatory compliance. Researchers may provide assistance in determining process parameters, developing prediction models, or conducting risk assessments.Studying foodborne pathogens in relation to LWAF introduce unique challenges in both the laboratory and the processing environment. There have been notable examples and observations of increased thermal resistance of foodborne pathogens in a LWAF matrix (Ma et al., 2009). The factors that influence this heat resistance have not been fully elucidated and are of great concern to LWAF processors who implement thermal interventions to control foodborne pathogens. Inoculation and recovery methods have variable success depending on the different qualities of LWAF products, such as pH or physical characteristics (Beuchat & Mann, 2014; Bowman et al., 2015). The type of processing intervention has also been shown to impact laboratory research in terms of residual effects, cell injury, and consistency when scaled up to industry (Rane, Bridges & Wu, 2020). The factors and circumstances that allow persistence and resistance of pathogens in LWAF must be further investigated in order to provide accurate data and recommendations to stakeholders who seek to improve the safety of their food products.Manufacturers of LWAF are faced with the complexities of maintaining a dry processing environment, as the introduction of water can be extremely detrimental to the safety of the food. Whether through cleaning, condensation, or other means, the introduction of even very small amounts of water can allow the formation of biofilms and the growth of foodborne pathogens. If biofilm formation occurs, the cells are far more resistant to desiccation and other stressors, such as sanitizers, allowing them to establish a long-term presence and avenue for contamination (Esbelin et al., 2018). While researchers and manufacturers are aware of the seriousness of this scenario, the best approaches for prevention and intervention are still not fully known. Conditions under which biofilms are established, survival of pathogens in biofilms, and cleaning methods for varieties of equipment should continue to be investigated.The food industry faces challenges of fully relying on the intrinsic factors that inhibit pathogen growth (such as low water activity) and must recognize potential contamination risks. GAPs and GMPs may be helpful in reducing these risks, but they should not be taken for granted or assumed to eliminate all risks. Research is needed to provide information on realistic contamination scenarios, knowledge about foodborne pathogens' survival strategies on LWAF, and parameters for interventions that may reduce risks associated with RTE and LWAF.Objectives:1.Determine the efficacy of intervention technologies to enhance the microbiological safety of ready-to-eat (RTE) and low-water activity foods (LWAF)2.Identify factors that contribute to resistance and persistence of foodborne pathogens in LWAF matrices3.Determine environmental conditions that contribute to persistence or growth of foodborne pathogens in foods4.Define factors that impact safety of RTE foods to address or prevent recalls and outbreaks

Acuff, Jennifer
University of Arkansas
Start date
End date
Project number
Accession number