Nuts and Grains: Microbiology and Preharvest Contamination Risks

Abstract

Low-water-activity foods have been involved in recalls and foodborne disease outbreaks. Increased consumption; better detection methods and reporting systems; improved surveillance, trace-back, and ability to connect sporadic foodborne illnesses; and inadequate implementation of food safety programs are some of the likely reasons for the increase in frequency of recalls and outbreaks linked to dry foods. Nuts and grains can be contaminated with foodborne pathogens at any stage during production, processing, storage, and distribution. Focusing on preharvest contamination, the various potential sources of contamination include soil, animal intrusion, contaminated harvesting equipment, harvest and preharvest handling, storage conditions, and others. The low water activity of nuts and grains prevents the growth of most foodborne pathogens on their surfaces. The long-term survival of bacterial foodborne pathogens (, O157:H7, and) on dry foods has been documented in the literature for different nut types. Preventing contamination is the key to avoiding foodborne disease risks linked to dry foods. The implementation of good agricultural practices and other food safety systems provides a proactive approach to address concerns thoroughly. A plethora of research is available on preventing the growth of mycotoxin-producing fungi on the surface of nuts and grains. Milling is an effective mechanism to reduce the microbial load on grains. This review focuses on providing information about associated foodborne microorganisms, preharvest contamination sources, and good agricultural practice recommendations for nuts and grains.

From managed aquifer recharge to soil aquifer treatment on agricultural soils: Concepts and challenges

“…The individuals most intensely exposed to such risks are the farmers and field workers in the Ag-SAT field who may come into direct contact with the TWW (WHO, 2006b). Crops that have fruit in contact with soil (e.g., nuts drying on the orchard floor) may not be suitable for Ag-SAT due to the high risk of bacterial pathogen contamination (e.g., salmonella, E. coli) (Brar and Danyluk, 2018). Since Ag-SAT has not, to date, been tested, the health threats stemming from prolonged TWW ponding and the quality of the produced crops are unclear.…”

Source Attribution of Salmonella in Macadamia Nuts to Animal and Environmental Reservoirs in Queensland, Australia

“…Salmonellosis outbreaks and recalls of nut products due to Salmonella contamination have become increasingly common, raising awareness of nuts as a potential vehicle for foodborne illness. Information about prevalence of human pathogens in nuts is limited (Brar and Danyluk, 2018). Zhang et al (2017) found 4.2% (95% confidence interval 2.40-6.90) Salmonella prevalence in macadamia nuts in the United States.…”

“…Using historical Salmonella typing data from QLD isolates from various sources collected between 1998 and 2017, we applied a source attribution model to attribute Salmonellapositive macadamia nut samples to animal and environmental source(s). As Salmonella contamination of nuts may be introduced at the plantation site (on the tree or during harvest) or along the postharvest processing path (Brar and Danyluk, 2018), we hypothesized that nonhuman sources in the plantation environment contaminated macadamia nuts.…”

The Role of the Salmonella spvB IncF Plasmid and Its Resident Entry Exclusion Gene traS on Plasmid Exclusion

“…Salmonella enterica is responsible for 78 million illnesses and 59 thousand deaths per year, worldwide (Havelaar et al, 2015). Non-typhoid Salmonella are primarily transmitted via fecal contamination of meat, eggs, dairy products, fruits, nuts, and vegetables (De Buyser et al, 2001;Brar and Danyluk, 2018;De Cesare, 2018;Li et al, 2018;Omer et al, 2018). In the United States, S. enterica causes 1 million illnesses each year, resulting in 19 thousand hospitalizations (Scallan et al, 2011).…”