From wheat grain to flour: a review of potential sources of enteric pathogen contamination in wheat milled products.

The number of food safety issues linked to wheat milled products have increased in the past decade. These incidents were mainly caused by the contamination of wheat-based products by enteric pathogens. This manuscript is the first of a two-part review on the status of the food safety of wheat-based products. This manuscript focused on reviewing the available information on the potential pre-harvest and post-harvest sources of microbial contamination, and potential foodborne pathogens present in wheat-based products. Potential pre-harvest sources of microbial contamination in wheat included animal activity, water, soil, and manure. Improper grain storage practices, pest activity, and improperly cleaned and sanitized equipment are potential sources of post-harvest microbial contamination for wheat-based foods. Raw wheat flour products and flour-based products are potentially contaminated with enteric pathogens such as Shiga toxin-producing E. coli (STECs), and Salmonella at low concentrations. Wheat grains and their derived products (i.e., flours) are potential vehicles for foodborne illness in humans due to the presence of enteric pathogens. A more holistic approach is needed for assuring the food safety of wheat-based products in the farm-to-table continuum. Future developments in the wheat supply chain should also be aimed at addressing this emerging food safety threat.

Effectiveness of Ultra-High Irradiance Blue-Light-Emitting Diodes to Control Salmonella Contamination Adhered to Dry Stainless Steel Surfaces.

Controlling Salmonella contamination in dry food processing environments represents a significant challenge due to their tolerance to desiccation stress and enhanced thermal resistance. Blue light is emerging as a safer alternative to UV irradiation for surface decontamination. In the present study, the antimicrobial efficacy of ultra-high irradiance (UHI) blue light, generated by light-emitting diodes (LEDs) at wavelengths of 405 nm (841.6 mW/cm2) and 460 nm (614.9 mW/cm2), was evaluated against a five-serovar cocktail of Salmonella enterica dry cells on clean and soiled stainless steel (SS) surfaces. Inoculated coupons were subjected to blue light irradiation treatments at equivalent energy doses ranging from 221 to 1106 J/cm2. Wheat flour was used as a model food soil system. To determine the bactericidal mechanisms of blue light, the intracellular concentration of reactive oxygen species (ROS) in Salmonella cells and the temperature changes on SS surfaces were also measured. The treatment energy dose had a significant effect on Salmonella inactivation levels. On clean SS surfaces, the reduction in Salmonella counts ranged from 0.8 to 7.4 log CFU/cm2, while, on soiled coupons, the inactivation levels varied from 1.2 to 4.2 log CFU/cm2. Blue LED treatments triggered a significant generation of ROS within Salmonella cells, as well as a substantial temperature increase in SS surfaces. However, in the presence of organic matter, the oxidative stress in Salmonella cells declined significantly, and treatments with higher energy doses (>700 J/cm2) were required to uphold the antimicrobial effectiveness observed on clean SS. The mechanism of the bactericidal effect of UHI blue LED treatments is likely to be a combination of photothermal and photochemical effects. These results indicate that LEDs emitting UHI blue light could represent a novel cost- and time-effective alternative for controlling microbial contamination in dry food processing environments.

Presence, Co-Occurrence, and Daily Intake Estimates of Aflatoxins and Fumonisins in Maize Consumed in Food-Insecure Regions of Western Honduras.

Foodborne mycotoxins are a significant food safety risk in developing countries. Our objective was to determine the occurrence of and exposure levels to aflatoxins (AFs) and fumonisins (FBs) in maize intended for human and animal consumption in food-insecure regions of western Honduras. Total AFs and FBs were quantified with a monoclonal antibody-based affinity spectrofluorimetric method. FBs were detected in 614/631 samples of maize destined for human consumption at 0.3 to 41 mg/kg (mean, 2.7 mg/kg). Of the 614 positive samples, 147 had FB levels exceeding the U.S. Food and Drug Administration (FDA) advisory threshold of 4.0 mg/kg. AFs were detected in 109/631 samples of maize for human consumption with concentrations between 1.0 and 490 µg/kg (mean, 10 µg/kg). AF levels in 34 samples exceeded the FDA regulatory limit (i.e., 20 µg/kg). The average probable daily intake of AFs in western Honduras ranged from 0 to 260 ng/kg body weight/day, and for FBs, the average probable daily intake ranged from 17 to 53 µg/kg body weight/day. AFs and FBs co-occurred in 106/631 samples with 60 samples containing both toxins at levels greater than the FDA regulatory levels. Samples of maize intended for animal feed had significantly higher AF (mean, 22 µg/kg) and FB (mean, 7.6 mg/kg) contamination levels than those observed in samples destined for human consumption. Thus, the maize supply chain in western Honduras is contaminated with mycotoxins at levels that pose health risks to both humans and livestock. More effective mycotoxin surveillance and implementation of effective mitigation strategies are needed to reduce mycotoxin contamination and exposure.

Effectiveness of Ultra-High Irradiance Blue Light-Emitting Diodes in Inactivating Escherichia coli O157:H7 on Dry Stainless Steel and Cast-Iron Surfaces.

The use of blue light-emitting diodes (LEDs) is emerging as a promising dry decontamination method. In the present study, LEDs emitting ultra-high irradiance (UHI) density at 405 nm (842 mW/cm2) and 460 nm (615 mW/cm2) were used to deliver high-intensity photoinactivation treatments ranging from 221 to 1107 J/cm2. The efficacy of these treatments to inactivate E. coli O157:H7 dry cells was evaluated on clean and soiled stainless steel and cast-iron surfaces. On clean metal surfaces, the 405 and 460 nm LED treatment with a 221 J/cm2 dose resulted in E. coli reductions ranging from 2.0 to 4.1 log CFU/cm2. Increasing the treatment energy dose to 665 J/cm2 caused further significant reductions (>8 log CFU/cm2) in the E. coli population. LED treatments triggered a significant production of intracellular reactive oxygen species (ROS) in E. coli cells, as well as a significant temperature increase on metal surfaces. In the presence of organic matter, intracellular ROS generation in E. coli cells dropped significantly, and treatments with higher energy doses (>700 J/cm2) were required to uphold antimicrobial effectiveness. The mechanism of the bactericidal effect of UHI blue LED treatments is likely to be a combination of photothermal and photochemical effects. This study showed that LEDs emitting monochromatic blue light at UHI levels may serve as a viable and time-effective method for surface decontamination in dry food processing environments.

Reduction in pathogenic load of wheat by tempering with saline organic acid solutions at different seasonal temperatures.

As a raw agricultural commodity, wheat is exposed to microbial contamination; therefore, enteric pathogens may be among its microbiota creating a food safety risk in milled products. This research evaluates (1) the effectiveness of organic acids dissolved in saline solutions to reduce the counts of pathogenic microorganisms in soft and hard wheat, and also investigates the effect of seasonal temperature on (2) survivability of pathogens in wheat kernels and on (3) pathogen inactivation during tempering with saline organic acid solutions. Wheat samples were inoculated with cocktails of either 5 serovars of Salmonella enterica, 5 E. coli O157:H7 or 6 non-O157 Shiga toxin-producing E. coli (STEC) strains to achieve a concentration of ~7 log CFU/g. Inoculated samples were allowed to stand for 7-days at temperatures (2.0, 10.8, 24.2, 32 °C) corresponding to those experienced during winter, spring/fall, and summer (average and maximum) in the main wheat growing regions in the state of Nebraska, USA. Besides water, solutions containing acid (acetic or lactic 2.5% or 5.0% v/v) and NaCl (~26% w/v) were used for tempering the wheat to 15.0% (soft) and 15.5% (hard) moisture at the different seasonal temperatures. The survival of pathogenic microorganisms throughout the resting period, and before and after tempering was analyzed by plating samples on injury-recovery media. The survival rate of pathogenic microorganisms on wheat kernels was higher at temperatures experienced during the winter (2.0 °C) and spring/fall (10.8 °C) months. Regardless of tempering temperature, the initial pathogen load was reduced significantly by all solutions when compared to the control tempered with water (P ≤ .05). The combination of lactic acid (5.0%) and NaCl was the most effective treatment against Salmonella enterica, E. coli O157:H7 and non-O157 STEC, with average reduction values of 1.8, 1.8 and 1.6 log CFU/g for soft wheat and 2.6, 2.4 and 2.4 log CFU/g for hard wheat, respectively. Implementation of organic acids and NaCl in tempering water may have the potential to reduce the risk of pathogen contamination in milled products.

Effects of processing method and solute interactions on pepsin digestibility of cooked proso millet flour.

Previous studies have reported a substantial decline in in vitro digestibility of proso millet protein upon cooking. In this study, several processing techniques and cooking solutions were tested with the objective of preventing the loss in pepsin digestibility. Proso millet flour was subjected to the following processing techniques: high pressure processing (200 and 600 MPa for 5 and 20 min); germination (96 h); fermentation (48 h); roasting (dry heating); autoclaving (121 °C, 3 h), and treatment with transglutaminase (160 mg/g protein, 37 °C, 2 h). To study the interaction of millet proteins with solutes, millet flour was heated with sucrose (3-7 M); NaCl (2-6 M); and CaCl2 (0.5-3 M). All processing treatments failed to prevent the loss in pepsin digestibility except germination and treatment with transglutaminase, which resulted in 23 and 39% increases in digestibility upon cooking, respectively, when compared with unprocessed cooked flours. Heating in concentrated solutions of sucrose and NaCl were effective in preventing the loss in pepsin digestibility, an effect that was attributed to a reduction in water activity (aw). CaCl2 was also successful in preventing the loss in digestibility but its action was similar to chaotrops like urea. Thus, a combination of enzymatic modification and cooking of millet flour with either naturally low aw substances or edible sources of chaotropic ions may be useful in processing of proso millet for development of novel foods without loss in digestibility. However, more research is required to determine optimum processing conditions.

Safety and Quality Assessment of Smallholder Farmers' Maize in the Western Highlands of Guatemala.

Maize ( Zea mays) is a staple in many developing countries but is known to be prone to pest (insects, birds, and rodents) and fungal infestation. In Guatemala, mycotoxin contamination of cultivated products may occur owing to such factors as environmental conditions and the use of traditional agriculture operations. To assess the current maize conditions in Guatemala, a small-scale study was performed. Mold and insect counts and mycotoxin (aflatoxin and fumonisin) concentrations were determined on 25 farms in two townships (Chiantla and Todos Santos) of the Huehuetenango Department. Total fungal counts were 3.6 to 6.83 log CFU/g with no significant differences ( P > 0.05) across farms at different altitudes. Farms where maize was not produced but was purchased were at higher risk of fumonisin contamination, whereas local producers were mostly affected by aflatoxins. Aflatoxin was present in maize from 100% of farms at 1.0 to 85.3 ppb, and fumonisin was detected on 52% of farms at 0.4 to 31.0 ppm. Average mycotoxin consumption amounts were above the recommended maximum intake for aflatoxin in both produced and purchased maize and above the provisional maximum tolerable daily intake for fumonisin in purchased maize. Estimated daily intake was 0.01 to 0.85 µg/kg of body weight per day for aflatoxin and 2.9 to 310.0 µg/kg of body weight per day for fumonisin. An entomological analysis revealed overall 32% prevalence of Ephestia kuehniella (flour moth), 16% prevalence of Sitophilus zeamais (maize weevil), and 8% prevalence of Tribolium sp. (flour beetle) on the analyzed farms. This study highlighted poor agricultural practices used in the highlands of Guatemala. Current practices should be revised for the production of maize that is safe for consumption by the population in this region.

Microbial Load of Hard Red Winter Wheat Produced at Three Growing Environments across Nebraska, USA.

Post-flowering weather variables in farm fields may influence the microbial loads of wheat grain. In this study, the effects of weather variables following wheat flowering on the microbiological quality of wheat were evaluated over two consecutive growing seasons (2011 to 2012 and 2012 to 2013) in the state of Nebraska, USA. Three hard red winter wheat lines, including two commercial cultivars (Overland and McGill) and one experimental line (NW07505), were planted in three regions with contrasting key weather variables (Southeast, South Central, and Panhandle district) to ensure that developing seeds were exposed to different weather conditions. The natural microbial flora and deoxynivalenol concentrations of 54 freshly harvested wheat samples (three samples per wheat line, with a total of 9 samples per district) were analyzed to evaluate the impacts of the weather conditions prevailing from flowering to harvesting in each growing location (district) and season on the microbiological quality and safety of wheat grain. In 2012, the values for aerobic plate counts, Enterobacteriaceae, yeasts, molds, and internal mold infection levels were significantly lower in grain samples collected from the Panhandle district than in grain harvested from the South Central and Southeastern districts. No significant differences in the yeast counts were found in grain collected from all districts in 2013, but the levels of internal mold infection and mold counts were significantly higher in grain from the Southeastern district than in grain from the Panhandle district. Deoxynivalenol was detected in all districts; however, the concentrations were below the advisory level of 1 mg/kg for processed wheat. Microbial growth during grain development seems to be dependent on the existence of a threshold level of weather variables during the season. In general, the microbial loads in wheat grain tended to be lower in those areas with lower relative humidity levels (below 55%) and with temperatures lower than 13.7°C and higher than 31.5°C.