ABSTRACT This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354... more ABSTRACT This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a nonpathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica serovar cocktail of Agona, Reading, Tennessee, Mbandaka, and Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear and Bigelow model was fit to survivor data via one-step regression. On the basis of D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in nonfat dry milk powder (DEf-80°C, 100.2 ± 5.8 min; DSal-80°C, 28.9 ± 1.0 min), peanut butter (DEf-80°C, 133.5 ± 3.1 min; DSal-80°C, 57.6 ± 1.5 min), almond meal (DEf-80°C, 34.2 ± 0.4 min; DSal-80°C, 26.1 ± 0.2 min), ground black pepper (DEf-80°C, 3.2 ± 0.8 min; DSal-80°C, 1.5 ± 0.1 min), and date paste (DEf-80°C, 1.5 ± 0.0 min; DSal-80°C, 0.5 ± 0.0 min). Although the combined laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C, 9.4 ± 0.1 min; DSal-80°C, 10.1 ± 0.2 min), the difference was ∼7%. The zT values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision. HIGHLIGHTS
Annual review of food science and technology, Apr 10, 2012
First recognized in 1895, X-ray irradiation soon became a breakthrough diagnostic tool for the de... more First recognized in 1895, X-ray irradiation soon became a breakthrough diagnostic tool for the dental and medical professions. However, the food industry remained slow to adopt X-ray irradiation as a means for controlling insects and microbial contaminants in food, instead using gamma and electron beam (E-beam) irradiation. However, the reinvention of X-ray machines with increased efficiency, combined with recent developments in legislation and engineering, is now allowing X-ray to actively compete with gamma irradiation and E-beam as a microbial reduction strategy for foods. This review summarizes the historical developments of X-rays and discusses the key technological advances over the past two decades that now have led to the development of several different X-ray irradiators capable of enhancing the safety and shelf life of many heat-sensitive products, including lettuce, spinach, tomatoes, and raw almonds, all of which have been linked to high profile outbreaks of foodborne illness.
ABSTRACT Some thermal processes, such as pistachio roasting, are not yet well characterized with ... more ABSTRACT Some thermal processes, such as pistachio roasting, are not yet well characterized with respect to the impact of product and process variables on Salmonella lethality. This study aimed to quantify the effects of process temperature, humidity, and initial product water activity (aw), on Salmonella lethality for in-shell pistachios. In-shell pistachios were inoculated with Salmonella Enteritidis PT 30 (∼8.5 log CFU/g), equilibrated (0.45 or 0.65 aw), and heated without soaking (“dry”) or after a pure-water or 27% NaCl brining pretreatment (“presoaked”). Inoculated pistachio samples (15 g) were heated in a laboratory-scale, moist-air convection oven at 104.4 or 118.3°C, humidities of ∼3, 15, or 30%, v/v (∼24.4, 54.4, or 69.4°C dew point), and air speed of 1.3 m/s. Salmonella survivors were quantified at six times during each treatment, targeting total reductions of ∼3 to 5 log. Survivor data were analyzed using analysis of variance to identify main effects (time, temperature, humidity, and initial aw) and two-term interactions with time. As expected, lethality increased (P < 0.05) with temperature and humidity. For example, the time to achieve a 4-log reduction decreased 50 to 80% when humidity increased from ∼3 to 30%. When the dry and presoaked treatments were analyzed separately, initial product aw (0.45 versus 0.65 aw or 0.75 versus 0.95 aw) did not affect lethality (P > 0.05). However, when comparing dry against presoaked treatments, the time to achieve a 4-log reduction decreased 55 to 85% (P < 0.05) for presoaked pistachios subjected to the same temperature-humidity treatment. Salt had no effect (P > 0.05) on lethality outcomes. These results, relative to initial aw, process humidity, brining, and salt effects on process lethality, are critically important and must be considered in the design and validation of thermal processes for Salmonella reduction in pistachio processing.
ABSTRACT Recent revisions to U.S. Department of Agriculture, Food Safety and Inspection Service (... more ABSTRACT Recent revisions to U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) compliance and safe harbor guidelines for ready-to-eat meat and poultry products addressed process humidity requirements. Given the lack of prior data for impingement-cooked products, the present study was conducted to evaluate the impact of process humidity on Salmonella lethality at the product core and surface and compliance of the results with FSIS lethality performance standards. Whole muscle beef strips, ground beef patties, whole muscle chicken breast fillets, and breaded ground chicken patties were inoculated with an eight-serovar cocktail of Salmonella. Beef and chicken samples were cooked in a pilot-scale moist-air impingement oven to a core temperature of 70.0 and 72.8°C, respectively, immediately quenched in liquid nitrogen, and dissected to obtain core and surface samples. Variables included oven temperature (218 and 232°C), air velocity (0.7 and 2.8 m/s), and oven humidity (0.7, 15, 30, or 70% moisture by volume [%, v/v]). Additional treatments were performed to examine the impact of supplemental critical control processes such as increased endpoint temperature, postoven carryover time, and pre- or postoven steam treatments. Salmonella reductions of >7 log units were reliably achieved in chicken patties regardless of the processing variables; however, none of the treatments reliably ensured >6.5-log reductions of Salmonella in ground beef. A majority of whole-muscle samples failed to meet the required performance lethality when processed at 0.7% (v/v) humidity; however, Salmonella inactivation was significantly improved (P < 0.05) at oven humidities of ≥30% (v/v). Dry oven conditions achieved greater Salmonella lethality at the core than at the surface for multiple products (P < 0.05). The efficacies of minimal and supplemental critical controls were dependent on product, process, and humidity (P < 0.05). Overall, process humidity and product variability should be considered in regulatory requirements and process validations. HIGHLIGHTS
Background: The Bio-Rad iQ-Check Listeria spp. Kit uses real-time PCR technology for detection of... more Background: The Bio-Rad iQ-Check Listeria spp. Kit uses real-time PCR technology for detection of Listeria species in select food matrixes and environmental surfaces. Objective: The iQ-Check Listeria spp. method was modified to reduce the enrichment medium volume for environmental sponges from 225 and 100 to 60 mL and to reduce the enrichment time for sponges and swabs from 25 ± 1 to as short as 18 h. The modified method was validated with stainless steel, polystyrene plastic, and sealed concrete using sponges or swabs with two different neutralizing buffers (Letheen Broth and HiCap™ Neutralizing Broth). In addition, the Bio-Rad Free DNA Removal Solution was used for all environmental samples. Methods: The iQ-Check Listeria spp. modified method was compared with the reference culture method in the U.S. Department of Agriculture Food Safety and Inspection Service Microbiology Laboratory Guidebook Chapter 8.10 using an unpaired study design. Results: In the method comparison study, th...
ABSTRACT This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354... more ABSTRACT This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a nonpathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica serovar cocktail of Agona, Reading, Tennessee, Mbandaka, and Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear and Bigelow model was fit to survivor data via one-step regression. On the basis of D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in nonfat dry milk powder (DEf-80°C, 100.2 ± 5.8 min; DSal-80°C, 28.9 ± 1.0 min), peanut butter (DEf-80°C, 133.5 ± 3.1 min; DSal-80°C, 57.6 ± 1.5 min), almond meal (DEf-80°C, 34.2 ± 0.4 min; DSal-80°C, 26.1 ± 0.2 min), ground black pepper (DEf-80°C, 3.2 ± 0.8 min; DSal-80°C, 1.5 ± 0.1 min), and date paste (DEf-80°C, 1.5 ± 0.0 min; DSal-80°C, 0.5 ± 0.0 min). Although the combined laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C, 9.4 ± 0.1 min; DSal-80°C, 10.1 ± 0.2 min), the difference was ∼7%. The zT values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision. HIGHLIGHTS
Annual review of food science and technology, Apr 10, 2012
First recognized in 1895, X-ray irradiation soon became a breakthrough diagnostic tool for the de... more First recognized in 1895, X-ray irradiation soon became a breakthrough diagnostic tool for the dental and medical professions. However, the food industry remained slow to adopt X-ray irradiation as a means for controlling insects and microbial contaminants in food, instead using gamma and electron beam (E-beam) irradiation. However, the reinvention of X-ray machines with increased efficiency, combined with recent developments in legislation and engineering, is now allowing X-ray to actively compete with gamma irradiation and E-beam as a microbial reduction strategy for foods. This review summarizes the historical developments of X-rays and discusses the key technological advances over the past two decades that now have led to the development of several different X-ray irradiators capable of enhancing the safety and shelf life of many heat-sensitive products, including lettuce, spinach, tomatoes, and raw almonds, all of which have been linked to high profile outbreaks of foodborne illness.
ABSTRACT Some thermal processes, such as pistachio roasting, are not yet well characterized with ... more ABSTRACT Some thermal processes, such as pistachio roasting, are not yet well characterized with respect to the impact of product and process variables on Salmonella lethality. This study aimed to quantify the effects of process temperature, humidity, and initial product water activity (aw), on Salmonella lethality for in-shell pistachios. In-shell pistachios were inoculated with Salmonella Enteritidis PT 30 (∼8.5 log CFU/g), equilibrated (0.45 or 0.65 aw), and heated without soaking (“dry”) or after a pure-water or 27% NaCl brining pretreatment (“presoaked”). Inoculated pistachio samples (15 g) were heated in a laboratory-scale, moist-air convection oven at 104.4 or 118.3°C, humidities of ∼3, 15, or 30%, v/v (∼24.4, 54.4, or 69.4°C dew point), and air speed of 1.3 m/s. Salmonella survivors were quantified at six times during each treatment, targeting total reductions of ∼3 to 5 log. Survivor data were analyzed using analysis of variance to identify main effects (time, temperature, humidity, and initial aw) and two-term interactions with time. As expected, lethality increased (P < 0.05) with temperature and humidity. For example, the time to achieve a 4-log reduction decreased 50 to 80% when humidity increased from ∼3 to 30%. When the dry and presoaked treatments were analyzed separately, initial product aw (0.45 versus 0.65 aw or 0.75 versus 0.95 aw) did not affect lethality (P > 0.05). However, when comparing dry against presoaked treatments, the time to achieve a 4-log reduction decreased 55 to 85% (P < 0.05) for presoaked pistachios subjected to the same temperature-humidity treatment. Salt had no effect (P > 0.05) on lethality outcomes. These results, relative to initial aw, process humidity, brining, and salt effects on process lethality, are critically important and must be considered in the design and validation of thermal processes for Salmonella reduction in pistachio processing.
ABSTRACT Recent revisions to U.S. Department of Agriculture, Food Safety and Inspection Service (... more ABSTRACT Recent revisions to U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) compliance and safe harbor guidelines for ready-to-eat meat and poultry products addressed process humidity requirements. Given the lack of prior data for impingement-cooked products, the present study was conducted to evaluate the impact of process humidity on Salmonella lethality at the product core and surface and compliance of the results with FSIS lethality performance standards. Whole muscle beef strips, ground beef patties, whole muscle chicken breast fillets, and breaded ground chicken patties were inoculated with an eight-serovar cocktail of Salmonella. Beef and chicken samples were cooked in a pilot-scale moist-air impingement oven to a core temperature of 70.0 and 72.8°C, respectively, immediately quenched in liquid nitrogen, and dissected to obtain core and surface samples. Variables included oven temperature (218 and 232°C), air velocity (0.7 and 2.8 m/s), and oven humidity (0.7, 15, 30, or 70% moisture by volume [%, v/v]). Additional treatments were performed to examine the impact of supplemental critical control processes such as increased endpoint temperature, postoven carryover time, and pre- or postoven steam treatments. Salmonella reductions of >7 log units were reliably achieved in chicken patties regardless of the processing variables; however, none of the treatments reliably ensured >6.5-log reductions of Salmonella in ground beef. A majority of whole-muscle samples failed to meet the required performance lethality when processed at 0.7% (v/v) humidity; however, Salmonella inactivation was significantly improved (P < 0.05) at oven humidities of ≥30% (v/v). Dry oven conditions achieved greater Salmonella lethality at the core than at the surface for multiple products (P < 0.05). The efficacies of minimal and supplemental critical controls were dependent on product, process, and humidity (P < 0.05). Overall, process humidity and product variability should be considered in regulatory requirements and process validations. HIGHLIGHTS
Background: The Bio-Rad iQ-Check Listeria spp. Kit uses real-time PCR technology for detection of... more Background: The Bio-Rad iQ-Check Listeria spp. Kit uses real-time PCR technology for detection of Listeria species in select food matrixes and environmental surfaces. Objective: The iQ-Check Listeria spp. method was modified to reduce the enrichment medium volume for environmental sponges from 225 and 100 to 60 mL and to reduce the enrichment time for sponges and swabs from 25 ± 1 to as short as 18 h. The modified method was validated with stainless steel, polystyrene plastic, and sealed concrete using sponges or swabs with two different neutralizing buffers (Letheen Broth and HiCap™ Neutralizing Broth). In addition, the Bio-Rad Free DNA Removal Solution was used for all environmental samples. Methods: The iQ-Check Listeria spp. modified method was compared with the reference culture method in the U.S. Department of Agriculture Food Safety and Inspection Service Microbiology Laboratory Guidebook Chapter 8.10 using an unpaired study design. Results: In the method comparison study, th...
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Papers by Elliot Ryser