Edward Richter | The Ohio State University (original) (raw)
Papers by Edward Richter
Applied and Environmental …, 1983
Some foods contain low numbers of microbes that may be difficult to enumerate by the plate count ... more Some foods contain low numbers of microbes that may be difficult to enumerate by the plate count method due to small food particles that interfere with the counting of colonies. Ludox colloidal silicon was coated with reducing agents to produce a nontoxic density material. Food homogenates were applied to a layered 10 and 80% mixture of modified Ludox and centrifuged at low speed. The top and bottom of the tube contained the food material, and the Ludox-containing portion was evaluated by conventional pour plate techniques. Plate counts of the Ludox mixture agreed with plate counts of the food homogenate alone. The absence of small food particles from pour plates resulted in a plate that was more easily read than pour plates of the homogenate alone. Modified Ludox was evaluated for its effect on bacteria at 4°C during a 24-h incubation period. No inhibition was observed. This method is applicable to food products, such as doughnuts, spices, tomato products, and meat, in which small food particles often interfere with routine plate counts or low dilution may inhibit colony formation. Inhibitory substances can be removed from spices, resulting in higher counts. Ludox is more economical than similar products, such as Percoll. Modified Ludox is easily rendered nontoxic by the addition of common laboratory reagents. In addition, the mixture is compatible with microbiological media.
Journal of dairy science, 1993
Biosensors are defined as indicators of biological compounds that can be as simple as temperature... more Biosensors are defined as indicators of biological compounds that can be as simple as temperature-sensitive paint or as complex as DNA-RNA probes. Food microbiologists are constantly seeking rapid and reliable automated systems for the detection of biological activity. Biosensors provide sensitive, miniaturized systems that can be used to detect unwanted microbial activity or the presence of a biologically active compound, such as glucose or a pesticide. Immunodiagnostics and enzyme biosensors are two of the leading technologies that have had the greatest impact on the food industry. The use of these two systems has reduced the time for detection of pathogens such as Salmonella to 24 h and has provided detection of biological compounds such as cholesterol or chymotrypsin. The continued development of biosensor technology will soon make available "on-line quality control" of food production, which will not only reduce cost of food production but will also provide greater sa...
Applied and environmental microbiology, 1990
Two types of commercial products for feeding zoo animals (a frozen meat product, referred to as z... more Two types of commercial products for feeding zoo animals (a frozen meat product, referred to as zoo food, and a dry product, referred to as dry food) were microbiologically examined for spoilage organisms (aerobic, psychrotrophic, coliform, Escherichia coli, mold, and yeasts) and pathogens (Salmonella spp., Listeria monocytogenes, and Campylobacter jejuni). Levels of microorganisms in frozen ground zoo food were compared with those in frozen ground beef and frozen ground turkey meat. The level of microbial contaminants in frozen ground zoo meat was found to be similar to that in frozen ground beef and higher than that in frozen ground turkey meat. Sixty percent of the frozen zoo meat samples were Salmonella positive, and all of the samples were L. monocytogenes positive. Dry zoo food was documented to have microbial levels lower than those in frozen zoo meat; the pathogen levels were less than 1/25 g of food. Defrosting zoo meat at 10, 25, and 37 degrees C for 24 h showed that 10 de...
Pediococcus acidilactici PO2 Bacteriocin Production in Whey Permeate and Inhibition of Listeria monocyfogenes in Foods
Journal of Food Science, 1993
... I CHII-CHERNG LIAO, AHMED E. YOUSEF, EDWARD R. RICHTER, and GRADY W. CHISM ... caused by this... more ... I CHII-CHERNG LIAO, AHMED E. YOUSEF, EDWARD R. RICHTER, and GRADY W. CHISM ... caused by this organism, is estimated to cost much more per incident than any other common but less serious foodborne disease, because of the high fatality rate (Todd, 1989). ...
Evaluation of an X-ray microprobe technique as a possible aid to detect salmonellae
Canadian Journal of Microbiology, 1982
The X-ray microprobe was examined as a possible aid in the detection of salmonellae. Results obta... more The X-ray microprobe was examined as a possible aid in the detection of salmonellae. Results obtained indicate that specific bacterial antigen (Salmonella) increased in phosphorus and sulfur after reaction with the fluorescein isothiocyanate tagged*** specific antibody. Nonspecific antigen (Escherichia coli) did not increase in phosphorus and sulfur after reaction with fluorescein isothiocyanate tagged anti-Salmonella antibody. The technique developed supports the hypothesis that X-ray microprobe analysis may be useful in detecting salmonellae, or other bacteria, by determining increases in the elemental constitutents of bacterial cells when reacted with elemental-tagged antibodies.
Effects of electroconductive heat treatment and electrical pretreatment on thermal death kinetics of selected microorganisms
Biotechnology and Bioengineering, 1992
Suspensions of yeast cell (zygo Saccharomyces bailii) in a phosphate buffer solution were subject... more Suspensions of yeast cell (zygo Saccharomyces bailii) in a phosphate buffer solution were subjected to conventional (hot water) and ohmic (electric current) heating under identical temperature histories. Experiments were also conducted with cells of Escherichia coli to compare the lethal effect of combination of sublethal electrical preteatment and conventional heating with conventional heating. The kinetic parameters (D,Z,K and E(a)) were determined for both organisms during different treatments. There was no significant difference in the death rate of yeast cells during conventional and ohmic heating at the voltage range used in this study. Results of electrical pretreatment and conventional heating on E. coli indicated differences under certain conditions when compared with pure conventional heating. Thus it is concluded that microbial death during ohmic heating was due primarily to thermal effects with no significant effect of electric current per se. Sublethal electrical pretreatment appears to offer potential for increased bacterial inactivation in certain cases.
Biosystems Engineering, 2004
Application of pulsed electric fields (PEF) to skim milk inoculated with Staphylococcus aureus wa... more Application of pulsed electric fields (PEF) to skim milk inoculated with Staphylococcus aureus was conducted in the study. Skim milk samples were treated by PEF, using fluid handling systems of both circulation and stepwise modes. Parameters for the PEF were 3Á7 ms pulse duration time, 250 Hz pulse repetition rate, 1 ml s À1 flow rate, 460 ms total treatment time, and 3Á5 kV mm À1 electric field strength. After the PEF-treatment, the samples were plated onto both tryptic soya agar and Baird Parker agar with egg yolk tellurite enrichment to enumerate the number of inactivated and injured cells. Survivals of PEF-treated S. aureus cells were also enumerated at refrigeration temperature for 2 weeks. There was a significant decrease in S. aureus cells caused by the two fluid handling systems (probability P50Á05). The difference in the inactivation due to the PEF treatment with the fluid handling systems was not significant (P>0Á05). After the PEF treatment, there was no significant injury of the PEF-treated cells (P>0Á05). Relative to the control samples, there was a significant reduction in the number of the PEF-treated cells at 48C for 2 weeks (P50Á05).
Applied and Environmental Microbiology, 2000
Both 25-g single-size ground beef samples and 375-g composite ground beef samples were tested by ... more Both 25-g single-size ground beef samples and 375-g composite ground beef samples were tested by a method combining an immunomagnetic separation (IMS) technique with a sandwich enzyme-linked immunosorbent assay (ELISA) system (IMS-ELISA). The results demonstrated that IMS-ELISA could detect the target, Escherichia coli O157:H7, at the level of 10 ؊1 CFU/g of sample in either the 25-or 375-g sample size.
Journal of Food Safety, 1994
Thirty seven strains of lactobacilli and leuconostocs were screened for bacteriocin production. A... more Thirty seven strains of lactobacilli and leuconostocs were screened for bacteriocin production. A bacteriocin-like substance (designated lacidin A) was detected in culture filtrate of Lactobacillus acidophilus OSU133. Lacidin A inhibited Enterococcus faecalis, L. acidophilus, Lactobacillus delbrueckii subsp. lactis, and Staphylococcus aureus. The bacteriocinogenic nature of lacidin A was confirmed by eliminating the inhibitory effects of acid, hydrogen peroxide and phage and by loss of activity upon hydrolysis with proteolytic enzymes. The bacteriocin is relatively heat-stable and has considerable bactericidal action against S. aureus in phosphate buffer. Lacidin A also demonstrated bacteriostatic action against S. aureus in brain heart infusion and heat-treated milk and liquid whole egg.
Journal of Food: Microbiology, Safety & Hygiene
Rapid and specific identification of foodborne pathogens is important for not only for food produ... more Rapid and specific identification of foodborne pathogens is important for not only for food producers but also consumers as well as food safety authorities. Foods can harbor pathogen bacteria of different species, thus it is also important to be able to detect different pathogens simultaneously from the food samples even though they are in very low number. Detection of bacteria depends on different factors such as the initial number, food matrix, sensitivity of the method, competitor microflora and physical state of the bacteria whether they are injured or not. Simultaneous detection of different bacteria yet adds another hurdle for the level of detection, and thus, different approaches have developed and tested so far to optimize the maximum recovery.
Antimicrobial activity of banana puree
Food Microbiology, 1989
... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banan... more ... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banana fruits grown in Hyderabad region. Pakistan J. Sci. Ind. ... 18851890. Ketiku, 1973 AO Ketiku, Chemical composition of unripe (green) and ripe plantain (Musa paradisiaca). ...
Antimicrobial activity of banana puree
Food Microbiology, 1989
... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banan... more ... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banana fruits grown in Hyderabad region. Pakistan J. Sci. Ind. ... 18851890. Ketiku, 1973 AO Ketiku, Chemical composition of unripe (green) and ripe plantain (Musa paradisiaca). ...
Concurrent Detection of Escherichia Coli O157:H7 and Salmonella from a Single Enrichment in 24 H
Journal of Food Safety, 2001
Concurrent Detection of Escherichia Coli O157:H7 and Salmonella from a Single Enrichment in 24 H
Journal of Food Safety, 2001
Applied and Environmental …, 1983
Some foods contain low numbers of microbes that may be difficult to enumerate by the plate count ... more Some foods contain low numbers of microbes that may be difficult to enumerate by the plate count method due to small food particles that interfere with the counting of colonies. Ludox colloidal silicon was coated with reducing agents to produce a nontoxic density material. Food homogenates were applied to a layered 10 and 80% mixture of modified Ludox and centrifuged at low speed. The top and bottom of the tube contained the food material, and the Ludox-containing portion was evaluated by conventional pour plate techniques. Plate counts of the Ludox mixture agreed with plate counts of the food homogenate alone. The absence of small food particles from pour plates resulted in a plate that was more easily read than pour plates of the homogenate alone. Modified Ludox was evaluated for its effect on bacteria at 4°C during a 24-h incubation period. No inhibition was observed. This method is applicable to food products, such as doughnuts, spices, tomato products, and meat, in which small food particles often interfere with routine plate counts or low dilution may inhibit colony formation. Inhibitory substances can be removed from spices, resulting in higher counts. Ludox is more economical than similar products, such as Percoll. Modified Ludox is easily rendered nontoxic by the addition of common laboratory reagents. In addition, the mixture is compatible with microbiological media.
Journal of dairy science, 1993
Biosensors are defined as indicators of biological compounds that can be as simple as temperature... more Biosensors are defined as indicators of biological compounds that can be as simple as temperature-sensitive paint or as complex as DNA-RNA probes. Food microbiologists are constantly seeking rapid and reliable automated systems for the detection of biological activity. Biosensors provide sensitive, miniaturized systems that can be used to detect unwanted microbial activity or the presence of a biologically active compound, such as glucose or a pesticide. Immunodiagnostics and enzyme biosensors are two of the leading technologies that have had the greatest impact on the food industry. The use of these two systems has reduced the time for detection of pathogens such as Salmonella to 24 h and has provided detection of biological compounds such as cholesterol or chymotrypsin. The continued development of biosensor technology will soon make available "on-line quality control" of food production, which will not only reduce cost of food production but will also provide greater sa...
Applied and environmental microbiology, 1990
Two types of commercial products for feeding zoo animals (a frozen meat product, referred to as z... more Two types of commercial products for feeding zoo animals (a frozen meat product, referred to as zoo food, and a dry product, referred to as dry food) were microbiologically examined for spoilage organisms (aerobic, psychrotrophic, coliform, Escherichia coli, mold, and yeasts) and pathogens (Salmonella spp., Listeria monocytogenes, and Campylobacter jejuni). Levels of microorganisms in frozen ground zoo food were compared with those in frozen ground beef and frozen ground turkey meat. The level of microbial contaminants in frozen ground zoo meat was found to be similar to that in frozen ground beef and higher than that in frozen ground turkey meat. Sixty percent of the frozen zoo meat samples were Salmonella positive, and all of the samples were L. monocytogenes positive. Dry zoo food was documented to have microbial levels lower than those in frozen zoo meat; the pathogen levels were less than 1/25 g of food. Defrosting zoo meat at 10, 25, and 37 degrees C for 24 h showed that 10 de...
Pediococcus acidilactici PO2 Bacteriocin Production in Whey Permeate and Inhibition of Listeria monocyfogenes in Foods
Journal of Food Science, 1993
... I CHII-CHERNG LIAO, AHMED E. YOUSEF, EDWARD R. RICHTER, and GRADY W. CHISM ... caused by this... more ... I CHII-CHERNG LIAO, AHMED E. YOUSEF, EDWARD R. RICHTER, and GRADY W. CHISM ... caused by this organism, is estimated to cost much more per incident than any other common but less serious foodborne disease, because of the high fatality rate (Todd, 1989). ...
Evaluation of an X-ray microprobe technique as a possible aid to detect salmonellae
Canadian Journal of Microbiology, 1982
The X-ray microprobe was examined as a possible aid in the detection of salmonellae. Results obta... more The X-ray microprobe was examined as a possible aid in the detection of salmonellae. Results obtained indicate that specific bacterial antigen (Salmonella) increased in phosphorus and sulfur after reaction with the fluorescein isothiocyanate tagged*** specific antibody. Nonspecific antigen (Escherichia coli) did not increase in phosphorus and sulfur after reaction with fluorescein isothiocyanate tagged anti-Salmonella antibody. The technique developed supports the hypothesis that X-ray microprobe analysis may be useful in detecting salmonellae, or other bacteria, by determining increases in the elemental constitutents of bacterial cells when reacted with elemental-tagged antibodies.
Effects of electroconductive heat treatment and electrical pretreatment on thermal death kinetics of selected microorganisms
Biotechnology and Bioengineering, 1992
Suspensions of yeast cell (zygo Saccharomyces bailii) in a phosphate buffer solution were subject... more Suspensions of yeast cell (zygo Saccharomyces bailii) in a phosphate buffer solution were subjected to conventional (hot water) and ohmic (electric current) heating under identical temperature histories. Experiments were also conducted with cells of Escherichia coli to compare the lethal effect of combination of sublethal electrical preteatment and conventional heating with conventional heating. The kinetic parameters (D,Z,K and E(a)) were determined for both organisms during different treatments. There was no significant difference in the death rate of yeast cells during conventional and ohmic heating at the voltage range used in this study. Results of electrical pretreatment and conventional heating on E. coli indicated differences under certain conditions when compared with pure conventional heating. Thus it is concluded that microbial death during ohmic heating was due primarily to thermal effects with no significant effect of electric current per se. Sublethal electrical pretreatment appears to offer potential for increased bacterial inactivation in certain cases.
Biosystems Engineering, 2004
Application of pulsed electric fields (PEF) to skim milk inoculated with Staphylococcus aureus wa... more Application of pulsed electric fields (PEF) to skim milk inoculated with Staphylococcus aureus was conducted in the study. Skim milk samples were treated by PEF, using fluid handling systems of both circulation and stepwise modes. Parameters for the PEF were 3Á7 ms pulse duration time, 250 Hz pulse repetition rate, 1 ml s À1 flow rate, 460 ms total treatment time, and 3Á5 kV mm À1 electric field strength. After the PEF-treatment, the samples were plated onto both tryptic soya agar and Baird Parker agar with egg yolk tellurite enrichment to enumerate the number of inactivated and injured cells. Survivals of PEF-treated S. aureus cells were also enumerated at refrigeration temperature for 2 weeks. There was a significant decrease in S. aureus cells caused by the two fluid handling systems (probability P50Á05). The difference in the inactivation due to the PEF treatment with the fluid handling systems was not significant (P>0Á05). After the PEF treatment, there was no significant injury of the PEF-treated cells (P>0Á05). Relative to the control samples, there was a significant reduction in the number of the PEF-treated cells at 48C for 2 weeks (P50Á05).
Applied and Environmental Microbiology, 2000
Both 25-g single-size ground beef samples and 375-g composite ground beef samples were tested by ... more Both 25-g single-size ground beef samples and 375-g composite ground beef samples were tested by a method combining an immunomagnetic separation (IMS) technique with a sandwich enzyme-linked immunosorbent assay (ELISA) system (IMS-ELISA). The results demonstrated that IMS-ELISA could detect the target, Escherichia coli O157:H7, at the level of 10 ؊1 CFU/g of sample in either the 25-or 375-g sample size.
Journal of Food Safety, 1994
Thirty seven strains of lactobacilli and leuconostocs were screened for bacteriocin production. A... more Thirty seven strains of lactobacilli and leuconostocs were screened for bacteriocin production. A bacteriocin-like substance (designated lacidin A) was detected in culture filtrate of Lactobacillus acidophilus OSU133. Lacidin A inhibited Enterococcus faecalis, L. acidophilus, Lactobacillus delbrueckii subsp. lactis, and Staphylococcus aureus. The bacteriocinogenic nature of lacidin A was confirmed by eliminating the inhibitory effects of acid, hydrogen peroxide and phage and by loss of activity upon hydrolysis with proteolytic enzymes. The bacteriocin is relatively heat-stable and has considerable bactericidal action against S. aureus in phosphate buffer. Lacidin A also demonstrated bacteriostatic action against S. aureus in brain heart infusion and heat-treated milk and liquid whole egg.
Journal of Food: Microbiology, Safety & Hygiene
Rapid and specific identification of foodborne pathogens is important for not only for food produ... more Rapid and specific identification of foodborne pathogens is important for not only for food producers but also consumers as well as food safety authorities. Foods can harbor pathogen bacteria of different species, thus it is also important to be able to detect different pathogens simultaneously from the food samples even though they are in very low number. Detection of bacteria depends on different factors such as the initial number, food matrix, sensitivity of the method, competitor microflora and physical state of the bacteria whether they are injured or not. Simultaneous detection of different bacteria yet adds another hurdle for the level of detection, and thus, different approaches have developed and tested so far to optimize the maximum recovery.
Antimicrobial activity of banana puree
Food Microbiology, 1989
... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banan... more ... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banana fruits grown in Hyderabad region. Pakistan J. Sci. Ind. ... 18851890. Ketiku, 1973 AO Ketiku, Chemical composition of unripe (green) and ripe plantain (Musa paradisiaca). ...
Antimicrobial activity of banana puree
Food Microbiology, 1989
... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banan... more ... Chaudhry and Frooqi, 1970 TM Chaudhry and MAR Frooqi, Chemical composition of guava and banana fruits grown in Hyderabad region. Pakistan J. Sci. Ind. ... 18851890. Ketiku, 1973 AO Ketiku, Chemical composition of unripe (green) and ripe plantain (Musa paradisiaca). ...
Concurrent Detection of Escherichia Coli O157:H7 and Salmonella from a Single Enrichment in 24 H
Journal of Food Safety, 2001
Concurrent Detection of Escherichia Coli O157:H7 and Salmonella from a Single Enrichment in 24 H
Journal of Food Safety, 2001