bluuebunny/crossref_metadata_2025 huggingface dataset:
Fungi in Foods
Authors: KOBURGER J. A. , FARHAT B. Y.
Published: December 2016

Five media, with added antibiotics, were compared for their ability to recover yeasts and molds from 31 foods. Overall, no significant difference in recovery was found among Mycophil, Plate Count, Malt, or Potato dextrose agars but all were superior to Sugar Free agar. On the basis of recovery of organisms, availability, ease of management, and cost, Plate Count agar with antibiotics is recommended for routine enumeration of yeasts and molds in foods.
Survival of Clostridium perfringens During Preparation of Precooked Chicken Parts
Authors: CRAVEN STEPHEN E. , LILLARD H. S. , MERCURI A. J.
Published: December 2016

Vegetative cells of Clostridium perfringens were completely destroyed and the number of viable spores was reduced by procedures used to process precooked chicken thighs and breasts. A mixed inoculum of vegetative cells of C. perfringens CDC strains 7947 and 7948 was killed in thighs and breasts cooked in water at 82 C for 20 min and at 93 C for 15 min. Heat-sensitive spores of C. perfringens strain 7947 were reduced to low levels after 43 min at 82 C and completely eliminated after 38 min at 93 C. Heat-resistant spores of C. perfringens strain 7948 were not reduced when water-cooked at 82 C for 50 min nor completely destroyed after 45 min at 93 C. C. perfringens 7948 spores survived during frozen storage of inoculated thighs which were cooked at 82 C for 20 min (40–50%) and at 93 C for 45 min (23–30%). Numbers of spores were further reduced after reheating frozen pieces at 192 C for 30 min. Thighs were coated with inoculated batter and breading and flash fried at 192 C for 30, 45, or 60 sec resulting in destruction of more than 99% of vegetative cells and more than 90% of heat-resistant spores.
Evaluation of Household Dishwashing Machines for use in Small Institutions1
Authors: BRYAN FRANK L. , DeHART GARNETT H.
Published: December 2016

Performance of three kinds of household dishwashing machines was evaluated with respect to certain criteria for performance of commercial spray-type machines. These criteria concern removal of soil from tableware, achievement of a specified “cumulative heat factor,” and reduction of bacteria on tableware below a maximum permissible count. Machines of one group had a sanitizing wash or rinse in their cycles. This step ended only after temperature of the sanitizing wash or rinse water reached a minimum of 150 F. These machines met the criteria regardless of the temperature of their inlet water. The second type of machine had no sanitizing wash or rinse in its cycle. The third type had a sanitizing step, but it ended after 15 min regardless of the temperature of the water; this type also had a forced hot-air drying feature. Machines of the second and third groups met the criteria only when the temperatures of their inlet water was 155 F or higher.
Some Functional Properties of Succinylated Single Cell Protein Concentrate
Authors: McELWAIN M. D. , RICHARDSON T. , AMUNDSON C. H.
Published: December 2016

Single cell protein concentrate was prepared by extracting dried Candida utilis with 0.2 N NaOH at 95 C for 10 min. The soluble protein was precipitated at pH 3.5, washed, and lyophilized. Portions of the protein isolates were succinylated so that 84% of the free amino groups were blocked. Alkaline extractions under optimum conditions gave a yield of 25 to 30% of total solids. Nucleic acid content of the isolates was 10.4% whereas protein comprised 67.3%. Succinylated (SI) and nonsuccinylated (NSI) single cell protein concentrate exhibited similar solubilities above pH 4, the apparent isoelectric point. At pH values below 4, SI was quite insoluble whereas NSI was very soluble at pH 2. Digestibilities as measured by percentage of lysine released from the protein by pepsin and pancreatin were 32.7%, 18.6%, and 3.3% for NSI, whole egg, and SI, respectively. Stabilities of emulsions prepared from corn oil (20–50%) tended to be lower when gelatin was used at the 1% level compared to NSI and SI. However, higher levels of gelatin tended to yield more stable emulsions compared to NSI and SI. Stabilities of emulsions prepared from NSI and SI tended to be comparable with NSI being slightly better. Viscosities of emulsions increased with increasing oil content and increasing emulsifier concentration.
Understanding and Teaching the Most Probable Number Technique1
Authors: OBLINGER J. L. , KOBURGER J. A.
Published: December 2016

The most probable number (MPN) technique is extensively used in food microbiology. However, because statistics involved often are cumbersome and it is difficult to obtain some of the widely scattered literature, many individuals are not able to delve into the subject to gain a thorough understanding of the method. To overcome these inherent difficulties, this review and discussion was prepared as an introduction and aid in presenting the MPN method to students and individuals working in food microbiology.
Effects of Light on Concentrations of Some Volatile Materials in Milk
Authors: BASSETTE R.
Published: December 2016

Gas chromatographic analyses of head-space vapors of steam distillates from milk enabled me to monitor part per billion changes in concentrations of acetaldehyde, propanal, methyl sulfide, acetone, butanone, n-pentanal, and n-hexanal before and after milks were exposed to sunlight in a clear glass flask and fluorescent light in a plastic jug, n-Pentanal and n-hexanal increased about the same under either light (19.6 to 68.5 ppb and 19.1 to 83.6 ppb, respectively). Acetaldehyde increased much more under sunlight than under fluorescent light. Methyl sulfide increased slightly in concentration under 44 h of fluorescent light (6.8 to 11.6 ppb) but did not change appreciably during exposure to 1 h of sunlight. Changes in concentrations of the same compounds, except acetone and butanone, were determined in raw; laboratory pasteurized; and plant pasteurized, homogenized, Vacu-Therm-treated milk exposed to sunlight for 20 min. Except for n-pentanal, all carbonyl compounds in pasteurized, homogenized, Vacu-Therm-treated milk changed less after exposure to 20 min sunlight than did the same compounds from either raw or laboratory pasteurized milk. n-Pentanal was relatively higher in exposed-pasteurized milk than in either raw or laboratory pasteurized milk. Differences between concentrations of volatile materials in exposed raw and in laboratory pasteurized milk were slight. Exposing skimmilk to sunlight for 20 min produced more acetaldehyde than similarly treating homogenized-pasteurized milk, indicating that nonfat fractions are precursors of acetaldhyde. Increases in all other carbonyl compounds could be attributed to the fat.
A Phage Typing System for Salmonellae: Salmonella senftenberg
Authors: GERSHMAN M.
Published: December 2016

A system is described for phage typing of Salmonella senftenberg. The system was developed using a number of bacteriophages that were isolated from sewage.
The Microflora of Parsley
Authors: KĂFERSTEIN F. K.
Published: December 2016

Commercially available parsley is a heavily contaminated product. The possible public health significance of this observation is discussed. Parsley with the roots intact is also heavily contaminated. However, microorganisms indicative of fecal contamination could be found much less frequently and less numerously. For this reason it is concluded that standards for Escherichia coli and/or D-streptococci might serve as a useful public health precaution.
A Microbiological Survey of Three Fresh Green Salads-Can Guidelines be Recommended for these Foods?
Authors: FOWLER JAMES L. , FOSTER JAMES F.
Published: December 2016

One hundred samples each of mixed green salad, green salad, and coleslaw were selected from two centralized food service divisions of large military hospitals. Samples were obtained 5 days per week in accordance with production schedules, and were analyzed for total plate count, total coliforms, both plate and Most Probable Number Methods, Escherichia coli, and Staphylococcus aureus. Extremely wide ranges were found in total plate counts and total coliform counts; while confirmed E. coli and S. aureus counts were quite low. The feasibility of establishing microbiological guidelines for these products is discussed.
Evaluation of Diluents Used for Total Counts1
Authors: OBLINGER J. L. , KENNEDY J. E.
Published: December 2016

A comparison was made between Butterfield's buffered phosphate solution. 0.1% peptone in distilled water. 0.5% peptone in distilled water, 0.85% NaCl in distilled water, and pure distilled water as diluents for total bacterial counts of 28 different food samples. Plates were incubated at 35 and 22 C for 2 and 5 days, respectively. Butterfield's diluent afforded the highest overall mean count for most samples regardless of the incubation temperature. Highest counts occurred with all diluents at 22 C. Although Butterfield's diluent. 0.1% peptone, and 0.5% peptone appeared to yield higher counts for most samples than did distilled water or 0.85% NaCl, statistically the mean counts obtained for the live diluents used were not significantly different from each other. It appears that no single diluent is suited for every possible sample type.
Microbiological Evaluation of Retail Ground Beef: Centralized and Traditional Preparation1
Authors: SHOUP J. G. , OBLINGER J. L.
Published: December 2016

An evaluation of the microbiological quality of retail ground beef prepared in a centralized operation (which has nearly statewide distribution) and in four local stores was undertaken. Forty retail samples were analyzed for total aerobes (22 C and 35 C), yeasts and molds, Clostridium perfringens, Staphylococcus aureus, total coliforms, Escherichia coli, enterococci, Salmonella, and fat content. Products prepared in the centralized operation exhibited trends toward better microbiological quality than that of traditionally prepared products. Salmonella screening of the samples resulted in the identification of S. infantis in one traditionally prepared sample.
Studies of Scharer's Original Method for Alkaline Phosphatase in Milk with a Modification Utilizing an Organic Buffer
Authors: SCHIEMANN D. A. , BRODSKY M. H.
Published: December 2016

Based on studies of Scharer's original (1938) method for alkaline phosphatase in milk, a modified procedure was developed utilizing two strengths of an organic buffer, 2-amino-2-methyl propanol. This modification, designated the AMP method, has the following advantages: (a) elimination of non-enzymatic substrate hydrolysis resulting from immersion in boiling water; (b) complete reaction of liberated phenol to form indophenol by control of temperature. pH. and volume of 2,6-dibromoquinonechloroimide; and (c) provision of a clear solution for spectrophotometric measurement following protein precipitation and filtration. The method is able to detect less than 0.1% of raw milk in pasteurized milk, and has a precision with a 1-h incubation period equivalent to the Kay and Graham method requiring 24 h incubation. A standard of 1.6 phosphatase activity units is proposed for pasteurized milk on the basis of equivalence to 2.3 Lovibond color units by the Kay and Graham method.
Assurance of Microbiological Safety in a University Feeding System
Authors: SOLBERG M. , MISKIMIN D. K. , KRAMER R. , RIHA W. E. , FRANKE W. C. , BUCHANAN R. L. , O'LEARY V. , BERKOWITZ K.
Published: December 2016

The sanitation surveillance system was developed with standards and follow-up actions as a part of an assurance program for microbiological safety in a university feeding system. The surveillance is based upon an adhesive contact and transfer tape system for surface monitoring and a micropore filter system for monitoring efficiency of the associated laundry operation. Results compiled from 3 years of operation generally show continued reductions in numbers of items testing below fully satisfactory. Specific systems of microbiological data analysis for detection of some mechanical or procedural breakdowns were developed. The overall cost for the entire laboratory part of the food safety assurance program was less than 0.5 cent per meal served.
Classification by Numerical Taxonomy of Staphylococci Isolated From the Bovine Udder
Authors: WECKBACH LANA S. , LANGLOIS B. E.
Published: December 2016

Three hundred and three isolates obtained from plating bovine foremilk samples on Baird-Parker Agar were grouped using numerical taxonomy. Clustering of the isolates according to their percent similarity resulted in 19 groups; of these, eight groups contained over nine members. The other 11 groups contained 38 isolates. All 19 groups were joined at the 75% similarity level, with 17 of the groups being joined above the 85% similarity level. Results indicate that all but 16 of the isolates belonged to the same genus (Staphylococcus). and they probably belonged to one species (Staphylococcus aureus) or at least to closely related species. All but 17 isolates were catalase-positive. The greatest variations among the groups were in utilization of carbohydrates, chromogenesis, gelatinase production. and growth at 0 and 7 C and in 15% salt.
Survival of Salmonella in Cheddar Cheese
Authors: WHITE CHARLES H. , CUSTER EDWARD W.
Published: December 2016

Salmonella newport, S. new-brunswick, and S. infantis were singly added to Cheddar cheese milk to evaluate the behavior of Salmonella in Cheddar cheese made from the milk and to obtain survival times when cheese was stored at different temperatures. Of a total of 48 lots of cheese inoculated with Salmonella, detectable numbers of these pathogens appeared in 16 samples aged at 4.5 C for 9 months and from six samples stored at 10 C. The information obtained under the conditions of this study indicates that these enteropathogenic microorganisms when initially present in large numbers in milk can survive for extended storage periods in Cheddar cheese of high pH made from the milk.
Effect of Freezing, Additives, and Packaging Techniques on the Quality of Processed Blue Crab Meat1,2
Authors: WEBB N. B. , TATE J. W. , THOMAS F. B. , CARAWAN R. E. , MONROE R. J.
Published: December 2016

Experiments were conducted to study the effect of freezing technique on quality of Blue crab meat. Freshly processed crabmeat was used as a control. The treatments were evaluated by a trained sensory panel and analyses for trimethyl amine (TMA), total volatile base (TVB), and pH. The first experiment involved comparisons of crabmeat pre-treated with malic acid vs. phosphate, can vs. vacuum packaging in plastic pouches and storage at −18 and −30 C for 8 months. The results indicated that freezing and storing of crabmeat in a conventional air-circulating freezer (−18 C) significantly reduced the quality (aroma, flavor, texture, appearance) when compared to fresh crabmeat. Even when stored at −30 C, the quality was substantially lower than that of fresh crabmeat after 1½ months of storage. The two packaging methods and application of malic acid or phosphates did not prevent quality deterioration. A second experiment included a similar design except that the effect of freezing crabmeat with dichlorodifluoromethane (“Freon” Food Freezant) was compared with conventional freezing. The same packaging method was used but the additives were omitted. Freezing with “Freon” for 1½ month caused no significant difference in meat quality when compared with fresh crabmeat (stored 0 days) but quality of the frozen crabmeat decreased significantly after 1½ months. Storage at −18 C was unsatisfactory for both freezing methods. TMA, TVB, and pH analyses were not of major value in assessing the quality of the fresh or frozen crabmeat.
Bacteriological Analysis of Ground Beef1
Authors: WESTHOFF DENNIS , FELDSTEIN FAYE
Published: December 2016

A survey on the bacteriological quality of ground beef in Maryland was conducted to provide information relating to establishment of bacterial standards on fresh meats. One hundred forty samples were obtained at the retail, processor, and slaughter-processor levels. Retail samples yielded the highest bacterial numbers. The mean coliform, fecal coliform, and Escherichia coli count per gram, for all samples, was 200, 10, and 5, respectively. The mean total aerobic plate count per gram was 7.9 × 106 (28 C) and 2.0 × 106 (35 C). Forty-three percent of all the samples analyzed exceeded 50 fecal coliform per gram, while 18% exceeded a total aerobic plate count of 1.0 × 107 per gram.
Bacterial, Shelf Life, and Consumer Acceptance Characteristics of Chopped Beef1
Authors: BERRY B. W. , CHEN ADA AI-TI
Published: December 2016

Several studies were initiated to evaluate factors that exert an influence on bacterial counts, shelf life, and consumer acceptance of commercially processed chopped beef. Bacterial counts in chub packaged (oxygen impermeable film) product underwent only slight increases when evaluated every 4 days over a 20-day storage period. Retail packaging of chopped beef after both 16 and 20 days of chub storage resulted in severely limited shelf life of the retail film wrapped product in terms of bacterial counts, surface discoloration, and flavor. Differences in the anatomical location (chuck, flank, navel, and head) of beef trimmings did not exert a major influence on chopped beef shelf life. However, the use of CO2 pellets did lower psychrotrophic bacterial numbers in some samples, with subsequently less surface discoloration and improved flavor. Reductions in bacterial counts occurred during the 3-day retail storage in oxygen permeable film only for chopped beef stored in chub form for a total 18 days before the 3-day storage.
Streptococci in Dried and Frozen Foods
Authors: MUNDT J. ORVIN
Published: December 2016

Streptococci were obtained on KF and bile-esculin agars from 209 (57%) samples of a variety of dried foods and from 299 (87%) samples of frozen vegetables. They were not obtained from dried tea, coffee, flavored drinks, or fruits. Numbers per gram were greater in frozen vegetables than in dried foods. Nearly 60% of the 2334 strains isolated were identified as follows: Streptococcus faecalis (8.9%), Streptococcus faecium (21.1%), S. faecium biotype casseliflavus (18.9%), Streptococcus lactis (2.2%), Streptococcus bovis (0.04%), Aerococcus (2.7%), and Leuconostoc (4.5%). The 1173 strains of unidentified streptococci formed 32 groups when characterized for growth at 10 and 45 C, in broth containing 6.5% NaCl, and in broth adjusted to pH 9.6; and the deamination of arginine. The isolated strains were classified into seven plant streptococcal (PS) types. Unidentified streptococci obtained from foods were as variable in their charcteristics as those obtained from plants. The variety of species obtained indicated that neither KF nor bile-esculin agars were reliable in the selection of S. faecalis from foods.
Biblical Food Processing1
Authors: SHURNEY G. A. , ZOTTOLA E. A.
Published: December 2016

Processing of milk into dry milk, cheese, and butter was an important part of Biblical man's survival in the desert wasteland. Meat processing was limited, and little of it was likely consumed during the 40 years of wandering of the Israelites. The Bible does mention processing of quail which were salted and dried. Locusts were a common food item for traveling Israelites and were prepared and consumed whenever found. This was done by boiling them in salt water, then baking, drying, or smoking before consuming. Cereal grain formed an important part of the Hebrews' diet. It was threshed and ground with a hand mill and then made into bread. Another method of processing was by using the mortar and pestle to make flour for bread. Manna seems to have been processed in a manner similar to that used for cereal grains. It was the sole source of food for many years while the Israelites traveled in the desert. Vegetables were not processed and are only briefly mentioned, whereas spices are referred to throughout the Old Testament. Because of the availability of natural vegetation and the difficulties of storing processed foods, extensive processing methods were not developed. Many of the processing techniques used by Biblical man are the same as those used by present-day Bedouin Arabs.
A Critical Study of the Multiuse Polyethylene Plastic Milk Container System
Authors: BODYFELT F. W. , MORGAN M. E. , SCANLAN R. A. , BILLS D. D.
Published: December 2016

The absorption of 11 of 16 common chemical substances by multiuse polyethylene plastic milk containers was not detected by the required contaminant detection device. The inability of the detector to respond to significant levels of several potentially hazardous chemical substances suggests that this multiuse milk container system may present a public health problem. Milk stored in five of the 11 “detector-accepted” bottles contained either pesticide residues in excess of legal tolerance limits or had objectionable off-flavors. The contaminant detector will detect volatile hydrocarbons and may not respond to absorbed toxic contaminants which may gain entrance to polyethylene milk containers through misuse by the consumer.
Enzymatic Refining of Unconventional Protein for Nutritional Purposes
Authors: BEDNARSKI WLODZIMIERZ , POZNANSKI STEFAN , JEDRYCHOWSKI LUCJAN , LEMAN JACEK , SZCZEPANIAK MIECZYSLAWA
Published: December 2016

Studies were made on the possibilities of refining protein from the fodder yeast, Candida utilis, from Kluyveromyces fragilis cells and from the field bean by enzymatic means using pepsin and papain, followed by the reverse synthesis of proteins from hydrolysates as treated with alpha-chymotrypsin. The yield of refined protein was about 75%, as measured by amounts of nitrogen substances precipitated in 15% trichloroacetic acid. The refined yeast proteins contained no nucleic acids, while field bean protein was free of trypsin inhibitors. The refined proteins appeared to be neutral in respect of flavor substances.
Thermal Energy Losses and Conservation in Sauerkraut Processing Plants
Authors: RAO M. A. , KENNY J. F. , KATZ J. , DOWNING D. L.
Published: December 2016

Sources and magnitudes of thermal energy losses, as well as fuels for energy, were examined in three sauerkraut processing plants in Western New York. The fuels for thermal energy accounted for 86 to 95% of the total energy purchased by the plants. With suitable energy conservation measures, present usage of thermal energy (Btu) per case containing 24 size 303 cans can be reduced by 6 to 33% depending on characteristics of the plant.
Principles of Risk Assessment for Illness Caused by Foodborne Biological Agents
Authors:   NATIONAL ADVISORY COMMITTEE ON MICROBIOLOGICAL CRITERIA FOR FOODS, REPRESENTED BY ROBERT BUCHANAN, CHAIR FOR THE SUBCOMMITTEE ON RISK ASSESSMENT
Published: December 2016

The Risk Assessment Subcommittee of the National Advisory Committee on Microbiological Criteria in Foods has prepared a generic document on the principles of risk assessment as applied to biological agents that can cause human foodborne disease. Typical biological agents include bacteria, viruses, fungi, helminths, protozoa, algae, parasites, and the toxic products that these agents may produce. Basic principles elaborated to characterize food pathogen risks include the four broadly accepted components of risk assessment. The role of surveillance and investigational activities to link biological agents and their food sources to consumer illness is described as is the role of predictive modeling for food pathogens.
Survival of Listeria monocytogenes Strains in a Dry Sausage Model
Authors: TOLVANEN RIINA , HELLSTRÖM SANNA , ELSSER DIETER , MORGENSTERN HEIKE , BJÖRKROTH JOHANNA , KORKEALA HANNU
Published: December 2016

The survival of five inoculated Listeria monocytogenes strains (DCS 31, DCS 184, AT3E, HT4E, and HR5E) was studied in dry fermented sausages prepared using two different starter cultures (starter A and B) with or without a protective Lactobacillus plantarum DDEN 2205 strain. L. monocytogenes was detected throughout ripening in every sausage sample in which the L. plantarum DDEN 2205 strain had not been used. The use of either starter A, with a high concentration of protective culture, or starter B, with a low concentration of protective culture, resulted in L. monocytogenes–negative sausages after 17 days of ripening. Differential survival was noted among the L. monocytogenes strains during fermentation. Strains AT3E and DCS 31 survived in sausages with protective cultures more often than did the other strains, whereas HT4E and HR5E were inhibited during ripening by all starter and protective cultures used. Protective cultures such as L. plantarum may be used as part of a hurdle strategy in dry sausage processing, but variations in susceptibility of different L. monocytogenes strains can create problems if other hurdles are not included.
Survival and Growth of Acid-Adapted and Unadapted Salmonella in and on Raw Tomatoes as Affected by Variety, Stage of Ripeness, and Storage Temperature
Authors: BEUCHAT LARRY R. , MANN DAVID A.
Published: December 2016

Consumption of raw round and Roma tomatoes has been associated with outbreaks of salmonellosis. A study was done to determine whether survival and growth of Salmonella in and on tomatoes is affected by variety of tomato, stage of ripeness, and storage temperature. The influence of acid adaptation of cells and site of inoculation on survival and growth was studied. Salmonella grew in stem scar and pulp tissues of round, Roma, and grape tomatoes stored at 12 and 21°C but not in those tomatoes stored at 4°C. Survival and growth was largely unaffected by variety and stage of ripeness at the time of inoculation. The pathogen did not grow on the skin of grape tomatoes stored at 4, 12, and 21°C. Survival and growth of Salmonella inoculated into stem scar and pulp tissues of round and Roma tomatoes were unaffected by exposure of cells to an acidic (pH 4.75) environment before inoculation. Results emphasize the importance of preventing contamination of tomatoes with Salmonella at all stages of ripeness, regardless of variety or previous exposure of cells to an acidic environment.
Effects of Potassium Sorbate on Postharvest Brown Rot of Stone Fruit
Authors: GREGORI R. , BORSETTI F. , NERI F. , MARI M. , BERTOLINI P.
Published: December 2016

The effect of potassium sorbate (K-sorb), a low-toxicity chemical, to control Monilinia spp. was investigated. Preliminary in vitro studies found the MIC of K-sorb for conidial germination and mycelial growth was, respectively, 260 and 1,250 mg/liter. Immersion of naturally infected peach and nectarine fruit in a solution (15 g/liter) of K-sorb for 120 s reduced brown rot by over 80% in four of five trials. Although treated fruits showed a significant reduction in firmness with respect to the control, they did not reach the overripe stage and retained acceptable quality parameters. In an attempt to elucidate the mechanism of action for K-sorb, the inhibition of enzymatic activity by K-sorb was also tested. In a radial diffusion assay, the addition of K-sorb to agarose reduced polygalacturonase (PG) activity across the concentrations considered. The greatest reduction (54.3%, with respect to the control) was obtained at a sorbate concentration of 15 g/liter. PG kinetic activity of Monilinia laxa observed by a spectrophotometric assay peaked after 40 min in all samples tested. PG activity was significantly higher in the control than in the samples with increased K-sorb concentrations. In conclusion, based on these findings, K-sorb can be recommended as a low-toxicity antifungal compound against Monilinia spp. in peaches and nectarines with its mode of action probably depending in part on the inhibition of PG activity in M. laxa.
Comparison of Shiga-Like Toxin II Expression between Two Genetically Diverse Lineages of Escherichia coli O157:H7
Authors: DOWD SCOT E. , WILLIAMS JASON B.
Published: December 2016

The existence of two separate lineages of Escherichia coli O157:H7 has previously been reported, and research indicates that one of these lineages (lineage I) might be more pathogenic toward human hosts. We postulated that the lineage more pathogenic expresses higher levels of Shiga toxin 2 (Stx2) than do the nonpathogenic lineage II. A comprehensive set of methodologies were used to investigate the difference in Stx2 protein and mRNA expression between the two lineages. An initial Stx2-specific enzyme-linked immunosorbent assay was conducted, and lineage I overall demonstrated significantly more toxin proteins expressed (P < 0.01). Gene expression analyses all showed significantly higher stx2 gene expression in lineage I (P = 0.02). PCR mapping revealed a possible explanation for decreased amounts of stx2 transcripts in the potentially nonpathogenic lineage II isolates, suggesting that genomic changes have modified the toxin-encoding region of the phage. This study provides additional data to support the existence of two diverse lineages of E. coli O157:H7, one of which may have lower pathogenic potential in relation to human hosts. The PCR described also provides a possible screening tool for E. coli O157 populations to differentiate these lineages. This study provides useful information on the ecology of E. coli O157, with broad implications within the clinical, scientific, and livestock industries.
Antimicrobial Resistance and Association with Class 1 Integrons in Escherichia coli Isolated from Turkey Meat Products
Authors: KHAITSA M. L. , OLOYA J. , DOETKOTT D. , KEGODE R.
Published: December 2016

The objective of this study was to quantify the role of class 1 integrons in antimicrobial resistance in Escherichia coli isolated from turkey meat products purchased from retail outlets in the Midwestern United States. Of 242 E. coli isolates, 41.3% (102 of 242) tested positive for class 1 integrons. A significant association was shown between presence of class 1 integrons in E. coli isolates and the resistance to tetracycline, ampicillin, streptomycin, gentamicin, sulfisoxazole, and trimethoprim-sulfamethoxazole. Attributable risk analysis revealed that for every 100 E. coli isolates carrying class 1 integrons, resistance was demonstrated for ampicillin (22%), gentamycin (48%), streptomycin (29%), sulfisoxazole (40%), trimethoprimsulfamethoxazole (7%), and tetracycline (26%). Non–integron-related antimicrobial resistance was demonstrated for ampicillin (65%), gentamycin (16.9%), streptomycin (42.1%), sulfisoxazole (35.8%), and tetracycline (49.7%). Population-attributable fraction analysis showed that class 1 integrons accounted for the following resistances: gentamycin, 71% (50 of 71), amoxicillin–clavulanic acid, 19.6% (6 of 33), nalidixic acid, 34% (7 of 21), streptomycin, 28% (30 of 107), sulfisoxazole, 38% (40 of 106), and tetracycline, 14%, (26 of 185). In conclusion, although class 1 integrons have been implicated in resistance to antimicrobial agents, other non–integron resistance mechanisms seem to play an important part.
Antigenicity and Viability of Anisakis Larvae Infesting Hake Heated at Different Time-Temperature Conditions
Authors: VIDAČEK SANJA , de las HERAS CRISTINA , SOLAS MARIA TERESA , MENDIZÁBAL ANGEL , RODRIGUEZ-MAHILLO ANA I. , TEJADA MARGARITA
Published: December 2016

Heat treatments (40 to 94°C, 30 s to 60 min) were applied to different batches of Anisakis simplex L3 larvae isolated from hake ovaries and viscera to study the effect of heat on the viability of the larvae measured as mobility, emission of fluorescence under UV light, and changes in color after staining with specific dyes, and on A. simplex antigenic proteins. The aim was to determine the lowest time-temperature conditions needed to kill the larvae to avoid anisakiasis in consumers, and to evaluate whether high temperature modifies the antigenicity of A. simplex extracts. Heating at 60°C for 10 min (recommended by some authors) was considered unsafe, as differences in viability between batches were found, with some larvae presenting spontaneous movements in one batch. At higher temperatures (≥70°C for ≥1 min), no movement of the larvae was observed. Antigenic protein Ani s 4 and A. simplex crude antigens were detected in the larvae heated at 94 ± 1°C for 3 min. This indicates that allergic symptoms could be provoked in previously sensitized consumers, even if the larvae were killed by heat treatment.
Microbiological Sampling of Carcasses by Excision or Swabbing with Three Types of Sponge or Gauze
Authors: MARTÍNEZ BERNARDO , CELDA M. FELICIDAD , ANASTASIO BEGOÑA , GARCÍA INÉS , LÓPEZ-MENDOZA M. CARMEN
Published: December 2016

Fifty-five bovine, 50 equine, 60 ovine, and 50 porcine carcasses were sampled in a slaughterhouse in eastern Spain. Two samples were taken from each carcass, one using the excision method and the other using the swabbing method. Four different materials were used for swabbing: cellulose, polyurethane, or viscose sponges, and medical gauze. Samples were collected at the end of the process by four different people before the carcasses were taken to the cooler. The samples were examined for total viable bacteria counts (TVCs) and Enterobacteriaceae counts (ECs). The mean TVC for all species sampled by excision was 4.50 log CFU/cm2, which was significantly higher than the 3.53 log CFU/cm2 obtained by swabbing. The TVCs obtained using gauze and the cellulose and polyurethane sponges were significantly higher (P < 0.05) than the corresponding TVCs obtained using viscose sponges. Animal species, the person who collected the samples, and microbiological load also had a significant effect on TVC. ECs were obtained from 82.8% of excision samples, from larger percentages of samples obtained using cellulose or polyurethane sponges or gauze swabs, but from smaller percentages of samples obtained using viscose sponges. The Enterobacteriaceae load significantly influenced the EC. In contrast, animal species and the person who collected the samples had no significant effect. The cellulose sponge, polyurethane sponge, and gauze gave high mean log counts of aerobic bacteria and Enterobacteriaceae, which makes these swab types suitable for use in slaughterhouses for the purpose of assessing production process hygiene.
The Combination of Lactate and Diacetate Synergistically Reduces Cold Growth in Brain Heart Infusion Broth across Listeria monocytogenes Lineages
Authors: STASIEWICZ MATTHEW J. , WIEDMANN MARTIN , BERGHOLZ TERESA M.
Published: December 2016

Combinations of organic acids are often used in ready-to-eat foods to control the growth of Listeria monocytogenes during refrigerated storage. The purpose of this study was to quantitatively assess synergy between two organic acid growth inhibitors under conditions similar to those present in cold-smoked salmon, and to assess the effect of evolutionary lineage on response to those growth inhibitors. Thirteen strains of L. monocytogenes, representing lineages I and II, were grown at 7°C in broth at pH 6.1 and 4.65% water-phase NaCl, which was supplemented with 2% potassium lactate, 0.14% sodium diacetate, or the combination of both at the same levels. Our data suggest that lineages adapt similarly to these inhibitors, as the only significant growth parameter difference between lineages was a minor effect (± 0.16 day, P = 0.0499) on lag phase (λ). For all strains, lactate significantly extended λ, from 2.6 ± 0.4 to 3.8 ± 0.5 days (P < 0.001), and lowered the maximum growth rate (μmax) from 0.54 ± 0.06 to 0.49 ± 0.04 log(CFU/ml)/day (P < 0.001), compared with the control. Diacetate was ineffective alone, but in combination with lactate, synergistically increased λ to 6.6 ± 1.6 days (P < 0.001) and decreased μmax to 0.34 ± 0.05 log(CFU/ml)/day (P < 0.001). Monte Carlo simulations provided further evidence for synergy between diacetate and lactate by predicting signficantly slower growth to nominal endpoints for the combination of inhibitors. This study shows potassium lactate and sodium diacetate have significant synergistic effects on both λ and μmax of L. monocytogenes at refrigeration temperature in broth, and justifies combining these inhibitors, at effective levels, in food product formulations.
Listeria monocytogenes Contamination in Pork Can Originate from Farms
Authors: HELLSTRÖM SANNA , LAUKKANEN RIIKKA , SIEKKINEN KIRSI-MAARIT , RANTA JUKKA , MAIJALA RIITTA , KORKEALA HANNU
Published: December 2016

The presence of Listeria monocytogenes in the pork production chain was followed from farm to slaughterhouse by examining the farm and slaughterhouse levels in the same 364 pigs, and finally by analyzing the cut meats from the same pig lots. Both organic and conventional farms were included in the study. Altogether, 1,962 samples were collected, and the 424 L. monocytogenes isolates were analyzed by pulsed-field gel electrophoresis. The results from microbial analyses were combined with data from an on-farm observation and a questionnaire to clarify the associations between farm factors and prevalence of L. monocytogenes. The prevalence of L. monocytogenes was 11, 1, 1, 24, 5, 1, and 4% in feed and litter, rectal swabs, intestinal contents, tonsils, pluck sets (including lungs, heart, liver, and kidney), carcasses, and meat cuts, respectively. The prevalence was significantly higher in organic than in conventional pig production at the farm and slaughterhouse level, but not in meat cuts. Similar L. monocytogenes genotypes were recovered in different steps of the production chain in pigs originating from the same farm. Specific farm management factors, i.e., large group size, contact with pet and pest animals, manure treatment, use of coarse feed, access to outdoor area, hygiene practices, and drinking from the trough, influenced the presence of L. monocytogenes in pigs. L. monocytogenes was present in the production chain, and transmission of the pathogen was possible throughout the chain, from the farm to pork. Good farm-level practices can therefore be utilized to reduce the prevalence of this pathogen.
Protective Effect of Sucrose on the Membrane Properties of Lactobacillus casei Zhang Subjected to Freeze-Drying
Authors: LI HAIPING , LU MEIJUN , GUO HONGFANG , LI WEI , ZHANG HEPING
Published: December 2016

The purpose of this research was to investigate the influence of sucrose at 2.0, 4.0, and 8.0% as a protectant during freeze-drying on the viability and membrane properties of Lactobacillus casei Zhang. Membrane properties were determined using zeta potential, hydrophobicity, fluidity, and integrity before and after freeze-drying. Exposing L. casei Zhang to sucrose protected it from drastic changes in cell surface electrophoretic mobility and hydrophobicity in contrast with the untreated condition, and the effect was dose related. Sucrose caused an increase in membrane fluidity compared with the control sample. Moreover, 2.0% sucrose decreased the general polarization values less than 4.0 or 8.0% sucrose, while 4.0% sucrose and 8.0% sucrose had no significant difference in decreasing general polarization values (P < 0.05). L. casei Zhang freeze-dried in the presence of 2.0% sucrose retained up to 23.7% membrane integrity, whereas cells freeze-dried with 4.0 and 8.0% sucrose had 32.4 and 37.6% membrane integrity compared with that of L. casei Zhang before freeze-drying. Correspondingly, the number of survivors of L. casei Zhang, determined by the plate count method, decreased from 8.02 to 0.63 log CFU/ml after freeze-drying in the absence of sucrose. However, in the presence of 2.0, 4.0, and 8.0% sucrose, the numbers of survivors were 2.01, 2.87, and 3.20 log CFU/ml after freeze-drying, respectively. The present work suggested that sucrose was an effective membrane protectant at 2.0, 4.0, or 8.0% on the surface zeta potential, hydrophobicity, fluidity, and integrity of L. casei Zhang.
Exposure of Campylobacter jejuni to 6°C: Effects on Heat Resistance and Electron Transport Activity
Authors: HUGHES REBECCA-AYME , COGAN TRISTAN , HUMPHREY TOM
Published: December 2016

Human infection with Campylobacter jejuni is frequently associated with the consumption of foods, especially chicken meat, which have been exposed to a range of temperatures during processing, storage, and cooking. Despite the public health importance of C. jejuni, little is known about the effects of cold exposure (refrigeration) on the subsequent ability of this pathogen to survive heat challenge. This work examined the effect of rapid exposure to 6°C for 24 h on the heat resistance at 52°Cof19 C. jejuni strains originally isolated from various sources. The resulting death curves were analyzed with the Weibull model. Unlike cold-exposed cells of Escherichia coli and Salmonella, which have been reported to show significant increased sensitivity to heat, such exposure had only a marginal effect on heat resistance of the C. jejuni strains in this study. A possible explanation for this effect is that rapid chilling renders C. jejuni cells unable to adapt to reduced temperatures in an active manner. This hypothesis is supported by the observation that exposure to 6°C for 24 h resulted in a significant and marked reduction in electron transport system activity when compared with controls at 37°C.
Frequency of Toxoplasma gondii in Pork Meat in Ocotlán, Jalisco, Mexico
Authors: GALVÁN-RAMIREZ M. L. , MADRIZ ELISONDO A. L. , RICO TORRES C. P. , LUNA-PASTÉN H. , RODRÍGUEZ PÉREZ L. R. , RINCÓN-SÁNCHEZ A. R. , FRANCO R. , SALAZAR-MONTES A. , CORREA D.
Published: December 2016

Toxoplasmosis is an infection caused by Toxoplasma gondii, an intracellular obligate parasite. Its transmission has usually been attributed to ingestion of undercooked or raw meat. The frequency of T. gondii in pork, the most common meat for human consumption in Jalisco, Mexico, is unknown; in Guadalajara city high prevalence of human toxoplasmosis has been documented. Forty-eight samples of pork meat from butcher shops in Ocotlán city were analyzed. Through bioassay, 50 g of tissue was homogenized in an acidic pepsin solution and inoculated subcutaneously to previously immunosuppressed mice. Blood samples from the mice tail vein were obtained before inoculation and 7, 14, 28, and 45 days postinoculation to analyze anti-Toxoplasma immunoglobulin (Ig) M and IgG antibody kinetics by indirect enzyme-linked immunosorbent assay. For histopathology, small fragments of the brain, lungs, heart, and skeletal muscle were extracted on day 45 and were stained with hematoxylin and eosin. Also, DNA was extracted from the pork meat for PCR amplification of the B1 gene. Even though all pork samples were negative by histopathology and PCR, IgG and IgM antibodies against T. gondii were detected in 1 of the 48 inoculated mice, reflecting a frequency of 2.1% positive pork meat, which is lower than expected but similar to that found in other regions.
Assessment of Food as a Source of Exposure to Mycobacterium avium subspecies paratuberculosis (MAP)†,‡
Authors:   ADOPTED 28 SEPTEMBER 2007, WASHINGTON, DC, References Updated 20 March 2009, Washington, DC, NATIONAL ADVISORY COMMITTEE ON MICROBIOLOGICAL CRITERIA FOR FOODS
Published: December 2016

The National Advisory Committee on Microbiological Criteria for Foods assessed the importance of food as a source of exposure to Mycobacterium avium subspecies paratuberculosis (MAP). MAP is the causative agent of Johne's disease, which affects primarily the small intestine of all ruminants. The significance of MAP as a human pathogen is unknown and is being investigated by several research groups. This document also reviews the efficacy of current detection methods, processing interventions, and MAP inactivation. Research needs related to MAP are provided. The Committee reached the following conclusions: current methods for detection of MAP have significant limitations, and a standard method for the detection of viable MAP cells is needed. Aside from MAP-infected domestic ruminant animals, the organism is found infrequently. If MAP in cattle is controlled, the source of MAP in other animals, food, and water may largely be eliminated. Milk, particularly raw milk, may be a likely food source for human exposure to MAP. Given the prevalence of MAP in U.S. cattle herds, ground beef may be a potential source of MAP. Although humans may be exposed to MAP through a variety of routes, including food and the environment, the frequency and amount of exposure will require additional research.
Role of surface hydrology in determining the seasonal cycle of Indian summer monsoon in a general circulation model
Authors: Agrawal Shubhi , Chakraborty Arindam
Published: December 2016

Abstract. Rainfall during summer monsoon season (June–September; JJAS), that accounts for about 80 % of the yearly total over Indian region, is herald by its onset over Kerala in June. And these four summer monsoon months contribute 19 %, 32 %, 29 % and 20 % of the seasonal rainfall, respectively. Therefore, it is important that this seasonal cycle is captured by general circulation models (GCMs) used to understand and predict monsoon. In this study, using decade-long simulations of an atmospheric GCM, we show that surface hydrology over India as well as over its surrounding regions plays a central role during the onset phase of monsoon and thus modulates seasonal cycle. The model, in its default configuration, simulates early onset and excess precipitation (about double of that observed) over the Gangetic plain (GP) in June. Moreover, the model has large positive surface soil moisture bias over India throughout the year and negative bias over the arid-semiarid regions to the north-west of India during the pre-monsoon months. From multiple sensitivity experiments, it is discerned that the remote dry soil moisture bias in the model over the Western Central Asia region intensifies the tropospheric low-level circulation causing excessive moisture advection, followed by moisture convergence over the GP in the beginning of June, and an early onset. Local soil moisture over GP makes a diminutive contribution to precipitation bias in June. But as the season progresses and the remote influence weakens, the increased local soil moisture regulates surface and near-surface conditions which subsequently reduces moisture convergence over GP, reducing precipitation in the later phase of monsoon. The results presented here can be useful for diagnosis and improvement of land surface models.
Uncertainty budget in snow thickness and snow water equivalent estimation using GPR and TDR techniques
Authors: Di Paolo Federico , Cosciotti Barbara , Lauro Sebastian E. , Mattei Elisabetta , Callegari Mattia , Carturan Luca , Seppi Roberto , Zucca Francesco , Pettinelli Elena
Published: December 2016

Abstract. Snow water equivalent is a fundamental parameter for hydrological and climate change studies but its measurement is usually time consuming and destructive. Electromagnetic methods could be a valid alternative to conventional techniques, being fast and non-invasive. In this work we analyze the reliability of a combined GPR/TDR method to estimate snow thickness and snow water equivalent. To estimate GPR accuracy we perform a calibration test where measured and predicted radar data are compared in terms of two-way travel time. Furthermore we implement a complete analysis of the uncertainty budget in order to evaluate the "weight" of each uncertainty on the snow parameters computation chain. We found that GPR, supported by TDR data, is quite reliable as it measures snow thickness and snow water equivalent with an accuracy comparable to that of a traditional method but, in general, with a slightly larger uncertainty.
Book Review: Universities and Regional Development: A Critical Assessment of Tensions and Contradictions
Authors: Kettunen Juha
Published: December 2016

Edited by Rómulo Pinheiro, Paul Benneworth and Glen A. JonesLondon and New York: Routledge, 2014. 265 pp.