Factors affecting quality and safety of fresh-cut produce.

The quality of fresh-cut fruit and vegetable products includes a combination of attributes, such as appearance, texture, and flavor, as well as nutritional and safety aspects that determine their value to the consumer. Nutritionally, fruit and vegetables represent a good source of vitamins, minerals, and dietary fiber, and fresh-cut produce satisfies consumer demand for freshly prepared, convenient, healthy food. However, fresh-cut produce deteriorates faster than corresponding intact produce, as a result of damage caused by minimal processing, which accelerates many physiological changes that lead to a reduction in produce quality and shelf-life. The symptoms of produce deterioration include discoloration, increased oxidative browning at cut surfaces, flaccidity as a result of loss of water, and decreased nutritional value. Damaged plant tissues also represent a better substrate for growth of microorganisms, including spoilage microorganisms and foodborne pathogens. The risk of pathogen contamination and growth is one of the main safety concerns associated with fresh-cut produce, as highlighted by the increasing number of produce-linked foodborne outbreaks in recent years. The pathogens of major concern in fresh-cut produce are Listeria monocytogenes, pathogenic Escherichia coli mainly O157:H7, and Salmonella spp. This article describes the quality of fresh-cut produce, factors affecting quality, and various techniques for evaluating quality. In addition, the microbiological safety of fresh-cut produce and factors affecting pathogen survival and growth on fresh-cut produce are discussed in detail.

The REFLECT statement: methods and processes of creating reporting guidelines for randomized controlled trials for livestock and food safety.

The conduct of randomized controlled trials in livestock with production, health, and food-safety outcomes presents unique challenges that may not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A two-day consensus meeting was held on November 18-19, 2008 in Chicago, Ill, United States of America, to achieve the objective. Prior to the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock production specialists, journal editors, assistant editors, and associate editors. Prior to the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items may need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines for Randomized Control Trials) statement for livestock and food safety (LFS) and 22-item checklist. Fourteen items were modified from the CONSORT checklist, and an additional sub-item was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health, and food-safety outcomes.

Fate of Listeria monocytogenes during freezing, thawing and home storage of frankfurters.

Little information is available regarding the fate of Listeria monocytogenes during freezing, thawing and home storage of frankfurters even though recent surveys show that consumers regularly store unopened packages in home freezers. This study examined the effects of antimicrobials, refrigerated storage, freezing, thawing method, and post-thawing storage (7 degrees C) on L. monocytogenes on frankfurters. Inoculated (2.1 log CFU/cm(2)) frankfurters formulated without (control) or with antimicrobials (1.5% potassium lactate plus 0.1% sodium diacetate) were vacuum-packaged, stored at 4 degrees C for 6 or 30 d and then frozen (-15 degrees C) for 10, 30, or 50 d. Packages were thawed under refrigeration (7 degrees C, 24 h), on a countertop (23 +/- 2 degrees C, 8 h), or in a microwave oven (2450 MHz, 1100 watts, 220 s followed by 120 s holding), and then stored aerobically (7 degrees C) for 14 d. Bacterial populations were enumerated on PALCAM agar and tryptic soy agar plus 0.6% yeast extract. Antimicrobials completely inhibited (p < 0.05) growth of L. monocytogenes at 4 degrees C for 30 d under vacuum-packaged conditions, and during post-thawing aerobic storage at 7 degrees C for 14 d. Different intervals between inoculation and freezing (6 or 30 d) resulted in different pathogen levels on control frankfurters (2.1 or 3.9 log CFU/cm(2), respectively), while freezing reduced counts by <1.0 log CFU/cm(2). Thawing treatments had little effect on L. monocytogenes populations (<0.5 log CFU/cm(2)), and post-thawing fate of L. monocytogenes was not influenced by freezing or by thawing method. Pathogen counts on control samples increased by 1.5 log CFU/cm(2) at d-7 of aerobic storage, and reached 5.6 log CFU/cm(2) at d-14. As indicated by these results, consumers should freeze frankfurters immediately after purchase, and discard frankfurters formulated without antimicrobials within 3 d of thawing and/or opening.

An evaluation of central nervous system cross-contamination due to carcass splitting in commercial beef-packing plants.

Four experiments were conducted in commercial beef-packing facilities The objectives of these experiments were to: (i) determine and validate a carcass sampling technique and location to determine if central nervous system (CNS) cross-contamination exists/occurs; (ii) determine if residual CNS tissue contamination remains on splitting saws after sanitation procedures; (iii) determine the prevalence of CNS cross-contamination in commercial slaughter facilities; (iv) determine whether washing treatments reduce or eliminate CNS tissue presence in carcass-splitting saws; (v) determine the effectiveness of commercial spray-washing systems in removing CNS tissue from beef carcasses; and (vi) compare residual CNS tissue levels on the blade and in the housings of the Jarvis Buster IX and Buster IV carcass-splitting saws. CNS tissue remained, albeit at very low levels, in the housings and on the blades of carcass-splitting saws after carcass splitting and operational sanitation. Additionally, after splitting carcasses, CNS tissue remaining in the splitting saw housings and on saw blades was found to cross-contaminate subsequent carcasses during splitting. Most splitting saw operational sanitation procedures reduced the amount of CNS tissue remaining in the splitting saw housings and on splitting saw blades, but no treatment eliminated CNS tissue from either to levels below the detection limit of the assay (6 ng/100 cm2). Washing in carcass spray-washing cabinets at three of the five commercial beef-packing facilities reduced, but did not eliminate, presence of CNS tissue in the aitch bone area of carcasses. Carcass spray washing in cabinets at three of the five facilities reduced (P < 0.05) the concentration of CNS tissue in the fourth thoracic vertebra area. While extremely low concentrations of CNS tissue remained in the splitting saw housings, on the splitting saw blades, and on carcasses, it is unknown whether these levels would pose a human food safety risk because the exact amount of bovine spongiform encephalopathy-infected spinal cord capable of transmitting the disease to humans is dependent on the infectivity titer, which is not readily known.

Post-slaughter traceability.

Traceability programs can cover the whole of life, or parts of it, for individual animals or groups/lots of animals. Of 13 country or community traceability programs for cattle/beef, 11 are mandatory (4 encompass, or are scheduled to encompass, birth to retail; 7 cover birth to slaughter) while 2 are voluntary and encompass birth to slaughter. Of 10 country or community traceability programs for swine/pork, 2 are mandatory (1 covers birth to retail; 1 covers birth to slaughter) while 8 are voluntary. Of 6 country or community traceability programs for sheep/sheep-meat, 3 are mandatory (1 encompasses birth to retail; 2 encompass birth to slaughter) while 3 are voluntary. Mandatory birth to retail programs that include "post-slaughter individual animal identification (IAID) traceability" have been implemented for cattle/beef, swine/pork and sheep/sheep-meat by the European Union and for cattle/beef by Japan. Many of the voluntary as well as mandatory, birth to slaughter traceability programs for all three species are presumed (though that is not specified) to include "post-slaughter group/lot identification (GLID) traceability" - e.g., those qualifying products for shipment to the European Union. "Post-slaughter IAID traceability" can be accomplished in very-small, small, medium, large and very-large packing plants using single-carcass processing units, tagging and separation/segregation, and/or deoxyribonucleic acid (DNA) fingerprinting technology but all of these approaches are time-consuming and costly; and, to-date, in most countries, there has been no reason compelling enough to cause industry to adopt such protocols or technology.

Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7.

The objective of this study was to model with logistic regression the growth/no growth interface of different initial inoculation levels (10(1), 10(3) and 10(5) CFU/ml; study 1), or nonadapted vs acid-adapted (study 2) Escherichia coli O157:H7 as influenced by pH, NaCl concentration and incubation temperature. Study 1 was conducted with a mixture of four E. coli O157:H7 strains grown (35 degrees C, 24 h) in tryptic soy broth (TSB). Study 2 was conducted with the same mixture of four E. coli O157:H7 strains grown (35 degrees C, 24 h) in glucose-free TSB with 1% added glucose (final pH 4.83), or in diluted lactic acid meat decontamination runoff fluids (washings; final pH 4.92), or nonadapted cultures prepared in glucose-free TSB (final pH 6.45), or in water washings (final pH 6.87). Parameters included incubation temperature (10-35 degrees C), pH (3.52-7.32), and NaCl concentration (0-10% w/v). Growth responses were evaluated for 60 days turbidimetrically (610 nm) every 5 days in 160 (study 1) and 360 (study 2) combinations in quadruplicate samples, with a microplate reader. The lower the initial inoculum the higher were the minimum pH and a(w) values permitting growth. Differences in the pH and a(w) growth limits among inoculum concentrations increased at 15 and 10 degrees C. Acid-adapted cultures were able to grow at lower pH than nonadapted cultures, while at temperatures below 25 degrees C, growth initiation of nonadapted cultures stopped at higher a(w) compared to acid-adapted cultures for the whole pH range of 3.52 to 7.32. A comparison with available data indicated that our model for acid-adapted E. coli O157:H7 in different environments may provide representative growth probabilities covering both nonadapted and stress-adapted contaminants.

Decontamination of beef subprimal cuts intended for blade tenderization or moisture enhancement.

The prevalence of Escherichia coli O157:H7 on beef subprimal cuts intended for mechanical tenderization was evaluated. This evaluation was followed by the assessment of five antimicrobial interventions at minimizing the risk of transferring E. coli O157:H7 to the interior of inoculated subprimal cuts during blade tenderization (BT) or moisture enhancement (ME). Prevalence of E. coli O157:H7 on 1,014 uninoculated beef subprimals collected from six packing facilities was 0.2%. Outside round pieces inoculated with E. coli O157:H7 at 10(4) CFU/100 cm2 were treated with (i) no intervention, (ii) surface trimming, (iii) hot water (82 degrees C), (iv) warm 2.5% lactic acid (55 degrees C), (v) warm 5.0% lactic acid (55 degrees C), or (vi) 2% activated lactoferrin followed by warm 5.0% lactic acid (55 degrees C) and then submitted to BT or ME. Prevalence (n=196) of internalized (BT and ME) E. coli O157:H7 was 99%. Enumeration of E. coli 0157:H7 (n=192) revealed mean surface reductions of 0.93 to 1.10 log CFU/100 cm2 for all antimicrobial interventions. E. coli O157:H7 was detected on 3 of the 76 internal BT samples and 73 of the 76 internal ME samples. Internal ME samples with no intervention had significantly higher mean E. coli O157:H7 populations than did those internal samples treated with an intervention, but there were no significant differences in E. coli O157:H7 populations among internal BT samples. Results of this study demonstrate that the incidence of E. coli O157:H7 on the surface of beef subprimal cuts is low and that interventions applied before mechanical tenderization can effectively reduce the transfer of low concentrations of E. coli O157:H7 to the interior of beef subprimal cuts.

Determining the prevalence of Escherichia coli O157 in cattle and beef from the feedlot to the cooler.

Prevalence of Escherichia coli O157 on cattle entering the slaughter floor may range from 10 to > 70%. This study was conducted to determine the effect of E. coli O157 prevalence in fecal pats collected from feedlot pen floors on subsequent E. coli O157 prevalence on carcasses at various points in the slaughter process. Fecal pats from the feedlot pen floor were collected within 3 days before slaughter. During cattle processing at the slaughter facility, additional samples were collected from the hide, from the colon, and from the carcasses before and after evisceration and after final decontamination. Of 15 lots (a group of cattle from the same pen from a feedlot) sampled, 87% had at least one positive fecal pat from the feedlot floor, 47% had a positive hide sample, 73% had a positive colon/fecal sample, and 47% had a positive carcass sample preevisceration; however, only 8% of lots had a positive carcass sample postevisceration or after final intervention. Of the total samples tested (n = 1,328), 24.7, 14.7, 27.6, 10.1, 1.4, and 0.3% of fecal pats from the feedlot floor, hide, colon, preevisceration, postevisceration, and final intervention samples, respectively, were positive for E. coli O157. Pens with greater than 20% positive fecal pats from the feedlot floor had 25.5% hide, 51.4% colon, and 14.3, 2.9, and 0.7% carcass samples positive at preevisceration, at postevisceration, and after final intervention, respectively. However, fecal pats from feedlot floor samples that contained less than 20% positive fecal samples showed lower pathogen prevalence, with 5.0% hide, 7.5% colon, and 6.3, 0, and 0% carcass positive samples at preevisceration, postevisceration, and post-final intervention, respectively. Data from this study can be used as part of risk assessment processes in order to identify mitigation strategies to minimize prevalence of E. coli O157 on fresh beef carcasses.

Molecular characterization of Escherichia coli O157:H7 hide contamination routes: feedlot to harvest.

This study was conducted to identify the origin of Escherichia coli O157:H7 contamination on steer hides at the time of harvest. Samples were collected from the feedlot, transport trailers, and packing plant holding pens and from the colons and hides of feedlot steers. A total of 50 hide samples were positive for E. coli O157:H7 in two geographical locations: the Midwest (25 positive hides) and Southwest (25 positive hides). Hide samples were screened, and the presence of E. coli O157: H7 was confirmed. E. coli O157:H7 isolates were fingerprinted by pulsed-field gel electrophoresis and subjected to multiplex PCR procedures for amplification of E. coli O157:H7 genes stx1, stx2, eaeA, fliC, rfbEO157, and hlyA. Feedlot water trough, pen floor, feed bunk, loading chute, truck trailer side wall and floor, packing plant holding pen floor and side rail, and packing plant cattle drinking water samples were positive for E. coli O157:H7. Pulsed-field gel electrophoresis banding patterns were analyzed after classifying isolates according to the marker genes present and according to packing plant. In this study, hide samples positive for E. coli O157:H7 were traced to other E. coli O157:H7-positive hide, colon, feedlot pen floor fecal, packing plant holding pen drinking water, and transport trailer side wall samples. Links were found between packing plant side rails, feedlot loading chutes, and feedlot pens and between truck trailer, different feedlots, and colons of multiple cattle. This study is the first in which genotypic matches have been made between E. coli O157:H7 isolates obtained from transport trailer side walls and those from cattle hide samples within the packing plant.

An evaluation of the effectiveness of FreshCase technology to extend the storage life of whole muscle beef and ground beef.

The objective of this study was to identify the maximum time of refrigerated storage before aerobic psychrotrophic bacteria (APB) grew to a level indicative of spoilage (7 log cfu/g) or other indicators of spoilage were observed for whole muscle beef and ground beef packaged using FreshCase technology. Storage life for beef steaks stored in FreshCase packages at 4°C was 36 d, with ground beef stored in FreshCase packages at 4°C lasting 10 d. Additionally, greater ( < 0.05) a* (redness) values were detected in FreshCase packaged samples of both beef steaks and ground beef over storage time. At the point of spoilage, off-odors were detected at very low levels in all samples along with low thiobarbituric acid values (< 2 mg malonaldehyde/kg). Therefore, use of FreshCase technology in whole muscle beef and ground beef is a viable option to extend storage life.

An evaluation of the effectiveness of FreshCase technology to extend the storage life of whole-muscle pork and ground pork sausage.

The objective of this study was to identify the maximum time of refrigerated storage before aerobic psychrotrophic bacteria grew to a level indicative of spoilage (7 log cfu/g) or other indicators of spoilage were observed for whole-muscle pork and ground pork sausage packaged using FreshCase technology. Pork chops and pork sausage were packaged using conventional vacuum packaging without nitrite in film (Control) or using FreshCase technology and were compared with respect to microbial counts, pH, instrumental color measurements, lipid oxidation level, and sensory properties. The storage life was 45 d for pork chops stored in FreshCase packages at 1°C and 19 d for ground pork sausage stored under the same condition. Results indicated that both pork chops and sausage stored in FreshCase packages retained redder color ( < 0.05) than those stored in Control packages. No differences ( > 0.05) existed between Control and FreshCase packaged samples for any off-odor detection for either pork chops or sausage. Moreover, levels of oxidative rancidity in all packages had low thiobarbituric acid reactive substances values. The results indicated that FreshCase technology can be used to extend storage life of pork products without having adverse effects on pork quality.

Reduction of Listeria monocytogenes populations during exposure to a simulated gastric fluid following storage of inoculated frankfurters formulated and treated with preservatives.

The effect of a simulated gastric fluid (adjusted to pH 1.0 with HCl) on Listeria monocytogenes, inoculated postprocessing on pork frankfurters formulated with sodium lactate (SL) and sodium diacetate (SD) and not dipped or dipped in solutions of lactic acid or acetic acid, was evaluated during storage of the frankfurters at 10 degrees C for 40 days. Pork frankfurters containing 1.8% SL, 0.25% SD, 1.8% SL+0.125% SD, or 1.8% SL+0.25% SD were inoculated with 10(2)-10(3) CFU/cm2 of a 10-strain preparation of L. monocytogenes and were not dipped or dipped for 2 min in solutions of 2.5% lactic or acetic acid before they were vacuum-packaged and stored. Survival of L. monocytogenes was determined after exposure of frankfurters for 0, 20, 40, and 60 min to the simulated gastric fluid after storage for 0, 10, 20, 30, or 40 days. Growth of L. monocytogenes on frankfurters formulated with antimicrobials was inhibited in the order control

Traceability from a US perspective.

Traceability of a food consists of development of "an information trail that follows the food product's physical trail". Internationally, the US is lagging behind many countries in developing traceability systems for food in general and especially for livestock, poultry and their products. The US food industry is developing, implementing and maintaining traceability systems designed to improve food supply management, facilitate traceback for food safety and quality, and differentiate and market foods with subtle or undetectable quality attributes. Traceability, for livestock, poultry and meat, in its broadest context, can, could, or will eventually be used: (1) to ascertain origin and ownership, and to deter theft and misrepresentation, of animals and meat; (2) for surveillance, control and eradication of foreign animal diseases; (3) for biosecurity protection of the national livestock population; (4) for compliance with requirements of international customers; (5) for compliance with country-of-origin labeling requirements; (6) for improvement of supply-side management, distribution/delivery systems and inventory controls; (7) to facilitate value-based marketing; (8) to facilitate value-added marketing; (9) to isolate the source and extent of quality-control and food-safety problems; and (10) to minimize product recalls and make crisis management protocols more effective. Domestically and internationally, it has now become essential that producers, packers, processors, wholesalers, exporters and retailers assure that livestock, poultry and meat are identified, that record-keeping assures traceability through all or parts of the complete life-cycle, and that, in some cases, the source, the production-practices and/or the process of generating final products, can be verified. At issue, as the US develops traceback capabilities, will be the breadth, depth and precision of its specific traceability systems.

Current microbiological considerations in food preservation.

Changes in the composition and properties of certain foods, as well as development of food products to meet consumer demands relating to health, nutrition and convenience lead to concerns about the microbiological safety of such products. Concerns also arise from emergence or recognition of the importance of certain microbial food pathogens or spoilage organisms, as well as from modifications in food processing, handling, storage and preparation procedures. These facts necessitate continuous reevaluation of factors involved in the control of microbial growth in order to preserve foods and maintain their quality and safety.

Nonacid meat decontamination technologies: model studies and commercial applications.

Increased consumer awareness and concern about microbial foodborne diseases has resulted in intensified efforts to reduce contamination of raw meat, as evidenced by new meat and poultry inspection regulations being implemented in the United States. In addition to requiring operation of meat and poultry slaughtering and processing plants under the principles of the hazard analysis critical control point (HACCP) system, the new regulations have established microbiological testing criteria for Escherichia coli and Salmonella, as a means of evaluating plant performance. These developments have renewed and intensified interest in the development and commercial application of meat and poultry decontamination procedures. Technologies developed and evaluated for decontamination include live animal cleaning/washing, chemical dehairing, carcass knife-trimming to remove physical contaminants, steam/hot water-vacuuming for spot-cleaning/decontamination of carcasses, spray washing/rinsing of carcasses with water of low or high pressures and temperatures or chemical solutions, and exposure of carcass sides to pressurized steam. Under appropriate conditions, the technologies applied to carcasses may reduce mean microbiological counts by approximately one-three log colony forming units (cfu)/cm2, and some of them have been approved and are employed in commercial applications (i.e., steam-vacuuming; carcass spray-washing with water, chlorine, organic acid or trisodium phosphate solutions; hot water deluging/spraying/rinsing, and pressurized steam). The contribution of these decontamination technologies to the enhancement of food safety will be determined over the long term, as surveillance data on microbial foodborne illness are collected. This review examines carcass decontamination technologies, other than organic acids, with emphasis placed on recent advances and commercial applications.

Bacterial spore injury during extrusion cooking of corn/soybean mixtures.

This study examined the potential for injury of Bacillus globigii (Bacillus subtilis var. niger, strain ATCC9372) spores during extrusion cooking of a corn/soybean (70/30%, w/v) mixture. The barrel temperature in zone 1 was kept constant at 80 degrees C while it was varied from 100 to 120 and 140 degrees C in zone 2. Recovery and enumeration of spores surviving the extrusion cooking process were conducted with five culture media ranging from minimal to rich in nutrient composition. Numbers of spores counted with a minimal culture medium after extrusion at the low temperature were lower compared to recovery with more complete media. All culture media, including minimal and richer, were equally effective in recovering untreated spores. At the higher extrusion temperatures all media were equally effective in recovering the small numbers of viable spores. The results indicated that the spores of the organism may be injured at lower extrusion temperatures.

Fate of Listeria monocytogenes in raw and cooked ground beef with meat processing additives.

The effect of sodium lactate (1.8% w/w), sodium erythorbate (0.1% w/w), kappa-carrageenan (1% w/w), and the alginate meat binder (0.4% w/w, sodium alginate; 0.6% w/w lactic acid; and 0.075% w/w calcium carbonate) on Listeria monocytogenes survival and growth was determined in raw and cooked ground beef stored aerobically at 4 degrees C. There was no significant (P > 0.05) increase in numbers of L. monocytogenes during storage of raw ground beef. However, L. monocytogenes numbers were generally lower in treatments with sodium lactate, and higher in sodium erythorbate compared to controls and meat with other additives. Increases in total aerobic plate counts were less pronounced in raw meat formulated with sodium lactate and alginate meat binder than with other additives. Cooking meat with initial inoculum levels of 6.52 to 7.03 L. monocytogenes log CFU/g to 65 degrees C resulted in lower destruction (0.56 and 1.18 log CFU/g) in samples with added alginate meat binder and kappa-carrageenan, respectively, compared to the control. Survivors (2.11-3.73 log CFU/g) decreased initially and then increased slightly, but not significantly (P > 0.05), during storage (4 degrees C, 6 days) of the cooked products.

Bacterial growth in ground beef patties made with meat from animals fed diets without or with supplemental vitamin E.

A study was designed to determine populations of aerobic bacteria, coliforms, sorbitol-negative bacteria, and Listeria monocytogenes during display at 4 and 12 degrees C of ground beef patties made with meat from animals fed diets supplemented daily (for 100 days) with 0, 1,000, or 2,000 IU of vitamin E. The patties (113.5 g) were either left uninoculated or were inoculated with Escherichia coli O157:H7 or L. monocytogenes and were tray-overwrapped and stored (at 4 or 12 degrees C for 8 to 10 or 4 to 6 days, respectively) while being continuously exposed to fluorescent light in a display setting. Patties were visually evaluated for overall appearance (based on color and/or discoloration) twice a day and analyzed for microbiological counts at 2-day intervals during display at 4 degrees C and at 0, 1, 2, 3, 4, and 6 days during display at 12 degrees C. Use of beef from animals fed supplemental vitamin E ("high-vitamin E beef") resulted in ground beef patties which, when stored at 4 degrees C, maintained visually acceptable color longer than did patties made from control beef (from animals not fed supplemental vitamin E), but effects on microbial growth were less pronounced. In general, use of high-vitamin E beef versus control beef in patty manufacture had no major effect on populations of aerobic bacteria, coliforms, sorbitol-negative bacteria, or L. monocytogenes in ground beef patties displayed at 4 or 12 degrees C. Listeria monocytogenes multiplied at 12 degrees C, but growth was similar among ground beef patties made from high-vitamin E beef versus control beef. Overall, changes in bacterial populations were similar in ground beef patties derived from meat from animals with or without added vitamin E in their diets, but control ground beef became visually unacceptable sooner.

Ascorbic acid enhances destruction of Escherichia coli O157:H7 during home-type drying of apple slices.

Destruction of Escherichia coli O157:H7 was evaluated on inoculated apple slices dehydrated at two temperatures with and without application of predrying treatments. Half-ring slices (0.6 cm thick) of peeled and cored Gala apples were inoculated by immersion for 30 min in a four-strain composite inoculum of E. coli O157:H7. The inoculated slices (8.7 to 9.4 log CFU/g) either received no predrying treatment (control), were soaked for 15 min in a 3.4% ascorbic acid solution, or were steam blanched for 3 min at 88 degrees C immediately prior to drying at 57.2 or 62.8 degrees C for up to 6 h. Samples were plated on tryptic soy (TSA) and sorbitol MacConkey (SMAC) agar media for direct enumeration of surviving bacterial populations. Steam blanching changed initial inoculation levels by +0.3 to -0.7 log CFU/g, while immersion in the ascorbic acid solution reduced the inoculation levels by 1.4 to 1.6 log CFU/g. Dehydration of control samples for 6 h reduced mean bacterial populations by 2.9 log CFU/g (TSA or SMAC) at 57.2 degrees C and by 3.3 (SMAC) and 3.5 (TSA) log CFU/g at 62.8 degrees C. Mean decreases from initial inoculum levels for steam-blanched slices after 6 h of drying were 2.1 (SMAC) and 2.0 (TSA) log CFU/g at 57.2 degrees C, and 3.6 (TSA or SMAC) log CFU/g at 62.8 degrees C. In contrast, initial bacterial populations on ascorbic acid-pretreated apple slices declined by 5.0 (SMAC) and 5.1 (TSA) log CFU/g after 3 h of dehydration at 57.2 degrees C, and by 7.3 (SMAC) and 6.9 (TSA) log CFU/g after 3 h at 62.8 degrees C. Reductions on slices treated with ascorbic acid were in the range of 8.0 to 8.3 log CFU/g after 6 h of drying, irrespective of drying temperature or agar medium used. The results of immersing apple slices in a 3.4% ascorbic acid solution for 15 min prior to drying indicate that a predrying treatment enhances the destruction of E. coli O157:H7 on home-dried apple products.

Fate of Escherichia coli O157:H7, Salmonella typhimurium DT 104, and Listeria monocytogenes in fresh meat decontamination fluids at 4 and 10 degrees C.

Bacterial pathogens may colonize meat plants and increase food safety risks following survival, stress hardening, or proliferation in meat decontamination fluids (washings). The objective of this study was to evaluate the ability of Escherichia coli O157:H7, Salmonella Typhimurium DT 104, and Listeria monocytogenes to survive or grow in spray-washing fluids from fresh beef top rounds sprayed with water (10 or 85 degrees C) or acid solutions (2% lactic or acetic acid, 55 degrees C) during storage of the washings at 4 or 10 degrees C in air to simulate plant conditions. Inoculated Salmonella Typhimurium DT 104 (5.4 +/- 0.1 log CFU/ml) died off in lactate (pH 2.4 +/- 0.1) and acetate (pH 3.1 +/- 0.2) washings by 2 days at either storage temperature. In contrast, inoculated E. coli O157:H7 (5.2 +/- 0.1 log CFU/ml) and L. monocytogenes (5.4 +/- 0.1 log CFU/ml) survived in lactate washings for at least 2 days and in acetate washings for at least 7 and 4 days, respectively; their survival was better in acidic washings stored at 4 degrees C than at 10 degrees C. All inoculated pathogens survived in nonacid (pH > 6.0) washings, but their fate was different. E. coli O157:H7 did not grow at either temperature in water washings, whereas Salmonella Typhimurium DT 104 failed to multiply at 4 degrees C but increased by approximately 2 logs at 10 degrees C. L. monocytogenes multiplied (0.6 to 1.3 logs) at both temperatures in water washings. These results indicated that bacterial pathogens may survive for several days in acidic, and proliferate in water, washings of meat, serving as potential cross-contamination sources, if pathogen niches are established in the plant. The responses of surviving pathogens in meat decontamination waste fluids to acid or other stresses need to be addressed to better evaluate potential food safety risks.