Vapor-phase fabrication and properties of continuous-filament ceramic composites.

The continuous-filament ceramic composite is becoming recognized as necessary for new, high-temperature structural applications. Yet because of the susceptibility of the filaments to damage from traditional methods for the preparation of ceramics, vapor-phase infiltration has become the fabrication method of choice. The chemical vapor infiltration methods for producing these composites are now being studied in earnest, with the complexity of filament weaves and deposition chemistry being merged with standard heat and mass-transport relationships. Two of the most influential effects on the mechanical properties of these materials are the adhesion and frictional force between the fibers and the matrix, which can be controlled by a tailored interface coating. A variety of materials are available for producing these composites including carbide, nitride, boride, and oxide filaments and matrices. Silicon carbide-based materials are by far the most advanced and are already being used in aerospace applications.

Effect of a direct-fed microbial (Primalac) on structure and ultrastructure of small intestine in turkey poults.

The effects of dietary supplementation of the direct-fed microbial (DFM) Primalac in mash or crumbled feed on histological and ultrastructural changes of intestinal mucosa was determined in 2 populations of poults; 1 with and 1 without a Salmonella spp. challenge. Three hundred thirty-six 1-d-old female Large White turkey poults were randomly distributed into 8 treatment groups with 6 replicates of 7 poults in each pen. The poults were placed on 1 of 4 dietary treatments in a 2 x 2 x 2 factorial arrangement (mash or crumble feed, with or without DFM, not-challenged or challenged at 3 d of age). The DFM groups were fed a Primalac-supplemented diet from d 1 until the last day of the experiment (d 21). At 3 d of age, 50% of the poults were challenged with 1 mL of 10(10) cfu/ mL of Salmonella spp. (Salmonella enterica serovar Typhimurium, Salmonella Heidelberg, and Salmonella Kentucky) by oral gavage. The inoculated poults were housed in a separate room from nonchallenged controls. Feed and water were provided ad libitum for all birds. At d 21, 1 poult per pen (total of 6 poults per treatment) was randomly selected and killed humanely by cervical dislocation. After necropsy, the small intestine was removed, and tissue samples from duodenum, jejunum, and ileum were taken for light and electron microscopic evaluation. The DFM birds showed increased goblet cell (GC) numbers, total GC area, GC mean size, mucosal thickness, and a greater number of segmented filamentous bacteria compared with controls. Changes in intestinal morphology as observed in this study support the concept that poultry gut health and function, and ultimately bird performance, can be improved by dietary supplementation with DFM products such as Primalac as used in this study.

Influence of housing system, grain type, and particle size on Salmonella colonization and shedding of broilers fed triticale or corn-soybean meal diets.

Salmonella colonization in poultry may be influenced by grain type and particle size. Broilers reared either in nonlitter cage-based housing or in a conventionally floored litter house from 0 to 42 d were assigned to 1 of 4 dietary treatments: 1) ground corn-soybean meal (C, 560 microm), 2) coarsely ground corn-soybean meal (CC, >1,700 microm), 3) ground triticale-soybean meal (T, 560 microm), or 4) whole triticale-soybean meal (WT). A 4-strain cocktail of Salmonella enterica was orally gavaged into each chick at placement. Growth performance, cecal and fecal Salmonella populations, gizzard and proventriculus pH, intestinal size, jejunum histomorphometry, and carcass yields were measured. Broilers responded differently to the dietary treatments according to the housing system used. At 42 d, birds reared on litter and fed ground grain had greater BW than those fed coarse grain (2.87 vs. 2.71 kg), whereas cage-reared broilers fed ground triticale were heavier than those fed corn (2.75 vs. 2.64 kg). Broilers raised on litter had a better feed conversion ratio than those raised in cages (1.71 vs. 1.81 g/g). Independent of the housing system, relative eviscerated carcass weights of birds fed T and C were heavier than those of CC- and WT-fed broilers (762 vs. 752 g/kg). Generally, the jejunum villus area and mucosal depth were larger, whereas the small intestine was lighter and shorter in broilers raised on litter. Relative gizzard weights of broilers raised on litter and fed the coarser diets were heavier than those of broilers reared in cages and fed finely ground diets. Feeding whole or coarsely ground grains decreased cecal Salmonella populations in 42-d-old broilers (3.8, 3.9, 4.4, and 4.4 log most probable number/g for CC, WT, C, and T, respectively). Additionally, 42-d-old broilers reared on litter had lower cecal Salmonella populations than those in cages (3.8 vs. 4.4 log most probable number/g). In conclusion, as a feed ingredient, triticale is a good alternative to corn, resulting in improved BW and reduced Salmonella colonization. Broilers raised on litter may have achieved lower cecal Salmonella populations than caged birds because access to litter may have modulated the intestinal microflora by increasing competitive exclusion microorganisms, which discouraged Salmonella colonization.

Effects of a direct-fed microbial (primalac) on turkey poult performance and susceptibility to oral Salmonella challenge.

A study was conducted to determine 1) the effect of a dietary direct-fed microbial (DFM) on turkey poult performance, 2) the effect of a DFM on a Salmonella challenge, and 3) the effect of feed processing on the efficacy of the dietary DFM. Day-of-hatch Large White female poults were placed in 2 rooms in 2 Petersime batteries per room. Twelve pens of 7 birds each were used in each battery (24 pens per room, 336 birds total). One of 4 dietary feed treatments was assigned to each pen (6 pens per room for each diet). One room housed non-Salmonella-challenged poults, and the other room housed poults challenged with a 1-mL oral gavage of Salmonella (10(10) cfu/mL). A single batch of starter ration was split into 4 parts and used to provide 4 dietary treatments: 1) mash feed with no DFM (M), 2) mash feed with DFM (Primalac; 0.9 kg/tonne of feed, MD), 3) pelleted (20-s steam conditioning at 80 degrees C) and crumbled feed with no DFM (C), and 4) pelleted and crumbled feed with DFM (CD). Feed and deionized, distilled water were provided ad libitum. Data were collected and analyzed separately for each room. Mortality was recorded for each pen on a daily basis and totaled by week and for the 3-wk period. Individual BW and feed consumption, by pen, were measured weekly. Weekly and cumulative BW gains and feed to gain ratios (F:G) were calculated. Liver, spleen, total and lower intestinal tract weights, intestinal length, and most-probable-number Salmonella populations were determined for one randomly selected bird per pen. Feeding processed feed resulted in improved BW and F:G. Feeding the DFM improved 3-wk cumulative F:G in birds not gavaged and reduced relative intestinal weight in birds gavaged. Salmonella populations were reduced 1 log by feeding DFM. Dietary DFM improved bird performance, reduced Salmonella populations, and was not affected by feed processing.

Genotypes, serotypes, and antibiotic resistance profiles of Salmonella isolated from commercial North Carolina turkey farms.

This study was designed to determine the serotypes, genotypes, and antibiotic resistance (AbR) patterns of 42 Salmonella isolates recovered from either fecal or litter samples of 12 commercial turkey farms across two seasons (summer and winter) and two ages (3 and 19 weeks). Isolates were serotyped on the basis of the Kauffmann-White scheme. Genotyping was done by restriction digestion of cDNA (XbaI) and subsequent pulsed-field gel electrophoresis (PFGE). The AbR was determined with Sensititre susceptibility plates. Serovar Kentucky was the most prevalent serotype (26%), followed by Senftenberg (19%), Muenster (17%), Mbandaka (10%), Javiana (7%), Hadar (5%), Heidelberg (5%), 8,(20):nonmotile (5%), Agona (2%), Infantis (2%), and 4,12:r:-(2%). Serovars Kentucky, Heidelberg, Hadar, and 8,(20):nonmotile were isolated only from the 19-week-old bird samples, whereas Senftenberg and Muenster were isolated only from the young birds (3 weeks old). Isolates within any one serotype showed minor PFGE banding pattern differences, but dendogram analysis indicated that sequence variability between serotypes was more significant than within serotypes. Isolates were resistant to tetracycline (86%), sulfisoxazole (71%), streptomycin (64%), gentamicin (41%), ampicillin (36%), kanamycin (26%), sulfamethoxazole-trimethoprim (7%), nalidixic acid (5%), cefoxitin (2%), and ceftiofur (2%). One isolate (Muenster) was resistant to nine antibiotics (2%), and the others were resistant to six (7%), five (12%), four (10%), three (21%), two (24%), and one (10%) antibiotic. Only two isolates (5%) were susceptible to all antibiotics tested. The AbR patterns were affected by age; on average, strains recovered from young birds were resistant to more than four drugs compared with fewer than three in older birds (P < 0.05). This study showed that Salmonella enterica subsp. enterica serotypes, genotypes and AbR patterns were affected by bird age but not by season or farm.

Modeling the growth and death kinetics of Salmonella in poultry litter as a function of pH and water activity.

Contaminated poultry litter, serving as a reservoir for Salmonella, can be linked to both food safety concerns when contaminated birds enter processing plants and environmental concerns when used as a fertilizer. Predictive modeling allows for the estimation of microbial growth or inactivation as a function of controlling environmental growth factors. A study was conducted to observe the combined effects of pH and water activity (A(w)) at a constant temperature on Salmonella populations in used turkey litter to predict microbial response over time. Litter, first pH-adjusted and then inoculated with a 3-strain Salmonella serovar cocktail to an initial concentration of approximately 10(7) cfu/g, was placed into individual sealed plastic containers with saturated salt solutions for controlling A(w). A balanced design including 3 A(w) values (0.84, 0.91, 0.96), 3 pH values (4, 7, 9), and a constant temperature of 30 degrees C was used, with litter samples periodically removed and analyzed for Salmonella populations, pH, and A(w). At each combination of environmental factors, the Churchill or exponential inactivation mathematical models were used to describe the growth and death of Salmonella over time. Salmonella populations exhibited growth (approximately 2 log) with little decline up to 42 d in litter environments of pH 7 and 9 and a A(w) of 0.96. As litter A(w) and pH levels were reduced, populations declined, with the most drastic reductions (approximately 5 log in 9 h) occurring in low-pH (4) and low-A(w) (0.84) environments. Generalized models for bacterial growth and death under grouped pH environments were successfully developed to predict Salmonella behavior in litter over time. These findings suggest that the best management practices and litter treatments that lower litter A(w) to < or =0.84 and pH to < or =4 are effective in reducing Salmonella populations. The use of a single equation to predict the growth and decline of Salmonella populations as a function of pH and A(w) has potential application for use in the development of effective pathogen control strategies at the farm level.

Salmonella populations and prevalence in layer feces from commercial high-rise houses and characterization of the Salmonella isolates by serotyping, antibiotic resistance analysis, and pulsed field gel electrophoresis.

Salmonella species are recognized as a major cause of foodborne illnesses that are closely associated with the consumption of contaminated poultry and egg products. The objectives of this study were to evaluate the Salmonella populations and prevalence in layer feces during the laying cycle and molting of the hen and to characterize the layer fecal Salmonella isolates by serotyping, antibiotic resistance analysis, and pulsed field gel electrophoresis. Fecal samples were collected from a commercial layer complex consisting of 12 houses. Composite fecal samples across each row were collected as a function of bird age [18 wk (at placement), 25 to 28 wk (first peak of production cycle), 66 to 74 wk (molting), and 75 to 78 wk (second peak of production cycle)]. Bird ages and molting practice did not significantly affect (P > 0.05) Salmonella populations with an average of 1.25, 1.27, 1.20, and 1.14 log most probable number/g for the 18-, 25- to 28-, 66- to 74-, and 75- to 7-wk birds, respectively. However, the 18-wk birds had the highest prevalence of Salmonella (55.6%), followed by the 25- to 28-wk birds (41.7%), 75- to 78-wk birds (16.7%), and 66- to 74-wk birds (5.5%). Of the 45 Salmonella isolates characterized, the most predominant serovar was Salmonella Kentucky (62%). Thirty-five percent of the Salmonella isolates were resistant to at least 1 antibiotic. As expected, considerable genetic diversity was observed within and across the different serovars.

Identification of eggshell membrane proteins and purification of ovotransferrin and beta-NAGase from hen egg white.

Exposure of selected Gram-positive and Gram-negative bacterial pathogens to egg shell membranes (ESM) significantly reduced their thermal resistance and/or inactivated cells. Although the components responsible for this antibacterial activity have not been conclusively identified, several proteins associated with the ESM activity have been identified including beta-N-acetylglucosaminidase, lysozyme and ovotransferrin, with each displaying varying degrees of antibacterial activity. Numerous attempts to purify active fractions of beta-N-acetylglucosaminidase, lysozyme and ovotransferrin from the ESM proved somewhat limited; however, hen egg white (HEW) beta-N-acetylglucosaminidase was purified using a two-step chromatographic procedure, isoelectric focusing followed by cation exchange chromatography. Pure fractions of ovotransferrin were also obtained in the process. SDS-PAGE electrophoresis and Matrix-Assisted Laser Desorption Time-of-Flight Mass Spectrometry were then used to partially characterize the individual protein components. Purified protein fractions such as these will be required in order to fully elucidate the mechanism responsible for the antimicrobial properties associated with the ESM.

Coupling of strain, stress, and oxygen non-stoichiometry in thin film Pr0.1Ce0.9O2-δ.

Stress and strain in thin films of Pr0.1Ce0.9O2-δ, supported on yttria stabilized zirconia (YSZ) and sapphire substrates, induced by large deviations from oxygen stoichiometry (δ = 0) were investigated by in situ high temperature X-ray diffraction and wafer curvature studies. The measured stresses and strains were correlated with change in δ, measured in situ using optical transmission spectroscopy of defect centers in the films and compared with prior chemical capacitance studies. The coefficient of chemical expansion and elastic modulus values for the films were found to be 18% less than, and 16% greater than in the bulk, respectively. Irreproducible stress and strain during cycling on YSZ substrates was observed and related to microstructural changes as observed by TEM. The enthalpy of defect formation was found to be similar for films supported on sapphire and YSZ, and appeared to decrease with tensile stress, and increase with compressive stress. Larger stresses observed for YSZ supported films as compared to sapphire supported films were found and accounted for by the difference in film orientations.

Thermal resistance of Salmonella enterica serotypes, Listeria monocytogenes, and Staphylococcus aureus in high solids liquid egg mixes.

Decimal reduction times (D-values) were determined for Salmonella enterica serotypes, Listeria monocytogenes, and Staphylococcus aureus in two high solids egg mixes designated A and B (water activity [a(w)] = 0.76 and 0.82; solids = 53.12 and 52.63%; pH = 5.09 and 5.29; viscosity = 183 and 119 centipoise/s, respectively) using a low-volume (0.06 ml) sealed glass capillary tube procedure. For Salmonella, D-values ranged from 0.035 (70 degrees C) to 0.193 min (64 degrees C) in product A and from 0.048 to 0.193 min in product B. For Listeria, D-values ranged from 0.133 (70 degrees C) to 0.440 min (64 degrees C) in product A and from 0.074 to 0.364 min in product B. For Staphylococcus, D-values ranged from 0.332 (70 degrees C) to 1.304 min (64 degrees C) in product A and from 0.428 to 1.768 min in product B. For Listeria, the D-values of all heating temperatures were significantly higher (P < 0.01) in product A than in product B. The similar trend was also observed for Salmonella and Staphylococcus but only at 66 degrees C for Salmonella and 64 degrees C for Staphylococcus. Greater temperature dependence was observed for Salmonella inactivation in the low a(w) and low pH product (A), while the product (B) with the higher a(w) and pH had greater temperature dependence for Listeria. Compared across both egg mixes and all heating temperatures, the Staphylococcus strains were from 6.2 to 11.7 times more heat resistant than S. enterica serotypes and from 2.2 to 7.5 times more heat resistant than L. monocytogenes.

Enzymatic and microbiological inhibitory activity in eggshell membranes as influenced by layer strains and age and storage variables.

Eggshell membranes (ESM) have been shown to exhibit antibacterial activity. The purpose of this study was to evaluate the enzymatic and biological [decimal reduction times (D-values)] activities of ESM as a function of bird breed, age, and ESM stabilization treatments. Younger White Leghorn (WL) hens produced ESM with 28% higher lysozyme activity than Rhode Island Red (RIR) layers. In contrast, older WL layers produced ESM with 17% less lysozyme activity than ESM from RIR layers. Similarly, beta-N-acetylglucosaminidase (beta-NAGase) ESM activities differed by hen age within breeds with younger hens yielding 14 to 16% more enzyme activity. D54 degrees C-values of Salmonella Typhimurium cells preexposed to WL ESM did not differ as a function of bird age (33, 50, and 81 wk). The ESM Lysozyme and beta-NAGase activities varied somewhat over a 6-mo storage study after treatment with 1 of 5 stabilization methods [i.e., storage at 4 degrees C, -20 degrees C, or ambient air storage after freeze drying, air drying (23 degrees C), or forced-air drying (50 degrees C)]. Both air and forced-air drying yielded significant reductions in beta-NAGase and lysozyme ESM activity (ca 12 to 30%) after the initial 24 h and then remained fairly stable during the extended storage. Freeze-dried samples retained the most enzymatic activity (95%) throughout the 6-mo trial, whereas refrigerated ESM lost 20 and 18% of the beta-NAGase and lysozyme activities, respectively. Frozen ESM lost 22% of the beta-NAGase activity, whereas lysozyme was nearly unaffected after 6 mo. The ESM biological activities against S. Typhimurium were not adversely impacted by layer breed or age. No significant loss in biological activity of ESM was detected 24 h after processing or after 6 mo of storage for refrigerated, frozen, and freeze-dried membranes, whereas significant reductions were observed for air- and heat-dried ESM. These findings demonstrate that ESM enzyme and biological activities are relatively constant across layer breeds and over extended storage. Based on these and other findings, ESM may have potential commercial value as a processing adjuvant in food and pharmaceutical product applications.

Efficacy of nisin-coated polymer films to inactivate Salmonella Typhimurium on fresh broiler skin.

Nisin is an antimicrobial peptide produced by the food-grade microorganism Lactococcus lactis subsp. lactis. This peptide inhibits many gram-positive bacteria, and when combined with chelating agents it inhibits gram-negative bacteria such as Salmonella sp. The efficacy of packaging films treated with nisin-containing formulations to reduce Salmonella contamination of fresh broiler drumstick skin and increase the refrigerated shelf life was investigated. Three films (5.1 cm2) of varying hydrophobicities (polyvinyl chloride [PVC], linear low density polyethylene, nylon) were coated with one of three liquid formulations (pH 3.5 to 3.8) composed of 100 microg/ml nisin and varying concentrations of citric acid, EDTA, and Tween 80. The treated films were applied either wet or dry to 5.1-cm2 broiler drumstick skin samples inoculated with a nalidixic acid-resistant (NAr) strain of Salmonella Typhimurium. After incubation at 4 degrees C for 24 h the populations of surviving Salmonella TyphimuriumNAr organisms were recovered from the skin and film samples using a rinse procedure and enumerated on brain heart infusion agar containing 800 ppm NA. Log reductions (untreated versus treated skin) in Salmonella TyphimuriumNAr populations ranged from 0.4 to 2.1. Treatment formulation compositions and wet versus dry treatment application also influenced the extent of kill. The shelf life of refrigerated broiler drumsticks was extended by 0.6 to 2.2 days following a 3-min immersion in a nisin-containing treatment solution and subsequent storage in a foam tray pack containing a nisin-treated PVC overwrap and a nisin-treated absorbent tray pad. These findings demonstrated that Salmonella Typhimurium and spoilage microorganism populations on the surface of fresh broiler skin and drumsticks can be significantly reduced using immersion treatments, absorbent tray pads, and packaging films treated with nisin-containing formulations.

Inhibition of Salmonella on poultry skin using protein- and polysaccharide-based films containing a nisin formulation.

The objective of this study was to examine the use of protein- arid polysaccharide-based films containing bacteriocin formulations for inhibiting salmonellae on fresh broiler skin. The lethality of the films containing a nisin-based formulation was determined against Salmonella Typhimurium-contaminated broiler drumstick skin samples coated with the film. In the first study, varying concentrations of nisin (0, 100, 300, and 500 microg/ml) plus 3% citric acid, 5.0 mM EDTA, and 0.5% Tween 80 were incorporated into 0.5% calcium alginate films at a 20% level (wt/wt) and then applied to Salmonella TyphimuriumNAr-contaminated skin samples (log10 5.0) at a 1:2 weight ratio (film:skin). Salmonella TyphimuriumNAr skin population reductions ranged from 1.98 to 3.01 log cycles after a 72-h exposure at 4 degrees C. In comparison to the 0- and 100-microg/ml nisin concentrations, significantly greater population reductions were achieved at nisin concentrations of 300 and 500 microg/ml. In related studies, the 500-degreesg/ml nisin formulation was incorporated into 0.75 and 1.25% agar gels and applied to contaminated broiler drumstick skin samples (log10 7.0). Salmonella TyphimuriumNAr skin population reductions following a 96-h exposure at 4 degrees C were 1.8-(1.25% agar gel) and 4.6-log cycles (0.75% agar gel). These results demonstrated that the inclusion of nisin-based treatments into either calcium alginate or agar gels that were subsequently applied to contaminated broiler drumstick skin yielded significant Salmonella TyphimuriumNAr population reductions ranging between 1.8 to 4.6 log cycles after 72 to 96 h of exposure at 4 degrees C. The level of kill was affected by film type and gel concentration (i.e., gel network formation), exposure time, and nisin concentration.

Altering the thermal resistance of foodborne bacterial pathogens with an eggshell membrane waste by-product.

Eggshells from egg-breaking operations are a significant waste disposal problem. Thus, the development of value-added by-products from this waste would be welcomed by the industry. The ability of extracted eggshell membranes containing, several bacteriolytic enzymes (i.e., lysozyme and beta-N-acetylglucosaminidase) or other membrane components to alter the thermal resistance of gram-positive and gram-negative bacterial pathogens was evaluated. Mid-log phase cells of Salmonella Enteritidis (SE), Salmonella Typhimurium (ST), Escherichia coli O157:H7 (EC), Listeria monocytogenes Scott A (LM), and Staphylococcus aureus (SA) were suspended in 100 ml of 0.1% peptone water (pH 6.9, 10(7-8) CFU/ml) containing either 0 (control) or 10 g of an eggshell membrane extract and incubated at 37 degrees C for 45 min. Following exposure, membrane-free samples (1.5 ml) were heated in a 56 degrees C (LM, SA), 54 degrees C (SE, ST), or 52 degrees C (EC) water bath from 0 to 14 min in sealed glass reaction vials (12 by 32 mm), and the survivors were recovered on brain heart infusion agar. Population reductions ranging from 27.6% (SA) to 99.8% (LM) (ST, 43.8%; SE, 47.5%; EC, 71.8%) were observed for cells treated for 45 min with extracted membrane, as compared to controls. D-value reductions ranging from 0 (LM) to 87.2% (SE) (SA, 36.7%; EC, 83.3%; ST, 86.3%) were observed when membrane-treated cells were subsequently heat inactivated. The effects of exposure pH, time, temperature, and organic load on membrane activity were also evaluated with Salmonella Typhimurium. Exposure pH (5.0 versus 6.9), time (15 versus 45 min), and temperature (4 degrees C versus 37 degrees C) did not significantly reduce the impact of eggshell membranes on D-values. However, the presence of organic matter (0.1% peptone water versus skim milk) significantly reduced the thermal resistance-reducing capacity of the membranes. These preliminary findings provide information on the potential use of extracted eggshell membranes to alter bacterial heat resistance.

Thermal resistance of bacterial spores in milk-based beverages supplemented with nisin.

The effect of nisin, added in the form of Nisaplin, on the thermal resistance of bacterial spores and the effects of medium composition, exposure time, and pH on nisin enhancement of heat sensitivity were evaluated. Nisin apparently required specific nutrients to sensitize spores to heat. For example, D130 degrees C values of approximately 10 s were observed in sodium phosphate buffer with and without 6% sucrose with no significant (P> or =0.05) differences detected as a result of increased nisin concentration. In a nutrient-rich chocolate milk model system (CMMS), increasing either the time of exposure to nisin (5, 15, or 24 h) before heating or nisin concentration (0, 2,000, or 4,000 IU/ml) increased the sensitivity of Bacillus stearothermophilus spores to heat. In the CMMS with 10 to 12% fat cocoa powder, increasing nisin concentration (at 5 h of exposure) significantly (P< or =0.05) reduced D130 degrees C values; D130 degrees C values were 21.7, 17.2, and 17.8 s, respectively, for the 0-, 2,000-, and 4,000-IU/ ml nisin treatments. Fifteen and 24 h of exposure further reduced D130 degrees C values in the nisin-containing treatments compared to the control (0 IU of nisin per ml). A lower-fat CMMS (0 to 1% fat cocoa powder) had lower D130 degrees C values (19.3, 15.8, and 14.7 s for the 0-, 2,000-, and 4,000-IU/ml nisin treatments, respectively). Nisin activity was enhanced by lowering pH in the CMMS (10 to 12% fat cocoa powder), with reductions in D130 degrees C values across all pH values (ranging from 18.0% at pH 6.4 to 41.9% at pH 5.0). zD values were 9.6, 9.0, and 8.4 degrees C for the 0-, 2,000-, and 4,000-IU/ml nisin treatments, respectively. Spores of B. licheniformis yielded results similar to those obtained with B. stearothermophilus. For example, decreasing CMMS (10 to 12% fat cocoa powder) pH values from 6.4 to 5.0 produced D100 degrees C values of 3.3, 2.8, and 2.8 min (pH 6.4) and 1.0, 0.8, and 0.8 min (pH 5.0) for the 0-, 2,000-, and 4,000-IU/ml nisin treatments. This study clearly verified that the addition of Nisaplin to dairy-based beverages, such as a chocolate milk drink, or other foods intended to be heated reduces the thermal resistance of selected bacterial spores. Increased spore sensitivity to heat may provide food processors with an opportunity to reduce their thermal processes and expenses while maintaining product quality, functionality, and shelf stability.

Nisin in milk sensitizes Bacillus spores to heat and prevents recovery of survivors.

Decimal reduction times (D values) were determined for Bacillus cereus T spores and B. stearothermophilus ATCC 12980 spores in skim milk supplemented with various concentrations (0, 2,000, and 4,000 IU/ml) of the bacteriocin nisin by using an immersed, sealed capillary tube procedure. For both organisms, the addition of nisin lowered the apparent D values. For B. cereus, the addition of 2,000 IU of nisin per ml to skim milk before heating significantly (P< or =0.05) lowered the apparent D value compared to the control treatment. The D values at 97 degrees C were 7.0, 4.8, and 4.7 min for the control and 2,000- and 4,000-IU/ml nisin treatments, respectively. At 103 degrees C, the D values were 1.5, 0.85, and 0.88 min for the control and 2,000-and 4,000-IU/ml nisin treatments. When calculated across both nisin treatments, the mean reductions in apparent D values at 97, 100, and 103 degrees C due to addition of nisin in comparison to the controls were 32, 20, and 42%, respectively. The zD values for B. cereus ranged from 8.0 to 8.9 degrees C. With B. stearothermophilus, the apparent D values at 130 degrees C were reduced by 13 and 21% respectively, because of the presence of 2,000 or 4,000 IU of nisin per ml. The D values were 16.0, 13.8, and 12.5 s for the control and 2,000- and 4,000-IU/ml nisin treatments, respectively. There was a significant (P< or =0.05) decrease in the apparent D value between the control and 4,000-IU/ml treatment. Overall, log populations of survivors for B. stearothermophilus compared to the control were lower at any given sampling time due to the presence of nisin. The results of these studies suggest that spore control is likely due to enhanced sensitivity of spores to heat and the presence of residual nisin in the recovery medium that could prevent outgrowth of survivors.

Hydrogen peroxide as an alternative hatching egg disinfectant.

The present study examined the effectiveness of H2O2 at different concentrations to disinfect broiler hatching eggshell surfaces and to maintain hatching potential. Under pure culture conditions, .50% H2O2 yielded over a 6 log kill in 30 s of three potential eggshell bacterial contaminants. Under higher H2O2 demands, such as occurs on eggshell surfaces, H2O2 concentrations of 5% (vol/vol) were required to disinfect the shell surfaces (approximately 5 log reduction). Hatchability of fertile eggs from a 44-wk-old flock was significantly increased by 2% following spraying 5% H2O2 in comparison to untreated controls. Level of contaminated eggs and "early-dead" embryos were significantly reduced in the H2O2-treated eggs. In comparison with formaldehyde fumigation, no significant difference in hatchability due to H2O2 treatment was detected in eggs from a 30- or 56-wk-old flock. Eggshell permeability, as measured by egg moisture loss in an incubator, was not significantly affected by H2O2 (5%) or formaldehyde fumigation when compared with untreated or water-sprayed control eggs. These results demonstrated that H2O2 compared favorably to formaldehyde as a hatching egg disinfectant without adversely affecting hatching potential. Under some conditions, H2O2 actually improved the hatching potential of fertile broiler eggs compared with hatchability of untreated eggs.

Comparison of ozone and formaldehyde as poultry hatchery disinfectants.

Ozone and formaldehyde were compared as poultry hatchery disinfectants in a poultry setter, and evaluated for effectiveness. Escherichia coli, Pseudomonas fluorescens, Salmonella typhimurium, and Proteus spp. were inoculated onto open petri plates and exposed to ozone or onto filter paper strips and exposed to ozone or formaldehyde in a poultry setter. Ozone (1.41 to 1.68% by weight) resulted in significant bacterial reductions of greater than 4 log10 on the open plates and greater than 3 log10 on filter paper strips, whereas formaldehyde (triple strength) resulted in greater than 7 log10 reduction on filter paper strips. Ozone was similarly lethal to organisms on filter paper strips at 90% relative humidity (RH) and 13.9 C, and at 50% RH and 37.7 C. Although under the conditions of this study formaldehyde (triple strength) was more lethal than ozone, ozone killed greater than 99.9% of the starting microbial populations. In the event that formaldehyde can no longer be used in the hatchery, an effective alternative may be ozone.

Biocidal activity of ozone versus formaldehyde against poultry pathogens inoculated in a prototype setter.

Ozone was evaluated as an alternative hatchery disinfectant to replace formaldehyde in the event that the Environmental Protection Agency regulates the use of formaldehyde under the Toxic Substances Control Act. Cultures of Staphylococcus, Streptococcus, and Bacillus species previously isolated from poultry hatcheries and selected culture collections of Escherichia coli, Pseudomonas fluorescences, Salmonella typhimurium, Proteus species, and Aspergillus fumigatus were spread-plated on open petri plates and independently fumigated with ozone or formaldehyde in a prototype laboratory poultry setter. Ozone (1.52% to 1.65% by weight) resulted in bacterial reductions of greater than 4 to 7 log10 and fungal reductions of greater than 4 log10, whereas formaldehyde achieved reductions of greater than 7 log10 and greater than 5 log10, respectively, after 8 min of exposure to either disinfectant. Potential mutagenic effects were observed in ozonated E. coli colonies resulting in decreased superoxide dismutase activity and increased catalase activity when compared with nonozonated control colonies. In this study ozone reduced microorganism counts but not as much as formaldehyde. Ozone may be used as a disinfectant against selected microorganisms, although further testing under actual hatchery conditions is needed before making recommendations to the industry.

Thermal and biological treatments to control psychrotrophic pathogens.

Over the past decade, advances in egg processing technologies have permitted commercial production of ultrapasteurized liquid whole egg (LWE) products with a shelf-life of greater than 10 wk at 4 C. The inactivation and control of psychrotrophic pathogens such as Listeria monocytogenes and Aeromonas hydrophila in extended shelf-life LWE and conventionally pasteurized egg products is an ongoing food safety concern. This manuscript reports on the common features of these two psychrotrophic pathogens, their incidence in egg products, and their survival, growth potential, and heat resistance in liquid egg. Furthermore, this manuscript reports in detail on the results of two specific studies conducted in our laboratory whose objectives were: 1) to determine the heat resistance (D-values) of A. hydrophila in LWE using a low-volume immersed sealed glass capillary tube (ISCT) procedure; 2) to assess the impact of methodology (i.e., ISCT procedure vs a conventional capped test tube procedure) on the apparent thermal resistance of A. hydrophila; and 3) to report on the use of the bacteriocin nisin to restrict the survival of L. monocytogenes in ultrapasteurized LWE stored at refrigeration temperatures.