Small molecule binding to surface-supported single-site transition-metal reaction centres.

Despite dominating industrial processes, heterogeneous catalysts remain challenging to characterize and control. This is largely attributable to the diversity of potentially active sites at the catalyst-reactant interface and the complex behaviour that can arise from interactions between active sites. Surface-supported, single-site molecular catalysts aim to bring together benefits of both heterogeneous and homogeneous catalysts, offering easy separability while exploiting molecular design of reactivity, though the presence of a surface is likely to influence reaction mechanisms. Here, we use metal-organic coordination to build reactive Fe-terpyridine sites on the Ag(111) surface and study their activity towards CO and C2H4 gaseous reactants using low-temperature ultrahigh-vacuum scanning tunnelling microscopy, scanning tunnelling spectroscopy, and atomic force microscopy supported by density-functional theory models. Using a site-by-site approach at low temperature to visualize the reaction pathway, we find that reactants bond to the Fe-tpy active sites via surface-bound intermediates, and investigate the role of the substrate in understanding and designing single-site catalysts on metallic supports.

Association of oral contraceptives and tubal ligation with risk of early natural menopause.

STUDY QUESTION: What is the association of oral contraceptives (OCs) and tubal ligation (TL) with early natural menopause? SUMMARY ANSWER: We did not observe an association of OC use with risk of early natural menopause; however, TL was associated with a modestly higher risk. WHAT IS KNOWN ALREADY: OCs manipulate hormone levels, prevent ovulation, and may modify the rate of follicular atresia, while TL may disrupt the blood supply to the ovaries. These mechanisms may be associated with risk of early menopause, a condition associated with increased risk of cardiovascular disease and other adverse health outcomes. STUDY DESIGN, SIZE, DURATION: We examined the association of OC use and TL with natural menopause before the age of 45 years in a population-based study within the prospective Nurses' Health Study II (NHSII) cohort. Participants were followed from 1989 to 2017 and response rates were 85-90% for each cycle. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants included 106 633 NHSII members who were premenopausal and aged 25-42 years at baseline. Use, duration and type of OC, and TL were measured at baseline and every 2 years. Menopause status and age were assessed every 2 years. Follow-up continued until early menopause, age 45 years, hysterectomy, oophorectomy, death, cancer diagnosis, or loss to follow-up. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% CIs adjusted for lifestyle, dietary, and reproductive factors. MAIN RESULTS AND THE ROLE OF CHANCE: Over 1.6 million person-years, 2579 members of the analytic cohort experienced early natural menopause. In multivariable models, the duration, timing, and type of OC use were not associated with risk of early menopause. For example, compared with women who never used OCs, those reporting 120+ months of OC use had an HR for early menopause of 1.01 (95% CI, 0.87-1.17; P for trend=0.71). TL was associated with increased risk of early menopause (HR = 1.17, 95% CI, 1.06-1.28). LIMITATIONS, REASONS FOR CAUTION: Our study population is homogenous with respect to race and ethnicity. Additional evaluation of these relations in more diverse populations is important. WIDER IMPLICATIONS OF THE FINDINGS: To our knowledge, this is the largest study examining the association of OC use and TL with early natural menopause to date. While TL was associated with a modest higher risk of early menopause, our findings do not support any material hazard or benefit for the use of OCs. STUDY FUNDING/COMPETING INTEREST(S): The study was sponsored by UO1CA176726 and R01HD078517 from the National Institutes of Health and Department of Health and Human Services. The work was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The authors have no competing interests to report. TRIAL REGISTRATION NUMBER: N/A.

Wave packets in the anomalous Ostrovsky equation.

The anomalous Ostrovsky equation, which describes waves in vertically sheared ocean flows and magnetoacoustic waves, possesses steadily propagating, finite-amplitude, localized wave-packet solutions. It is shown here that these solutions can be obtained asymptotically, using Whitham modulation theory, as the solution to a nonlinear eigenvalue problem. This allows the various wave-packet solutions to be delineated and compared to solutions of the full equations of motion. A periodic solution with an embedded wave train is also constructed.

Structure and formation of highly luminescent protein-stabilized gold clusters.

Highly luminescent gold clusters simultaneously synthesized and stabilized by protein molecules represent a remarkable category of nanoscale materials with promising applications in bionanotechnology as sensors. Nevertheless, the atomic structure and luminescence mechanism of these gold clusters are still unknown after several years of developments. Herein, we report findings on the structure, luminescence and biomolecular self-assembly of gold clusters stabilized by the large globular protein, bovine serum albumin. We highlight the surprising identification of interlocked gold-thiolate rings as the main gold structural unit. Importantly, such gold clusters are in a rigidified state within the protein scaffold, offering an explanation for their highly luminescent character. Combined free-standing cluster synthesis (without protecting protein scaffold) with rigidifying and un-rigidifying experiments, were designed to further verify the luminescence mechanism and gold atomic structure within the protein. Finally, the biomolecular self-assembly process of the protein-stabilized gold clusters was elucidated by time-dependent X-ray absorption spectroscopy measurements and density functional theory calculations.

Adult adiposity and risk of early menopause.

STUDY QUESTION: Is adult adiposity associated with early menopause? SUMMARY ANSWER: Overall and abdominal adiposity were non-linearly associated with odds for early natural menopause with elevated odds observed among women who were underweight in early or mid-adulthood compared to lean-normal weight women. WHAT IS KNOWN ALREADY: High and low adiposity have been associated with reproductive function and may potentially impact timing of menopause. It is unclear whether various aspects of adiposity are associated with risk of early menopause. STUDY DESIGN, SIZE, DURATION: Prospective cohort study that examined data from 78 759 premenopausal women from the Nurses' Health Study II who were followed from 1989 to 2011 for incidence of early natural menopause. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants were aged 25-42 years and premenopausal at baseline in 1989, when information on menopausal status, height and weight was reported via questionnaire. Information on menopausal status, type of menopause (natural, surgical, radiation/chemotherapy), hormone therapy use and weight was updated every two years along with information on smoking, physical activity and other behavioral and health-related factors. Multivariable logistic regression was used to estimate odds ratios for early menopause, defined as natural menopause before age 45 years, by aspects of adiposity. MAIN RESULTS AND THE ROLE OF CHANCE: Early natural menopause was reported by 2804 participants. Body mass index (BMI) was non-linearly associated with risk for early menopause. Compared to women with BMI = 18.5-22.4 kg/m2, those with BMI < 18.5 kg/m2 had a significant 30% higher odds of early menopause (95% confidence interval (CI) = 1.08, 1.57), while women with BMIs between 25.0-29.9 kg/m2 had significant 21-30% lower odds. Odds were not higher in women with BMI ≥ 35.0 kg/m2 in fully adjusted analysis. Non-linear associations with higher odds in underweight women were also observed for age 18 and age 35 BMI, though lower odds for overweight women was only observed for age 35 BMI. Odds were highest among women with age 18 BMI < 18.5 kg/m2 reporting severe weight cycling. LIMITATIONS, REASONS FOR CAUTION: Though weight and early menopause status were self-reported, validation studies conducted among Nurses' Health Study participants suggest that self-reported weight is highly correlated with directly measured weight, and prospective self-reported menopausal status is highly reproducible. It is possible that underweight women may have been misclassified with an earlier age at menopause if being underweight led to amenorrhea. WIDER IMPLICATIONS OF THE FINDINGS: In one of the few studies to prospectively examine a variety of adiposity measures and risk for early menopause, our findings that women who were underweight in early or mid-adulthood had elevated risk for early menopause can assist in efforts to better understand the etiology of early menopause. Additional prospective research is needed to understand how low adiposity may physiologically impact timing of menopause. STUDY FUNDING/COMPETING INTEREST(S): This study was conducted with funding from NIH UM1CA176726 and R01HD078517. The authors declare no conflicts of interest. TRIAL REGISTRATION NUMBER: Not applicable.

Whitham modulation theory for the Ostrovsky equation.

This paper derives the Whitham modulation equations for the Ostrovsky equation. The equations are then used to analyse localized cnoidal wavepacket solutions of the Ostrovsky equation in the weak rotation limit. The analysis is split into two main parameter regimes: the Ostrovsky equation with normal dispersion relevant to typical oceanic parameters and the Ostrovsky equation with anomalous dispersion relevant to strongly sheared oceanic flows and other physical systems. For anomalous dispersion a new steady, symmetric cnoidal wavepacket solution is presented. The new wavepacket can be represented as a solution of the modulation equations and an analytical solution for the outer solution of the wavepacket is given. For normal dispersion the modulation equations are used to describe the unsteady finite-amplitude wavepacket solutions produced from the rotation-induced decay of a Korteweg-de Vries solitary wave. Again, an analytical solution for the outer solution can be given. The centre of the wavepacket closely approximates a train of solitary waves with the results suggesting that the unsteady wavepacket is a localized, modulated cnoidal wavetrain. The formation of wavepackets from solitary wave initial conditions is considered, contrasting the rapid formation of the packets in anomalous dispersion with the slower formation of unsteady packets under normal dispersion.

Seasonality of suicide behavior in Northwest Alaska: 1990-2009.

OBJECTIVES: Suicide is a leading cause of death worldwide, and disproportionately affects Indigenous populations. Seasonal suicide patterns are variable in the literature, and could offer novel approaches to the timing and focus of prevention efforts if better understood. With a suicide surveillance system in place since 1989, this study offers an unprecedented opportunity to explore seasonal variations in both fatal and non-fatal suicide behavior in an Indigenous Arctic region. STUDY DESIGN: Cross-sectional. METHODS: In this descriptive study, we analyzed data collected from 1990 to 2009 in the rural northwest region of Alaska, both graphically and using the chi-squared test for multinomials. RESULTS: We found a significant monthly variation for suicide attempts, with a peak in suicide behavior observed between April and August (P = 0.0002). Monthly variation was more pronounced among individuals ≤29 years of age, and was present in both males and females, although the seasonal pattern differed by sex. CONCLUSIONS: Our findings of a significant seasonal pattern in suicide behavior, with monthly variation (summer peak) in non-fatal suicide behavior among younger age groups, and among both males and females can assist planners in targeting subpopulations for prevention at different times of the year.

Wave-packet formation at the zero-dispersion point in the Gardner-Ostrovsky equation.

The long-time effect of weak rotation on an internal solitary wave is the decay into inertia-gravity waves and the eventual emergence of a coherent, steadily propagating, nonlinear wave packet. There is currently no entirely satisfactory explanation as to why these wave packets form. Here the initial value problem is considered within the context of the Gardner-Ostrovsky, or rotation-modified extended Korteweg-de Vries, equation. The linear Gardner-Ostrovsky equation has maximum group velocity at a critical wave number, often called the zero-dispersion point. It is found here that a nonlinear splitting of the wave-number spectrum at the zero-dispersion point, where energy is shifted into the modulationally unstable regime of the Gardner-Ostrovsky equation, is responsible for the wave-packet formation. Numerical comparisons of the decay of a solitary wave in the Gardner-Ostrovsky equation and a derived nonlinear Schrödinger equation at the zero-dispersion point are used to confirm the spectral splitting.

Modulational instability of co-propagating internal wavetrains under rotation.

Weakly-nonlinear unidirectional long internal waves in a non-rotating frame are well described by the Korteweg-de Vries equation (KdV). Within the KdV framework, all isolated monochromatic wavetrains are stable to modulational instability. However, analysis of a coupled nonlinear Schrödinger equation system (CNLS) has shown that all systems of two co-propagating monochromatic wavetrains in the KdV are modulationally unstable. To take into account the effect of the background rotation of the Earth on long internal waves, this analysis is extended here to derive the CNLS for the rotation-modified KdV, or Ostrovsky, equation. Rotation stabilises wavetrain pairs when the wavelengths of both waves comprising the wavetrains are longer than the linear wave with maximum group velocity. The particular case when the wavetrains have different wavenumbers but the same linear group speed is emphasised.

Association of inflammation markers with menstrual symptom severity and premenstrual syndrome in young women.

STUDY QUESTION: Are markers of chronic inflammation associated with menstrual symptom severity and premenstrual syndrome (PMS)? SUMMARY ANSWER: Serum levels of inflammatory markers, including interleukin (IL)-2, IL-4, IL-10, IL-12 and interferon (IFN)-γ were positively associated with menstrual symptom severity and/or PMS in young women. WHAT IS KNOWN ALREADY: Chronic inflammation has been implicated in the etiology of depression and other disorders that share common features with PMS, but whether inflammation contributes to menstrual symptom severity and PMS is unknown. STUDY DESIGN, SIZE, DURATION: Cross-sectional study of 277 women aged 18-30 years, conducted in 2006-2011. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants provided information on menstrual symptoms, lifestyle, diet, anthropometry and other factors by questionnaire and/or direct measurement, and a mid-luteal phase fasting blood sample was taken between 7 a.m. and 12 p.m. Total, physical and affective menstrual symptom scores were calculated for all participants, of whom 13% (n = 37) met criteria for moderate-to-severe PMS and 24% (n = 67) met PMS control criteria. Inflammatory factors assayed in serum included IL-1ß, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, IL-13, tumor necrosis factor-α, granulocyte macrophage colony stimulating factor, IFN-γ and C-reactive protein. MAIN RESULTS AND THE ROLE OF CHANCE: After adjustment for age, smoking status and BMI, total menstrual symptom score was positively associated with levels of IL-2 (percentage difference in women at the 75th percentile of total symptom score versus at the 25th percentile = 24.7%; P = 0.04), IL-4 (21.5%; P = 0.04), IL-10 (28.0%; P < 0.01) and IL-12 (42.0%; P = 0.02) in analyses including all participants. Affective menstrual symptom score was linearly related to levels of IL-2 (percentage difference at 75th percentile versus 25th percentile = 31.0%; P = 0.02), while physical/behavioral symptom score was linearly related to levels of IL-4 (19.1%; P = 0.03) and IL-12 (33.2%; P = 0.03). Additionally, mean levels of several factors were significantly higher in women meeting PMS criteria compared with women meeting control criteria, including IL-4 (92% higher in cases versus controls; P = 0.01); IL-10 (87%; P = 0.03); IL-12 (170%; P = 0.04) and IFN-γ (158%; P = 0.01). LIMITATIONS, REASONS FOR CAUTION: Our study has several limitations. While a single blood sample may not perfectly capture long-term levels of inflammation, ample data suggest that levels of cytokines are stable over time. Although we did not base our assessment of PMS on prospective symptom diaries, we used validated criteria to define PMS cases and controls, and excluded women with evidence of comorbid mood disorders. Furthermore, because of the cross-sectional design of the study, the temporal relation of inflammatory factors and menstrual symptoms is unclear. WIDER IMPLICATIONS OF THE FINDINGS: To our knowledge, this is among the first studies to suggest that inflammatory factors may be elevated in women experiencing menstrual symptoms and PMS. Additional studies are needed to determine whether inflammation plays an etiologic role in PMS. STUDY FUNDING/COMPETING INTERESTS: This study was funded by the Departments of Public Health and Nutrition and by a Faculty Research Grant, University of Massachusetts Amherst. No conflicts declared. TRIAL REGISTRATION NUMBER: N/A.

Modified reduced Ostrovsky equation: integrability and breaking.

The modified reduced Ostrovsky equation is a reduction of the modified Korteweg-de Vries equation, in which the usual linear dispersive term with a third-order derivative is replaced by a linear nonlocal integral term, representing the effect of background rotation. Here we study the case when the cubic nonlinear term has the same polarity as the rotation term. This equation is integrable provided certain slope constraints are satisfied. We demonstrate, through theoretical analysis and numerical simulations, that when this constraint is not satisfied at the initial time, wave breaking inevitably occurs.

Are existing measures of overall diet quality associated with peak bone mass in young premenopausal women?

BACKGROUND: Low peak bone mass in young adulthood is associated with an increased risk of osteoporosis and fracture after menopause, and an understanding of the modifiable factors that contribute to low peak bone mass is important for fracture prevention. Diet is an important modifiable factor linked to bone health and, although studies have examined the role of individual dietary components in bone health, bone growth and maintenance are complex processes, and such studies may not adequately represent the role of diet in these processes. METHODS: To address this issue, a cross-sectional analysis of 226 healthy, premenopausal women aged 18-30 years was conducted to determine whether existing indices of overall diet quality are associated with bone density in premenopausal women nearing peak bone mass. Bone density was measured using dual-energy X-ray absorptiometry and diet quality was measured using two overall diet scores based on current dietary guidelines: the Recommended Food Score and the Alternate Healthy Eating Index (AHEI). RESULTS: In the multiple linear regression, bone density did not increase across quartiles of either diet quality score and was not associated with continuous diet quality variables. Furthermore, none of the individual AHEI components (e.g. fruit intake, vegetable intake) were associated with bone density. CONCLUSIONS: These findings suggest that existing diet quality scores are not appropriate for studies of peak bone mass, most likely because they do not give sufficient weight to foods and nutrients important to bone health. We recommend the development of a diet pattern index that better predicts bone mass measures.

General anaesthesia for the cocaine abusing patient. Is it safe?

BACKGROUND: Commonly, cocaine abusing patient are scheduled for elective surgery with a positive urine test for cocaine metabolites. As many of these patients were clinically non-toxic [normal arterial pressure and heart rate, normothermic, and a normal (or unchanged from previous) ECG, including a QTc interval <500 ms], we have recently proceeded with elective surgery requiring general anaesthesia in this patient group. METHODS: Forty urine cocaine positive patients were compared with an equal number of drug-free controls in a prospective, non-randomized, blinded analysis. Intraoperative mean arterial blood pressure, ST segment analysis, heart rate and body temperature were recorded and compared. RESULTS: Cardiovascular stability during and after general anaesthesia in cocaine positive, non-toxic patients was not significantly different when compared with an age and ASA matched drug-free control group. CONCLUSIONS: These results demonstrate that the non-toxic cocaine abusing patient can be administered general anaesthesia with no greater risk than comparable age and ASA matched drug-free patients.

Dynamics of laser-induced electroconvection pulses.

We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/degrees C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10-20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left (right) side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches approximately 0.3. We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

Bioaccumulation profiles of chemical contaminants in fish from the lower Willamette River, Portland Harbor, Oregon.

Twenty-five PCBs (polychlorinated biphenyls), 15 organochlorine (OC) pesticides, and mercury were determined in fish from the Willamette River in Oregon, including a Portland Harbor superfund site. Fish were collected during the summer of 2000 along a 20-mile stretch of the lower Willamette River. Concentrations of sumPCBs (sum of 25 individually determined PCB congeners) and sumDDTs (sum of p,p'-DDT, p,p'-DDE, and p,p'-DDD) in fish ranged from 14 to 530 and from 18 to 510 ng/g-wet weight, respectively. SumPCBs concentrations at all sites exceeded US EPA fish advisory's screening values. Hexachlorobiphenyl congener 153 was the most abundant of the PCBs detected and p,p'-DDE was the most abundant OC pesticide detected. Low levels of dieldrin were detected in fish at all sites with the highest concentration at the superfund site (4.6 ng/g-wet weight), while other OC pesticides tested were near or below detection limits (approximately 2 ng/g). In general, organic chemical contaminant concentrations were highest in fish from the superfund site and were lower further upriver. Smallmouth bass had the highest levels of OC compounds of three fish species examined. They also had the largest site-to-site variations whereas black crappie had little variation throughout the study area. Mercury levels in fish ranged from 13 to 520 ng/g. Historical fish residue data are limited from the Portland Harbor superfund site, what data is available is over a decade old, generally consisted of only a few fish (< or = 3) and analyses quantified only a few PCB congeners (< 3).

Thermal inactivation D- and z-values of Salmonella serotypes and listeria innocua in chicken patties, chicken tenders, franks, beef patties, and blended beef and turkey patties.

Commercially formulated meat products, including chicken patties, chicken tenders, franks, beef patties, and blended beef and turkey patties, were obtained from processors. Each product was inoculated with 7 to 8 logs of Salmonella (Senftenberg, Typhimurium, Heidelberg, Mission, Montevideo, and California) or Listeria innocua. The inoculated meat samples were heat treated at 55 to 70 degrees C. At each temperature, the decimal reduction time (D) was obtained by linear regression of survival curves. Values of D and the temperature difference required for the thermal inactivation curve to drop a logarithmic cycle (z) were determined for the Salmonella serotypes and L. innocua in each product. At 55 to 70 degrees C. for the five tested products, the D-values for the Salmonella serotypes and L. innocua were 26.97 to 0.25 min and 191.94 to 0.18 min, respectively, and their z-values were 7.60 to 9.83 degrees C and 4.86 to 8.67 degrees C, respectively. Significant differences were found for the D- and z-values among the five products. This study will better enable processors to determine the process lethality of pathogens in commercial meat products.

Process lethality and product yield for chicken patties processed in a pilot-scale air-steam impingement oven.

Chicken breast patties were processed in a pilot-scale air-steam impingement oven to a patty center temperature of 55 to 80 degrees C. Thermal processing was conducted at an air temperature of 149 degrees C, an air velocity of 7 to 13 m3/min, and a wet bulb temperature of 39 to 98 degrees C. From thermal histories, the total process lethality of the patties was calculated for Salmonella spp. and Listeria innocua using the previously published z-values. The effect of product temperature, wet bulb temperature, and air velocity on process lethality was analyzed using a regression model. The process lethality of Salmonella spp. and L. innocua in the cooked chicken patties was correlated to the patty center temperatures and cooking conditions. The process lethality was strongly correlated to product temperature and was affected by cooking conditions. Process lethality started to increase rapidly at the product temperature around 67 degrees C. Regression analysis was used to correlate the product yield with cooking conditions. Depending on air velocity, product yield decreased 10 to 14% with increasing endpoint temperature from 55 to 80 degrees C and increased 2 to 9% with increasing wet bulb temperature from 39 to 98 degrees C. The effect of air velocity on the yield interacted with product temperature and wet bulb temperature.

Predicting the activity of phenolic antioxidants: theoretical method, analysis of substituent effects, and application to major families of antioxidants.

A procedure based on density functional theory is used for the calculation of the gas-phase bond dissociation enthalpy (BDE) and ionization potential for molecules belonging to the class of phenolic antioxidants. We show that use of locally dense basis sets (LDBS) vs full basis sets gives very similar results for monosubstituted phenols, and that the LDBS procedure gives good agreement with the change in experimental BDE values for highly substituted phenols in benzene solvent. Procedures for estimating the O--H BDE based on group additivity rules are given and tested. Several interesting classes of phenolic antioxidants are studied with these methods, including commercial antioxidants used as food additives, compounds related to Vitamin E, flavonoids in tea, aminophenols, stilbenes related to resveratrol, and sterically hindered phenols. On the basis of these results we are able to interpret relative rates for the reaction of antioxidants with free radicals, including a comparison of both H-atom-transfer and single-electron-transfer mechanisms, and conclude that in most cases H-atom transfer will be dominant.

Heat transfer properties, moisture loss, product yield, and soluble proteins in chicken breast patties during air convection cooking.

Chicken breast patties were processed in an air convection oven at air temperatures of 149 to 218 C, air velocities of 7.1 to 12.7 m3/min, and air relative humidities of 40 to 95%. The air humidity was controlled via introducing steam into the oven. The patties were processed to a final center temperature of 50 to 80 C. Heat flux, heat transfer coefficient, moisture loss in the cooked chicken patties, the product yield, and the changes of soluble proteins in the product were evaluated for the cooking system. During cooking, heat flux varied with the processing time. Heat flux increased with increasing air humidity. The effective heat transfer coefficient was obtained for different cooking conditions. Air humidity in the oven affected the heat transfer coefficient. The moisture loss in the cooked products increased with increasing the final product temperature and the oven air temperature. The soluble proteins in the cooked patties decreased with increasing the final product temperature. Increasing humidity increased heat transfer coefficient and therefore reduced cooking time. Reducing oven temperature, reducing internal temperature, and increasing air humidity increased the product yield. Soluble proteins might be used as an indicator for the degree of cooking. The results from this study are important for evaluating commercial thermal processes and improving product yields.

Thermal inactivation of Salmonella senftenberg and Listeria innocua in ground chicken breast patties processed in an air convection oven.

Ground chicken breast patties were thermally processed in a lab-scale air convection oven at air temperatures of 163, 177, 190, 204, or 218 C to final patty center temperatures of 50, 55, 60, 65, 70, 75, or 80 C. The cooking time increased with increasing product temperature and decreased with increasing oven air temperature. Prior to thermal processing, approximately 7 log10(cfu/g) of Salmonella senftenberg and Listeria innocua were inoculated into the chicken patties. Survival of S. senftenberg and L. innocua decreased with increasing patty temperature. After the patties were processed to a final center temperature of 70 to 80 C, 1 to 4 log10 (cfu/g) of S. senftenberg and 3 to 5 log10(cfu/g) of L. innocua were detected in the cooked patties. A significant difference in the thermal inactivation of S. senftenberg and L. innocua was obtained between the chicken patties cooked in an air convection oven and the patties cooked in a water bath. More surviving S. senftenberg and L. innocua were found in the patties cooked in an air convection oven than in the patties cooked in a water bath.