An investigation of the shelf life of cold brew coffee and the influence of extraction temperature using chemical, microbial, and sensory analysis.

The shelf-life of cold and hot water extraction coffees based on sensory and chemical profiles and microbial growth was examined, which also allowed the study of the influence of extraction temperature on the chemical and sensorial profiles of coffee. The shelf life of refrigerated cold- and hot-brewed coffee was limited not by microbial stability but rather by deterioration in sensory attributes. Further work is recommended to elucidate the mechanisms of coffee staling in a refrigerated environment, with particular interest in the degradation products of chlorogenic acid, as a significant decline in chlorogenic acid concentration was found over the storage period. Cold-extracted coffees were found to be chemically and sensorially different beverages from coffees extracted at high temperatures. Additionally, the cold-brewed coffees had greater sensory flavor stability over the storage time than the hot-brewed treatment. Practical application: This study advances the industry's understanding of the shelf life of ready-to-drink bottled cold coffees and demonstrates that lower brewing temperatures lead to greater flavor stability over shelf life. The findings also provide brewing parameters that can help guide product developers in modulating the flavor of commercial cold coffees.

The Effect of Different Freezing Rates and Long-Term Storage Temperatures on the Stability of Sliced Peaches.

The purpose of this research was to determine if freezing rates and holding temperatures influence peach quality during short- and long-term frozen storage. Fresh peaches (Prunus persica) were purchased locally, sliced, dipped in 2% ascorbic acid then drained, and packaged. The study was divided into two experiments, one to determine the effect of the freezing rate on peach quality and the second to determine the effect of frozen holding temperatures on peach quality. For the freezing rate experiment, freshly packaged peaches were placed in freezers at different temperatures (-7°C, -12°C, -18°C, -29°C, and -77°C) then removed for testing when the core temperature of the peaches reached the temperature of all freezer temperatures. The second experiment determined the long-term holding effect on quality using both fresh and prefrozen peaches held at -7°C, -12°C, -18°C, -29°C, and -77°C through 360 days. Quality measurements included freeze thaw and weight loss, lightness, firmness, moisture content, ascorbic acid equivalent antioxidant capacity (AAEAC), hexanal detection using gas chromatography (GC), scanning electron microscopy (SEM), and sensory evaluation. During the freezing phase (experiment 1), peach weight loss and surface ice crystal pore size significantly decreased with increased freezing rates. Peaches held at -77°C and -29°C maintained overall quality to a greater degree than the higher holding temperatures. However, all samples enzymatically browned when thawed; therefore, frozen peaches may best if used in the frozen state or in applications where appearance is a critical factor. In general, fresh and prefrozen peaches were not acceptable by the sensory panelists after 270 days of frozen storage.

The Effects of Residual Air and Viscosity on the Rate of Heat Penetration of Retort Food Simulant in Pouch When Using Static and Oscillating Motions.

The objectives of this work were to determine the effect of 3 levels of residual air and 2 different retort motions on the value of the average heating slope of the rate of heat penetration of 3 different viscosities of a food simulant in flexible retort pouches. Pouches were thermally processed in a water spray automated batch retort system using 2 different methods of motion: static and oscillating continuously at a speed of 10.5 rotations per min (RPM) with an angle of 15°. Nine residual air and viscosity combinations were processed during each experimental run: low viscosity with no residual air (LV-NRA), medium viscosity with no residual air (MV-NRA), high viscosity with no residual air (HV-NRA), low viscosity with medium residual air (LV-MRA), medium viscosity with medium residual air (MV-MRA), high viscosity with medium residual air (HV-MRA), low viscosity with high residual air (LV-HRA), medium viscosity with high residual air (MV-HRA), and high viscosity with high residual air (HV-HRA). As the amount of residual air in the pouches increased, the average heating slope value decreased in both static and oscillating motions. As the viscosity of the product increased the amount of residual air affected the average heating slope less in static and oscillating motions. Overall, the oscillating motion resulted in faster rates of heat penetration in all viscosities compared to static mode. The oscillating motion reduced processing times up to 27% compared to static mode. PRACTICAL APPLICATION: This research can be applied to food manufacturers that are retorting foods in pouches. Residual air in pouches has been studied previously; however, with the development of new retort motions, more research needs to be conducted about the effect of residual air in a pouch using the different motions. Food manufacturers can use this information to optimize their amount of residual air based on their product viscosity and retort motion. This could dramatically lower processing time which would save money and increase output as well as potentially increases product quality. This research is aimed at influencing food manufacturers, process authorities, and product developers.

Thermal inactivation of desiccation-adapted Salmonella spp. in aged chicken litter.

Thermal inactivation of desiccation-adapted Salmonella spp. in aged chicken litter was investigated in comparison with that in a nonadapted control to examine potential cross-tolerance of desiccation-adapted cells to heat treatment. A mixture of four Salmonella serovars was inoculated into the finished compost with 20, 30, 40, and 50% moisture contents for a 24-h desiccation adaptation. Afterwards, the compost with desiccation-adapted cells was inoculated into the aged chicken litter with the same moisture content for heat treatments at 70, 75, 80, 85, and 150°C. Recovery media were used to allow heat-injured cells to resuscitate. A 5-log reduction in the number of the desiccation-adapted cells in aged chicken litter with a 20% moisture content required >6, >6, ∼4 to 5, and ∼3 to 4 h of exposure at 70, 75, 80, and 85°C, respectively. As a comparison, a 5-log reduction in the number of nonadapted control cells in the same chicken litter was achieved within ∼1.5 to 2, ∼1 to 1.5, ∼0.5 to 1, and <0.5 h at 70, 75, 80, and 85°C, respectively. The exposure time required to obtain a 5-log reduction in the number of desiccation-adapted cells gradually became shorter as temperature and moisture content were increased. At 150°C, desiccation-adapted Salmonella cells survived for 50 min in chicken litter with a 20% moisture content, whereas control cells were detectable by enrichment for only 10 min. Our results demonstrated that the thermal resistance of Salmonella in aged chicken litter was increased significantly when the cells were adapted to desiccation. This study also validated the effectiveness of thermal processing being used for producing chicken litter free of Salmonella contamination.

Predictive model development for adsorption of aromatic contaminants by multi-walled carbon nanotubes.

In the present study, Quantitative Structure-Activity Relationship (QSAR) and Linear Solvation Energy Relationship (LSER) techniques were used to develop predictive models for adsorption of organic contaminants by multi-walled carbon nanotubes (MWCNTs). Adsorption data for 29 aromatic compounds from literature (i.e., the training data) including some of the experimental results obtained in our laboratory were used to develop predictive models with multiple linear regression analysis. The generated QSAR (r(2) = 0.88), and LSER (r(2) = 0.83) equations were validated externally using an independent validation data set of 30 aromatic compounds. External validation accuracies indicated the success of parameter selection, data fitting ability, and the prediction strength of the developed models. Finally, the combination of training and validation data were used to obtain a combined LSER equation (r(2) = 0.83) that would be used for predicting adsorption of a wide range of low molecular weight aromatics by MWCNTs. In addition, LSER models at different concentrations were generated, and LSER parameter coefficients were examined to gain insights to the predominant adsorption interactions of low molecular weight aromatics on MWCNTs. The molecular volume term (V) of the LSER model was the most influential descriptor controlling adsorption at all concentrations. At higher equilibrium concentrations, hydrogen bond donating (A) and hydrogen bond accepting (B) terms became significant in the models. The results demonstrate that successful predictive models can be developed for the adsorption of organic compounds by CNTs using QSAR and LSER techniques.

Analysis of Salmonella and enterococci isolated from rendered animal products.

The objectives of this study were to determine the current status of bacterial contamination in rendered animal products and to analyze Salmonella and enterococci isolates from the samples. One hundred and fifty samples were provided by various rendering companies across the United States, including the following meal types: feather, meat, meat and bone, meat and bone from poultry, poultry, and blood meals. The average pH of the meals ranged from 6.16 to 7.36, and the moisture content ranged from 1.9% to 11.5%. The total bacterial counts were in the range of 1.7 to 6.68 log10 CFU/g, with the highest in blood meal and the lowest in meat meal. Enterococcus species were detected in 81.3% of the samples and accounted for up to 54% of the total bacterial counts in some samples. Both blood meal and feather meal were more contaminated (P < 0.05) with enterococci than other meal types, although all blood meals were from a single company. Salmonella was detected in 8.7% of the samples. Escherichia coli was not detected in any of the samples, but coliforms were detected in four samples. Among enterococci isolates, three were vancomycin resistant. Thirteen serotypes of Salmonella displayed 16 pulsed-field gel electrophoresis patterns. Pulsed-field gel electrophoresis analysis has indicated that Salmonella contamination was not persistent in the plant environment over time. The D-values for the Salmonella isolates at 55, 60, and 65 degrees C were in the ranges of 9.27-9.99, 2.07-2.28, and 0.35-0.40 min, respectively. These results suggest that the presence of Salmonella in the finished products may be due to postprocessing contamination. This study has also revealed that the rendering industry has microbiologically improved its products since earlier studies were conducted.

Drought impact on forest growth and mortality in the southeast USA: an analysis using Forest Health and Monitoring data.

Drought frequency and intensity has been predicted to increase under many climate change scenarios. It is therefore critical to understand the response of forests to potential climate change in an effort to mitigate adverse impacts. The purpose of this study was to explore the regional effects of different drought severities on tree growth and mortality. Specifically, we investigated changes in growth and mortality rates across the southeastern United States under various drought and stand conditions using 1991-2005 Forest Health and Monitoring (FHM) plot data from Alabama, Georgia, and Virginia. Drought effects were examined for three species groups (pines, oaks, and mesophytic species) using the Palmer drought severity index (PDSI) as an indicator of drought severity. Stand variables, including total basal area, total tree density, tree species richness, slope, and stand age, were used to account for drought effects under varying stand conditions. The pines and mesophytic species exhibited significant reductions in growth rate with increasing drought severity. However, no significant difference in growth rate was observed within the oak species group. Mean mortality rates within the no-drought class were significantly lower than those within the other three drought classes, among which no significant differences were found, for both pines and mesophytic species. Mean mortality rates were not significantly different among drought classes for oaks. Total basal area, total tree density, and stand age were negatively related to growth and positively related to mortality, which suggests that older and denser stands are more susceptible to drought damage. The effect of basal area on growth increased with drought severity for the oak and mesophytic species groups. Tree species richness was negatively related to mortality for the pine and mesophytic species groups, indicating that stands with more species suffer less mortality. Slope was positively related to mortality within the mesophytic species group, and its effect increased with drought severity, indicating a higher mortality on sites of greater slope during severe-drought conditions. Our findings indicate that pines and mesophytic species are sensitive to drought, while oaks are tolerant of drought. The observed differential growth and mortality rates among species groups may alter the species composition of southeastern U.S. forests if drought episodes become more frequent and/or intense due to climate change. The significant effects of stand conditions on drought responses observed in our study also suggest that forest management may be used as a tool to mitigate drought effects.

Effect of combining nisin and/or lysozyme with in-package pasteurization for control of Listeria monocytogenes in ready-to-eat turkey bologna during refrigerated storage.

This study investigated the efficacy of in-package pasteurization combined with pre-surface application of nisin and/or lysozyme to reduce and prevent the subsequent recovery and growth of Listeria monocytogenes during refrigerated storage on the surface of low-fat turkey bologna. Sterile bologna samples were treated with solutions of nisin (2 mg/ml=5000 AU/ml), lysozyme (10 mg/ml=80 AU/ml) and a mixture of nisin and lysozyme (2 mg nisin+10mg lysozyme/ml) before in-package pasteurization at 65 degrees C for 32s. In-package pasteurization resulted in an immediate 3.5-4.2 log CFU/cm(2) reduction in L. monocytogenes population for all treatments. All pasteurized treatments also resulted in a significant reduction of L. monocytogenes by 12 weeks compared to un-pasteurized bologna. In-package pasteurization in combination with nisin or nisin-lysozyme treatments was effective in reducing the population below detectable levels by 2-3 weeks of storage. Results from this study could have a significant impact for the industry since a reduction in bacterial population was achieved by a relatively short pasteurization time and antimicrobials reduced populations further during refrigerated storage.

Effect of combining nisin and/or lysozyme with in-package pasteurization on thermal inactivation of Listeria monocytogenes in ready-to-eat turkey bologna.

Achieving a targeted lethality with minimum exposure to heat and preservation of product quality during pasteurization is a challenge. The objective of this study was to evaluate the effect of nisin and/or lysozyme in combination with in-package pasteurization of a ready-to-eat low-fat turkey bologna on the inactivation of Listeria monocytogenes. Sterile bologna samples were initially treated with solutions of nisin (2 mg/ml = 5,000 AU/ml = 31.25 AU/cm2), lysozyme (10 mg/ml = 80 AU/ml = 0.5 AU/cm2), and a mixture of nisin and lysozyme (2 mg/ml nisin + 10 mg/ml lysozyme = 31.75 AU/cm2). Bologna surfaces were uniformly inoculated with a Listeria suspension resulting in a population of approximately 0.5 log CFU/cm2. Samples were vacuum packaged and subjected to heat treatment (60, 62.5, or 65 degrees C). Two nonlinear models (Weibull and log logistic) were used to analyze the data. From the model parameters, the time needed to achieve a 4-log reduction was calculated. The nisin-lysozyme combination and nisin treatments were effective in reducing the time required for 4-log reductions at 62.5 and 65 degrees C but not at 60 degrees C. At 62.5 degrees C, nisin-lysozyme-treated samples required 23% less time than did the control sample to achieve a 4-log reduction and 31% less time at 65 degrees C. Lysozyme alone did not enhance antilisterial activity with heat. Results from this study can be useful to the industry for developing an efficient intervention strategy against contamination of ready-to-eat meat products by L. monocytogenes.