In this study, we determined the effect of nutritive sweeteners at 0 to 0.50 moles/kg on lipid oxidation in a model cookie system. Confocal microscopy using Bodipy 493 as a fat soluble dye showed that the fat formed a continuous phase surrounding the starch granules regardless of sugar type. The impact of glucose concentration on lipid oxidation was monitored by lipid hydroperoxides and headspace hexanal during storage at 55°C. Low concentrations of glucose (0.09) were strong inhibitors. At equal molar concentrations, reducing sugars (glucose and fructose) inhibited lipid oxidation, greater than a two months increase in lag phase compared to the control. Sucrose inhibited lipid oxidation, but to a much lesser extent than reducing sugars. The inhibition of lipid oxidation is potentially due to sugar’s ability to bind water. Additionally, reducing sugars may exhibit this effect due to their ability to act as a hydrogen donor which could inactivate free radicals or due to the production of Maillard reaction products (MRPs). For example, the l-values were lower and b-values were higher for cookies with non-reducing sugars compared to cookies with sucrose indicating that there were more MRPs. The addition of cysteine, sulfites, and ascorbic acid acted as a strong browning inhibitors however cysteine was showed to be antioxidative. When compared to synthetic antioxidants, glucose proved to be a strong natural alternative. These results could be utilized to develop effective means of controlling water activity and extending shelf-life of low moisture baked goods.

Cronobacter sakazakii is a gram-negative opportunistic pathogen known to survive in dry environments and food matrices, such as infant formula. This foodborne bacterium can cause fatal human infections of the blood, central nervous system, and gastrointestinal tract; it is also problematic in wounds and urinary tract infections. Preterm infants and immunocompromised individuals are in higher risk categories related to necrotizing enterocolitis, neonatal sepsis, and meningitis due to this organism. Therefore, there is a need for increased understanding of how this bacterium is able to persist in thermally treated low-moisture products that do not support growth. The objective of this research is to identify genes and mechanisms in C. sakazakii that contribute to its resistance to desiccation and survival in low-moisture food matrices, including powdered infant formula. C. sakazakii sequence type 4 (ST4) is of particular interest as it is often the cause of neonatal infections originating from contaminated feedings of powder infant formula. The method chosen to explore these genetic patterns is massively parallel transposon insertion sequencing (Tn-seq). The E. coli strain MFDpir was used to facilitate transposon insertional mutagenesis to create a library of mutated C. sakazakii. Three different C. sakazakii ST4 isolates of different origins (clinical, environmental, and infant formula-derived) were selected for this study. Once transposon mutagenesis occurred with the aid of E. coli MFDpir, the three mutant libraries were subjected to desiccation stress in a closed system equilibrated to 11.3% relative humidity. The surviving mutant genomes were analyzed with Tn-seq. The sequencing data revealed that, while transposition events did occur successfully within the genomes of each of the selected C. sakazakii isolates, these events were not dense enough to draw biological conclusions nor statistical inferences concerning which genes contribute to this organism’s uncanny desiccation tolerance. However, we concluded that the Tn-seq method is a promising tool with this organism of interest, despite incomplete results in this first round of experimentation.

No description available.

Pathogens in low-moisture foods are an emerging food safety concern due to increased survival and thermotolerance in matrices with low water activity. However, limited data is publicly available for the thermotolerance of Listeria monocytogenes, Salmonella spp., and Enterococcus faecium NRRL B-2354 (a Salmonella surrogate). The aims of this study were to identify differences in thermal inactivation rates between these organisms in three different low-moisture foods. Three model low-moisture foods (peanut butter, powder infant formula, and wheat flour) were inoculated with either E. faecium, a Salmonella spp. cocktail, or a L. monocytogenes cocktail using a dry inoculation method for a total of 9 treatments. Samples were heat treated in a hot water bath at predetermined temperatures, and bacterial survival was detected via direct plating on tryptic soy agar with 0.6% yeast extract. In peanut butter and most of the powder infant formula treatments, Salmonella spp. had significantly higher D-values than L. monocytogenes using comparable temperatures (p < 0.05). However, D-values between Salmonella spp. and L. monocytogenes were comparable in wheat flour and one of the treatment temperatures in powder infant formula (p > 0.05). For all but one of the treatments at the same temperature, E. faecium had significantly higher D-values than L. monocytogenes and Salmonella spp. in each food matrix (p < 0.05). The observed matrix effect on thermotolerance for each of the bacteria was reported in descending order as powder infant formula > peanut butter > wheat flour in the majority of the comparable D-values. While Salmonella continues to be the pathogen of concern in low-moisture foods due to survival and outbreaks, these results indicate L. monocytogenes can exhibit similar thermotolerances in relevant model low-moisture foods matrices.

Vegetative, non-sporeforming foodborne pathogens show notable survival and uncanny thermotolerance in low water activity (aw) foods. Controlled studies on Listeria monocytogenes, Salmonella spp., and Enterococcus faecium NRRL B-2354 (a Salmonella surrogate) in a variety of food matrices support thermal process validation studies required to achieve global food safety objectives. In this study, we determined and compared thermal inactivation rates using independent six-strain cocktails of pathogens in three plant-based butters. Direct determinations of decimal reduction times (D-values) for L. monocytogenes, Salmonella, and E. faecium, in corresponding butters were inoculated using peanut oil, almond oil, or sunflower oil. Thermal Death Time (TDT) studies for the organisms were conducted in triplicate. Uniform bagged plant- based butter samples of Salmonella spp. or L. monocytogenes, or E. faecium alone were sandwiched in copper plates immobilized with recessed magnets. Samples underwent rapid heat treatments via water immersion under isothermal conditions ranging from 70°C to 85°C. Bacterial destruction in peanut butter (46% fat, 0.20 aw @ 25°C), almond butter, (50% fat, 0.32 aw @ 25°C), or sunflower butter (56% fat, 0.15 aw @ 25°C) was determined by direct plating. The TDT studies showed Salmonella spp. had consistently higher D-values than L. monocytogenes in all treatments, but pair-wise comparisons found no statistical difference when assessing the thermotolerance of the two pathogens in the individual plant-based butters tested (p > 0.005). These data support Salmonella as the primary pathogen of concern in low water activity foods and show the heat resistance of L. monocytogenes can approximate destruction kinetics observed for Salmonella spp. in low aw matrices. E. faecium exhibited the highest thermotolerance. This further supports the utility of this surrogate for Salmonella spp. and L. monocytogenes in high fat, low-moisture foods similar to the plant-based butters tested. Thermotolerance differences between a dry talc vs. peanut oil-based inoculation procedures in peanut butter were also evaluated. Surprisingly, the oil-based inoculations resulted in lower D- values (p > 0.01) for Salmonella spp. and the surrogate when compared to the dry inoculum.

<p>In recent years, numerous multistate foodborne outbreaks have been reported that are often associated with low moisture foods (LMFs). The survival of microorganisms in low moisture conditions has become one of the major concerns in the food industry. With the increasing number of recalls, it is necessary to ensure food safety by developing and validating the process parameters. Establishing a thermal process requires a detailed understanding of the inactivation kinetics of the target pathogen with respect to both the process (temperature, time, equipment) and the product conditions (water activity, composition). Along with the most widely used conventional thermal processing, there has been an increase in the demand for natural or minimally processed foods. As a result, many alternative non-thermal processing approaches that provide antimicrobial benefits while retaining the quality attributes of the food product are under investigation. This research focused on studying the inactivation kinetics of foodborne pathogens <em>Salmonella enteritidis</em> PT30 and <em>Cronobacter</em> <em>sakazakii</em> in powdered LMFs using both the thermal and non-thermal (cold plasma) processing technologies. The efficacy of a dielectric barrier discharge cold plasma equipment was tested against pathogens <em>Salmonella</em> <em>enteritidis</em> PT30 and <em>Cronobacter</em> <em>sakazakii</em> in LMFs at 70 kV, resulting in 3.8 log reduction in <em>Cronobacter</em>, and 4.41 log reduction in <em>Salmonella</em> after 5 min of cold plasma treatment in pea protein. The cellular damage to the pathogens was examined by transmission electron microscopy (TEM), and the reactive oxygen (ROS: OH, O) and nitrogen (RNS: N₂, N₂⁺) species were identified using optical emission spectroscopy. The RMSE for the model was found to be between 0.11 and 0.36 with the low standard error of the parameters (δ, n, and log N₀), which illustrated that the Weibull model was a good fit for the experimental inactivation data. </p> <p>In the thermal processing study, the inactivation kinetic parameters of these pathogens were estimated at 70, 80, and 90 °C at 0.11, 0.22, and 0.33 water activity in pea protein powder. The non-isothermal temperature profiles were simulated by building a two dimensional, axisymmetric heat transfer model of the test cell. The inactivation parameters D_ref, z_T, and z_aw were estimated in MATLAB by using a one-step non-linear regression analysis, which was a combination of the primary log-linear model with the secondary modified-Bigelow model. The model was found to be a good fit, showing lower root mean square error (RMSE) and residuals. Further, <em>Enterococcus</em> <em>faecium</em> was observed to have higher D-values at all the processing temperatures and water activity levels as compared to <em>Salmonella enteritidis</em> PT30 and <em>Cronobacter</em> <em>sakazakii</em>, which provides valuable evidence that <em>Enterococcus</em> <em>faecium</em> can be used as a surrogate microorganism for validating the thermal process for pea protein powder.</p>