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Foodborne outbreaks associated with Shiga toxin-producing Escherichia coli (STEC) contaminated wheat flour have been an increasing food safety concern in recent decades. However, there is little literature aimed at investigating the impact of different flour types on the persistence of STEC during storage and thermal inactivation. Therefore, two serovars of STEC, O121 and O157, were selected to inoculate each of five different types of common wheat flours: whole wheat, bleached, unbleached, bread, and self-rising. Inoculated flours were examined for the stability of STEC during storage for up to 42 days at room temperature (RT) and aw ~0.56. Additionally, the thermal resistance of O121 and O157 under isothermal conditions at 60, 70, 80, and 90°C was analyzed for the inoculated flours. STEC storage persistence at RT was generally not affected by flour type, however, decreases of 1.2 and 2.4 log CFU/day within whole wheat flour for O121 and O157, respectively, were significantly lower than other flours. Though few differences were identified in relation to flour type, O121 exhibited significantly better survival rates than O157 during both equilibrium and storage periods. Compared to an approximate 6 log reduction in the population of O157, O121 population levels were reduced by a significantly lower amount (~3 log) during the entire storage period at RT. At each isothermal temperature, the impact of flour type on the thermal resistance capabilities of O121 or O157 was not a significant factor and resulted in similar survival curves regardless of serovar. Instead of exhibiting linear survival curves, both O121 and O157 displayed nonlinear curves with some shoulder/tail effect. Similar for both O121 and O157, the predicted decimal reduction time (D-value) decreased from approximately 25 min to around 8 min as the isothermal temperature increased from 60°C to 90°C. Results reported here can contribute to risk assessment models concerning contamination of STEC in wheat flour and add to our understanding of the impacts of flour type and STEC serovar on desiccation stability during storage and isothermal inactivation during thermal treatment. [ABSTRACT FROM AUTHOR]

The microbiome, an important aspect of fish aquaculture, is influenced by exogenous factors in the rearing environment including the composition and nutrient quality of the diet. To reduce reliance on fishmeal, alternative protein sources including yeast (Saccharomyces cerevisiae), have been successfully used in many aquafeeds. To investigate the effect of supplemented lysed and dried yeast on the fish physiology, including the intestinal epithelial‐associated microbiome composition, rainbow trout (Oncorhynchus mykiss) were fed a standard commercial diet or one of four additional in‐house extruded experimental diets containing 0%, 20%, 40% or 60% yeast nutrient supplement as a menhaden fishmeal substitute for 16 weeks. The commercial diet, 0%, and 20% supplement‐fed fish had similar average weight gains that were significantly (p < 0.05) higher in comparison to groups with a higher percentage of yeast. To examine if the yeast‐supplemented diet had any impact on the intestinal epithelial‐associated microbiome, both phylum‐ and family‐level comparisons of the microbial communities across treatments were made. The dominant families were Mycoplasmataceae and Fusobacteriaceae with Mycoplasma spp. and Cetobacterium somerae being the dominant organisms, respectively. Results from bioinformatics analysis showed little community variation between experimental diets, suggesting that lysed and dried yeast will serve as a dietary supplement without causing large shifts in the intestinal microbiome community. [ABSTRACT FROM AUTHOR]