Relative Resistance of the Red, Dry, and Rough (RDAR) and Smooth and White (SAW) Morphotypes expressed by Salmonella to a steam blanching treatment

The acquired ability of Salmonella to express varying morphotypes when placed in nutrient-limited conditions is hypothesized to predict increased resistance to food processing interventions. Two of the morphotypes expressed by Salmonella are Red, Dry and Rough (RDAR) and Smooth and White (SAW). Increased resistance is predicted for the RDAR morphotype due to the expression of thin aggregative fimbriae (tafi) coupled with production of cellulose and other potentially protective extracellular polysaccharides. SAW strains are hypothesized to be less resistant due to their lack of tafi and cellulose production. Strains of Salmonella, previously classified as RDAR (n=3) and SAW (n=3), were separately inoculated on the shell surface of hazelnuts and steam blanched (88°C, 1 minute) to determine resistance patterns between the two morphotypes. The steam treatment resulted in insignificant reduction (<1.0 log CFU/g) of all Salmonella strains; therefore, differences in the relative resistance of the two morphotypes were unable to be determined. Additional, steam treatments with longer hold times will be tested to further explore the potential difference between morphotypes

Influence of cheese-making recipes on the composition and characteristics of Camembert-type cheese

Bloomy rind cheeses, including Camembert and related varieties, can he produced using alternative processes that vary based on milk preacidification, cutting, curd handling, and ripening parameters. Modification of these parameters creates distinct cheeses such as lactic curd, stabilized curd, and hybrids of the two. The objective of this study was to determine the influence of 5 Camembert-type cheese recipes on the composition and characteristics during ripening. Five varieties of Camembert-type cheese were produced: (1) lactic curd, (2) sweet curd, (3) washed curd, (4) solubilized curd, and (5) stabilized curd. Cheeses were aged at 13 degrees C for 10 d, during the mold growth phase, and 7 degrees C from d 11 until 50. Key quality metrics including texture development, pH (center and surface), and color were monitored throughout shelf-life. Compositional evaluation (d 5; fat, protein, moisture, salt, and minerals) grouped cheeses into 3 categories: (1) lactic curd, (2) sweet and washed curd, and (3) solubilized and stabilized curd. The lactic curd and stabilized curd were consistently the most different varieties for composition and quality metrics. Moisture content of Camembert-type varieties ranged from 53.15 to 57.99%, Ca ranged from 0.23 to 0.45%, and P ranged from 0.21 to 0.40%. All varieties followed the expected pH evolution on the rind and in the paste with the pH of the rind reaching 7 by d 10, and paste pH reaching 7 between 35 and 50 d. The displacement of the paste (distance traveled upon cutting) for the lactic curd was the greatest among the 5 varieties, reaching an average of 27 +/- 1.9 mm (mean +/- standard error) after 50 d of ripening and 60 min of flow time. The stabilized curd on the other hand traveled the shortest distance, reaching an average of 4 +/- 0.4 mm at the same time point. Browning, considered a defect in mold-ripened cheeses, was observed in all varieties, but was most substantial for lactic curd (lightness, L*, decreased from 87.19 to 68.58). Based on these quality metrics the shelf-life of these recipes was estimated with the lactic curd having the shortest, and the stabilized curd having the longest. Examining Camembert-type cheese quality metrics for these 5 varieties can assist cheesemakers during recipe formulation and selection of cheese-making practices to achieve optimum product quality

Flow rate of depuration system has minimal impact on Vibrio parahaemolyticus decontamination in Pacific oysters (Crassostrea gigas)

Vibrio parahaemolyticus infections in the United States have been linked to consumption of raw oysters. Depuration has the potential to reduce contamination in live oysters after harvest. This study investigated the impact of depuration flow rate to reduce V. parahaemolyticus in raw oysters. Pacific oysters (n = 35 per trial) were inoculated with a cocktail of V. parahaemolyticus (10290, 10292, 10293, BE 98-2029, and 027-1c1) in freshly prepared artificial seawater (70 L). The inoculated oysters were depurated with flow rates of 15, 20, 25, and 35 L/min at 12.5 degrees C for up to 5 days and V. parahaemolyticus contamination was determined using a three-tube most probable number (MPN) method. V. parahaemolyticus reductions were as flow rate moderately increased from 15 L/min (2.39 log MPN/g reduction in 5 days) to 35 L/min (3.39 log MPN/g reduction). These results suggest that depuration efficacy can be enhanced by increasing depuration flow rate to 35 L/min. Practical applications Vibrio parahaemolyticus can contaminate raw shellfish, including oysters, during their production and lead to outbreaks of foodborne illness. Depuration, a post-harvest process, may be used by the shellfish industry to reduce the persistence of V. parahaemolyticus. Previous studies have demonstrated that the depuration process can reduce V. parahaemolyticus in oysters; however, further optimization of the process is necessary to achieve US Food Drug Administration's targeted reduction goal (>3.52 log MPN/g). This study evaluated the impact of depuration flow rate on the reduction of V. parahaemolyticus in Pacific oysters. Increasing flow rates (15-35 L/min) during depuration enhanced the clearance of V. parahaemolyticus in these oysters; however, these conditions were unable to consistently achieve the target of >3.52 log MPN/g reduction. This study provides a reference for the industry on the variability of V. parahaemolyticus in individual oysters and demonstrates that practical modifications (i.e., flow rate) can be implemented in depuration systems to maximize bacterial clearance

Callahan Poster - JWC.pdf

The acquired ability of Salmonella to express varying morphotypes when placed in nutrient-limited conditions is hypothesized to predict increased resistance to food processing interventions. Two of the morphotypes expressed by Salmonella are Red, Dry and Rough (RDAR) and Smooth and White (SAW). Increased resistance is predicted for the RDAR morphotype due to the expression of thin aggregative fimbriae (tafi) coupled with production of cellulose and other potentially protective extracellular polysaccharides. SAW strains are hypothesized to be less resistant due to their lack of tafi and cellulose production. Strains of Salmonella, previously classified as RDAR (n=3) and SAW (n=3), were separately inoculated on the shell surface of hazelnuts and steam blanched (88°C, 1 minute) to determine resistance patterns between the two morphotypes. The steam treatment resulted in insignificant reduction (<1.0 log CFU/g) of all Salmonella strains; therefore, differences in the relative resistance of the two morphotypes were unable to be determined. Additional, steam treatments with longer hold times will be tested to further explore the potential difference between morphotypes

Callahan Poster - JWC.pptx

The acquired ability of Salmonella to express varying morphotypes when placed in nutrient-limited conditions is hypothesized to predict increased resistance to food processing interventions. Two of the morphotypes expressed by Salmonella are Red, Dry and Rough (RDAR) and Smooth and White (SAW). Increased resistance is predicted for the RDAR morphotype due to the expression of thin aggregative fimbriae (tafi) coupled with production of cellulose and other potentially protective extracellular polysaccharides. SAW strains are hypothesized to be less resistant due to their lack of tafi and cellulose production. Strains of Salmonella, previously classified as RDAR (n=3) and SAW (n=3), were separately inoculated on the shell surface of hazelnuts and steam blanched (88°C, 1 minute) to determine resistance patterns between the two morphotypes. The steam treatment resulted in insignificant reduction (<1.0 log CFU/g) of all Salmonella strains; therefore, differences in the relative resistance of the two morphotypes were unable to be determined. Additional, steam treatments with longer hold times will be tested to further explore the potential difference between morphotypes

Before and After: Evaluation of Microbial and Organic Loads in Produce Handling and Packing Operations with Diverse Cleaning and Sanitizing Procedures

Inadequate cleaning and/or sanitation (C/S) of food contact surfaces (FCSs) has been frequently reported during Produce Safety Rule inspections; however, limited data are available evaluating the effectiveness of C/S processes in produce operations. Different C/S practices were evaluated in four fresh produce operations for their efficacy in reducing microbial and organic loads on various FCSs. Microbial (aerobic plate counts; APC) and organic (ATP) loads were quantified during production, after cleaning, and after sanitizing, if applicable. Operations included: a berry packinghouse (BerryPK; wet cleaning), a blueberry harvest contractor (BerryHC; cleaning + sanitizing, C+S), and two mixed vegetable packinghouses (MixedV1; C+S, and MixedV2; rinsing + sanitizing, R+S). Following wet cleaning, significant reductions in APCs (p < 0.05) were seen on high-density polyethylene (HDPE) storage trays (n = 50) in BerryPK (3.1 ± 0.9 to 2.5 ± 0.7 log CFU/100 cm2). In BerryHC, a greater reduction in APCs was seen on HDPE harvest buckets (n = 25) following C+S (3.8 ± 0.5 to 1.1 ± 0.4 log CFU/100 cm2), compared to wet cleaning only in BerryPK. Stainless steel and conveyor belt FCSs (n = 16) in MixedV1 were sampled, and a significant reduction in APCs (p < 0.05) was observed when comparing in-use (4.8 ± 1.3 log CFU/100 cm2) to post-C+S (3.9 ± 0.7 log CFU/100 cm2). When similar FCSs (n = 17) were sampled in MixedV2, R+S also led to significant reduction in APCs (3.3 ± 0.6 to 1.9 ± 0.6 log CFU/100 cm2) (p < 0.05). ATP testing in fresh produce settings yielded inconsistent results, with no correlation between organic and bacterial loads detected during production (R2 = 0.00) across four operations, and weak correlations observed after cleaning (R2 = 0.18) and after sanitation (R2 = 0.33). The results from this study provide the foundational basis for future research on practical and effective C/S methods tailored to the produce industry

Application of Whole Genome Sequencing to Understand Diversity and Presence of Genes Associated with Sanitizer Tolerance in Listeria monocytogenes from Produce Handling Sources

Recent listeriosis outbreaks linked to fresh produce suggest the need to better understand and mitigate L. monocytogenes contamination in packing and processing environments. Using whole genome sequencing (WGS) and phenotype screening assays for sanitizer tolerance, we characterized 48 L.&nbsp;monocytogenes isolates previously recovered from environmental samples in five produce handling facilities. Within the studied population there were 10 sequence types (STs) and 16 cgMLST types (CTs). Pairwise single nucleotide polymorphisms (SNPs) ranged from 0 to 3047 SNPs within a CT, revealing closely and distantly related isolates indicative of both sporadic and continuous contamination events within the facility. Within Facility 1, we identified a closely related cluster (0–2 SNPs) of isolates belonging to clonal complex 37 (CC37; CT9492), with isolates recovered during sampling events 1-year apart and in various locations inside and outside the facility. The accessory genome of these CC37 isolates varied from 94 to 210 genes. Notable genetic elements and mutations amongst the isolates included the bcrABC cassette (2/48), associated with QAC tolerance; mutations in the actA gene on the Listeria pathogenicity island (LIPI) 1 (20/48); presence of LIPI-3 (21/48) and LIPI-4 (23/48). This work highlights the potential use of WGS in tracing the pathogen within a facility and understanding properties of L.&nbsp;monocytogenes in produce settings