About

Professor Abby Snyder leads the Microbial Food Safety and Spoilage Lab within the Department of Food Science at Cornell University, located in Stocking Hall. Her lab's research encompasses a diverse range of skills including wet-lab microbiology, bioinformatics, qualitative surveys, and modeling. The lab regularly engages in extension outreach and collaborates closely with food processing facilities in New York State. A notable sub-research group within her lab is the Microbial Safety of Infant Feeding Lab, which focuses specifically on the microbial safety of formula and breastmilk. Professor Snyder's lab welcomes prospective graduate students, undergraduates, postdoctoral researchers, and visiting scholars to join their efforts in advancing microbial food safety and spoilage research.

Research topics

• Biology
• Food science
• Environmental engineering
• Ecology
• Psychology
• Microbiology
• Environmental health
• Biochemistry
• Biotechnology
• Environmental science
• Medicine
• Business

Selected publications

• Variable fluid mechanics explain why static efficacy tests overestimate sanitizer performance against Listeria

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-05-13

  articleSenior author

  ABSTRACT Pathogen cross-contamination during food production is primarily controlled through environmental sanitation. However, sanitizer efficacy is often studied in bench-scale experiments that poorly approximate the fluid dynamics of sanitization and limits our understanding of commercial sanitization efficacy. This study paired computational fluid dynamics (CFD) estimates of shear stress with experimental measurements of Listeria innocua reduction on stainless steel following treatment with 100 ppm hypochlorite sanitizer. At the pilot-scale, sanitizer spray manually applied by researchers achieved a 2.6 ± 0.4 log CFU/surface reduction; however, microbial reduction from manual operation of sanitizer spray equipment differed significantly between researchers (p < 0.05). Microbial reduction varied by location following stationary, bench-scale spray application of sanitizer for 3 s. The greatest reduction was at the point of sanitizer spray impingement (7.5 ± 0.5 log CFU/surface) and directly adjacent to the impingement point (6.4 ± 0.7 log CFU/surface) where shear stress was the highest. Significantly less microbial reduction (0.4 ± 0.1 log CFU/surface) occurred where shear stress was lowest in the fluid-film of sanitizer running down from the impingement point (p < 0.05). Static submersion of inoculated coupons in sanitizer for 3 s resulted in a log reduction of 2.3 ± 0.1 log CFU/surface. Discrepancies between bench-scale spraying, pilot-scale spraying, and submerged coupons demonstrate the need for sanitizer efficacy testing under realistic conditions to better estimate the risk reduction achieved through sanitation programs. IMPORTANCE Sanitation is critical for controlling pathogen cross-contamination during food production. These findings highlight the limitations of traditional approaches to sanitizer efficacy testing, not because they are invalid, but because they do not reflect the level of microbial reduction typically achieved in application. We demonstrate that these differences in outcomes are attributable to fluid dynamics and exposure, which are not well approximated in submerged coupon experiments. Accurate estimation of microbial reduction from sanitizer application is needed to guide food safety policy decisions. For example, overestimation of the risk reduction conferred by sanitizer treatment may result in food safety policies that neglect other sources of microbial reduction within sanitation programs.

  PublisherDOI

• Superheated Steam Can Rapidly Inactivate Bacteria, But Manual Operation of Commercial Units Resulted in Limited Efficacy During Dry Surface Sanitization

  Journal of Food Protection · 2025-02-01 · 3 citations

  articleOpen accessSenior authorCorresponding

  • Temperature decreases >4.5 cm from the impingement limit the radius for sanitation. • Short exposure (10 s) led to high kill (9.6 log) at the impingement point. • Training and experience with a unit significantly increased microbial inactivation. • With training and experience, the highest reduction was 3.56 ± 1.27 log CFU/cm 2 . • Optimizing steam dispersal and trainings may improve large-surface sanitization. Although bench-scale studies have shown that superheated steam is effective for microbial inactivation on surfaces, commercial systems in the hands of human operators have not been evaluated. The first aim of this study was to characterize the temperature of stainless-steel surfaces treated with a commercial unit. The geometric center of the stainless-steel surface was treated with superheated steam at 400 °C from a fixed position. Surface temperatures exceeded 300 °C at the impingement point during 5 min exposure but decreased as surface thickness and distance increased. Ambient temperature (23.5, 12.8, 4 °C) negatively impacted surface temperatures. Next, we evaluated the thermal inactivation of spot-inoculated Enterococcus faecium NRRL B-2354 on stainless steel surfaces. Inactivation of E. faecium decreased from 9.6 ± 0.1 log CFU/cm 2 after 10 s of treatment at the point of impingement to 2.8 ± 0.7 log CFU/cm 2 after 10 s of treatment at a distance 4.6 cm away from the impingement point ( p < 0.05). Finally, we assessed the effects of training on manual operation by human subjects. Human subjects ( N = 24) who completed trainings were asked to treat inoculated stainless-steel surfaces. While training improved manual operation of the unit and microbial inactivation of E. faecium ( p < 0.05), the highest average reduction achieved by human subjects was only 3.6 ± 1.3 log CFU/cm 2 . These findings suggest that the tight radius of high surface temperatures around the nozzle limits the effectiveness of manually operated superheated steam units for microbial inactivation. Thus, equipment design improvements are needed to ensure uniform treatment and adequate surface sanitation.

  PublisherDOI

• Cell recovery and DNA extraction methods skew relative abundance estimations of foodborne pathogens and spoilage organisms on stainless steel surfaces

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-11-04

  preprintOpen accessSenior authorCorresponding

  Abstract Studies investigating surface microbiota in food facilities often include estimates of relative abundance. However, obtaining accurate relative abundance values can be challenging. Differences among microbes can lead to different degrees of cell recovery from the surface and different DNA extraction yields that skew downstream relative abundance estimates. Here, we evaluated (1) the impact of cell recovery from surfaces using sponge swabs and (2) DNA extraction protocol on the relative abundance estimates of relative abundance on artificially inoculated surfaces. Our results showed that Escherichia coli (Gram-negative cell) , Listeria monocytogenes (Gram-positive cell), Bacillus cereus (bacterial spore), Alicyclobacillus suci (bacterial spore), Exophiala phaeomuriformis (fungal cell), Aspergillus fischeri (fungal spore) differed significantly (p&lt;0.05) in their recovery rates from stainless steel surfaces, ranging from 2.9%±3.0% recovery to 94.9%±3.0% recovery. Modification of the DNA extraction protocol by extending the bead-beating step by 10 min generally improved DNA yields, though the impact varied by organism. For example, DNA yields of E. coli increased from 70 to 84 ng/mL while that of L. monocytogenes increased only from 23.2 to 29.2 ng/mL. Amplicon sequencing results indicated that the differences in cell recovery and DNA extraction among microbial species skewed the relative abundance estimates from inoculated surfaces. For example, the estimated relative abundance of L. monocytogenes was 9-17%, which was lower than its actual relative abundance (25%). These results underscore the limitations of surface microbiota characterization in food facilities and highlighted the need to improve current recovery and DNA extraction methods. Importance Amplicon sequencing has been used to characterize microbial communities on facility surfaces. However, few studies have evaluated the accuracy of the amplicon sequencing workflow for quantifying spoilage and pathogenic organisms in these microbial communities. Here, we assessed the accuracy for amplicon sequencing to evaluate the relative abundance of spoilage and pathogenic organisms commonly found in food processing environments. The results revealed biases in relative abundances due to limitations in cell recover and DNA extraction methods. These findings revealed the potential biases in surface microbiota characterization in food facilities, and the need to refine current recovery and extraction methods to enhance the accuracy of microbiota characterization.

  PublisherDOI

• A simulation model to quantify the efficacy of dry cleaning interventions on a contaminated milk powder line

  Applied and Environmental Microbiology · 2025-04-17 · 4 citations

  articleOpen accessSenior author

  ABSTRACT Outbreaks of Salmonella in low moisture foods have been caused by cross-contamination from the processing environment into product. We used Monte Carlo simulations to model the impact of hypothetical cross-contamination scenarios of Salmonella from production equipment into milk powder. Model outputs included the quantity and extent of the contaminated product from a production line. Outputs were used to compare the efficacy of cleaning interventions. Cross-contamination of potential dry cleaning surrogates was also modeled. Input parameters for the model included log reductions from wiping an inoculated surface with a dry towel and transfer coefficients from an inoculated surface to milk powder. After a 2-log CFU contamination breach ( Salmonella introduced to an 8.4 cm 2 stainless-steel surface on the processing line before production), the number of consumer-sized milk powder units (300 g) contaminated with Salmonella was 72 [24, 96] (median [p5, p95] across 1,000 simulation iterations). The average concentration of Salmonella within contaminated units was −2.33-log CFU/g [–2.46, –1.86]. Wiping the contaminated surface with a dry towel before the production of milk powder reduced the number of contaminated units to 26 [12, 64]. Flushing the contaminated surface with 150 kg of milk powder prior to milk powder production reduced the number of contaminated units to 0 [0, 41]. Flushing with 300 kg of milk powder further reduced the number of contaminated milk powder units to 0 [0, 16]. Enterococcus faecium resulted in a similar number of contaminated units (74 [44, 93]) compared with Salmonella (72 [24, 96]) after a 2-log CFU contamination breach. IMPORTANCE This work demonstrates the utility of modeling as a decision support tool to (i) estimate Salmonella cross-contamination into product under different scenarios, (ii) compare different cleaning interventions, and (iii) help inform the selection of a Salmonella surrogate for cleaning validation studies. Risk models can describe the tradeoffs associated with different dry cleaning strategies in low moisture food environments. For example, the model presented in this study can estimate the differences in product contamination as a consequence of flushing a processing line with increasing quantities of material. Additionally, outputs from this model can be used to evaluate the risk of cross-contamination from a contaminated dry cleaning tool. Finally, comparing outputs from a simulation model is an alternative method for comparing Salmonella surrogates used in dry cleaning validation. Simulation model outputs (i.e., prevalence and concentration of contaminated units) may be more broadly interpretable than comparing transfer coefficients alone, enhancing decision support.

  PublisherDOI

• Reduction of <i>Listeria</i> on stainless steel surfaces is impacted by sanitizer application method

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-04-09

  preprintOpen accessSenior authorCorresponding

  ABSTRACT Pathogen cross-contamination during food production is controlled through sanitation. However, sanitizer efficacy is often studied in bench-scale experiments (e.g., submerged coupons in static or stirred sanitizer) which poorly approximate fluid dynamics. This limits our understanding of how effective sanitization is in commercial application. This study paired computational fluid dynamic (CFD) estimates of shear stress during spray application of sanitizer with measurements of Listeria innocua reduction on stainless steel by 100 ppm hypochlorite sanitizer under various application methods. Static submersion of inoculated coupons for 3 s resulted in a log reduction of 2.3 ± 0.1 log CFU. Bench-scale spray application for 3 s had the largest microbial reduction at the point of sanitizer spray impingement (7.5 ± 0.5 log CFU) and directly adjacent to the impingement point (6.4 ± 0.7 log CFU) where shear stress was the highest. Surface locations below the impingement point that only received fluid film sanitizer run-off had a significantly lower microbial reduction of 0.4 ± 0.1 log CFU (p &lt; 0.05). At the pilot scale, sanitizer spray manually applied by operators achieved a 2.5 ± 0.4 log CFU reduction, which was significantly lower than what was achieved during bench-scale spray application (p &lt; 0.05). Microbial reduction from manual operation of spray equipment was also significantly different among operators (p &lt; 0.05). Discrepancies between bench-scale spraying, pilot-scale spraying, and submerged coupons underscores the need for sanitizer validation under realistic conditions to better understand the risk reduction achieved through sanitation programs during food processing.

  PublisherOA PDFDOI

• Virtual Food Safety Education Programs Reveal Significant Opportunities for Accessible and Effective Distance Learning

  Food Protection Trends · 2025-01-01 · 3 citations

  articleSenior author

  The demand for food safety extension programing continued throughout the COVID-19 pandemic, even as in-person training was restricted for over a year in the U.S. Consequently, innovation in virtual education occurred rapidly. Here we share the outcomes from our experience offering 23 courses to &gt;2,000 very small food processors in 11 states between 2020 and 2021. Courses were taught in English and Spanish, offered in both synchronous and asynchronous modalities, and varied in structure, in collaboration with our in-state partners. Our goal is to provide successful strategies rooted in the pedagogy of adult education to help direct future work in virtual food safety education. For example, a clear positive outcome involved improved accessibility among audiences due to reduced travel costs and increased audio-visual options. The use of Universal Design for Learning and Resilient Pedagogy frameworks supported participant engagement, which could also be enhanced through the use of chat functions, breakout rooms, office hours, and applying Bloom’s taxonomy to learning outcomes in food safety education. Positive participant feedback suggested that, now that restrictions relaxed, the opportunities available in virtual food safety education will remain an important, complementary option to in-person trainings to improve accessibility, engagement, and learning outcomes in the future.

  PublisherDOI

• The Effect of Different Climate Sensitivity Priors on Projected Climate: A Probabilistic Analysis

  Geophysical Research Letters · 2025-05-10 · 1 citations

  articleOpen access

  Abstract Understanding equilibrium climate sensitivity (ECS, equilibrium warming in response to a doubling of CO 2 ) uncertainty is fundamental for making reliable climate projections. We leverage the Hector simple climate model in a probabilistic framework to explore how different ECS priors influence uncertainty in long‐term (2081–2100) temperature projections. This method demonstrates a computationally efficient probabilistic workflow that explores the effects of parameter priors on climate projections. Excluding process and paleoclimate evidence in ECS priors widens resulting temperature projection uncertainty (a 5%–95% confidence range of 1.12–3.03°C and 1.09–3.33°C, respectively), while synthesizing all lines of evidence narrows temperature projection uncertainty (1.24–2.89°C; 5–95% CI), suggesting a more robust range of future temperature outcomes.

  PublisherOA PDFDOI

• Moisture Matters: Unintended Consequences of Performing Wet Sanitation in Dry Environments

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-11-26

  preprintOpen accessSenior authorCorresponding

  ABSTRACT Cross-contamination of low-moisture foods (LMFs) with pathogens from equipment and environmental surfaces during production is a food safety concern. Wet sanitation is sometimes employed to mitigate cross-contamination in LMF facilities, but the introduction of moisture to otherwise dry environments can inadvertently promote microbial growth. This study evaluated the risks associated with wet sanitation in LMF facilities by characterizing evaporation kinetics on powdered infant formula (PIF)-soiled surfaces, monitoring relative humidity (RH) in an LMF facility during and after wet sanitation, and assessing the growth of Salmonella , Listeria monocytogenes , Cronobacter sakazakii , and Enterococcus faecium spot inoculated on PIF-soiled stainless steel coupons under dynamic RH conditions. As expected, higher RH slowed drying of PIF-soiled surfaces, prolonging periods when the soil’s water activity ( a w ) was high enough to support microbial growth. Correspondingly, all four organisms grew significantly at 81% and 97% RH over 120 h ( P &lt; 0.05), while only E. faecium grew significantly below 81% RH ( P &lt; 0.05). Monitoring of RH during and after wet sanitation in a commercial facility revealed spikes up to 100% RH during sanitation and sustained RH above 75% for more than 7 h in poorly ventilated areas. When those facility RH conditions were simulated in the laboratory, Salmonella populations on PIF-soiled coupons increased by more than 3.5 log CFU within 66 h. These findings demonstrate the potential for wet sanitation to unintentionally enable environmental pathogen growth and highlight the importance of moisture and RH control in LMF facilities. IMPORTANCE Wet sanitation is commonly employed by low-moisture food (LMF) manufacturers for allergen changeovers and to prevent cross-contamination from surfaces, but regulators, manufacturers, and researchers have all expressed concerns that wet sanitation may promote the growth of pathogens in otherwise dry production environments. Despite these concerns, research on the impact of wet sanitation on facility relative humidity (RH) and its influence on microbial proliferation in low-moisture production environments remains limited. This study provides evidence that wet sanitation substantially increases facility RH, leading to persistent hydration of soiled surfaces, creating conditions that enable microbial growth. These findings reinforce concerns over the use of wet sanitation in LMF production. This also demonstrates the need for reducing water use in LMF production facilities, implementing RH control strategies, as well as the adoption of alternative or supplemental dry sanitation strategies to mitigate microbial risks.

  PublisherOA PDFDOI

• Assessing Hot Water Reconstitution Practices and Labeling of Powdered Infant Formula to Enhance Microbial Safety Involving Cronobacter spp

  medRxiv · 2025-03-23

  preprintOpen accessSenior authorCorresponding

  ABSTRACT Cronobacter spp. contamination in powdered infant formula (PIF) can cause infections in high-risk infants. Public health guidelines for caregivers of high-risk infants advise reconstitution using water heated to at least 70°C (158°F) for microbial inactivation. This study evaluated changes to water temperature under different heating and cooling scenarios during formula preparation, aiming to identify which conditions best ensure a minimum treatment temperature of 158°F (70°C). Factors such as vessel type, lid usage, vessel removal from the heat source, and water volume were tested for their effects on heat retention. The popular “hot shot” method which uses a small volume of hot water followed by a larger volume of room temperature water was also evaluated. In many scenarios, water temperatures fell below 158°F (70°C) during the preparation steps prior to PIF reconstitution. The water temperature prior to transfer to the bottle, bottle material, capacity, and volume significantly impacted temperature ( p &lt; 0.001). The temperature of formula immediately following shaking was as high as 179.5±1.6°F (81.9±0.9°C) and as low as 138.0±1.3°F (58.9±0.7°C), depending on the preparation conditions. Bottle material and capacity, water volume, and initial water temperature significantly impacted the temperature of PIF reconstitution treatments. Small volumes (2 fl. oz) of water in small glass bottles cooled the quickest. The hotshot method yielded reconstitution temperatures below 158°F (70°C). Measuring the temperature of hot water in the baby bottle and adding PIF when it cooled to 165°F (73.8°C) resulted in formula temperatures at or above 158°F (70°C) in almost all cases. Labels from PIF products available in the U.S. were reviewed and lacked detailed information about how caregivers of high-risk infants should use hot water to reconstitute PIF. The findings of this study can help shape guidelines that improve PIF reconstitution practices.

  PublisherOA PDFDOI

• A Pilot Study for Building Student Metacognitive Skills and Self-Perception in a Food Microbiology Lecture Course

  Teaching & Learning Inquiry The ISSOTL Journal · 2025-03-31

  articleOpen accessSenior author

  Metacognition, or the monitoring of one’s own learning, is an underutilized tool in STEM education. Previous research suggests instructional strategies that attempt to improve student metacognitive skills could increase student resilience and retention in STEM classes. This pilot initiative aimed to improve student metacognitive skills and self-perception. To do so, metacognitive-based instructional strategies were added to the curriculum of a food microbiology lecture course. These instructional strategies encouraged students to build their metacognitive skills within a supportive classroom community. Student metacognitive skills, self-perception, and learning strategies were assessed throughout the semester. By the end of the semester, over a third of students reported using at least three higher-order learning strategies. Additionally, there were some significant changes in students’ sense of belonging and self-efficacy, with an overall positive improvement compared to their previous science lectures. This study found that metacognitive-based instructional strategies can be an important tool for improving students’ experiences in a food microbiology class.

  PublisherOA PDFDOI

Frequent coauthors

• Yu Wang

  Peking Union Medical College Hospital

  53 shared

• Yi Chen

  23 shared

• Randy W. Worobo

  Cornell University

  18 shared

• Katherine Calvin

  Joint Global Change Research Institute

  17 shared

• Marshall Wise

  Joint Global Change Research Institute

  16 shared

• Wenfeng Liu

  Xiamen University of Technology

  15 shared

• Xin Zhao

  Joint Global Change Research Institute

  12 shared

• Shiyu Cai

  11 shared