March 11, 2025 - Mario Cobo, Ph.D. Candidate (Worobo Lab), Cornell University

Speaker Bio
Mario Cobo graduated from the University of Rochester in 2018 with a Bachelor of Science (BSc.) degree in Molecular Genetics. Following graduation, he joined Cornell University's Microbial Extension Program in Geneva, NY, under the mentorship of Dr. Randy W. Worobo. Over three years in the program, Mario gained extensive experience in various food safety topics, including shelf-life testing, UV validations, High-Pressure Processing (HPP), challenge studies, microbial validations, and examinations. In 2021, Mario transitioned to graduate school under Dr. Worobo's mentorship, starting a Master’s program that later evolved into a PhD. His doctoral research focuses on the use of potential protective cultures, such as Bacillus coagulans, for low-acid food products in combination with HPP. His work spans microbial isolation, growth modeling, genomic analysis, spore survival, and protective applications. In addition to his thesis, Mario has contributed to a variety of smaller projects related to food safety, food processing, and food microbiology. Today, Mario will present part one of one of his recent extension projects, highlighting the thermal inactivation of Salmonella in low-moisture foods and providing critical insights into food safety and processing optimization

Thermal processing is a critical control measure to ensure the microbial safety for ready-to-use therapeutic foods (RUTFs) such as lipid-based nutrient supplements (LNS). This study investigated the thermal inactivation kinetics of Salmonella in three LNS formulations: a peanut butter-based product, a chickpea-based product, and a peanut butter-based “worst case scenario” product with added sugar and oil. Seven Salmonella strains were combined into a standardized cocktail to inoculate the LNS formulations. Inoculated samples underwent thermal treatments in water and oil baths at temperatures ranging from 87°C to 115°C. For each condition, the decimal reduction time (D-value) and the temperature increase required for a tenfold reduction in the D-value (Z-value) were calculated. Experimental protocols ensured uniform sample thickness to minimize temperature gradients and come-up time, with vacuum sealing employed to maintain consistency during heating. Post-treatment, samples were reconstituted and plated for bacterial enumeration. Results indicated significant variability in Salmonella thermal resistance across formulations and heating methods. D-values for the peanut butter-based product ranged from 388.86 seconds at 87°C to 9.65 seconds at 115°C, while the chickpea-based product and the “worst-case scenario” formulation exhibited higher thermal resistance under comparable conditions. Z-values varied across products and heating methods, with combined Z-values for water and oil baths ranging from 14.22°C to 33.72°C, reflecting differences in formulation composition and heating media. These findings emphasize the importance of product-specific validation to ensure effective thermal processing for Salmonella inactivation, tailored to reduction needs and product formulations. This research provides valuable insights for optimizing thermal processing parameters to produce safe, shelf-stable LNS products, particularly for vulnerable populations reliant on RUTFs for nutrition.