The Effect of Fat Content on the Inactivation and Recovery of Listeria spp. in Ready-To-Eat Foods After High Pressure Processing

Authors

Yhuliana Kattalina Niño Fuerte, University of Nebraska-LincolnFollow

First Advisor

Mary-Grace C. Danao

Committee Members

Bing Wang, Gary Sullivan, Subash Shrestha

Date of this Version

8-2024

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Food Science and Technology

Under the supervision of Professor Mary-Grace C. Danao

Lincoln, Nebraska. August 2024

Comments

Copyright 2024, Yhuliana Kattalina Niño Fuerte. Used by permission

Abstract

High-pressure processing (HPP) is recognized by the United States Department of Agriculture Food Safety and Inspection Service (USDA FSIS) as a post-lethality treatment to control Listeria monocytogenes in ready-to-eat (RTE) meat and poultry products. A scoping review of 603 journal articles, which ultimately was narrowed down to 16 articles, revealed that the efficacy of HPP varies with fat content. The studies demonstrated that L. monocytogenes inactivation by HPP tends to be lower in RTE meats with greater than 5% fat content, compared to products with lower than 5% fat. The wide range of HPP parameters used in these studies have made it challenging to estimate fat’s baroprotective effects. However, building on the results of the scoping review, an experiment was designed and conducted to assess the impact of fat content (5, 15 and 25%) and pressure levels (300, 450 and 600 MPa) on the inactivation of L. innocua in emulsified pork sausages. Two L. innocua strains were used to inoculate the samples, which were then treated with HPP at 18 °C for 3 min. Microbial counts were assessed using direct plate counts on TSYEA after incubation at 32 °C for 48 h. The results showed significant differences (p < 0.05) at 450 MPa, with greater reductions observed in samples with 5 and 15% fat compared to those with 25% fat, suggesting fat exhibits a baroprotective effect somewhere between 15 and 25% fat content. No significant differences were observed at 300 MPa (p > 0.05), while at 600 MPa, L. innocua was reduced to below detectable levels in all samples. Three polynomial models were developed. Results showed there was a significant interaction between fat content and pressure and the model with the main and interaction effects, log₁₀ (N₀/N_P)_F = β₀ + β₁F + β₂P + β₃FP, had an adjusted coefficient of correlation (R²_adj) and root mean square error (RMSE) of 0.971 and 0.365 log reduction. The bias factor (B_f) after cross-validation showed this model is fail-safe. Its accuracy factor (A_f) was 1.434, suggesting more data are needed to develop a robust model for practical application.

Advisor: Mary-Grace C. Danao