Food Science and Technology,

 

Department of Food Science and Technology: Master of Science with Project Option

First Advisor

Rossana Villa Rojas

Committee Members

Byron Chavez, Curtis Weller

Date of this Version

Spring 2025

Document Type

Project

Citation

A project report 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 Rossana Villa Rojas

Lincoln, Nebraska, Spring 2025

Comments

Copyright 2025, Daniela Segura. Used by permission

Abstract

This study evaluated Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella inactivation in black peppercorns treated with hydrogen peroxide (HP) vapor via fluidization. The selected parameter for dwell temperature was 60ºC for 60 minutes. The reduction of both Salmonella and E. faecium, along with changes in water activity, color, and residual hydrogen peroxide, were measured before, immediately after treatment and at 24 and 48 hours post-treatment. Results showed that E. faecium exhibited a significantly greater reduction (4.63 ± 0.55 log CFU/g) compared to Salmonella (2.94 ± 0.16 log CFU/g) (p < 0.05), making E. faecium unsuitable as a surrogate for Salmonella in these conditions. Treatment led to a significant decrease in water activity and moisture content (p < 0.05). Color changes were perceptible to the naked eye, as indicated by a ΔE > 3. Storage time did not significantly affect water activity and moisture content (p > 0.05). Residual hydrogen peroxide reached up to 350 ppm immediately post-treatment and showed a decreasing trend over storage time. These findings suggest that while HP vapor treatment can reduce microbial populations in black peppercorns, E. faecium NRRL B2354 is not an appropriate surrogate for Salmonella under these specific conditions, and further optimization of the process is needed to enhance microbial inactivation and minimize quality loss.

Advisor: Rossana Villa Rojas

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