Biological Systems Engineering


First Advisor

Rossana Villa Rojas

Second Advisor

Jeyamkondan Subbiah

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agricultural and Biological Systems Engineering, Under the Supervision of Professors Rossana Villa Rojas and Jeyamkondan Subbiah. Lincoln, Nebraska: May, 2022

Copyright © 2022 Edel M. Summers


The purpose of the present study was to assess the effectiveness of hydrogen peroxide vapor (HPV) at inactivating Salmonella inoculated in whole black pepper when used as fluidizing gas media. HPV treatment was conducted at two different temperatures (45°C and 60°C) and two dwell times (30 min and 60 min). Microbial reduction and residual hydrogen peroxide were measured at three storage times: 0 h (immediately after treatment), 24 h and 48 h post-treatment. The effect of HPV on the quality of whole black peppercorn was evaluated 48 h post-treatment based on changes in piperine content, total phenolics, antioxidant activity, total volatile compounds, and color. Reduction in Salmonella population ranged from 1.41 – 2.83 log CFU/g. The lowest average log reduction was observed in samples treated at 45°C for 30 minutes at storage time 0 h, and the highest reduction was measured in samples treated at 60°C for 60 minutes after 48 h of storage. Statistical analysis showed no significant influence of temperature, dwell time or their interactions (all p-values > 0.05). Storage time was the only main effect of significance (p-value Salmonella population between storage times of 24 h and 48 h and between 0 h and 48 h. Residual hydrogen peroxide of up to 500 ppm was still detected on samples after 48 h of storage. No significant differences between treated and untreated whole black peppercorn were found for most quality parameters: piperine, total phenolic, antioxidant activity, and volatile compounds. On the other hand, a significant difference in color was observed between treated and untreated whole black peppercorn. This study shows that fluidization with HPV for the inactivation of Salmonella in black peppercorn achieved microbial reductions but not to pasteurization levels. The study highlights the need to explore further process design modifications before conclusions can be made on the efficacy of HPV treatment as a means for low-moisture foods pasteurization.

Advisors: Rossana Villa Rojas and Jeyamkondan Subbiah