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ARS Home Southeast Area Raleigh, North Carolina Food Science and Market Quality and Handling Research Unit Research





- Breidt, Frederick
- Johanningsmeier, Suzanne
- Perez Diaz, Ilenys
- Qureshi, Muquarrab
- 2023
- 2022
- 2021
- Publications
- Food Safety, (Animal and Plant Products) (108)

Research Project: **Location:
                            Food Science and Market Quality and Handling Research Unit** Project Number: 6070-41420-009-000-D
                        
                        Project Type: In-House Appropriated Start Date: Apr 19, 2021
                        
                        End Date: Apr 18, 2026 **Objective:**
                        
                        1. Determine how food components influence pathogen die-off in acidic food products. Modeling pH and acid effects on pathogen reduction in ready-to-eat vegetable fermentations.

2. Determine how processing conditions influence survival of fungal spores, toxins and vegetative cells in fermented or acidified vegetables. Supporting research to reduce food waste by fermentation. **Approach:**
                        
                        Objective 1: Determine how food components influence pathogen die-off in acidic food products.

Goal/hypothesis 1: Our hypothesis is that buffer capacity (BC) models can be used to link pH with acid accumulation and therefore log reduction times for bacterial pathogens in a binary (lactic and acetic) acid RTE vegetable fermentations. The goal is to develop methods for determining the safety of a variety of different RTE fermentations based on pH. 

Experimental design overview:
1. BC modeling of pH and lactic and acetic acid concentrations in a brined vegetable medium. BC models for pH and acid concentration will be developed using the combined buffering of CJ (or other vegetable brines) with the buffering of added acids. 
2. What are the typical acid mixtures produced by heterolactic LAB? It is important to know the ratio of lactic and acetic acids typical of low salt fermentations because the acids have different antimicrobial effects.
3. How do acid mixtures affect pathogen (STEC) die-off in vegetable brines? Determination of log reduction times based on protonated lactic acid and acetic acid mixtures in ACJ.
4. Can the BC of unfermented brines be used to accurately model pH changes in fermentations? BC models will be used to assess pH changes resulting from acid production by LAB in CJ brine and cucumber and cabbage fermentations. 
5. Validation of BC models for estimating pathogen die-off in fermentation based on pH. Reduction of bacterial pathogens will be estimated based on pH of cucumber and cabbage fermentation brines and data compared to CJ and cabbage or cucumber fermentations.

0bjective 2: Determine how processing conditions influence survival of fungal spores, toxins and vegetative cells in fermented or acidified vegetables.

Goal/hypotheses: Discovery: Identify fungi that are present on spoiling cucumbers. Hypothesis 1: In addition to inhibition of bacterial pathogens (Objective 1) organic acids and pH will prevent growth or persistence of fungal cells and/or toxins in RTE vegetable fermentation brines. Hypothesis 2: LAB may produce acids and antifungal compounds active against fungal cells, and persistence of fungal toxins in fermentation brines may be reduced by LAB due to degradation or LAB binding. The goal is to develop recommendations for safe preservation of surplus vegetables by fermentation.

Experimental design overview:
1. What fungi are present on spoiling cucumbers? Identification of the fungi typically present on spoiling cucumbers.
2. Do LAB present in cucumber fermentation produce antifungal compounds? LAB strains will be screened for antifungal compounds  
3. Do fungal cells and/or toxins persist during fermentation of CJ by LAB? Fungi and/or toxins will be inoculated into ACJ brines or cucumber fermentations to measure die-off during fermentation due to acid accumulation and possibly antifungal compounds produced by LAB.


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