EFFICACY OF AQUEOUS INOCULATION IN LOW-WATER ACTIVITY MATRIX ON SALMONELLA ENTERICA SEROTYPE AGONA THERMAL RESISTANCE AND STABILITY DURING STORAGE

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Description

Methods used to inoculate foods may impact the results of Salmonella survival and thermal resistance studies. Currently, there is little information as to the most effective means to inoculate Salmonella into low-moisture food products for use in process validation studies. The objective of this... Show moreMethods used to inoculate foods may impact the results of Salmonella survival and thermal resistance studies. Currently, there is little information as to the most effective means to inoculate Salmonella into low-moisture food products for use in process validation studies. The objective of this study is to assess the resulting 42 d storage stability and thermal resistance of Salmonella inoculated by liquid addition in food and inert carrier matrices. Salmonella enterica serovar Agona 447967 was inoculated into ground pepper, oat flour, and sand at approximately 9-10 log CFU/g using a hand mixing procedure and stored at 25°C, 32% relative humidity (RH). After a 2 d equilibration, the samples were tested for inoculation homogeneity. Distribution of Salmonella populations proved uniform in black pepper and sand but not in oat flour. Subsequent testing for stability by enumeration with both tryptic soy agar with 0.6% yeast extract (TSAYE) and xylose lysine desoxycholate (XLD) agars was performed weekly with black pepper and sand only. Thermal resistance was determined periodically during storage using aluminum test cells for pepper and glass vial for sand as sample holders. Over 42 d, the average starting Salmonella populations in pepper and sand were 7.88 ± 0.13 and 7.69 ± 0.11 log CFU/g, respectively, and final populations were 6.14 ± 0.06 and 6.52 ± 0.07 log CFU/g, respectively. Population changes were significantly different (P < 0.05). For pepper the thermal resistance did not change significantly during storage (P > 0.05) and were similar to values reported by other researchers using alternative inoculation techniques. However, thermal resistance measured in sand (D90ᵒC = 3.39 ± 0.41 min) was substantially higher than that measured in black pepper (D75ᵒC-value = 4.99 ± 0.21 min) or other literature values. Overall a liquid inoculation protocol proved efficacious for small particles such as ground black pepper or sand but was unable to provide a uniform distribution of cell populations in a powder such as oat flour.
M.S. in Food Safety and Technology, July 2016 Show less

Details
Department

NCFST / National Center for Food Safety and Technology

Title

EFFICACY OF AQUEOUS INOCULATION IN LOW-WATER ACTIVITY MATRIX ON SALMONELLA ENTERICA SEROTYPE AGONA THERMAL RESISTANCE AND STABILITY DURING STORAGE

Institution

Illinois Institute of Technology

Creator(s)

Liao, Li

Advisor(s)

Grasso-Kelley, Elizabeth M.

Date

2016
2016-07

Description

Methods used to inoculate foods may impact the results of Salmonella survival and thermal resistance studies. Currently, there is little information as to the most effective means to inoculate... Show moreMethods used to inoculate foods may impact the results of Salmonella survival and thermal resistance studies. Currently, there is little information as to the most effective means to inoculate Salmonella into low-moisture food products for use in process validation studies. The objective of this study is to assess the resulting 42 d storage stability and thermal resistance of Salmonella inoculated by liquid addition in food and inert carrier matrices. Salmonella enterica serovar Agona 447967 was inoculated into ground pepper, oat flour, and sand at approximately 9-10 log CFU/g using a hand mixing procedure and stored at 25°C, 32% relative humidity (RH). After a 2 d equilibration, the samples were tested for inoculation homogeneity. Distribution of Salmonella populations proved uniform in black pepper and sand but not in oat flour. Subsequent testing for stability by enumeration with both tryptic soy agar with 0.6% yeast extract (TSAYE) and xylose lysine desoxycholate (XLD) agars was performed weekly with black pepper and sand only. Thermal resistance was determined periodically during storage using aluminum test cells for pepper and glass vial for sand as sample holders. Over 42 d, the average starting Salmonella populations in pepper and sand were 7.88 ± 0.13 and 7.69 ± 0.11 log CFU/g, respectively, and final populations were 6.14 ± 0.06 and 6.52 ± 0.07 log CFU/g, respectively. Population changes were significantly different (P < 0.05). For pepper the thermal resistance did not change significantly during storage (P > 0.05) and were similar to values reported by other researchers using alternative inoculation techniques. However, thermal resistance measured in sand (D90ᵒC = 3.39 ± 0.41 min) was substantially higher than that measured in black pepper (D75ᵒC-value = 4.99 ± 0.21 min) or other literature values. Overall a liquid inoculation protocol proved efficacious for small particles such as ground black pepper or sand but was unable to provide a uniform distribution of cell populations in a powder such as oat flour. Show less

Type

Thesis

File type

application/pdf

Subject

Inoculation
Low-Water Activity
Pepper
Salmonella
Sand
Thermal Resistance

Access

Restricted Access

Rights

In Copyright
http://rightsstatements.org/page/InC/1.0/

Identifier

http://hdl.handle.net/10560/4067

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