Validating Salmonella inactivation during thermal processing of the physically heat-treated chicken litter as soil amendment and organic fertilizer.

Validating Salmonella inactivation during thermal processing of the physically heat-treated chicken litter as soil amendment and organic fertilizer.

Jan. 1, 2012 - Jan. 31, 2014

2012-193

$147,344.00

Xiuping Jiang, Ph.D.
Clemson University

Jinkyung Kim, Ph.D.

Final Report

There is a growing demand for the physically heat-treated chicken litter being used as soil amendment and organic fertilizer for plant growth. However, chicken litter is often contaminated with human pathogens such as Salmonella spp.Heat treatments have been recommended to reduce or eliminate these pathogens, but no scientific research has been reported to validate if these treatments are adequate to produce the finished products free from pathogenic microorganisms. This proposed study will determine the thermal resistance of a mixture of four Salmonella serotypes at temperatures recommended for heat treatment of chicken litter. Several key environmental factors such as moisture level, nutrient variation, and the freshness of chicken litter will be evaluated. Furthermore, a practical method for combining moist heat treatment with drying process will be investigated for rapidly inactivating Salmonella in broiler chicken litter.The results from this study will provide some practical guidelines on time-temperature combination to treat chicken litter of different properties to produce the finished products as Salmonella-free. The ultimate goal of this project is to help the produce industry to grow safe fresh produce using organic fertilizers free from human pathogens.

Technical Abstract

Chicken litter, commonly used as soil amendment and organic fertilizer, may contain harmful human pathogens such as Salmonella spp.  Although the physically heat-treated chicken litter has been recommended and used by produce growers, there is a lack of scientific data to prove if the heating processes in terms of time-temperature combination are adequate to kill human pathogens. This proposed study is to validate Salmonella inactivation during the heating processes as recommended for the physically heat-treated chicken litter by taking consideration of several factors such as type, dryness and freshness of chicken litter, and develop a two-step heat treatment for rapid pathogen inactivation.  In this proposed study, we will use a mixture of four Salmonella serotypes (Typhimurium, Enteritidis, Heidelberg, and Senftenberg) which are inoculated at level of ca. 7 log CFU/g broiler chicken litter with different levels of moisture (20, 30, 40, and 50%).  To determine the thermal inactivation rates of Salmonella, the inoculated chicken litter will be exposed to 75, 80, 85, and 150^oC for a period of time until the final moisture level is below 10~12% as recommended by several guidelines (Objective I).  Since the chicken litter varies significantly in chemical composition, microbial flora and physical properties, we will compare the thermal resistance of Salmonella in both broiler chicken and egg-laying hen litter, and determine the change of Salmonella heat resistance as affected by different storage ages of the broiler chicken litter collected from the same farm (Objective II).  Furthermore, we’ll evaluate a two-step heat treatment of chicken litter by applying moist heat at 65^oC first to inactivate Salmonella rapidly, followed by drying the chicken litter to the desired moisture level (<12%) at 80^oC  (Objective III).  The results from this study will validate the effectiveness of the recommended thermal processes for producing the physically heat-treated chicken litter free from Salmonella contamination, and provide the industry with an effective heat treatment method for treating raw chicken litter.  The ultimate goal of this proposed study is to help the produce industry to grow safe products for human consumption using pathogen-free soil amendment and fertilizer.  This proposal will address the identified research area (1.1) of “Compost, Soil Amendment Fertilizer Use and Cultivation Practices”.