An official website of the United States government.
<OL> <LI>Predict: To develop a mathematical model and carry out numerical simulation to predict the pressure distribution and the effect of composition on it in heterogeneous meat and poultry samples. <LI> Validate: To experimentally measure the pressure at several locations within the heterogeneous meat samples and compare the results with the numerical predictions.<LI>. Predict: To develop a predictive microbial pressure inactivation kinetics model for Pseudomonas and Salmonella in heterogeneous meat and poultry samples.<LI>Validate: To measure and validate microbial survival within heterogeneous meat and poultry samples subjected to HHPP and compare the results with numerical predictions. </OL>Expected Outputs: The results from this research will show whether the pressure distribution inside the heterogeneous meat and poultry sample during HHPP is uniform or not. Applying composite solid mechanics theory to predict pressure distribution in fibrous (composite) food materials under pressure is an entirely new approach and no one has yet solved the solid-fluid interaction problem during HHPP of foods. <P>At the end of the proposed research, quantitative information about pressure distribution (uniformity or non-uniformity) in a fibrous and bone containing meat will be obtained. The mathematical models and numerical simulation programs will be validated with experimental data in terms of pressure distributions, as well as microbial survival data. Effects of processing parameters like holding time, vessel size, food sample composition, on the pressure distributions will be identified. Data on microbial inactivation kinetics in meat and poultry samples will be generated.
Non-Technical Summary: High Hydrostatic Pressure Processing (HHPP) has gained wider acceptance as a viable technology in the last few years because of its various benefits. The major advantage being that the process is generally independent of sample size and shape, unlike thermal and other non-thermal processes. This project addresses one of the most important issues related to HHPP, i.e., whether the pressure distribution is uniform in a food product. It can safely be assumed that the internal pressure is uniform (isostatic) for liquids and homogeneous solids. However, for heterogeneous solid food samples, the internal pressure may not be uniform. We hypothesize that for heterogeneous meat and poultry products that contain fibers and bones, the internal pressure distribution will not be uniform and the internal pressure will be less than the applied pressure, which may lead to under processing and unsafe products. We have obtained preliminary microbial inactivation data on high pressure processed chicken and turkey samples showing lower lethality near the bones, which supports our hypothesis. The overall objective of our proposed research is to predict and validate non-isostatic nature of HHPP for heterogeneous food samples. It responds to the priority area no. 2 described in section d. Improving Food Quality and Value, program code 93430, of the RFA emphasizing advanced and innovative processing, engineering, and technologies. We will carry out mathematical modeling and numerical simulation of HHPP to predict pressure distribution and its impact on microbial inactivation. The predictions will be validated with experimental data on pressure distribution as well as microbial inactivation. Knowledge of non-uniform pressure distribution is critical to quantify the process lethality, which directly influences the quality and safety of the food product. The results of this research will aid regulatory agencies (such as USDA and USFDA) in developing guidelines for food processors. <P> Approach: We will model and numerically simulate pressure distribution in solid foods using solid mechanics theory to assess the stress exerted on the microbial cell due to the applied pressure. Finite element method will be use to carry out numerical simulation. We will introduce a composite model where the fibrous network of meat product is described as an array of interconnected trusses and the matrix as a nonlinear highly compliant solid. Pressure distribution inside a meat sample will be measured using dry copper powder tablets following the method described by Minerich and Labuza (2003). We wil also use a tactile film pressure indicators to record pressure distribution. Meat samples will be injected with a selected bacteria at specific locations to evaulate pressure induced inactivation and injury to bacterial cells. The data will be used to develop inactivation kinetics models.