Speaker
Description
Several high temperature food processing and safety applications involve the movement of fluids through a soft material. For example, during baking vapors are formed, which cause swelling and shrinkage of the porous matrix. Vapor-air mixture and CO2 formed due to leavening, result in texturization of the baked products such as cookies and crackers. In low moisture foods, antimicrobial gases flow through a bed of low moisture foods such as spices, basil leaves, etc. To effectively design a process, permeability of the porous matrix is needed and one needs to calculate fluid velocity as a function of pressure distribution. Regions of high pressure near the thinner walls can cause stress-crack formation in baked products. Challenges are posed by in situ measurement with deformable materials and the restricted spatial and temporal resolution make it difficult to quantify pore-level parameters; thus, very limited information is available on transport properties. In this study, a CFD-based pore-scale model was developed to investigate the mechanistic aspects of fluid flow in food matrices during baking. An AI-assisted segmentation tool was used to analyze X-ray micro-computed tomography images of cookie samples. A pore network model was employed to calculate Reynolds numbers, thereby characterizing the fluid flow regime. The Navier–Stokes and continuity equations, along with Darcy’s law, were solved to determine the transport properties. The results indicated that porosity ranges from 0.15 to 0.48 and generally increases with baking time. The highest value of local porosity occurred at the cookie edge. The flow regime in the pore channels remained laminar. The CFD results showed that fluid velocity fluctuates along the flow direction, whereas pressure decreases gradually. The average permeability obtained from simulations and experiments ranged from 10^-12 to 10^-11 m2 and from 10^-11 to 10^-10 m2, respectively. The Kozeny–Carman model confirmed that porosity is the underlying variable governing cookie permeability. These findings provide a deeper understanding of transport mechanisms, contributing to quality assessment and process optimization in the food industry. In a different application, similar pore scale simulations were conducted for a bed of basil leaves to identify stagnant regions, where antimicrobial gas may not reach. Strategies were recommended to the industry to modify the process to enhance safety of low moisture foods.
| Country | United States |
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