Alemayehu Ambaw

Multiscale Modeling of Food Processes

Food unit operations involve complex transport phenomena. As experimental characterization of transport processes is not usually straightforward, mathematical models are often used to improve our understanding of them, and, more importantly, to design and optimize food processes. Contrary to typical engineering materials such as steel or brick, food tissues are intrinsically multiscale assemblies with different characteristics at each spatial scale. As a consequence, multiscale modeling is required. This article gives a systematic introduction to multiscale modeling in food processes, including imaging techniques for food microstructure, model formulation, and numerical solution techniques. Several applications in food process engineering will be presented. The article concludes with a discussion on future prospects for the use of multiscale modeling.

Down-regulation of respiration in pear fruit depends on temperature

The respiration rate inside plant organs such as pear fruit is controlled both by diffusion limitation of oxygen and through additional regulatory processes in a temperature-dependent manner.

Analysis of the effects of package design on the rate and uniformity of cooling of stacked pomegranates

Forced-air cooling (FAC) of pomegranate fruit was investigated.CFD model was developed, validated and used to analyse the cooling characteristics.Stack design markedly affected the airflow profile, rate and uniformity of cooling.High and low cooling regions inside the stack were identified and quantified.Pattern of high and low temperature regions depended on package design. Computational fluid dynamics (CFD) model was developed, validated and used to analyse cooling characteristics of two different package designs (CT1 and CT2) used for postharvest handling of pomegranate fruit. The model incorporated geometries of fruits, packaging box, tray and plastic liner. Thin layer of plastic material with conservative interface heat flux was used to model liners. The accuracy of the model to predict airflow and temperature distributions were validated against experimental data. The model predicted airflow through the stacks and cooling rates within experimental error. Stack design markedly affected the airflow profile, rate and uniformity of cooling. The cooling rate of the two package designs differed by 30% and plastic lining increased the average 7/8th cooling times from 4.0 and 2.5h to 9.5 and 8.0h for the CT1 and CT2 stacks, respectively. Profile of high and low temperature regions depended considerably on packaging box design.