Determinacion de h en alimentos

International Journal of Food Engineering
Volume 7, Issue 4 2011 Article 15

Determining the Convective Heat Transfer Coefficient (h) in Thermal Process of Foods
Pedro Esteves Duarte Augusto, University of Campinas Marcelo Cristianini, University of Campinas

Recommended Citation: Augusto, Pedro Esteves Duarte and Cristianini, Marcelo (2011) "Determining the Convective Heat TransferCoefficient (h) in Thermal Process of Foods," International Journal of Food Engineering: Vol. 7: Iss. 4, Article 15. DOI: 10.2202/1556-3758.2208 Available at: http://www.bepress.com/ijfe/vol7/iss4/art15 ©2011 Berkeley Electronic Press. All rights reserved.

Determining the Convective Heat Transfer Coefficient (h) in Thermal Process of Foods
Pedro Esteves Duarte Augusto and Marcelo CristianiniAbstract
Thermal processing is the most important and utilized method for food preservation, being those carried out with the food inside the package the most appropriated for safety consumption guarantee. During processing, the packaged food is surrounded by a heat transfer medium, in general a fluid as water, steam, air or its mixtures. Therefore, the definition of the convective heat transfercoefficient (h) is important for several process studies, although the available data is scarce, especially in food thermal processes. Although there is several methods for determining the h values, the non-regular food geometries and transient characteristics of thermal processes, makes difficult using most of the methods. This work aimed to describe an appropriated method to determining theconvective heat transfer coefficient (h) in thermal process of foods. KEYWORDS: computational fluid dynamics (CFD), convective heat transfer coefficient (h), food thermal processing Author Notes: The authors acknowledge and thank the São Paulo Research Foundation (FAPESP), for the financial support received in the project 2007/04121-6.

Augusto and Cristianini: h Values in Thermal Process of Foods1. Introduction Thermal processing is one the safer and most utilized method for food preservation. During thermal process, food is heated until a specific temperature, which is maintained for a pre-determined time and then cooled. The thermal effects of this process must ensure microbial and enzymes inactivation, obtaining a safety and stable food product. However, the thermal effects can alsochange sensory (desirable or undesirable) and nutritional (undesirable) properties. Then, extreme care is necessary in process design in order to avoid both sub-processing and over-processing. Thus, thermal process optimization is extremely desired. Thermal process can be carried out with the food packaged, being then the most safety method as there is no contact between the processed food and its(contaminated) surrounding. This process can be done for a wide range of foods, as liquid, solids and particulates, and is often called as Appertization in tribute to Nicolas Appert, who developed this method in 1809 (Appert, 1810). Since then, despite the advances and developments in food preservation, the in-package food thermal processing is still the most important preservation method. Thedesign of thermal process for food should consider the characteristics of heat transfer by the heating and cooling media to the product and through it. Physical, chemical and microbiological characteristics of the product, package and equipment, should be considered as well for guarantee of food safety and balancing sensory and nutritional characteristics, and costs (Augusto et al. 2009). Duringthermal processing, the package-food system is surrounded by a heat transfer medium, generally a fluid as water, steam, air or their mixtures. This fluid will then transfer thermal energy to the product (heating phase) and from the product (cooling phase). Thus, the product will be heated and cooled by a convective heat transfer mechanism. This process is schematic in Figure 1, where  the heat flow...