Water vapour transport through large defects in flexible packaging: modeling, gravimetric measurement and magnetic resonance imaging
The limited mechanical resistance of flexible packaging materials means that they are prone to puncturing during processing and transport. The present work is concerned with food powder packaging, where defects between 0.5 and 1 mm in size have been detected. According to a generally accepted model for water vapour transport through large pores, defects of this size should strongly compromise the barrier properties of the packaging. In spite of this, no significant deterioration of the product has been observed, implying either that the standard model is wrong or that the water transport is inhibited by other phenomena. A study was undertaken to elucidate the mechanism of water absorption through pores into a dehydrated soup product. The first part of the study examined the water diffusion through model pores, using gravimetric measurements with silica gel as absorbing medium. The results show that the standard model gives predictions of at best 2 and at worst 20 times too high. Another model, published 25 years prior to the standard model but then largely forgotten, was found to agree well with experimental data. The second part of the study involved the use of magnetic resonance imaging to visualize the mechanism of water absorption in the product. It was found that the absorption proceeded in two independent steps. First, the powder next to the pore quickly absorbed water, and then the water spread evenly throughout the bulk at a much slower rate. Copyright © 2000 John Wiley & Sons, Ltd.
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Document Type: Research Article
Affiliations: Nestlé Product Technology Center Kemptthal, Nestec SA, CH-8310 Kemptthal, Switzerland
Publication date: 2000-07-01
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