Determination of porosity and particle size of natural bulk materials using image analysis

✍ Scribed by Hinz, T. H. ;Eggers, R.

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 1011 KB
• Volume: 40
• Category: Article
• ISSN: 0027-769X
• DOI: 10.1002/food.19960400305

✦ Synopsis

Porosity and particle volume are important properties of solids in numerous technical processes. Dehydration in food technology often leads to a decrease of particle size, combined with a change of porosity. Knowledge of the moisture dependence of these properties helps to avoid quality losses during drying. Common methods of porosity determination like mercury porosimetry or B.E.T. gas adsorption do not allow moisture variation. Therefore, a porosity evaluation method consisting of a combination of image analysis and gas displacement in a pycnometer is developed. Taking helium as the gas allows to measure open as well as encapsulated pore volume of the biological product. With particular consideration of basic geometrical particle shape of the investigated natural bulk materials, the disadvantage of image analysis being a two-dimensional measuring method is limited. Experimental results are of high reproducibility and show good agreement with literature data and a standard porosimetry method. Particle size prediction derived from a combination of particle volume balance and estimated porosity shows good agreement between calculated and measured particle size, even under variation of moisture content. This comparison also indicates the high reliability of the presented porosity analysis.