Laser Light Backscattering to Monitor Moisture Content and Essential Oil Changes of Ginger Root During Hot-Air and Freeze Drying
- Publication Type
- Poster
- Authors
- Argyropoulos, D; Romano, G; Nagle, M; Parmar, A; Müller, J
- Year of publication
- 2013
- Conference name
- IFT 2013
- Conference location
- Chicago, USA
- Conference date
- 13 - 16 July 2013
Automated optical systems are being increasingly applied for a contactless evaluation of quality properties in the food industry. A common preliminary step for the manufacturing of convenient products includes dehydration in order to achieve the required moisture content for further processing. The objective of this research was to evaluate the use of a CCD camera in combination with laser diodes emitting at different wavelengths of 532, 635, 650 and 780 nm to detect changes in moisture and essential oil contents of ginger root slices (Zingiber Officinale Rosc.) during conventional hot-air and freeze drying. For the standard laboratory analysis, Karl Fischer Titration was used to determine the moisture content while the oil of the root was isolated by hydro-distillation. The microstructure of the samples was also observed under a scanning electron microscope. Backscattering images were acquired at regular intervals, analyzed in terms of radius maximum and the data were correlated with the values obtained by the destructive measurements. As far as the hot-air drying trials are concerned, a decrease in moisture content caused a reduction in photon scattering determined by diminished light propagation on the root. Although good results between the image parameter and the moisture content for hot-air drying were obtained, weak correlations for freeze drying and all wavelengths were reported. This can be attributed to the solid state of water and to the sublimation effect occurring during freeze drying. Regarding oil loss, the behavior of all wavelengths may raise some doubt on the ability to predict essential oil content. SEM images indicated the development of open pores in freeze dried slices and a relative dense structure in the hot-air dried samples. The presented optical technique demonstrated a promising method to be applied for in-line monitoring of moisture content of food in established industrial convection drying systems.