Laser triangulation principle. 

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... the food industry the agglomeration process of powders increases the particle size as well as its porosity and then modifies end-user properties such as wettability, sinkability, dispersibility and solubility. The main application of agglomeration is to produce instant products (e. g. instant coffee, milk powder, cocoa beverages, etc.) that acquire the ability for dispersing and rapidly dissolving in liquids (water, milk, etc.) [1]. Furthermore, many of the physical and structural properties of agglomerates such as density, surface properties, size and shape, influence the particles rigidity and then modify their behavior during handling [2,3]. The measurement of these physical properties is important since they affect the behavior of powder particles during storage, packing and processing. The size parameter (usually associated to diameter, surface or volume) describes the geometry of the object regardless of its form [4]. The shape parameter characterizes the object regardless of the size. Currently, the measurement of the shape parameters of agglomerates is performed from 2D data, usually from microscope images. One of the shape parameters frequently used in the characterization of objects is the sphericity. However, there are no works to report measurements of sphericity in the characterization of agglomerates of milk powder from 3D data. There are different methods for characterization of agglomerated particles. In [5] the shape of agglomerates is computed from 2D microscope images by finding the circle that best fits the estimated area on each image, assuming that particles have a circular shape. A highly accurate technique is the use of confocal microscopy [6] that creates sharp images of a specimen, normally blurred with conventional microscopes; however, stimulating fluorescence from dyes that should be applied to the specimen, can modifies the agglomerates properties. Another method to characterize agglomerate is the use of mercury porosimetry applying various pressure levels to the sample. This technique is not suitable to characterize agglomerates, normally fragile, that are broken during the measurement [7]. The work presented in [8] computes the porosity of fragile agglomerates from only three images acquired with a CCD camera. The work described in [9,10] present a method based on silhouettes extraction of multiple views to estimate the volume of the envelope of milk powder agglomerates; agglomerates concavities are not considered. The works in [11-13] developed methods to estimate the shape of particles using 2D shape parameters from image analysis techniques. The aim of this paper is to propose a methodology to characterize the shape of agglomerated particles of milk powder using 3D parameters. This methodology is based on a laser displacement sensor that allows a three-dimensional reconstruction of the agglomerated particles. This approach can be extended to measure other particle systems. The shape of the agglomerates was analyzed using the following form factors: elongation, flatness, aspect ratio and sphericity. Also, the particle volume is determined since it is used as a basic parameter to determine the particle sphericity. The positioning system is shown in Fig. 1. The agglomerate is placed on the object holder that rotates, drive n by a stepper motor, at ∆ θ degrees increments controlled by a PIC-STEP control board. The laser displacement sensor (LDS) is rigidly mounted on a linear positioning system that moves along z -axis at ' z increments ( ' z 30 P m ). The LDS used works on optical triangulation principle. A laser diode (wavelenght 650 nm) is the light source, projecting a spot onto the surface to be measured. The LDS is mounted on the linear positioning system. The LDS controller estimates the distance between its emitter and the target (agglomerate surface). Fig. 2 shows the laser triangulation principle. The measurement technique is based on the LDS model LK-G10 from KEYENCE [14]. Table 1 shows the technical specifications of the sensor. According to the law of reflection, the reflected beam has the same angle that the incident, so we ...