A novel optical technique for the detection of stone fragments in fruits

摘要

Because of the growing demand for healthy and high quality food products many efforts are made to develop new sensing systems for food analysis. In this work we demonstrate the use of a new technique for the detection of stone fragments in fruits, based on the transmission of laser light via scattering. The goal of our research was to develop a technique which could be used for the detection of stone fragments in a broad range of product types in different conditions. We paid special attention to wet products; a product class for which stone identification with the standard X-ray based detection technique is difficult. We studied products with different sizes, textures, internal structures and water contents. In a first part we defined the specifications of the sending side. To detect as much as possible scattered light, the wavelength should not coincide with any absorption line. A literature study about the composition of fruits combined with a study of measured absorption spectra of different products allowed us to select the optimum wavelength. In a next step we performed absorbance measurements and calculated the minimum power of the incident beam applying Beer's law. After the selection of the optimum wavelength and power, we built a proof-of-principle set-up and demonstrated the use of transmission via scattering for the detection of stone fragments in olives, peaches and prunes.