SETTING UP OF SIMPLIFIED OPTICAL TOOLS FOR THE EVALUATION OF FRUIT AND VEGETABLES
Creators: name: CIVELLI, RAFFAELE
Publisher: name: Universit� degli Studi di Milano
Year: 2014

description: The fruit and vegetable sector met in recent years an important phase of expansion among consumers due to the high nutritive value and convenience of products. This trend is particularly evident for fresh-cut products (fruit and vegetables minimally processed in ready-to-eat packs) due to: (i) their ease of use, and (ii) nutritional properties. Monitoring the quality decay of fruits and vegetables is necessary to control quality parameter, e.g. the freshness level or the ripening degree, during the entire production chain and to ensure quality product for the consumer. The non-destructive technologies are currently used only by research institutions or big companies, due to their cost and complexity of use. Therefore, the sector is interested in new simplified systems for rapid analysis that can be performed along the chain and directly at point of sale with a double objective: to use the information from sensors to better manage the product, and to preserve the consumers' expectations providing additional selection criteria. Objectives of this thesis were the setting up, design and testing of innovative optical simplified devices dedicated to fruit and vegetable products chains. Low-cost and easy-to-use prototypes based on vis/NIR technology and/or multispectral image analysis were presented. In particular, (a) a compact-sized LED technology based device, for the prediction of the main qualitative/ripening parameters of the case studies was realized and tested, and (b) the applicability of multispectral imaging was studied with a view to a simplified optical system for freshness decay assessment. Different kinds of matrix were investigated (white grapes, salad, and apples), with particular attention to fresh-cut products (Valerianella locusta L. salad, Cripps Pink apples). The development stage of the developed system has reached an operative prototype level. An evolution and an engineering of the instrument is still desirable in order to obtain a handheld, user friendly, non-destructive and inexpensive device for farmers utilization in the field. Particular attention must be paid to the modularity concept (i.e. the possibility to adjust light sources with a specific choice of wavelengths for LEDs). This makes it possible to conceive the same simplified optical device for many different applications (i.e. ripeness evaluation, chemicals and physical properties prediction or shelf life analysis) and for different food matrix. Furthermore, an optimization in the calibration for each individual measuring channel is the other significant, since it ensures the reduction of signal to noise ratio for all the measured data. The multispectral imaging study still is at a preliminary level, but sufficient to demonstrate the applicability of this principle as a rapid and non-destructive approach to develop a simplified low-cost optical system for freshness decay assessment. Further work in necessary to develop the research based on this. This thesis demonstrates how the simplification of traditional optical techniques is possible. The proposed methodologies can be replicated and can be the starting point for new research lines regarding innovative technologies for the agro-food sector.