Raffaele Civelli

Testing of a simplified LED based vis/NIR system for rapid ripeness evaluation of white grape (Vitis vinifera L.) for Franciacorta wine

The aim of this work was to test a simplified optical prototype for a rapid estimation of the ripening parameters of white grape for Franciacorta wine directly in field. Spectral acquisition based on reflectance at four wavelengths (630, 690, 750 and 850 nm) was proposed. The integration of a simple processing algorithm in the microcontroller software would allow to visualize real time values of spectral reflectance. Non-destructive analyses were carried out on 95 grape bunches for a total of 475 berries. Samplings were performed weekly during the last ripening stages. Optical measurements were carried out both using the simplified system and a portable commercial vis/NIR spectrophotometer, as reference instrument for performance comparison. Chemometric analyses were performed in order to extract the maximum useful information from optical data. Principal component analysis (PCA) was performed for a preliminary evaluation of the data. Correlations between the optical data matrix and ripening parameters (total soluble solids content, SSC; titratable acidity, TA) were carried out using partial least square (PLS) regression for spectra and using multiple linear regression (MLR) for data from the simplified device. Classification analysis were also performed with the aim of discriminate ripe and unripe samples. PCA, MLR and classification analyses show the effectiveness of the simplified system in separating samples among different sampling dates and in discriminating ripe from unripe samples. Finally, simple equations for SSC and TA prediction were calculated.

Wavelength Selection with a View to a Simplified Handheld Optical System to Estimate Grape Ripeness

The aim of this work was to identify the three most significant wavelengths able to discriminate in the field those grapes ready to be harvested using a simplified, handheld, and low-cost optical device. Nondestructive analyses were carried out on a total of 68 samples and 1,360 spectral measurements were made using a portable commercial vis/near-infrared spectrophotometer. Chemometric analyses were performed to extract the maximum useful information from spectral data and to select the most significant wavelengths. Correlations between the spectral data matrix and technological (total soluble solids) and phenolic (polyphenols) parameters were carried out using partial least square (PLS) regression. Standardized regression coefficients of the PLS model were used to select the relevant variables, representing the most useful information of the full spectral region. To support the variable selection, a qualitative evaluation of the average spectra and loading plot, derived from principal component analysis, was considered. The three selected wavelengths were 670 nm, corresponding to the chlorophyll absorption peak, 730 nm, equal to the maximum reflectance peak, and 780 nm, representing the third overtone of OH bond stretching. Principal component analysis and multiple linear regression were applied on the three selected wavelengths in order to verify their effectiveness. Simple equations for total soluble solids and polyphenols prediction were calculated. The results demonstrated the feasibility of a simplified handheld device for ripeness assessment in the field.

A Simplified, Light Emitting Diode (LED) Based, Modular System to be Used for the Rapid Evaluation of Fruit and Vegetable Quality: Development and Validation on Dye Solutions.

NIR spectroscopy has proven to be one of the most efficient and ready to transfer tools to monitor product’s quality. Portable VIS/NIR instruments are particularly versatile and suitable for field use to monitor the ripening process or quality parameters. The aim of this work is to develop and evaluate a new simplified optoelectronic system for potential measurements on fruit and vegetables directly in the field. The development, characterization and validation of an operative prototype is discussed. LED technology was chosen for the design, and spectral acquisition at four specific wavelengths (630, 690, 750 and 850 nm) was proposed. Nevertheless, attention was given to the modularity and versatility of the system. Indeed, the possibility to change the light sources module with other wavelengths allows one to adapt the use of the same device for different foreseeable applications and objectives, e.g., ripeness evaluation, detection of particular diseases and disorders, chemical and physical property prediction, shelf life analysis, as well as for different natures of products (berry, leaf or liquid). Validation tests on blue dye water solutions have shown the capability of the system of discriminating low levels of reflectance, with a repeatability characterized by a standard deviation proportional to the measured intensity and in general limited to 2%–4%.

Application of near infrared spectroscopy and development of simplified optical devices for the fresh-cut fruit and vegetable sector

Introduction T he production of ready-to-eat (or fresh-cut or minimally-processed) fruits and vegetables has increased worldwide in recent years due to their nutritive properties, convenience and ease of use. The shelf-life of these products is affected by growing techniques, harvesting operations, processing (i.e. washing, trimming, peeling and/or cutting) and storage conditions that promote the biochemical and microbial instability of the product itself. In fact, the shelf-life of fresh-cut products is shorter than that of their unprocessed counterparts and therefore rapid and non-destructive methods should be developed to investigate the freshness decay, during or at the end of the distribution chain. These methods could be integrated into the production chain for better management of the shelf-life and meeting consumer expectations. Spectroscopy has been developed considerably in the fruit and vegetable sector over the last 20 years and its applicability for the evaluation of agro-food products has been widely demonstrated. Nevertheless, these technologies are currently adopted mainly by research centres or big companies equipped with laboratories and trained personnel, due to their cost and complexity of use. A simplification of these technologies is necessary to make them also accessible to operating staff in small and medium enterprises. The sector is therefore interested in new simplified systems for rapid analysis along every step of the chain and directly at the point of sale with a double objective: to use the information from sensors to better manage the product and to preserve consumer expectations by providing additional selection criteria. This article proposes a brief overview of spectroscopic applications for quality assessment of Valerianella salad and of apples, paying particular attention to fresh-cut products. Future perspectives about the simplification of these nondestructive techniques are explored.

A light emitting diode based simplified system for rapid grape ripeness monitoring

Introduction E stablishing ripeness at harvest is a crucial issue, since fruit quality is closely related to it. Non-destructive methods which could explore a large number of samples and give a rapid and comprehensive overview of ripening would be helpful. Grape ripeness monitoring in the orchard may provide valuable data to control wine quality. Ripening is a complex process during which biochemical changes occur at skin and pulp level. Routine measurements of ripening parameters, essential for both fruit and vegetables (e.g. soluble solids content, acidity, phenols, anthocyanins, firmness etc.) are needed to monitor these changes. Nowadays, the limited adoption of near infrared (NIR) technology by the viticulture sector can be attributed to cost, technical limitations, grower resistance and supplychain weakness. Research and innovation have enabled NIR devices to continually decrease their physical size while increasing the amount of collected data. Therefore, new NIR instrumentation tends to be more compact and portable. For this reason, to support small-scale producers, simplified, easy to use, low-cost systems for real-time assessment of fruit ripeness in the field are desirable. To reach this goal, considerable effort has recently been directed towards developing and evaluating different procedures for an objective identification of variables which contain useful information and for the elimination of variables containing mostly noise. The aim of this research was to design, build and test a prototype of a low-cost and user-friendly device to support smallscale growers in determining the optimal harvest date according to grape ripening degree. Specific objectives were (i) to identify the most significant wavelengths able to discriminate grapes ready to be harvested during the final ripening stages; (ii) to design a prototype of a simplified device using the selected wavelengths; and (iii) to test the prototype on Franciacorta grapes.