APPLICATION OF VIS/NIR SPECTROSCOPYFOR RIPENESS EVALUATIONAND POSTHARVEST QUALITY ANALYSISOF AGRO-FOOD PRODUCTS

Agro-food composition at harvest time is one of the most important factors determining the future quality of final products (e.g. wine from grapes and oil from olives). Quality parameters change in function of different product matrix. Measurement of fruits characteristics that impacts on product quality is a requirement for production improvement. Inspection of fruits during ripening is a critical point in all agri-food production chains. This control is usually performed only on small samples that are not always representative of the whole lot. The importance of this monitoring operation is easy to understand, as it determines the economic value of the entire stock. Traditionally, fruits quality evaluation is achieved by a visual and taste assessment of them and evaluation of the traditional quality parameters such as total soluble solids, acidity and texture. The conventional methods to determine fruits quality parameters are time consuming, require preparation of samples, are often expensive, and generally highlight only one or a few aspects of fruits quality. Therefore, there is a strong need in the modern food industry for a simple, rapid, and easy‐to‐use method for objectively evaluating the quality of fruits. This kind of tool would enable real‐time analyses at the receiving station and would allow the preliminary decision‐making about grapes during consignment thank to the rapid analysis of various parameters simultaneously. Since food quality is not an individual attribute but it contains a number of inherent characteristics of the food itself, to measure the optical properties of food products has been one of the most studied non-destructive techniques for the simultaneous detection of different quality parameters. In fact, the light reflected from food contains information about constituents in the inner layers of sample and at foodstuff surface also. To achieve objectives of this work, e.g. ripeness evaluation and postharvest quality characteristics of agro-food products, visible near‐infrared (vis/NIR) spectroscopy was chosen. In particular, vis/NIR spectroscopy is a rapid and non-destructive technique requiring minimal sample processing before analysis; coupled with chemometric methods, appears to be one of the most powerful analytical tools for studying food products. Chemometrics is an essential part of vis/NIR spectroscopy in food sector. To extract useful information present in the spectra multivariate analysis was carried out. Principal component analysis (PCA) was used for a qualitative analysis of the data and PLS regression analysis as a technique to obtain quantitative prediction of the parameters of interest. The general aim of this work is to study the application of vis/NIR spectroscopy for ripeness evaluation and postharvest quality analysis of agro-food products. In particular this technology was tested to analyse ripening parameters of olives and grapes before to be processed, or to monitor freshness decay of fresh-cut lettuce and apples during long cold storage in controlled atmosphere. Moreover, the feasibility of a simplified handheld and low-cost optical device, based on measurement and processing of diffuse spectral reflectance at a few appropriately selected wavelengths was proposed. This study was focused on identifying the most significant wavelengths able to discriminate in a quick and simple way (i) directly in the field, the blueberries, the grapes, the olives ready to be harvested, (ii) on-line, for the real time monitoring of trend of craft beer fermentation and to estimate qualitative and quantitative parameters or (iii) during shelf life, freshness levels of fresh-cut Lamb’s lettuce (Valerianella locusta Laterr.). The final aim of this work is to realize a simplified modular optical device (with few selected wavelengths) for single sample, non-destructive, and quick prediction of fruit ripeness degree and quality parameters evaluation. The first prototype of simplified optical device was realized for red grapes study and is characterized by the presence of four LEDs emitting at the wavelengths of interest. LED technology was chosen as illumination source of the sample, and allows obvious advantages in term of simplification and cost reduction. The design of the prototype of the simplified optical device was realised with particular attention to versatility and modularity. The possibility to adjust the light source with a specific choice of wavelengths for LEDs, makes it possible to use the same simplified optical device for many different application. This modular design allows an easy adjustment for different objective and for different kind of food sample matrix.