Resumen de Monitorización in situ de productos hortofrutícolas para garantizar su integridad mediante el uso de sensores espectrales de infrarrojo cercano
Horticultural products are a source of essential compounds from a nutritional perspective for humans. Additionally, they hold significant economic importance globally due to the large volume of products traded. Consumers demand that horticultural products meet specific criteria in each case, which are directly related to their quality, such as appearance, texture, flavour, and aroma. Moreover, the consumption of these products should not be detrimental to human health, and therefore, food safety must be ensured before they reach the final consumer. Furthermore, ensuring the authenticity of marketed fruits and vegetables is crucial, as deliberate or unintentional adulteration of horticultural products can cause severe health problems for humans and significant economic losses. Hence, those responsible for conducting quality control, safety, and authenticity inspections both in the field and in the industry, as well as consumers themselves, demand technological alternatives that provide precise, accurate, and useful information regarding the parameters determining product integrity-namely, their quality, safety, and authenticity. It is crucial that these technologies are not constrained by the time required for analysis, their destructive nature, or their costs. Near-infrared reflectance spectroscopy (NIRS) arises as a rapid, non-destructive, environmentally friendly, low-cost per analysis, and versatile alternative, allowing its incorporation at different points along the agri-food chain: in the field, in the industry, or even in supermarkets. The use of this technology for pre-harvest and post-harvest assurance of fruits and vegetables has been previously demonstrated, and it can be combined with other information and communication technologies to establish next-generation control systems. Progress in NIRS instrumentation in recent years has enabled the development of a wide variety of applications for ensuring the integrity of horticultural products, meeting the needs of producers (at the field level), the food industry, and supermarket distributors with instruments suitable for analysing food products at different points in the value chain. However, it is necessary to focus on various aspects related to optimising parameters concerning the acquisition of spectral information, the processing of NIRS data and interpretation of results, and the integration of the response obtained through this technology into decision support systems that enable the implementation of these spectral sensors in routine operations in the horticultural sector. Therefore, the aim of this Doctoral Thesis has been to analyse the potential of NIRS technology as a non-destructive, automatic, environmentally friendly, and multi-analyte sensor to be incorporated in situ in cultivation fields and in the industry to ensure the integrity of horticultural products such as almonds, spinach, and watermelons. To this end, portable sensors suitable for analysing quality and food safety parameters in the production fields (which allows for monitoring the product throughout its development on the plant), in the industry, and in the supermarket shelves, as well as for detecting fraud at the points where the product is received in the industry, were employed. Additionally, this Thesis includes the pieces of work carried out with online instruments and NIR-imaging systems aimed at ensuring the integrity of the analysed fruits and vegetables by simulating industrial sorting lines. Specifically, the work carried out with almonds enabled the rapid and non-destructive detection of fraud at different points in the value chain of this product using various strategies, including the innovative non-targeted control system developed using only spectral information from the product to classify batches as 'compliant' or 'non-compliant'. Furthermore, the work enabled the precise and accurate quantification of quality parameters such as fatty acid content, and the classification of almonds based on amygdalin content, a parameter related to the food safety of this nut. Likewise, the studies conducted with fresh intact spinach enabled to establish an analysis protocol for this product both in routine field operations and in the industry to monitor the crop throughout its development on the plant and to classify the leaves based on their nitrate content, a parameter related to the food safety of leafy vegetables regulated by Regulation (EU) 2023/915 at the European level. Finally, the work carried out with watermelons allowed the estimation of the optimal harvest time for these intact fruits (for which the determination of the NIR light penetration capability through the watermelons' rind was of paramount importance) and the evaluation of the sweetness of the pulp in the industry and supermarkets once they had been cut in half. The results obtained in the various works included in this Doctoral Thesis highlight the potential of NIRS technology to be incorporated both in-situ and 'online' into decision support systems in the almond, spinach, and watermelon sectors, providing a unique spectral fingerprint of each product that is highly useful from a traceability and product categorisation perspective. This enables different agents in the food chain to ensure that fruits and vegetables meet the established quality, safety, and authenticity criteria and comply with current regulations in each case.
