The present Doctoral Dissertation concerns the development and the application of two devices based on the Time-Resolved Reflectance Spectroscopy (TRS) technique, which were designed, developed, and characterized at the Department of Physics of Politecnico di Milano. The two systems, one based on an approach featuring contact between sample and probe (contact TRS device) and the other based on an approach featuring no contact between sample and probe (non-contact TRS device), are dedicated to the non-destructive optical characterization of turbid media. Specifically, they are suitable for application in the horticultural sector, i.e. for probing the internal quality of fruit and vegetables. The devices were tested during several measurement campaigns, in particular within the ESPERA Project, assessing the quality of Mantuan Protected Geographical Indication (PGI) pears, and within the Agridigit Project, assessing the quality of Mantuan PGI melons. In the first chapter, the theoretical background of the TRS technique is presented, focusing on its application to the quality assessment of fruit and vegetables. Firstly, an overview of the main non-invasive techniques probing fruit and vegetables is reported. After that, the physical principles and the main features of the Near Infrared Spectroscopy (NIRS) technique are shown. Then, the basic theory of diffuse optics is reported, including the models which describe the behavior of light in turbid media. After that, the main NIRS measurement approaches, including TRS, are described, highlighting the respective advantages and drawbacks. Finally, the techniques for acquisition and analysis of TRS data are reported. In the second chapter, the contact TRS device is presented. Firstly, the instrument is described in detail, including an overview of its modular structure and a specific description of each module. After that, the system characterization, based on an established procedure for the evaluation of the performance of diffuse optics devices, is reported. Finally, an experiment assessing the reproducibility of identical solid phantoms, based on the optical properties retrieved by three TRS devices, is shown. In the third chapter, some experiments on fruit performed employing the contact TRS device are presented, assessing the ability of the system to evaluate the maturity degree and the quality of fruit and vegetables. Firstly, three measurement campaigns on Mantuan PGI pears, of the cultivars ‘Abate Fetel’ and ‘Conference’, performed within the ESPERA Project, are reported. After that, a measurement campaign on Mantuan PGI melons, of the cultivar ‘Honey Moon’, performed within the Agridigit Project, is reported. In the fourth chapter, the non-contact TRS device is presented. Firstly, some simulations verifying the feasibility of non-contact TRS measurements on fruit are reported. After that, the novel components of the instrument are described in detail, namely the injection module featuring a fiber optic collimator and the detection module featuring a newly designed collection optical system. Finally, the system characterization, based on an established procedure for the evaluation of the performance of diffuse optics devices, is reported. In the fifth chapter, some experiments on fruit performed employing the non-contact TRS prototype are presented, assessing the ability of the system to evaluate the maturity degree and the quality of fruit and vegetables, compared to state-of-the-art TRS devices. Firstly, a shelf-life experiment on Mantuan PGI pears, of the cultivar ‘Abate Fetel’, performed within the ESPERA Project, employing the non-contact prototype and two contact TRS devices, is reported. After that, another shelf-life experiment on Mantuan PGI pears, of the cultivar ‘Abate Fetel’, performed within the ESPERA Project, employing the non-contact prototype and the above-mentioned contact TRS system, is reported.
La presente Tesi di Dottorato concerne lo sviluppo e l’applicazione di due strumenti basati sulla tecnica di spettroscopia in riflettanza risolta nel tempo (TRS), che sono stati progettati, sviluppati e caratterizzati presso il Dipartimento di Fisica del Politecnico di Milano. I due sistemi, uno basato su un approccio che prevede contatto tra campione e sonda (strumento ‘contact’ TRS) e l’altro basato su un approccio che non prevede alcun contatto tra campione e sonda (strumento ‘non-contact’ TRS), sono finalizzati alla caratterizzazione ottica non distruttiva di mezzi torbidi. Specificamente, sono adatti all’applicazione nel settore ortofrutticolo, ossia all’analisi della qualità interna di frutta e verdura. I dispositivi sono stati testati durante varie campagne di misura, in particolare nell’ambito del Progetto ESPERA, dedicato alla valutazione della qualità di pere mantovane IGP (Indicazione Geografica Protetta), e nell’ambito del Progetto Agridigit, durante il quale si è valutata la qualità di meloni mantovani IGP. Nel primo capitolo, è presentato il contesto teorico della tecnica TRS, focalizzandosi sulla sua applicazione all’analisi della qualità di frutta e verdura. In primo luogo, è riportata una panoramica delle principali tecniche non distruttive impiegate per analizzare frutta e verdura. Dopodiché, sono esposti i principi fisici e le principali caratteristiche della tecnica di spettroscopia nel vicino infrarosso (NIRS). In seguito, sono riportate le basi teoriche dell’ottica diffusiva, inclusi i modelli che rappresentano il comportamento della luce nei mezzi torbidi. Dopodiché, sono descritti i principali approcci di misura NIRS, inclusa la tecnica TRS, evidenziando i rispettivi vantaggi e svantaggi. Infine, sono riportate le tecniche di acquisizione ed analisi dei dati TRS. Nel secondo capitolo, è presentato lo strumento contact TRS. In primo luogo, il dispositivo è descritto dettagliatamente, includendo una panoramica della sua struttura modulare e una descrizione specifica di ogni modulo. Dopodiché, è riportata la caratterizzazione del sistema, basata su un protocollo assodato per la valutazione delle performance di dispositivi di ottica diffusiva. Infine, è mostrato un esperimento per la valutazione della riproducibilità di phantom solidi identici, in base alle proprietà ottiche riportate da tre dispositivi TRS. Nel terzo capitolo, sono presentati alcuni esperimenti su frutta effettuati impiegando lo strumento TRS contact, a valutazione dell’abilità del sistema di sondare il grado di maturazione e la qualità di frutta e verdura. In primo luogo, sono riportate tre campagne di misura su pere mantovane IGP, delle varietà ‘Abate Fetel’ e ‘Conference’, effettuate nell’ambito del Progetto ESPERA. Dopodiché, è riportata una campagna di misura su meloni mantovani IGP, della varietà ‘Honey Moon’, effettuata nell’ambito del Progetto Agridigit. Nel quarto capitolo, è presentato lo strumento non-contact TRS. In primo luogo, sono riportate alcune simulazioni a verifica della fattibilità di misure TRS senza contatto tra campione e sonda. Dopodiché, sono descritte dettagliatamente le componenti innovative dello strumento, ossia il modulo di lancio caratterizzato da un collimatore per fibra ottica e il modulo di raccolta caratterizzato da un sistema ottico appositamente progettato. Infine, è riportata la caratterizzazione del sistema, basata su un protocollo assodato per la valutazione delle performance di dispositivi di ottica diffusiva. Nel quinto capitolo, sono presentati alcuni esperimenti su frutta effettuati impiegando il prototipo TRS non-contact, al fine di stabilire l’abilità del sistema di sondare il grado di maturazione e la qualità di frutta e verdura, rispetto a dispositivi TRS allo stato dell’arte. In primo luogo, è riportato un esperimento di shelf-life su pere mantovane IGP, della varietà ‘Abate Fetel’, effettuato nell’ambito del Progetto ESPERA, in cui sono stati impiegati il prototipo non-contact e due dispositivi TRS contact. Dopodiché, è riportato un altro esperimento di shelf-life su pere mantovane IGP, della varietà ‘Abate Fetel’, effettuato nell’ambito del Progetto ESPERA, in cui sono stati impiegati il prototipo non-contact e il suddetto sistema TRS contact.
Development and application of Time-Resolved Reflectance Spectroscopy technology for non-destructive optical characterization of fruit and vegetables
Levoni, Pietro
2023/2024
Abstract
The present Doctoral Dissertation concerns the development and the application of two devices based on the Time-Resolved Reflectance Spectroscopy (TRS) technique, which were designed, developed, and characterized at the Department of Physics of Politecnico di Milano. The two systems, one based on an approach featuring contact between sample and probe (contact TRS device) and the other based on an approach featuring no contact between sample and probe (non-contact TRS device), are dedicated to the non-destructive optical characterization of turbid media. Specifically, they are suitable for application in the horticultural sector, i.e. for probing the internal quality of fruit and vegetables. The devices were tested during several measurement campaigns, in particular within the ESPERA Project, assessing the quality of Mantuan Protected Geographical Indication (PGI) pears, and within the Agridigit Project, assessing the quality of Mantuan PGI melons. In the first chapter, the theoretical background of the TRS technique is presented, focusing on its application to the quality assessment of fruit and vegetables. Firstly, an overview of the main non-invasive techniques probing fruit and vegetables is reported. After that, the physical principles and the main features of the Near Infrared Spectroscopy (NIRS) technique are shown. Then, the basic theory of diffuse optics is reported, including the models which describe the behavior of light in turbid media. After that, the main NIRS measurement approaches, including TRS, are described, highlighting the respective advantages and drawbacks. Finally, the techniques for acquisition and analysis of TRS data are reported. In the second chapter, the contact TRS device is presented. Firstly, the instrument is described in detail, including an overview of its modular structure and a specific description of each module. After that, the system characterization, based on an established procedure for the evaluation of the performance of diffuse optics devices, is reported. Finally, an experiment assessing the reproducibility of identical solid phantoms, based on the optical properties retrieved by three TRS devices, is shown. In the third chapter, some experiments on fruit performed employing the contact TRS device are presented, assessing the ability of the system to evaluate the maturity degree and the quality of fruit and vegetables. Firstly, three measurement campaigns on Mantuan PGI pears, of the cultivars ‘Abate Fetel’ and ‘Conference’, performed within the ESPERA Project, are reported. After that, a measurement campaign on Mantuan PGI melons, of the cultivar ‘Honey Moon’, performed within the Agridigit Project, is reported. In the fourth chapter, the non-contact TRS device is presented. Firstly, some simulations verifying the feasibility of non-contact TRS measurements on fruit are reported. After that, the novel components of the instrument are described in detail, namely the injection module featuring a fiber optic collimator and the detection module featuring a newly designed collection optical system. Finally, the system characterization, based on an established procedure for the evaluation of the performance of diffuse optics devices, is reported. In the fifth chapter, some experiments on fruit performed employing the non-contact TRS prototype are presented, assessing the ability of the system to evaluate the maturity degree and the quality of fruit and vegetables, compared to state-of-the-art TRS devices. Firstly, a shelf-life experiment on Mantuan PGI pears, of the cultivar ‘Abate Fetel’, performed within the ESPERA Project, employing the non-contact prototype and two contact TRS devices, is reported. After that, another shelf-life experiment on Mantuan PGI pears, of the cultivar ‘Abate Fetel’, performed within the ESPERA Project, employing the non-contact prototype and the above-mentioned contact TRS system, is reported.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/221413