La caratterizzazione chimica della frazione volatile delle nocciole di alta qualità ha un grande potenziale informativo per quanto riguarda le variabili esterne come le condizioni pedoclimatiche della regione di raccolta, la presenza di batteri e muffe, i trattamenti post-raccolta del prodotto e la qualità complessiva della nocciola grezza. In tale frazione ci sono centinaia di sostanze chimiche rilevabili (denominate caratteristiche), sia note, e quindi definite come analiti target, sia sconosciute - analiti non target. Tramite un'adeguata microestrazione in fase solida dello spazio di testa (HS-SPME) combinata a GC-MS 1D e 2D completa abbiamo confrontato - a livello non mirato - l'intero volatiloma rilevabile tra i campioni per discriminare le differenze biologiche tra gli stessi. I campioni sono stati selezionati tra le nocciole di alta qualità strategica a livello industriale (Akçakoca, Giresun e Tonda Gentile delle Langhe) e provenienti dai principali paesi di produzione, ovvero Turchia e Italia. La conservazione è stata condotta lungo la shelf-life fino a diciotto mesi (punti temporali a 0, 4, 6, 12, 16, 18 mesi) al fine di valutare la stabilità della frazione grassa e monitorare la sua evoluzione nel tempo. È stata eseguita la valutazione delle prestazioni tra i metodi di gascromatografia 1D e 2D, condotta sia con approcci non mirati che mirati e le metodiche di confronto adottate sono state: capacità di fornire informazioni - incluso l'aroma - e capacità di classificazione. Inoltre, la serie di aldeidi sature lineari (esanale, eptanale, ottanale e nonanale), che sono i prodotti di ossidazione secondaria dell'acido oleico e lineoleico, è stata oggetto dello sviluppo e della validazione di un metodo quantitativo veloce e accurato basato su HS-SPME mediante estrazione multipla dello spazio di testa e veloce (1D) GC-MS. I risultati quantitativi hanno mostrato un aumento costante della quantità totale di aldeidi sature lungo la shelf-life, che riflette anche le condizioni di conservazione considerate, con i campioni all'aria aperta caratterizzati da livelli di irrancidimento più elevati.
The chemical characterization of the volatile fraction of high quality hazelnuts has great informative potential regarding external variables like pedoclimatic conditions of the harvest region, presence of bacteria and moulds, post-harvest treatments of the crop and the overall quality of the raw kernel. In such fraction there are hundreds of detectable chemicals (referred to as features), both known, and therefore defined as target analytes, and unknown – untargeted analytes. By suitable headspace solid phase microextraction (HS-SPME) combined to 1D and comprehensive 2D GC-MS we compared - at an untargeted level - the entire detectable volatilome between samples to discriminate biological differences among samples. Samples were selected among industrially strategic high-quality hazelnuts (Akçakoca, Giresun, and Tonda Gentile delle Langhe cultivars/blends) and from major production countries, i.e., Turkey and Italy. Storage was conducted along shelf-life up to eighteen months (time points at 0, 4, 6, 12, 16, 18 months) in order to evaluate the fatty fraction stability and monitor its evolution over time. Performance evaluation between 1D and 2D gas chromatography methods conducted with both untargeted and targeted approaches, was performed and metrics of comparison adopted were: information capacity – including aroma - and classification capabilities. Moreover, the series of linear saturated aldehydes (hexanal, heptanal, octanal, and nonanal), that are the secondary oxidation products of oleic and lineoleic acid, was the object of the development and validation of a fast and accurate quantitative method based on HS-SPME by multiple headspace extraction and fast (1D)GC-MS. Quantitative results showed a constant increase in the total amount of saturated aldehydes along shelf-life, which also reflects the storage conditions considered, with the open air samples being characterized by higher rancidity levels.
"Definizione di pattern chimici diagnostici mediante cromatografia 1D/2D: strategie di fingerprinting avanzato per la qualificazione di nocciola"
CARATTI, ANDREA
2020/2021
Abstract
The chemical characterization of the volatile fraction of high quality hazelnuts has great informative potential regarding external variables like pedoclimatic conditions of the harvest region, presence of bacteria and moulds, post-harvest treatments of the crop and the overall quality of the raw kernel. In such fraction there are hundreds of detectable chemicals (referred to as features), both known, and therefore defined as target analytes, and unknown – untargeted analytes. By suitable headspace solid phase microextraction (HS-SPME) combined to 1D and comprehensive 2D GC-MS we compared - at an untargeted level - the entire detectable volatilome between samples to discriminate biological differences among samples. Samples were selected among industrially strategic high-quality hazelnuts (Akçakoca, Giresun, and Tonda Gentile delle Langhe cultivars/blends) and from major production countries, i.e., Turkey and Italy. Storage was conducted along shelf-life up to eighteen months (time points at 0, 4, 6, 12, 16, 18 months) in order to evaluate the fatty fraction stability and monitor its evolution over time. Performance evaluation between 1D and 2D gas chromatography methods conducted with both untargeted and targeted approaches, was performed and metrics of comparison adopted were: information capacity – including aroma - and classification capabilities. Moreover, the series of linear saturated aldehydes (hexanal, heptanal, octanal, and nonanal), that are the secondary oxidation products of oleic and lineoleic acid, was the object of the development and validation of a fast and accurate quantitative method based on HS-SPME by multiple headspace extraction and fast (1D)GC-MS. Quantitative results showed a constant increase in the total amount of saturated aldehydes along shelf-life, which also reflects the storage conditions considered, with the open air samples being characterized by higher rancidity levels.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14240/129008