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The aim of the study was to investigate the effect of food structure and composition on aroma release and sensory perception of composite foods. Dynamic sensory perception was assessed with Temporal-Check-All-That-Apply (TCATA) (n=72) while quantification of aroma release was done with in vivo nose space analysis using a commercial PTR-ToF-MS (Proton Transfer Reaction Time-of-Flight Mass Spectrometer, Ionicon Analytik, Innsbruck, Austria) (n=8, in triplicate). Six composite foods were prepared by combining two carriers (bread and wafer) with three formulations of chocolate-hazelnut spreads varying in fat and sugar content (high fat/high sugar; high fat/low sugar; low fat/high sugar). The spreads were spiked with a known quantity of 5 aroma compounds. Evaluations of the hazelnut spreads without carriers and for the carrier-spread combinations were performed. In general, fat and sugar content had little effect on flavour release and sensory perception of chocolate hazelnut spread. Addition of carriers increased aroma release and decreased flavour perception. We conclude that in vivo nose space analysis by direct injection mass spectrometry (PTR-MS) and dynamic sensory method (TCATA) allowed to investigate aroma release and perception of real food matrices (spreads and composite foods). Flavour release and sensory perception of hazelnut chocolate spreads is strongly affected by addition of carriers. However, it seems that sensory perception of composite foods is modulated by cognitive mechanisms.

Condiments such as spreads, dressings, or sauces are usually consumed together with carrier foods such as breads or vegetables. Dynamic interactions between condiments and carriers occur during consumption, which can influence aroma release and perception. This study investigated in vivo aroma release (PTR-MS) and dynamic sensory perception (time-intensity) of mayonnaises spiked with lemon aroma (limonene, citral). Mayonnaises were assessed without and with carrier foods (bread, potato). When different mayonnaises were consumed and assessed alone, aroma release and intensity perception were positively correlated. Interestingly, when mayonnaises were combined with carriers, aroma release and perception were no longer positively correlated. Addition of carriers increased release of limonene and citral into the nasal cavity during consumption but decreased perceived aroma intensity of condiments. The increase in aroma release induced by the carriers can be explained by differences in oral processing behaviors and by the increased surface area of mayonnaise-carrier combinations. Carrier addition is likely to modulate aroma perception of composite foods by cross-modal texture-aroma interactions. This work demonstrates that not only physicochemical characteristics of foods but also cross-modal interactions play a role in influencing flavor perception of composite foods.

This article is part of the special issue of the Flavour and Fragrance Journal entitled “On‐line monitoring of odorants using direct‐injection mass spectrometry” edited by Jean‐Luc Le Quere., Changes in the headspace volatile profile of tea infusion during brewing were determined by analysing the aliquots taken every 30 s using proton transfer reaction time‐of‐flight mass spectrometry in conjunction with principal component analysis and hierarchical cluster analysis. The effect of three different brewing temperatures (60, 70 and 80°C), two leaf sizes (broken and full leaves) and two water mineralizations (soft and hard), on the concentration of volatile compounds in the headspace of tea, was studied as a function of infusion time. An increase in brewing temperature resulted in increased volatile content in the headspace, reflecting an increase in extraction efficiency. Such differences on extraction efficiency were more pronounced with increasing brewing times. Leaf size had also a big impact on the extraction of volatile compounds, but mainly during the early phase of brewing. Water mineralization had a low but noticeable impact on the volatile content. Furthermore, clusters of samples prepared with different combinations of brewing parameters but resulting in analogous volatile profiles could be identified using hierarchical clustering analysis.

Food industry is searching for rapid and flexible instrumental tools to support sensory evaluations for quality control of food products. Monitoring volatile organic compounds (VOCs) from farm to fork through direct injection mass spectrometry techniques seems a promising possibility. This thesis focuses on the aspects of food quality related to the sensory part of aroma by presenting different applications of proton transfer reaction mass spectrometry (PTR-MS) for headspace and in vivo nose-space analysis. PTR-ToF-MS was used in combination with a selective reagent ionization device (SRI) and multipurpose autosampler for obtaining, through a rapid and non-invasive headspace analysis, VOCs fingerprint of different food matrixes like anhydrous milk fat (AMF), ultra-high temperature lactose-free milk (UHT LF milk) and raw hazelnuts. The results of Chapter 2, 4 and 5 confirmed that PTR-ToF-MS fingerprinting is a valid sensitive approach to collect information about VOCs evolution during shelf life at different conditions and to monitor degradation processes which can compromise food quality such as lipid oxidation. Results from Chapter 3 and 5 demonstrate that VOCs fingerprints can be used for supporting sensory quality control in agroindustry since both unsupervised and supervised data mining approaches gave positive results in discriminating sensory classes assigned through industry sensory tests. For both tested raw materials (AMF and raw hazelnuts), the good quality samples had lower concentrations for most of the detected mass peaks in VOCs fingerprints.Chapter 6 and 7 demonstrated the potentialities of coupling PTR-QiToF-MS in vivo nose-space analysis with dynamic sensory analysis to better investigate the complex relation between aroma release and perception and the impact of product and consumer characteristic on this relation. Chapter 6, showed that when consuming composite foods, decrease in sensory intensity perception was not due to a lower delivery of arom

Lactose-free dairy products undergo several chemical modifications during shelf life because of the reactivity of glucose and galactose produced by the lactose enzymatic hydrolysis. In this study, proton transfer reaction-mass spectrometry (PTR-MS), coupled with a time-of-flight (TOF) mass analyzer, was applied to get an insight on the phenomena occurring during the shelf life of ultrahigh-temperature (UHT) lactose-free milk (LFM). UHT LFMs produced by three different commercial lactase preparations were evaluated during storage at 20°C over a 150 days period, sampling the milk every 30 days. Production was repeated three times, on three consecutive weeks, in order to take milk variability into consideration. Principal component analysis applied to the whole “volatilome” data demonstrated the capability of PTR-TOF-MS in detecting the milk batch-to-batch variability: Freshly produced milk samples were distinguished based on the week of production at the beginning of shelf life. Additionally, a clear evolution of the volatiles organic compounds (VOCs) profiling during storage was highlighted. Further statistical analysis confirmed VOCs temporal evolution, mostly because of changes in methyl ketones concentration. Differences caused by the commercial lactases did not emerged, except for benzaldehyde. Altogether, data demonstrated PTR-TOF-MS analysis as a valuable and rapid method for the detection of changes in the VOCs profiling of UHT LFM.