Impact of fruit texture on the release and perception of aroma compounds during in vivo consumption using fresh and processed mango fruits
Introduction
Understanding flavour perception impact factors is an important challenge for the food-processing industry to be able to produce innovative and appreciated food products. Indeed, flavour is the main factor affecting consumers’ preferences.
Several studies have reported that flavour perception and in vivo flavour release from food was impacted by the nature and amount of aroma compounds, and also by other matrix components, such as lipids (Delahunty et al., 1996, Frank et al., 2011), polyphenols (Muñoz-González, Martin-Alvarez, Moreno-Arribas, & Pozo-Bayon, 2014), sugars, acids or alcohols (Malundo et al., 2001, Marsh et al., 2005, Muñoz-González et al., 2014) and pectins (Boland et al., 2006, Lubbers and Guichard, 2003). On the other hand food texture is a noticeable factor in flavour perception and is taken into consideration in flavour formulation (Aprea et al., 2006, Boland et al., 2004, Frank et al., 2012, Frank et al., 2011). The release of aroma compounds during eating is also known to be affected by human oral physiology and oral processing factors (saliva, chewing, breathing, oral cavity volume, in-mouth temperature, tasting time, etc.) (Buettner and Beauchamp, 2010, Buettner and Schieberle, 2000a, Buettner and Schieberle, 2000b).
Many in vivo and in vitro experimental studies have been conducted on model food systems spiked with volatile organic compounds (VOCs) to gain insight into the contribution of food texture, oral physiology and oral processing factors on the release of aroma compounds during consumption (Feron et al., 2014, Lubbers and Guichard, 2003, Poinot et al., 2013, Van Ruth and Roozen, 2000). However, very few studies have used real food matrices, such as fruits, to study the aroma release during oral processing (Frank et al., 2012, Ting et al., 2015, Ting et al., 2016).
Two techniques have been described in the literature for studying the in vivo release of aroma compounds during food consumption. First, atmospheric pressure chemical ionisation mass spectrometry (API-MS) and proton transfer reaction mass spectrometry (PTR-MS) are often used. They enable real-time monitoring of VOC release during consumption (Frank et al., 2012). The conventional MS instruments are equipped with a quadrupole mass filter that hinders discrimination of isobaric compounds, i.e. compounds with the same nominal mass that may occur in foods. Combining PTR with a time-of-flight (TOF) mass analyser, as first mentioned in 2004, could readily overcome this problem by boosting the mass resolution (Zardin, Tyapkova, Buettner, & Beauchamp, 2014). Secondly, quite simple techniques, amenable to any laboratory and based on the trapping of VOCs exhaled through the nasal cavity on either SPME fibres (Pionnier, Sémon, Chabanet, & Salles, 2005) or an adsorbant polymer like Tenax (Buettner and Schieberle, 2000a, Muñoz-González et al., 2014) have been developed. Further analysis of trapped VOCs by conventional GC-MS-EI leads to easier compound identification. However, these techniques do not deliver temporal profiles of VOC release during consumption, in contrast to PTR or API based techniques.
The main objective of this study was to understand the impact of fruit texture both in the release of VOCs during oral processing and in sensory perception. Mango fruit was used because of its richness in aroma compounds (Munafo et al., 2014, Pino et al., 2005). To assess the impact of texture, four mango samples were prepared from a homogenous mango fruit batch to obtain different textures: two fresh (fresh puree, fresh cubic pieces) and two dried (dried powder, dried cubic pieces) mango samples. Hence it was possible to carry out pairwise comparisons of fresh puree and fresh cubic pieces for aroma release in vivo since they were similar in their VOC composition. The same comparison was made between dried powder and dried cubic pieces because of their similar VOC compositions. VOCs from the assessors’ exhaled nostril breath during consumption of the mango products were trapped by a retronasal aroma-trapping device (RATD) containing Tenax and then analysed by GC–MS. The assessors watched a visual animation in order to calibrate their chewing and breathing cycles and swallowing time so as to limit intra- and inter-individual variability. VOCs from exhaled nostril breath were compared with those identified in the organic extracts of mango samples obtained by a convenient technique, i.e. solvent-assisted flavour evaporation (SAFE). Finally, four mango samples were evaluated by a trained sensory panel to discuss the relationship between VOCs detected in the assessors’ exhaled nostril breath and the sensory attributes of the panel.
Section snippets
Chemical reagents
The chemical solvents pentane, hexane, dichloromethane and methanol were purchased from Sigma-Aldrich (St. Louis, MO). The internal standard α-cedrene used for SAFE extraction and in vivo experiments was from Sigma-Aldrich. The authentic standards α-pinene, β-pinene, β-myrcene, δ-3-carene, camphene, α-phellandrene, β-phellandrene, α-terpinene, γ-terpinene, limonene, p-cymene, β-ocimene, α-terpinolene, α-gurjunene, α-caryophyllene, β-caryophyllene, 3-methylbutyl butanoate, heptanal,
Main physicochemical analysis of mango samples
The main physicochemical properties of mango samples, i.e. brix (°Bx), pH, titratable acidity (TA), water activity (aw) and dry matter (DM) of fresh and dried mango were similar to previously published values (Pott et al., 2005, Tharanathan et al., 2006) (Table 2). Aw was less than 0.6, which is the level required for the microbiological stability of dried fruits (Pott et al., 2005).
Aromatic profile of mango samples
The SAFE technique was used to determine, as accurately as possible, the whole aroma composition of mango
Conclusion
The current study highlighted the impact of fruit texture on the release and perception of aroma compounds during in vivo consumption. Although the RATD-based experimental methodology was unable to monitor VOC release in real-time in vivo experiments, it enabled us to draw general conclusions matching those reported with PTR-MS on real foods. The implemented methodology was quite simple and also enabled us to identify VOCs at low levels because of the several seconds of trapping during oral
Acknowledgements
We are very grateful to Christophe Bugaud from the QualiSud Research Unit and Xavier Bry from Montpellier University for their support in the statistical analysis and all the assessors from the QualiSud Research Unit involved in the in vivo experiments.
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