Individualization of Flavor Preferences: Toward a Consumer-centric and Individualized Aroma Science

Methods, principles, challenges, and perspectives of determining chloropropanols and their esters

Chloropropanols and their esters are a group of food contaminants that have various toxicities to the human body. Research and control to chloropropanols and their esters is important to food safety. Therefore, the sensitive, accurate, precise, and effective determination of chloropropanols and their esters is highly essential to study their concentration, formation, and mitigation. The indirect method, commonly applied in the determination of chloropropanols and their esters, is based on the cleavage of ester bond, extraction, and derivatization. The conventional indirect method will still be the mostly used method in the near future due to its good sensitivity and feasibility, although its parameters need to be chosen and optimized according to sample stuffs and chloropropanol concentrations. Meanwhile, direct method and other quantitative methods should also be developed for special applications, such as studying the profile of chloropropanol esters and rapid screening protocol. The challenges and future perspectives of these methods are discussed in this review. This review can provide a reference on the selection, designation, and modification of methods for determining chloropropanols and their esters.

Are organic acids really related to the sour taste difference between Chinese black tea and green tea?

Sour is an important taste in some foods, beers, and teas; organic acids, in particular, are thought to play a key role in the formation of the sour taste of beer. It has been generally thought that organic acids also contribute to some teas tasting sour. In this study, through sensory evaluation experiments with black tea (BT) and green tea (GT), the difference in the sour taste of BT and GT was quantitatively characterized. Then the organic acids in the two types of tea were identified and quantified via high‐performance liquid chromatography (HPLC) with taste activity value (TAV) analysis. The results showed that both teas had 12 identical common organic acids (including 11 taste‐active components), but the results of the TAV analysis were not consistent with those of the sensory evaluation. Therefore, there is no direct relationship between organic acids and the acidity in BT and GT. It is related to the interaction between organic acids and other substances, pH value, or other sour substances in tea infusions. The mechanism of the disappearance of sourness in tea infusions was also discussed. These results help us to understand the correlation between tastes in teas.

Foam Characteristics and Sensory Analysis of Arabica Coffee, Extracted by Espresso Capsule and Moka Methods

The coffee extraction methods modify the structure of the foam (when it is present) and the sensory profile of the beverage. In this research, three ways of extracting and two varieties of 100% Arabica were compared. Nineteen bars and fifteen bars were applied to the coffee thanks to the use of compatible capsules and machines. The method with the moka was considered, which acts at low pressures and does not allow the formation of foam (crema). In addition, the Brazil and Guatemala Arabica varieties were considered to understand the extent to which Arabica coffee can respond in structural and sensorial terms to the extraction techniques applied. The results show that 19-bar espresso coffees have a very stable crema with very small bubbles, which give a uniform and fine structure to the coffee crema. On the contrary, the pressure at 15 bars generates more unstable foams and bubbles that tend to be disproportionate, with more marked effects in the Brazil variety. The sensory profiles of the coffees respond to the extraction techniques applied. While the coffee extracted with the moka has sensory descriptors with rather low values, those obtained at 19 and 15 bars have much wider profiles. In conclusion, different pressure intensities to the coffee extraction affect the quality of crema and the solubilization of organoleptically active compounds.

Novel experimental approach to study aroma release upon reconstitution of instant coffee products

This study presents an experimental approach to study the kinetics and fast release of volatile organic compounds (VOCs) upon reconstitution of instant coffee products. A sampling setup coupled to PTR-ToF-MS (Proton Transfer Reaction Time-of-Flight Mass Spectrometry) for the automated and reproducible reconstitution of instant coffee products was developed to monitor the dynamic release of VOCs. A rapid release of aroma compounds was observed in the first seconds upon hot water addition ("aroma burst"), followed by subsequent decrease in headspace (HS) intensities over the course of analysis. Differences in time-intensity release profiles of individual VOCs were correlated to their Henry's Law constant, vapor pressure and water solubility. The setup and approach proposed here have shown to be sensitive and to respond to fast dynamic changes in aroma release. It allows studying VOCs release upon reconstitution and supports the development of novel technologies and formulations for instant products with improved aroma release properties.

Ethnicity, gender and physiological parameters: Their effect on in vivo flavour release and perception during chewing gum consumption

In this study, the impact of physiological parameters, ethnicity and gender on flavour perception and flavour release of chewing gum was investigated. Proton Transfer Reaction Mass Spectrometry in-nose monitoring of volatile organic compounds was coupled to discontinuous time intensity sensory evaluation for mint flavour and sweetness perception. Each of the 29 subjects, 14 European and 15 Chinese panelists (13 male and 16 females, age 24 ± 1.4 years old) consumed the samples in triplicates. Physiological parameters (oral cavity volume, salivary flow, acetone and isoprene concentration and fungiform papillae density) were measured. Significant differences for in vivo flavour release between Chinese and European panelists after 90 s of consumption and after the gum was removed from the mouth were found. Significant differences were observed also in flavour and sweetness perception while no gender effect was detected. In this work, for the first time an effect of ethnicity on in-nose flavour release monitored through PTR-MS was noticed during chewing gum consumption, in agreement with the findings from sensory evaluation. Single physiological parameters do not explain the relation between flavour in nose release and perception during consumption.

Persistence of aroma volatiles in the oral and nasal cavities: real-time monitoring of decay rate in air exhaled through the nose and mouth

The persistence of aroma compounds in breath after swallowing is an important attribute of the overall aroma experience during eating and drinking. It is mainly related to the coating of the oral tract with food residues and the interaction between volatile compounds and airway mucosa. We have studied the persistence of eight compounds (2,5-dimethylpyrazine, guaiacol, 4-methylguaiacol, phenylethylalcohol, ethylbutanoate, ethyloctanoate, isoamylacetate and 2-heptanone) both in-nose and in-mouth after administration of volatiles in gas phase (vapor) to five different panelists. By using volatiles in the gas phase, only the interaction with the mucosa is highlighted and the formation of a liquid coating in the oral and tracheal airway is avoided. The physicochemical properties of the compounds, mainly polarity and vapor pressure, determine the interactions of the volatiles with the airway mucosa. The use of different breathing protocols allowed the study of the differences between nasal and oral mucosa in volatile retention, with higher persistence of volatiles obtained in-mouth. Initial concentration also affected persistence, but only for compounds with high volatility and at low concentration.

Insight into the time-resolved extraction of aroma compounds during espresso coffee preparation: online monitoring by PTR-ToF-MS

Using proton-transfer-reaction time-of-flight mass-spectrometry (PTR-ToF-MS), we investigated the extraction dynamic of 95 ion traces in real time (time resolution = 1 s) during espresso coffee preparation. Fifty-two of these ions were tentatively identified. This was achieved by online sampling of the volatile organic compounds (VOCs) in close vicinity to the coffee flow, at the exit of the extraction hose of the espresso machine (single serve capsules). Ten replicates of six different single serve coffee types were extracted to a final weight between 20-120 g, according to the recommended cup size of the respective coffee capsule (Ristretto, Espresso, and Lungo), and analyzed. The results revealed considerable differences in the extraction kinetics between compounds, which led to a fast evolution of the volatile profiles in the extract flow and consequently to an evolution of the final aroma balance in the cup. Besides exploring the time-resolved extraction dynamics of VOCs, the dynamic data also allowed the coffees types (capsules) to be distinguished from one another. Both hierarchical cluster analysis (HCA) and principal component analysis (PCA) showed full separation between the coffees types. The methodology developed provides a fast and simple means of studying the extraction dynamics of VOCs and differentiating between different coffee types.