Resonance-enhanced multiphoton ionization time-of-flight mass spectrometry for the real-time analysis of a retronasal aroma compound from a cumin sandwich.

This study was focused on developing a process to objectively determine the release behavior of retronasal aromas in food in real time, which could contribute to the development of foods better suited to consumer preferences. In food, organic compounds with low molecular weight easily vaporize to elicit a retronasal aroma, and such compounds are referred to as volatile. In this study, the release of aroma during the eating of small sandwiches was measured and verified in real-time via resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS). Cumin and small slices of bread were used as food samples that would easily vaporize and could be detected in the breath of a person eating them. Laser pulses emitting at 266 nm during REMPI selectively detected the naturally occurring organic compound p-cymene in cumin. While it was being chewed, the time profile for p-cymene as a retronasal aroma compound showed the increases and decreases in the detection of this food in breaths released in a 6 s cycle (3 s intake, 3 s exhalation). Overall, the retronasal aroma increased and then decreased. The total ion signals of p-cymene obtained during chewing (integrated area under the time profiles) were slightly smaller when eating 1 g of bread than when eating 3 or 7 g. The bread samples were mixed with saliva during chewing, and the oral cavity became relatively saliva-rich. In other words, the bread was easily converted to a liquid food, and the vaporization of the p-cymene in cumin seemed to be suppressed with smaller slices of bread. Moreover, a fit function for the obtained time profile was proposed in the present study. The profile was constructed by combining the subtracted values of the two logistic functions and a trigonometric function. As a fit result, the start and end times of the overall transient time profile were both earlier when eating 1 g of bread than when eating 3 or 7 g; the start time was numerically ca. 3 s earlier, and on average, p-cymene was found to be emitted from the nose half a breath earlier under the present eating conditions.