Flavour and Mass Spectrometry

Abstract

The flavour of food, commonly called ‘taste’, is an essential determinant of food choice by the consumer. Flavour perception in the mouth results from at least two sensory modalities, aroma and taste, due to odour-active and taste-active compounds released from the food matrix on eating. Instrumental assessment of flavour should characterise odouriferous molecules present in the volatile organic compounds of food and sapid components, essentially present in the non-volatile fraction of food. Mass spectrometry (MS) plays a fundamental role in the studies dedicated to flavour characterisation. Coupled with gas chromatography (GC) and benefitting from the latest development in multidimensional GC, MS is the method of choice to identify and quantify aroma compounds. Analytical advances for aroma compounds identification are presented, which include ionisation methods – electron ionisation and chemical ionisation – and mass analysers – tandem mass spectrometry (MS/MS) and high-resolution mass spectrometry – issues, not to forget hyphenation to olfactometry (GC-MS/O). Significant developments in the coupling of advanced MS instruments to liquid chromatography (LC-MS and LC-MS/MS) resulted in the possibility to take charge of non-volatile taste compounds. The great diversity of chemical structures responsible for taste, particularly bitterness, is emphasised in a comprehensive, while not exhaustive, review. Recent developments in direct-injection MS technologies, such as atmospheric pressure chemical ionisation and proton transfer reaction, have allowed developments in two kinds of applications. First, in vivo studies that allow taking charge online and real-time of the dynamic nature of flavour release in the mouth during consumption has received substantial attention. Second, untargeted fingerprinting of the volatiles emitted by foodstuffs (‘volatilome’), completed by more and more accessible non-volatiles profiling, has evolved in a metabolomics approach of flavour that could be called ‘flavouromics’. Both domains are reviewed, with examples taken from the most recent literature.