Mass spectrometry of the acetal derivatives of selected generally recognized as safe listed aldehydes with ethanol, 1,2-propylene glycol and glycerol

摘要

The FEMA-GRAS list offers flavor chemists a repertoire of nearly 2000 chemicals for use in compounding natural and synthetic flavors for the U.S. marketplace. Aldehydes constitute an improtant class of these potential flavorants and are widely utilized to impart specific nuances. Alcohols such as ethanol, 1,2-propylene glycol and glycerol are commonly employed as solvents in compounded flavor systems due to their low odor and miscibility in a wide range of aqueous and organic matrices. However, alcohols and aldehydes react rapidly under anhydrous conditions to form acetal derivatives which often possess different sensory properties. This well knwon reaction is reversible and its equilibrium is influenced by time, temperrature, pH and moisture content. Mass spectra of acetals are currently under represented in commercial databases and few literature references are available. Our investigation involved a systematic mass spectrometric study of the acetal derivatives of selected GRAS aldehydes reacted with ethanol, 1,2-propylene glycol and glycerol. Aldehydes from different chemical classes representing saturated and unsaturated aliphatics, aromatics, heterocyclics, terpenoids and others were included for characterization. The corresponding acetals were synthesized, analyzed by GC-MS in electron ionization mode and their retention indices on a non-polar (polydimethylsiloxane) capillary column were determined. A database of mass spectra was produced which includes many previously unreported species. In total, over 60 individual mass spectra were recorded. The characteristic mass spectral fragmentation pathways for each class of acetal are described.