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Title: Preparation and characterization of 2-formyl-1,4,5,6-tetrahydropyridine, a compound with a cracker-like odor

item Takeoka, Gary
item Buttery, Ron

Submitted to: Journal of Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2011
Publication Date: 1/2/2012
Citation: Takeoka, G.R., Buttery, R.G. 2012. Preparation and characterization of 2-formyl-1,4,5,6-tetrahydropyridine, a compound with a cracker-like odor. Journal of Food Chemistry. 132:2131-2134.

Interpretive Summary: The flavors of bread, popcorn, aromatic rice (such as Basmati and jasmine), and tortillas are among the most popular and desirable of all foods. The appealing and attractive flavors of these foods are largely due to 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine. These two compounds have popcorn-like, cracker-like and roasty odors and are key contributors to the flavors of cereal products. In this study we synthesized and characterized a new flavor compound, 2-formyl-1,4,5,6-tetrahydropyridine. This compound has a pleasant cracker-like odor. Further studies are needed to determine if this compound occurs in food and, if so, to quantify its odor contribution.

Technical Abstract: 2-Acetyltetrahydropyridine is an important flavor constituent that imparts roasty, popcorn-like, and cracker-like odors to foods such as bread, rice, popcorn, taco shells and tortilla chips. We postulated that the homolog with a formyl group in the C-2 position, 2-formyltetrahydropyridine, might have similar desirable odor qualities. Synthesis of this compound was performed by oxidation of 2-piperidinemethanol with silver carbonate supported on Celite®. This reaction produced a major volatile (46.9% of the total volatiles) with a retention index of 1023 on DB-1. GC-O revealed that the unknown had a strong cracker-like odor. The electron impact mass spectrum of the unknown had the following major ions: m/z 82, 111, 54, 68, 28, 43. The m/z 53 to 54 ratio and m/z 82 to 83 ratio were consistent with a 1,4,5,6-tetrahydropyridine ring structure. GC-FTIR of the unknown revealed an N-H stretching band at 3435 cm-1 and a Fermi doublet at 2827 and 2713 cm-1 that indicated the presence of an aldehyde. A strong carbonyl absorption band was present at 1703 cm-1. The unknown was tentatively identified as 2-formyl-1,4,5,6-tetrahydropyridine based on its retention index, odor quality, mass spectrum, and vapor phase infrared spectrum.