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Title:Identification and characterization of mint lactones: trace-level odor-important aroma compounds in peppermint oil
Author(s):McKenna, Samantha Grace
Advisor(s):Cadwallader, Keith R.
Department / Program:Food Science & Human Nutrition
Discipline:Food Science & Human Nutrition
Degree Granting Institution:University of Illinois at Urbana-Champaign
gas chromatography-mass spectrometry (GC-MS)
Abstract:Mentha piperita L., commonly known as peppermint, is an essential oil bearing plant that was introduced to the United States in the early-19th century. By 1900 peppermint cultivation and oil production had reached the Pacific Northwest where the majority of peppermint oil in the United States is produced today. In 2015 the United States produced 5.9 million pounds of peppermint oil which is used in a wide variety of food and flavor applications including chewing gum, oral hygiene products, pharmaceuticals, confectionary, and liquor among others. Trace odorants are crucial to the flavor profile of well-balanced peppermint oil. Certain lactones have been identified in peppermint oils in trace levels that contribute important sweet, coconut, coumarin-like aroma characteristics to the oils. Among these lactones, collectively known as "mint lactones", (−)-mintlactone and (+)-isomintlactone are the most well characterized, although numerous others remain unidentified. Four peppermint oils were analyzed by gas chromatography-olfactometry (GCO) and gas chromatography-mass spectrometry (GC-MS) to identify the odor-active lactones. Since lactones are present at trace levels, a silica gel fractionation method was developed to isolate and concentrate the lactones from peppermint oil prior to GC analysis. A total of five odor-active "mint" lactones were detected, including (−)-mintlactone and two menthofurolactone (MFL) diastereomers ("MFL A" and "MFL B"). The lactones were quantitated using stable isotope dilution analysis (SIDA) with a 2H-labeled saturated mint lactone as the internal standard. The two diastereomers of menthofurolactone were resolved using chiral gas chromatography and their independent in-air odor thresholds and odor qualities were approximated using GCO. The enantiomeric ratio of the MFL diastereomers was also examined in relation to the menthofuran content of the oils and the concentrations of the MFL isomers. A model peppermint oil (MPO) system was also developed and used to study the degradation of menthofuran to form mint lactones. The concentrations of four lactone compounds, MFL A, MFL B, (−)-mintlactone, and (+)-isomintlactone, were tracked over a period of six months. After an initial increase in the concentrations of all four lactones, the levels at six months approached those found in actual peppermint oils. The MPO sample stored at ambient conditions maintained a constant enantiomeric ratio of the MFL diastereomers over time. A proposed scheme for the formation of lactones from menthofuran is presented.
Issue Date:2016-07-13
Rights Information:Copyright 2016 Samantha McKenna
Date Available in IDEALS:2016-11-10
Date Deposited:2016-08

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