Chemistry and stabilization of 2-acetyl-1-pyrroline

Hausch, Bethany Jean

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https://hdl.handle.net/2142/101273 Copy

Description

Title

Chemistry and stabilization of 2-acetyl-1-pyrroline

Author(s)

Hausch, Bethany Jean

Issue Date

2018-04-03

Director of Research (if dissertation) or Advisor (if thesis)

Cadwallader, Keith

Doctoral Committee Chair(s)

Engeseth, Nicki

Committee Member(s)

• Schmidt, Shelly
• Sweedler, Jonathan

Department of Study

Food Science & Human Nutrition

Discipline

Food Science & Human Nutrition

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

2-acetyl-1-pyrroline, unstable, polymerization, high resolution mass spectrometry, NMR, 2D NMR, dimer, stable isotope, deuterium exchange, 2-acetylpyridine, 2-acetyl-2-thiazoline, starch, complexation, stabilization, x-ray diffraction, differential scanning calorimetry, amylose inclusion complex

Abstract

2-Acetyl-1-pyrroline (2AP) is the characterizing aroma compound in aromatic rice, popcorn, Pandan leaf and bread flower. 2AP also contributes to the flavor of a diverse array of other foods, such as roasted nuts, sweet corn, bread crust, lobster and cooked mushrooms. 2AP has a pleasant popcorn or cracker-like aroma and a low odor threshold of 0.1 ppb. However, 2AP is unstable and is quickly lost in cooked foods, such as bread and popcorn. The instability of 2AP was noted along with its discovery in 1982, and, in the following year, it was hypothesized that 2AP may undergo a polymerization process. Much research has been done on 2AP in the intervening years: deducing 2AP’s formation pathway by the Maillard reaction, quantitation in various foods, development of new synthetic routes and attempts towards its stabilization. Despite this appreciable body of research, little has been done to determine the fate of 2AP to date. The current research fills the gap by establishing that 2AP polymerizes with supporting analytical data. To accomplish this, 2AP and its products were measured in water over time by electrospray high resolution mass spectrometry (ESI-HR-MS) and nuclear magnetic resonance (NMR). Dehydration occurs as polymerization proceeds, producing products with increasing degrees of unsaturation. The structure of 2AP’s hydrated dimer is proposed, along with a possible mechanism for its formation. MS deuterium exchange data and 2D NMR data are used to support this structure. Although numerous attempts have been made to stabilize 2AP, many proposed methods lack storage stability data. Even the more promising techniques require special storage conditions, such as low moisture or reduced temperature storage. In this work, starch complexation was evaluated for 2AP stabilization. The linear portion of starch, amylose, is able to form an α-helix around flavor compounds and other small molecules. The methodology was developed using the structurally similar 2-acetylpyridine (2APy). Complexation time was also reduced from 24 hours to under one hour, to limit the time 2AP is exposed to water, by using the addition of organic solvent and sonication. Complexes were characterized using x-ray diffraction, gas chromatographic analysis and differential scanning calorimetry. Loadings of up to 0.504 (±0.071)% 2AP were obtained and over half of the flavorant was retained after 2 weeks storage at 0% relatively humidity. After further development, this approach may offer a viable way to deliver 2AP in finished food products, mimicking the way 2AP is stabilized in nature.

Graduation Semester

2018-05

Type of Resource

text

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http://hdl.handle.net/2142/101273

Copyright and License Information

Copyright 2018 Bethany Hausch

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