GC+and+Flavor+Plan

Author & Date: Dan H. 12/9/10

Topic/Concept: Volatile compounds and the flavor of foods: an introduction to gas chromatography. Based on the "Chemistry of Flavor" activity in //Kitchen Chemistry*.//

Type of Activity: discussion, lab.

Prerequisite knowledge: none.

Resources required:


 * 1) flavorings/extracts/oils, or purees.
 * 2) Gas chromatograph, or chromatograms for a few flavorings.

Learning Objectives:


 * Students will develop a working understanding of flavor perception.
 * Students will be able to distinguish taste from aroma.
 * Students will be able to diagram the major components of a gas chromatograph.
 * Students will be able to draw a simple diagram explaining how a compound travels through the column of a gas chromatograph.
 * Students will be able to describe the significance of a peak on a chromatogram.
 * Students will be able to qualitatively describe how the retention time of a compound is affected by the
 * volatility of the components
 * temperature of the column
 * length of the column
 * flow rate of the carrier gas.
 * Students will develop a working model of the role of aroma in the perception of flavor.

Common Misconceptions:

Detailed Description of Activity:


 * 1) Ahead of time: prepare chromatograms of various flavorings/oils.
 * 2) Discussion: what do the students already know about flavor? Is it just about taste? Does smell factor in? How about appearance, texture, or even sound?
 * 3) Activity: challenge the students to identify a few purees by smelling them, tasting them with their noses blocked, and tasting them normally. Optionally, repeat the process with flavorings/oils put into a carrier (syrup, cracker, maltodextrin, etc)
 * 4) Discussion: based on the activity, what do the students say about the role of aroma in the perception of flavor? From the discussion, develop a simple model explaining the mechanism that leads to an individual's detection of an aroma, from the time the source of it is put into his/her mouth.
 * 5) Lecture/youtube video: introduction to gas chromatography.
 * 6) Discussion: we suspect that flavor depends heavily on volatile compounds, and that gas chromatography can separate and detect volatile compounds based on retention time. Can a gas chromatograph help to identify the flavor of a particular substance? What would we expect to see on the chromatograms of two substances with very similar tastes?
 * 7) Activity: based on a collection of chromatograms, challenge students to identify which might be similar/identical flavors, and which are combinations of other flavors.
 * 8) Discussion: applications to quality control, reverse engineering, and flavor development in the food industry. Uses of gas chromatography in forensics.

Assessment:

Associated files and images:

Comments:


 * Lister, T. //Kitchen Chemistry//. The Royal Society of Chemistry, 2005. pp.77-85.