Graduate Student Spotlight

The University of Minnesota is where some of the best and brightest future industry leaders are honing their research.

Each week we will feature a different graduate student and their current research efforts, giving you an opportunity to learn more about what is happening in our department, as well as the world of food science and nutrition research right now.


Kirsten WeissName
: Kirsten Weiss
Hometown: Minneapolis, Minn.
Degree Pursuing: Food Science MS M.S.
Adviser: Zata Vickers
Research Title
Research Focus: Evaluation of omission testing as a method for identifying important odorants in a mixture
Food odors are often complex mixtures of hundreds of volatile compounds.  Few of these compounds contribute to the perceived aroma. It is beneficial to the food industry to be able to reproduce a characteristic food aroma or identify off odors that result in an undesirable product. Therefore, it is important to have reliable methods for identifying and evaluating odor mixtures.  Omission testing is a common sensory evaluation strategy used for identifying the important odorants in a mixture. The premise of this method is that if a compound making an important contribution to an odor mixture is removed, doing so will produce a perceived difference in the mixture’s odor quality. This is easily observed if a removed compound provides a relatively intense and identifiable character to the mixture.  However, mixtures of compounds at the same perceived odor intensity are known to produce blending/fusing. Would assessors be able to perceive the omission of individual odorants in blended/fused mixtures? How much training would be required to accomplish this?

The objective of this study was to determine whether panelists could learn to discriminate between samples of a five compound odor mixture with all compounds at the same perceived intensity and the same mixture with any one or two of the five compounds removed.

We selected panelists (N = 22) based on their ability to correctly order the perceived intensities of five concentrations of each of 5 compounds (butyric acid, furaneol, methional, delta-decalactone, and acetylpropionyl). During preliminary test sessions we selected, for each panelist separately, concentrations of each of the first four of these compounds that were equivalent in intensity to acetylpropionyl. We then constructed, for each participant, a mixture of the five compounds that were matched in intensity. Panelists then participated in 20 sessions consisting of a series of A-not-A Tests using a replicated mixed design with corrective feedback.  During each of these sessions panelists were presented with ten, complete 5-component mixtures, five, 4-component mixtures (each missing a different component), and five, 3-component mixtures (each missing 2 different components). Results of the A-not-A Tests indicated that panelists could not discriminate between samples when one compound was removed.  Some panelists could discriminate between samples when two compounds were removed but not without difficulty.  Performance did not improve over the 20 sessions.  Results were similar for each compound. 

Panelists’ failure to learn to discriminate the 4-component mixtures from the 5-component mixtures shows that omission tests are unreliable for indicating the importance of an odor to a mixture.

How did you become interested in food science? 
I was originally interested in pursuing a degree in nutrition. I have three children, and I was interested in how food and diet affected their health. I fell in love with food science after taking Dr. Zata Vicker’s Introduction to Food Science course and immediately changed my plans.

How does your research parallel that of your adviser's?
My research is a replication (with a few changes) of a study that was done several years ago.  The results of the original study were unexpected and we wanted to determine what happened. 

What are your future plans?
I am graduating this summer and will be looking for work in the Twin Cities area.


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