Washington State University

Food Science

Numbered 20ml beer samples await sensory analysis

It Has To Taste Good

Negative impacts of stress on cropping systems, if measured at all, are typically measured in terms of yield loss and resultant economic loss. This project incorporates crop quality analysis, including sensory analysis and consumer acceptance, which are key to the subject crops.

Experiment Overview

Beer produced from hops grown under four types of pest-induced field stress (mites, aphids, powdery mildew, downy mildew) at three levels (low, medium, high) was presented to untrained consumers for sensory evaluation in a series of tests in April and May of 2011. Sensory testing included a duo-trio difference test to determine if consumers could perceive a difference between different levels of the various stresses. Following discrimination testing, consumers evaluated the acceptability of each treatment at each level.

A second set of beer samples, produced using three types of hops (Columbus, Galena, Nugget) at two levels of stunt viroid level (negative and positive) were also evaluated using the duo-trio difference test and consumer acceptance panel.

The hops from which the beers were produced were grown in our experimental plots near Prosser, Washington, and Corvallis, Oregon. Samples of the beers, also produced in Prosser, were brought to the WSU School of Food Science in Pullman, Washington, on April 7 and stored at 3°C. 

Test beers were brought to room temperature overnight. Twenty ml samples were poured under white light just before serving, then served in a clear wine glass covered with a petri dish to trap aroma. Panelists were provided with unsalted-top saltine crackers and water to cleanse their palates between samples.

Sensory Lab glassware array pre-test

Sensory laboratory pre-test glassware array.

Duo-Trio Difference Test I

In the duo-trio difference tests, 30 subjects were asked to indicate which of two coded samples they perceived to be different from a labeled reference and comment on why they perceived the selected sample as different.  Within each treatment, the low stress level served as a reference for comparison to the medium and the high stress levels. For each treatment, samples were presented to panelists in two flights: low vs medium, and low vs high. Results.

Duo-Trio Difference Test II

For the second set of samples, for each variety of hops, the negative sample (without stunt viroid) served as a reference for comparison to the positive level (with stunt viroid). Samples were presented to panelists in three flights: positive vs. negative for each variety of hops. Results.

Consumer Acceptance Tests

Consumer acceptance of the beer was determined using a 7-point hedonic scale. Samples were presented individually in coded glasses. Sixty consumers were asked to indicate how much they like each sample based on overall acceptance, appearance/ color and taste/ flavor attributesResults on overall acceptance, color, and taste attributes; results on flavor attributes.


The Tests

  • Conducted in April and May 2011
  • WSU School of Food Science sensory lab
  • Two types of tests:
    • Difference tests
    • Acceptance tests

The Hops

  • Grown in 2010
  • From Prosser, WA and Corvallis, OR
  • Three varieties
    • Columbus
    • Galena
    • Nugget

The Stresses

  • Four types:
    • mites
    • aphids
    • powdery mildew
    • downy mildew
  • Also stunt viroid across three hop varieties

The Subjects

  • Aged 21 and over
  • 54% to 62% male
  • 70 to 73.5% aged 21-35
  • most occasionally or frequently consume beer

The Attributes

  • Bitter
  • Sour
  • Sweet
  • Malty/Caramel
  • Hoppy
  • Yeasty
  • Green/Vegetal
  • Fruity
  • Cardboard
  • Aftertaste
  • For definitions, click here

The Results

The Report

  • Prepared by Dr. Carolyn Ross, Research Assistant Karen Weller, and Food Science student Maria Rosales Soto.
Washington State IPM Coordinator, WSU Irrigated Agriculture Research & Extension Center, Prosser WA 99350, 509-786-9287