In this section:
Difference Testing
A simple technique yielding powerful sensory information for many practical applications. These tests reliably verify if perceivable differences exist between a few samples.
Benefits of Difference Testing
- Quick and simple way to check sensory impacts
- Manage risk by achieving informed decision making
- Enhance product development and quality control measures
- Verify that a change in a supplier or processing or packaging introduces no perceptible change in aroma or flavour
Uses of Difference Testing
- Screen batches of ingredients
- Check for taints or off-notes
- Compare subtle aroma and flavour of products that may appear similar
- Discover staff sensitivity to key aromas/flavours
- Establish a difference exists before considering further testing such as attribute intensity rating or preference testing.
Several difference tests can be applied depending on trial objectives. Tests may focus solely on product appearance, aroma, flavour or texture or a combination of these aspects.
Types of difference tests include:
- Triangle – single out the odd sample
- Duo-trio – identify the sample that is the same as a reference sample
- Paired comparison – which sample smells/tastes more like…a specific attribute?
The triangle method is quite common for food trials, while the duo-trio method is most commonly applied for wines or other products with lingering flavours or sensations. If an impact is detected, then further sensory work can be done to pin point what that difference is and what extent it exists in a product.
SARDI’s employs a trained sensory panel consisting of members of the community who are analytical and judicious. Panellists have considerable experience evaluating food and wine products using a consumer-based descriptive language. Projects have included detecting differences in products such as wine, dried grapes, prawns, fish, cheese and confectionery.
Case Study — Wine
Objective
To establish whether wines made from high- and low-yielding vines show perceivable differences. Pairs of wines were compared from 2 consecutive growing seasons for overall differences in aroma or taste characteristics.
Method
Cabernet Sauvignon wines were made using standard small-scale winemaking conditions.A panel of 25 trained assessors performed 2 duo-trio tests under standard conditions. The high- and low-yielding vine treatments from each vintage were compared with each other.
In each comparison, the first sample presented was a labelled reference, followed by two other coded samples, one of which was identical to the reference. The instructions to panellists were to smell and taste the samples and identify the same sample as the reference. Follow up questions included how sure they were about their response and comments on the reasons for their choice.
Results
| Wine Comparisons | Correct identificatios, 25 assessors |
Corresponding p-values1 |
Significant difference? |
| Low yield 2009 vs. High yield 2009 | 72% (18) | 0.007 | yes (p<0.05) |
| Low yield 2010 vs. High yield 2010 | 60% (15) | 0.115 | no |
1 Measure of evidence for difference, a smaller p-value indicates larger sample difference.
Note: All figures are for demonstration purposes.
Interpretation of results
For the 2009 vintage wines, 18 out of 25 assessors correctly identified the wine that matched the reference, which was the cut off point for a significant difference indicating that the low- and high-yielding vineyard treatments produced perceivably different wines.
Many assessors who gave correct responses agreed that sensory differences were small. Generally, the wine from lower yielding vines was perceived as having slightly more fruit intensity and softer mouthfeel than the wine from higher yielding vines.
The 2010 vintage wines made from low- and high-yield vines could not be distinguished based on overall aroma or flavour characteristics.
Reviewing these results, we can consider the 2009 wines suitable for further sensory evaluation such as descriptive analysis to describe and quantify the specific sensory attributes that are perceived as different.
Contact
Andrew Barber
Principal Scientist
E-mail: andrew.barber@sa.gov.au Phone: +61 8 8303 9342/ 0407 793 872
Sensory Facility: Wine Innovation West Building, Hartley Grove, Urrbrae, South Australia 5064
