(QC/sensory)2

Question 1

DIFFERENCE-FROM-CONTROL (DFC) METHOD

Answer 1

• Rating the overall difference from control.
• Rating differences on specific attributes from control.
• Collecting diagnostic information on the nature of the difference.

Question 2

Advantages of DFC method:

Answer 2

• Simplicity (panelist need to familiarized with the control product and calibrated to the DFC scale through exposure to
  a variety of samples).
• High flexibility
• Ease of panel training related to the DFC method.

Question 3

Disadvantages of DFC method:

Answer 3

• The overall difference rating does not provide specific guidance on the nature of the difference that could be used to identify its source.
• A sample that represents the control product must always be available.

Question 4

Implementing a difference-from-control QC
program:

Answer 4

1. Establish sensory specifications
2. Implementing the in-plant QC/sensory function
3. Product sampling, data analysis and reporting

Question 5

Step 1: Establish sensory specifications

Answer 5

a) Initial sample screening
b) Sensory Descriptive Evaluations and Sample Selection for Consumer Testing

Question 6

Samples are screened to remove

Answer 6

redundancy and provide a small number of samples that represent the full range of sensory differences that occur during
production.

Question 7

The samples can also be evaluated for

Answer 7

descriptive properties, which can provide useful diagnostic information about the magnitude of the DFC ratings

Question 8

Sensory Descriptive Evaluations and Sample Selection for
Consumer Testing
- DFC ratings on specific attributes should be collected

Answer 8

on products that differ in several sensory properties

Question 9

To develop the QC/sensory specifications,

Answer 9

the screened set of samples can be given to a consumer test.

Question 10

The resulting consumer acceptability ratings can be correlated with

Answer 10

the trained panel’s DFC ratings obtained
from the same samples.

Question 11

The QC/sensory specification limit is set to maintain

Answer 11

the overall
acceptance rating of the product at an acceptably high level

Question 12

The correlation analysis should consider both

Answer 12

the consumers’
overall acceptance rating and the attribute acceptance
ratings.

Question 13

Training should involve

Answer 13

ü Repeated exposures to the control product and to a
set of reference products that represent the entire
range of the DFC scale.
ü Encourage regular feedback on the accuracy and
reproducibility of each panelist’s rating.