Introduction to sensory analysis and shelf life
This session first introduces basic sensory analysis concepts to set a common background among course participants. Following this, the importance of sensory shelf life will be analyzed and published values will be considered. The design of a sensory shelf-life study will be discussed.

Topics
What does sensory analysis answer?
Discrimination, descriptive and acceptability studies
How to estimate sensory shelf life with the aid of discrimination tests
Importance of sensory shelf life
Published and preliminary values
Initial design considerations: maximum storage time, testing intervals and sample quantity to store.
Basic and reverse storage designs.

DAY 1
Afternoon

Survival analysis statistics
This session focuses on using consumers’ acceptance or rejection of the stored food sample in estimating sensory shelf life applying survival analysis statistical tools.

Topics
What are survival analysis data?
Censoring concepts
Acceptance and rejection functions
Obtaining experimental data and how to interpret them
Estimating the rejection function
Estimating sensory shelf life with corresponding confidence intervals
Advantages of the methodology

Applied exercises and questions.

Evening Dinner (optional)

Survival analysis (continued)
Shelf-life estimations using the R statistical package: the R-statistical package in combination with Excel will be used to obtain percent consumer rejection versus storage time, and estimated shelf-lives with confidence intervals. Real data obtained from a strawberry flavored yogurt will be processed. Participants will receive a copy of the R package to take away with them, together with instructions and necessary procedures to process sensory shelf-life data.

Survival analysis (continued)
Extensions of the methodology:
Use of covariates: shelf-life changes due to formulation changes or when the product is targeted at different populations.
Can each consumer taste only one sample?
Determination of consumer acceptance limits to sensory defects in UHT milk.
Optimizing the concentration of a food ingredient. Comparison with classical JAR scales.
Influence of context: willingness to buy and willingness to consume a banana.

Cut-off point methodology
In this session cut-off point methodology will be addressed as an alternative to survival analysis statistics. The cut-off point defines the relationship between the acceptability of products with different degrees of spoilage and the analytical values of spoilage measured by a panel of trained assessors.

Topics
When is it necessary to apply the cut-off point methodology?
Experimental design to obtain the cut-off point.
Statistical calculation of the cut-off point.
Cut-off point calculations based on acceptance/rejection data.
Extension of the cut-off point to determine sensory specifications.

Evening – Course Dinner (optional)

Cut-off point methodology (continued)

Topics
Zero-order and first-order kinetics.
Using the cut-off point to determine sensory shelf life.
The presentation will be illustrated will real data obtained from a shelf-life study of sunflower oil.

Sensory test and exercises:
Exercises on kinetics, cut-off points and corresponding shelf-lives. Two-way ANOVA, linear regressions and confidence intervals will be obtained using Excel.