Sensory Evaluation and Packaging
Domain 7 covers sensory evaluation and packaging. The exam tests panel design, test selection, packaging function and the link between package and shelf-life.
Core rules
- Sensory tests are discrimination (difference), descriptive (profile) and affective (preference/acceptance).
- A trained panel describes; an untrained consumer panel measures liking. Samples need random three-digit codes, constant temperature and light, and controlled order to reduce bias.
- The triangle test asks which of three samples differs; guessing probability is one-third.
- Packaging functions are containment, protection, preservation, communication and convenience.
- MAP replaces oxygen with gases such as CO2 and N2; vacuum removes air; aseptic packaging keeps a sterile product sterile.
- Active packaging interacts with the product or headspace; intelligent packaging indicates condition.
Worked example
Thirty panelists do a triangle test and 18 identify the odd sample. The 5% critical value for n = 30 is 15 correct responses. Since 18 > 15, reject the null hypothesis: there is a detectable difference. Reasoning: the chance of 18 or more correct by guessing alone is below 5%. The result does not say which sample is preferred; that needs an affective test.
Traps
- Using a difference test to claim preference.
- Ignoring order and carry-over effects between samples.
- Confusing 'best before' with 'use by'; the latter is a safety date.
- Assuming any plastic is a complete barrier; oxygen and moisture transmission differ widely.