Lab 16 Instrumental versus Sensory Analysis of Texture Flashcards
Describe the double compression test.
- Designed to mimic the force needed to chew and breakdown food
- Data can be used to determine a wide range of physical parameters
Describe the triangle test.
- 2 samples are the same and 1 is different
- Panelists are asked which sample tastes different from the other two
- Panelists may also be asked to describe what the difference was (e.g., sweeter, saltier, etc.)
What is a continuous dependent variable?
- An infinite set of values within an interval (e.g., pH - 2.66, 4.59, 6.71, etc.)
What are nominal values?
- Values that have no order (or ordering is not equally spaced)
- e.g., yes/no, correct/incorrect
What are ordinal values?
- Values can be ranked/have natural order
- e.g., Likert scale: strongly dislike, neutral, strongly like
What is a parametric test?
- Assume underlying statistical distribution (e.g., normal distribution, equal variance, equal sample sizes)
- Used when dependent variable is continuous
- e.g., t-test, ANOVA, Pearson correlation
What is a non-parametric test?
- Do not assume that data are normally distributed
- Use ranked data rather than actual data values (since actual data is not used tests have less statisical power)
- Must be used when dependent variable is ordinal or nominal (can also be used for continuous data if assumptions are violated)
Why do non-parametric tests have less statistical power than parametric tests?
- Since actual data is not used (ranked data is used)
For the following non-parametric test, describe the independent variable, the dependent variable, and an equivalent parametric test.
Wilcoxon signed-rank test
- Independent variable: categorical with two related groups
- Dependent variable: ordinal or continuous but not normally distributed
- Equivalent parametric test: paired t-test
For the following non-parametric test, describe the independent variable, the dependent variable, and an equivalent parametric test.
Mann-Whitney
- Independent variable: categorical with two unrelated groups
- Dependent variable: ordinal or continuous but not normally distributed
- Equivalent parametric test: independent t-test
For the following non-parametric test, describe the independent variable, the dependent variable, and an equivalent parametric test.
Kruskal-Wallis
- Independent variable: categorical with 3 or more unrelated groups
- Dependent variable: ordinal or continuous but not normally distributed
- Equivalent parametric test: one-way ANOVA
For the following non-parametric test, describe the independent variable, the dependent variable, and an equivalent parametric test.
Friedman test
- Independent variable: categorical with 3 or more related groups or with 2 independent variables
- Dependent variable: ordinal or continuous but not normally distributed
- Equivalent parametric test: repeated measures ANOVA and two-way ANOVA
What does a monotonically increasing function look like?
Name 3 non parametric correlation tests.
- Spearman correlation
- Chi-square test of association
- Binomial distribution
Describe Spearman correlation.
- Tests the strength of a monotonic association
- Variables can be continuous or ordinal
- Performs Pearson correlation on ranked data
Describe the chi-squared test of assocation.
- Tests the strength of a relationship between two categorical variables
- Variables must have two or more groups
- For a triangle test the two variables are incorrect/correct and observed/expected
Describe a binomial distribution test.
- Similar to chi-squared (independent, categorical variables)
- Can only be used for exactly 2 possible outcomes (groups)
Briefly describe descriptive sensory analysis.
Trained panelists rate the intensity of a product’s properties (e.g., taste, aroma, texture, appearance).
Briefly describe discriminatory sensory analysis.
- Commonly use untrained panelists; performed to determine if two or more products are perceptibly different
- While simple to conduct, such tests have the disadvantage that they do not typically quantify or describe the differences between products.
Sensory analyses are great for determining how consumers perceive products. How are they limited?
- Inability to produce objective data related to the physical properties of the food like hardness, adhesiveness, cohesiveness, springiness, and chewiness.
- This is where instrumental analyses are useful.
How can objective data regarding the physical properties of food be measured?
- Texture profile analysis: double compression test
- Samples are compressed twice using a texture analyzer to provide insight into how samples behave when chewed.
- Often called ‘two bite test’.
Given this TPA output, how can you calculate springiness?
Length 2/length 1
Given this TPA output, how can you calculate cohesiveness?
Area 2/ Area 1
Given this TPA output, how can you calculate chewiness?
Hardness x Springiness x Cohesiveness
What needs to be calibrated before use when using a TA-XT plus texture analyzer?
Force (using 2kg weight) and height (bring probe to within 5mm of surface of platform)
