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Brett Character: Sensory Issues and Techniques

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Title: Brett Character: Sensory Issues and Techniques


1
Brett Character Sensory Issues and Techniques
  • Patricia Ann Howe
  • ASCENT Laboratory and Consulting

2
Sensory Issues- Outline
  • Subjective vs Objective measurements
  • Causative chemicals
  • Headspace concentrations
  • Thresholds
  • Descriptive vocabulary
  • Quality judgments
  • Assigning cause and the associated baggage

3
Subjective vs Objective
  • Is all tasting subjective?

4
subjective
  • 4 a (1) peculiar to a particular individual
    PERSONAL ltsubjective judgmentsgt
  • 4 a (2) modified or affected by personal views,
    experience, or background lta subjective account
    of the incidentgt
  • 4 b arising from conditions within the brain or
    sense organs and not directly caused by external
    stimuli ltsubjective sensationsgt c arising out
    of or identified by means of one's perception of
    one's own states and processes lta subjective
    symptom of diseasegt -- compare OBJECTIVE 1c

5
objective
  • 1 d involving or deriving from sense perception
    or experience with actual objects , conditions,
    or phenomena ltobjective awarenessgt ltobjective
    datagt
  • 3 a expressing or dealing with facts or
    conditions as perceived without distortion by
    personal feelings, prejudices, or interpretations
    ltan objective historygt ltan objective judgmentgt
  • 3 b of a test limited to choices of fixed
    alternatives and reducing subjective factors to a
    minimum
  • synonym see MATERIAL, FAIR

6
Causative Chemicals
  • What is Brett character, anyway?

7
Brett character in wines
  • 4 ethyl phenol from p-coumaric acid-Common
    descriptors include medicinal, phenolic, band
    aids, horse sweat, sweaty saddle, leather,or
    horse stable.
  • 4 ethyl guaiacol from ferulic acid-
  • Common descriptors include smoky, spent fire or
    fireplace, and spicy

8
Mousiness (N-Heterocyclic Compounds)
  • 2 acetyltetrahydopyridine (ACTPY)-associated with
    catabolism of L-lysine (and L-ornithine)
  • 2 acetylpyrroline (ACPY)- associated with
    L-ornithine
  • Both are produced by Dekkera-Brettanomyces and
    some lactic acid bacteria
  • In low concentrations said to have a popcorn or
    cracker aroma

9
Headspace Concentrations
  • Can we relate concentration to what we perceive?

10
Units of Concentration
11
Headspace Concentration
  • We dont smell the actual concentration of a
    compound in the wine
  • We can only smell what is in the headspace ABOVE
    the wine
  • The relationship between liquid concentration and
    headspace concentration is affected by many things

12
Effects on Vapor Pressure and Evaporation
  • Polar nature of the molecules and other
    intermolecular forces-polar molecules usually
    have lower vapor pressure
  • Surface area-increases the rate of evaporation,
    not the actual vapor pressure
  • Temperature-increases the rate AND affects vapor
    pressure by overcoming intermolecular forces
  • Concentration of the vapor molecules above the
    liquid-if equilibrium is achieved the rate is
    constant

13
Intermolecular Forces (Van der Waal Forces)
  • Hydrogen bonding (strongest)
  • Dipole-dipole (second strongest)
  • Ion-Dipole
  • London dispersion Forces (weakest)
  • Ion-Ion (strongest interparticle force within
    compounds)

14
Thresholds
  • Everybody talks about them, but what are they?

15
Thresholds
  • Conceptual The minimum energy level required for
    perception.
  • Empirical The level at which detection occurs
    50 of the time.
  • Factual There is no one energy level below which
    detection never occurs and above which detection
    always occurs

16
Complications in Finding Thresholds
  • There is variability in the point at which
    observers change their response
  • There is variability even within a single
    individual
  • Even within the same experimental session, the
    point at which people change their responses will
    differ
  • There are also differences between people

17
Why Thresholds?
  • A popular approach in flavor research is to
    presume that only those chemical compounds
    present in concentrations above their threshold
    will contribute to the perceived aroma.
  • -Sensory Evaluation of Food Principles and
    Practices Lawless and Heymann (1998)

18
Thresholds of Perception (Boidron, J.N, P
Chatonnet, and M. Pons 1988) all given in ppb
(ug/L)
19
Ave Brett vs Ave 4 Ethyl Phenol
20
Linear Regression for Taster F
21
Linear Regression for Taster G
22
Descriptive Vocabulary
  • What can we say….

23
Learning to Use Descriptive Vocabulary
  • Practice-tasting is both physical and mental and
    requires training and practice.
  • Use of standards-without standards, vocabulary
    cannot be developed and agreed upon. Standards
    provide a common and unifying experience.
  • Spiked samples-a way to evaluate your performance
    at the actual time of tasting.

24
Use of the Aroma Wheels
  • Identify common wine aromas
  • Group the aromas by similarity
  • Easy to use, and easily understood
  • Use analytical, not judgmental terms
  • Terms are linked to physical standards
  • Terms are NOT exclusive

25
Descriptive Vocabulary
  • We are not able to identify compounds
  • We cannot say with absolute certainty that what
    we smell as horse sweat or band-aids is 4
    ethyl phenol
  • We CAN say that it sure smells LIKE 4 ethyl phenol

26
Quality Judgments
  • Somebodys got to do it….

27
Expert Tasters
  • Wine Makers
  • Wine Writers
  • Masters of Wine
  • Wine Critics
  • Offer product quality judgments based on personal
    experience
  • Offer quality judgments on the effects of
    particular treatments
  • Very familiar with different wines

28
Factors which influence the quality of an opinion
  • Psychological biases
  • Physical limitations
  • Time constraints
  • Conflicts of interest
  • Personal desires
  • External manipulations
  • Self doubt
  • Blind spots
  • Ego
  • Competition
  • Incompetence
  • Over thinking

29
Causal Associations
  • Is it human nature to find something to blame?

30
Causal Associations
  • We are not able to identify the source of aromas.
  • We cannot say with absolute certainty that what
    we smell as horsey or band-aids is due to
    Brett growth.
  • We CAN say that it sure is LIKELY from Brett
    growth.

31
Causal Associations and Quality
  • As winemakers, we are required to make causal
    associations from sensory input.
  • As expert tasters, we are required to make
    quality judgments based on that same input.
  • As human beings, it is difficult to not to mix
    the two functions and make causal associations of
    quality.

32
Causal Associations and Quality
  • As winemakers we taste something a little
    horsey… LIKE 4 ethyl phenol. We assign cause
    Likely Brett infection.
  • As expert tasters, our quality judgment is
    clouded by knowledge of possible future changes
    in the wine due to a likely infection.
  • As human beings, this wine is less good if we
    are afraid of those changes, and better if we
    want to head that direction. The wine is NOT
    evaluated for what it is NOW.

33
Brett Character Sensory Issues and Techniques
  • Patricia Ann Howe
  • ASCENT Laboratory and Consulting
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