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FOOD2000 > Week 2 > Flashcards

Week 2 Flashcards

1
Q

Quality

A

Suitability of a product for a specified purpose - judged against defined criteria

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2
Q

Shelf life

A

Period of time food is considered suitable for sale

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3
Q

Food safety

A

free of harmful chemical, physical or biological contaminants

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4
Q

Functionality

A

properties that contribute usefulness for a specific purpose e.g. dough strength

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5
Q

Importance of quality

A
  • Consumer acceptability - sensory properties
  • Product consistency for both fresh consumption and processing - Nutrition value
  • Reducing waste - meeting specifications
  • Trade (price and market share)
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6
Q

How is quality measured?

A
  • Subjective (visual, texture, flavor)
  • Objective (texture, color, nutritional, microbiological)
  • Quantitative and qualitative measured
  • Traditional analytical, instrumental and sensory analysis
  • Consumer acceptability
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7
Q

Visual quality attributes:

A
  • The first quality attributes experienced by consumers
  • Morphology (size/shape), appearance (color, gloss, clarity, consistency) - Physical defects
  • Blemishes
    Appearance has a halo effect that modifies subsequent perception of flavor and overall acceptability
  • visual quality attributes are used for the differentiation of grading for beef
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8
Q

quantitive colour systems

A

many systems for quantifying colour - RDB, CMYK
CIE Lab* widly adopted for foods - designed to approximate human vision
L* Lightness
aRed-Green
b Blue- Yellow

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9
Q

Texture

A

Related to the rheological properties of food
- Elastic (solid) can be deformed and will return to shape after distress - Viscous (liquid) resistance to flow
- Plastic (solid) can be molded

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10
Q

Liquids

A
  • Newtonian eg. water, sugar syrup
  • Non-newtonian eg. cornstarch+water (shear thickening), tomato sauce (shear
    thinning)
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11
Q

Textual quality definition

A

ISO definition - combination of mechanical, geometrical nd surface attributes perceptible by mechanical, tactile, visual and auditory receptors

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12
Q

Texture is experienced by:

A

Finger tips: complex ray of mechanoreceptors
- Lips
- Upper surface of tongue: very sensitive to detection of particle size, shape, lubrication
and friction
- Jaw and teeth: sensitive mechanical attributes

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13
Q

Texture analysis in the mouth

A

Consumers evaluate a lot of things about food texture during a short residence time in the mouth

  • Evaluated by hand or in mouth (firmness, springiness, rate of recovery)
  • First bite (firmness/ hardness, deformability, factorability, number of particles)
  • chew-down (degree ob breakdown, cohesiveness, smoothness, adhesion to teeth and gums, meltability)
  • residual after swallowing (number of chews, mouthful after swallow, oral coating

Texture interacts with the way taste chemicals are released from the food matrix

  • awareness of texture if often subconscious - when expectations are not met, the reaction may be strongly negative
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14
Q

Instrumental assessment of texture

A

Texture can be decomposed into measurements of resistance to force - Compression test eg. squeezing
- Shear tests eg. shearing through a food matrix
- cut/break tests eg. applying force to cause a fracture
- Tensile stretch tests eg. pulling a muffin apart
- Theological (viscosity and shear) tests in fluid or semi solid foods
Texture analysis is complementary to physicochemical analysis eg. particle & bulk density

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15
Q

Taste and aroma are combines in flavour perception

A
  • Favour is one of the most important factors in food choice
  • The same flavors can be perceived differently by different people - Tastants are released during mastication and delivered to taste
    receptors on the tongue and mouth surfaces
  • Odorants are sensed through the nose but also released form the
    food matric to the oral cavity headspace and saliva
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16
Q

5 taste modalities: bitter, sweet, salty, sour, umami

A

Detected by specific taste receptors on the tongue or in the mouth
- Receptors encoded by different genes
- Variability of expression between individuals

Sweet - sugar, amino acids
Sour - organic acids
Salty - NaCI, K and Mg salts
Bitter - many fundamentally different substances, response involves - 35 different proteins important for recognising poison
Umami - glutamic and aspartic acid, meat broth, MSG

17
Q

Sensory evaluation

A

Discrimination testing
- Is product A identical to product B
Preference, acceptance, hedonics testing
- Is product A better than product B? How much do you like it?
Descriptive analysis
- What does the product taste/feel like?

18
Q

Sensory characteristic - Technique or evaluating characteristic

Hardness

A

Place sample between molar teeth and bite down evenly, evaluating the force required to compress the food

19
Q

Sensory characteristic - Technique or evaluating characteristic

Cohesiveness

A

Place sample between molar; compress and evaluate the amount of force deformation before rupture

20
Q

Sensory characteristic - Technique or evaluating characteristic

Adhesivness

A

Place sample on tongue, press it against the palate and evaluated the force required to remove it with the tongue

21
Q

Sensory characteristic - Technique or evaluating characteristic

factorability

A

Place sample between molar teeth and bite down evenly until the food crumbles, cracks or shatters, evaluating the force with which the food moved away from the teeth

22
Q

Sensory characteristic - Technique or evaluating characteristic

Chewiness

A

place sample in the mouth and masticate at one chew per second at a force equal to that required to penetrate a gum drop in 0.5 seconds, evaluating the number of chews required to reduce the sample to a state ready for swallowing

23
Q

Factors affecting quality

A

Genetics (variety)
- Environmental factors
- Soil, nutrients, solar irradiation, rainfall, temperature
- Time to anthesis
- Post harvest management
- Testing methods

24
Q

Stages of a typical analytics procedure

A
  • Sample
  • sample preparation ^Main sources of analytical error
  • Measuring
  • Data analysis
  • Interpretation of the data

Critical aspect/consideration
- Verification of the procedure - comparison with known standard values - Appropriateness of methods
- Cost, practicality
- Does it measure what it is intended ot measure

25
Q

Types of samples analsyed

A
  • Raw materials
  • To determine that a delivery conforms to standards (composition,
    contaminants)
  • To assure consistency of supply
  • To evaluate new suppliers
  • Finished material to determine that product meets standards and claims
  • Process control samples ot monitor operation
  • Complain samples
  • Competitors samples
26
Q

Sampling error, sample storage and replication

A

Common errors from sampling
- Uneven distribution of constituents in foods - Limitations of sampling devices
- Inadequate size of sample
Changed after sampling due to inappropriate storage
- Loss of moisture, microbial spoilage, absorption into containers, loss of volatiles, enzyme reactions, oxidants
Adequate replication
- Technical replicates vs true replicates

27
Q

Sampling protocols

A
  • Random
  • Stratifies
  • Systematic
  • Judgment
28
Q

Traditional analytical techniques (destructive sampling)

A

Spectrometric (spectral properties, calorimetry, NMR)
Chromatographic
Enzymatic (products of biochem reactions)
Immunochemical (ELISA)
Electrophoretic (PAGE, agarose gel electrophoresis)
Gravimetric, volumetric, conductimetric

29
Q

high-throughput data collection (destructive sampling).

A
  • high throughput methods with reasonable accuracy
  • digital technologies for monitoring and recording
  • real time, non-invasive
  • trade-off between cost, accuracy/ precision, throughput
30
Q

Near infra-red reflectance (NIR) spectroscopy

A
  • Each type of molecule vibrates in a unique way
  • When these vibrations interact with infra-red light they create a unique spectrum
  • Deconvoluted signal compared with spectra in a calibration database to identify
    quantify molecules in the sample -
    Rapid analysis of many foods
  • Grains, horticultural produce
  • Moisture, protein, start, oil fat..
  • Non destructive, non invasive, high throughout
  • Solid and liquid samples
  • Highly portable, on the go
31
Q

X-ray fluorescence (XRF)

A
  • Handheld XRF analyser disrupts electron in inner shell of atoms - replacement electrons from outer shells emit energy - varies with element
  • Elemental signature of product to match that of environment its come from
  • To provide consumers assurance of provenance food fraud

FOOD2000 (13 decks)

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