Objective Evaluation of Food. Categories of Objective Methods 1. Chemical Methods 2. Physicochemical...

Objective Objective Evaluation of FoodEvaluation of Food

Categories of Categories of Objective MethodsObjective Methods

1. Chemical Methods 1. Chemical Methods

2. Physicochemical Methods 2. Physicochemical Methods

3. Microscopic Examination 3. Microscopic Examination

4. Physical Properties4. Physical Properties

AppearanceAppearance

1. Photo 1. Photo

2. Photocopying 2. Photocopying

ColorColor

Hue: Hue: Predominant Wavelength Predominant Wavelength

Value: Value: LightnessLightness

Chroma: Purity( Saturation) Chroma: Purity( Saturation)

Geometrical CharacteristicsGeometrical Characteristics

1. Size and Shape 1. Size and Shape

Size and ShapeSize and ShapeA. Length A. Length

B. Width B. Width

C. Perimeter C. Perimeter

D. UniformityD. Uniformity



2. Volume 2. Volume

Volume Volume

1. Displacement Method 1. Displacement Method

2. Index to Volume2. Index to Volume

Texture Texture

Texture Texture 1. 1. Mechanical MeasurementsMechanical Measurements

HardnessHardness – The force required to obtain a – The force required to obtain a given deformation. given deformation.

CohesivenessCohesiveness – Strength of the bonds – Strength of the bonds which holds a food together.which holds a food together.

Adhesiveness – Adhesiveness – Attraction to another Attraction to another surface surface

Fracturability - Fracturability - Ease with which Ease with which something shatters something shatters

ViscosityViscosity – Rate of flow per unit of force or – Rate of flow per unit of force or time. time.

Texture Texture 1. 1. Mechanical MeasurementsMechanical Measurements

ViscosityViscosity – Rate of flow per unit of – Rate of flow per unit of force or time. force or time.

GumminessGumminess – Denseness that persists – Denseness that persists through-out chewing. through-out chewing.

SpringnessSpringness – Ease or time takes to – Ease or time takes to return to original height return to original height

ChewinessChewiness – Length of time in seconds – Length of time in seconds required to masticate a sample at required to masticate a sample at the rate of one chew per second.the rate of one chew per second.

Texture TestsTexture Tests

Involve subjecting food Involve subjecting food to stress or applying to stress or applying

force force

Texture Testing: Texture Testing: Penetrometer – Cone Penetrometer – Cone attachment, measures attachment, measures

distancedistance

Texture Testing:Texture Testing:Warner Bratzler Shear:Warner Bratzler Shear:

The force necessary to shear a The force necessary to shear a

cylindrical sample of meatcylindrical sample of meat

Texture Testing:Texture Testing:Puncture testing – The Magness- Puncture testing – The Magness- Taylor puncture test measures the Taylor puncture test measures the force to penetrate the flesh of fruit force to penetrate the flesh of fruit or vegetables. or vegetables.

Texture of Liquids and Texture of Liquids and

Viscoelastic FoodsViscoelastic Foods

Rheology – The science of flow and Rheology – The science of flow and deformation of materials, both deformation of materials, both liquid and solid.liquid and solid.

Viscosity and Consistency Viscosity and Consistency

Line spread – Time it takes batter Line spread – Time it takes batter to flow between two marks on the to flow between two marks on the stem of a funnel.stem of a funnel.

Viscosity and Consistency

Bostwick Consistometer: Bostwick Consistometer: Distance a food flows Distance a food flows under its own weight in a under its own weight in a given time period.given time period.

Liquid MeasurementsLiquid Measurements

Flow Flow

Viscosity Viscosity


Laminar Flow - Laminar Flow - Mechanism Mechanism by which by which fluidfluid (such as water) (such as water) moves slowly along a smooth moves slowly along a smooth channel or through a tube with channel or through a tube with smooth walls with fluid particles smooth walls with fluid particles following straight-line paths following straight-line paths parallel to channel or wallsparallel to channel or walls


Turbulent Flow - Turbulent Flow - Mechanism by which Mechanism by which fluidfluid (such as water) moves (such as water) moves over or past a rough over or past a rough surfacesurface


Newtonian Fluid – Newtonian Fluid – Homogeneous liquids Homogeneous liquids such as liquids sugar such as liquids sugar syrups, oils, very dilute syrups, oils, very dilute fruit juices. fruit juices.

Absolute ViscosityAbsolute Viscosity


Apparent Viscosity – Apparent Viscosity – Used to talk about Non-Used to talk about Non-Newtonian Fluids Newtonian Fluids


Absolute ViscosityAbsolute Viscosity – Measured – Measured in poise , which is defined as a in poise , which is defined as a force of 1 dyn/cmforce of 1 dyn/cm22, which , which produces a 1 cm/sec difference produces a 1 cm/sec difference in velocity of tow planes in velocity of tow planes separated by 1 cm of liquid. separated by 1 cm of liquid.


Factors that effect viscosity:Factors that effect viscosity:

Temperature Temperature

Concentration Concentration

Texture of Doughs and Texture of Doughs and Baked Products Baked Products

Measure the Measure the consistency and consistency and

stability of dough stability of dough

Stress:Stress:

Intensity of a force Intensity of a force acting on a plane at a acting on a plane at a given point.given point.

Stress:Stress:

3 2 3 2

1

Types of Stress:Types of Stress:

1.Tensile - 1.Tensile - Pulling away from the Pulling away from the forceforce

2.Compression2.Compression- stress toward the - stress toward the plane on which the force is acting plane on which the force is acting

3.Shear3.Shear – tearing at a tangent or at – tearing at a tangent or at an angle away from the force an angle away from the force

Stress:Stress:

Types of Stress:Types of Stress:

1.1. Tensile Tensile

2.2. Compression Compression

3.3. ShearShear



2. Volume 2. Volume

3. Texture 3. Texture

4. Moisture 4. Moisture

5. Fat 5. Fat

Objective Evaluation of Food. Categories of Objective Methods 1. Chemical Methods 2. Physicochemical...

Documents

Transcript of Objective Evaluation of Food. Categories of Objective Methods 1. Chemical Methods 2. Physicochemical...