Objective Evaluation of Food. Categories of Objective Methods. 1. Chemical Methods 2. Physicochemical Methods 3. Microscopic Examination 4. Physical Properties. Appearance. 1. Photo 2. Photocopying . Color Hue: Predominant Wavelength Value: Lightness
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Categories of Objective Methods 1. Chemical Methods 2. Physicochemical Methods 3. Microscopic Examination 4. Physical Properties
Appearance 1. Photo 2. Photocopying
Color Hue: Predominant Wavelength Value: Lightness Chroma: Purity( Saturation)
Geometrical Characteristics 1. Size and Shape
Size and Shape A. Length B. Width C. Perimeter D. Uniformity
Geometrical Characteristics 1. Size and Shape 2. Volume
Volume 1. Displacement Method 2. Index to Volume
Texture 1. Mechanical Measurements Hardness – The force required to obtain a given deformation. Cohesiveness – Strength of the bonds which holds a food together. Adhesiveness – Attraction to another surface Fracturability - Ease with which something shatters Viscosity – Rate of flow per unit of force or time.
Texture 1. Mechanical Measurements Viscosity – Rate of flow per unit of force or time. Gumminess – Denseness that persists through-out chewing. Springness – Ease or time takes to return to original height Chewiness – Length of time in seconds required to masticate a sample at the rate of one chew per second.
Texture Tests Involve subjecting food to stress or applying force
Texture Testing: Penetrometer – Cone attachment, measures distance
Texture Testing: Warner Bratzler Shear: The force necessary to shear a cylindrical sample of meat
Texture Testing: Puncture testing – The Magness- Taylor puncture test measures the force to penetrate the flesh of fruit or vegetables.
Texture of Liquids and Viscoelastic Foods Rheology – The science of flow and deformation of materials, both liquid and solid.
Viscosity and Consistency Line spread – Time it takes batter to flow between two marks on the stem of a funnel.
Viscosity and Consistency Bostwick Consistometer: Distance a food flows under its own weight in a given time period.
Liquid Measurements Flow Viscosity
Liquid Measurements Laminar Flow - Mechanism by which fluid (such as water) moves slowly along a smooth channel or through a tube with smooth walls with fluid particles following straight-line paths parallel to channel or walls
Liquid Measurements Turbulent Flow - Mechanism by which fluid (such as water) moves over or past a rough surface
Liquid Measurements Newtonian Fluid – Homogeneous liquids such as liquids sugar syrups, oils, very dilute fruit juices. Absolute Viscosity
Liquid Measurements Apparent Viscosity – Used to talk about Non-Newtonian Fluids
Liquid Measurements Absolute Viscosity – Measured in poise , which is defined as a force of 1 dyn/cm2, which produces a 1 cm/sec difference in velocity of tow planes separated by 1 cm of liquid.
Liquid Measurements Factors that effect viscosity: Temperature Concentration
Texture of Doughs and Baked Products Measure the consistency and stability of dough
Stress: Intensity of a force acting on a plane at a given point.
Stress: 1 3 2
Types of Stress: 1.Tensile - Pulling away from the force 2.Compression- stress toward the plane on which the force is acting 3.Shear – tearing at a tangent or at an angle away from the force