# Rheology of Food - study of deformation and flow of material

Rheology of Food

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Rheology of Food - study of deformation and flow of material

## 1. Types of Flow Behavior

### 1.1. NON - NEWTONIAN

1.1.1. TIME INDEPENDENT

1.1.1.1. viscosity depend on shear rate BUT independent of shearing time

1.1.1.2. "APPARENT VISC." - visc. at spec. rate

1.1.1.3. Pseudoplastic ( no yield stress rquire/ shear thinning )

1.1.1.4. Dilatant (no yield stress rquire/ shear thickening )

1.1.1.5. Bingham ( yield stress require)

1.1.1.6. Casson Plastics ( yield stressrequire )

1.1.1.7. SHEAR THINNING

1.1.1.7.1. DECREASE viscosity with INCREASE shear rate

1.1.1.8. SHEAR THICKENING

1.1.1.8.1. INCREASE viscosity with INCREASE shear rate

1.1.2. TIME DEPENDENT

1.1.2.1. Thixotropic

1.1.2.1.1. DECREASE in apparent visc. with TIME under constant shear rate/stress, follow with gradual recovery

1.1.2.2. Rheopectic

## 2. Stress and Strain

### 2.1. Strain

2.1.1. a quantitative measure to an extent

2.1.2. Strain(Ɛ) = Change in length (L - Lo) / Original length (L)

2.1.3. defromation of element (change in shape)

### 2.2. Stress

2.2.1. a force per unit area

2.2.2. intensity of force

2.2.3. Stress = Force (F) / Area (A)

2.3.1. h

## 3. Viscosity

### 3.4. FACTOR THAT AFFECT ON VISCOSITY

3.4.1. Shear rate

3.4.1.1. High

3.4.1.2. Moderate

3.4.1.3. Low

3.4.2. Shear time

3.4.3. Temperature

3.4.4. Pressure

## 4. Rheological Models

### 4.2. TYPES OF MODEL

4.2.1. HERSCHEL - BULKLEY MODEL

4.2.1.1. indication of Newtonian and Non-Newtonian flow, provide material without yield stress

4.2.2. POWER LAW MODEL

4.2.2.1. shows no yield stress

4.2.2.2. non-linear relationship with shear stress and rate

4.2.3. BINGHAM PLASTIC MODEL

4.2.3.1. shows yield stress

## 5. Rheometry

### 5.3. TYPES OF RHEOMETRY

5.3.1. FUNDAMENTAL

5.3.1.1. using well-define test fixture (geometry) and test condition

5.3.1.2. gives absolute value of viscosity

5.3.1.3. Rotational Viscometer

5.3.1.3.1. involve the use of known test fiture in contact with sample

5.3.2. EMPIRICAL

5.3.2.1. Bostwick Consistometer

5.3.2.1.1. measuring consistency, flow rate and visc.

5.3.2.2. Falling Ball Viscometer

5.3.2.2.1. measures viscosity of transparent Newtonian liquids

5.3.2.3. Glass Capillary Viscometer

5.3.2.3.1. measure viscosity of low viscous Newtonian food under flow of normal gravitational force