1. Food Analysis Lecture 14 (3/9/2010) Rheological Principles for Food Analysis Qingrong Huang Department of Food Science http://foodsci.rutgers.edu/huang/Food_Analysis/FA2010.htm

2. Reading Materials Reading Chapter 30 Questions: Page 515, Study Questions: 4-6

3. Shear Rate Shear flow between parallel plates Shear rate =d(  L/h)/dt or

4. Fluid Viscosity Newtonian Fluids: where  is the stress, is the shear rate, and  is the Newtonian the viscosity. Apparent viscosity (  ) is defined as If  is a constant, then it is a Newtonian fluid; otherwise it is non-Newtonian fluid.

5. Newtonian Fluids

6. Shear Thinning vs. Shear Thickening Most of the fluid foods are not Newtonian fluids;

7. Rheological Fluid Models Herschel-Bulkley Model =0] Newtonian Model: [n=1; k=µ;σ 0 =0] Power law Model: [=0] Power law Model: [σ 0 =0] Bingham Plastic Model [n=1;K=µ pl ] Bingham Plastic Model [n=1;K=µ pl ]

8. Rheometry Concentric Cyclinders M: torque

9. Cone and Plate

10. Stress shear rate

11. Steady Shear Rotational Viscometry Experimental Procedures: Test fixture selection - e.g. cone plate or C.C. Speed (shear rate) selection Data collection - values of torque & speed Shear calculations - shear stress and shear rate Model parameter determination - applicable rheological model

12. Rheological Properties of Solids Large strain testing - compression and tension (i.e., extension) test can be used to determine large strain and fracture food properties. - Texture Profile Analysis (TPA) Effective of relative huminity

13. Scope of the Mid-Term Class notes; Food Analysis book Quiz, labs, and end-of-chapter questions 80 min in-class exam, close book, no discussion

14. 1. Solutions & Concentration ppm ppt wt% Mol/L N Dilution Solution preparation Buffer, pH meter Lab

15. 2. Data Analysis Mean Standard deviation Accuracy and precision Confidence Interval Q-test Curve fitting

16. 3. pH Total acidity pH, degree of ionization, pKa Buffer and buffer capacity pH meter Lab

17. 4. Spectroscopy Basic Principles of UV, Fluorescence, IR E=h Interference Energy level Beer’s law Absorption and emission Instrumentation : - monochromator, interferometer, PMT, thermocouple detector, light source, photo diode detector Data interpretation Applications Labs

18. Rheological Properties of Foods Basic concepts of stress, strain, deformation Relationship between stress and strain Different rheological models: Newtonian, power law Lab