1 / 16

Food Analysis Lecture 13 (3/2/2010)

Food Analysis Lecture 13 (3/2/2010). Infrared (3). Qingrong Huang Department of Food Science http://foodsci.rutgers.edu/huang/Food_Analysis/FA2010.htm. Reading Materials. Reading Chapter 24 & chapter 30 Questions: Page 515, Study Questions: 1-3. ATR-FTIR.

juliet
Download Presentation

Food Analysis Lecture 13 (3/2/2010)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Food Analysis Lecture 13 (3/2/2010) Infrared (3) Qingrong Huang Department of Food Science http://foodsci.rutgers.edu/huang/Food_Analysis/FA2010.htm

  2. Reading Materials Reading Chapter 24 & chapter 30 Questions: Page 515, Study Questions: 1-3

  3. ATR-FTIR ATR-FTIR: Attenuated Total Reflectance FTIR - A surface sensitive technique; - The evanescent wave penetrates only a small distance through the crystal (typically about a micro meter), depending on the refractive index of the IR-transparent crystal, the internal reflectance element (IRE).

  4. Near-IR Spectroscopy NIR (800-2500 nm) is more widely used for quantitative analysis of foods than are mid-IR.

  5. Near-IR Spectroscopy

  6. Near-IR Spectroscopy Reflectance (R) is defined as: R=I/I0 I: the intensity of radiation reflected from the sample at a given wavelength I0: the intensity of radiation reflected from the reference at the same wavelength Reflectance data are expressed most commonly as log (1/R), analogous to absorbance in transmission spectroscopy.

  7. NIR Applications

  8. Rheological Principles for Food Analysis Qingrong Huang Department of Food Science Reading Chapter 30 Questions: Page 515, Study Questions: 4-6

  9. Flow Properties of Foods

  10. Fundamentals of Rheology • Rheology: the study of the deformation and flow of all materils. • Viscosity: defined as the internal resistance to flow. • Stress (): the measurement of force, defined as the force (N) • divided by area (A, meters2), Pascals (Pa) • Two types of stress: • Normal stress: the force directly perpendicular to a surface • - tension or compression, eg. Chewing gum • Shear stress: the force parallel to the sample surface • - e.g. the spreading of butter over a slice of toast

  11. Normal vs. Shear Stress Normal stress Shear stress When a stress is applied to a food, the food deforms or flow. Strain (): is a dimensionless quality representing the relative deformation of a material.

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

  13. 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.

  14. Newtonian Fluids

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

  16. Rheological Fluid Models • Herschel-Bulkley Model • Newtonian Model: [n=1; k=µ;σ0=0] • Power law Model: [σ0=0] • Bingham Plastic Model [n=1;K=µpl]

More Related