Food Science Project

1. Food Science Project Dr. Bernhard Tittmann Pennsylvania State University February 24, 2003

2. Outline • Objective • Non-contact Ultrasound • Principle • Transducers, NCA-1000, Set-up • Velocity and Attenuation calculations • Sample Preparation • Results • Conclusions

3. Objective

4. Non-Contact UltrasoundPrinciple • Losses due to acoustic impedance mismatch between air and material are formidable but overcome by NCA1000 • NCA 1000 is characterized by >150dB dynamic range and a Time-of-Flight (ToF) measurement accuracy of ±10ns under ambient air conditions • Measures ToF, thickness, velocity, and integrated response (area underneath transmitted or reflected signals in dB) of materials in time domain.

5. Configuration of Non-Contact Transducers Piezoelectric Element Z1 (Acoustic Impedance of Final Matching Layer in Contact With Air) Final Matching Layer Za (Acoustic Impedance of Air) Air Transmission of Ultrasound in Air

6. NCA-1000-2E Setup

7. Velocity Calculation The analyzer automatically calculated the sound wave velocity through the sample VS = VAIR (tAIR – t1 – t2) / (tTOTAL – t1 – t2) VS - the velocity through the sample VAIR - the velocity through air tAIR - the time of flight without the sample present t1 and t2 - times from two transducers to sample tTOTAL - the time of flight with the sample.

8. Attenuation Calculation Transmitter • Integrated Response is the area under the reflected peak • By subtracting the integrated response of the signal traveling through the sample and air from the integrated response of the signal traveling only through air gives the total attenuation Sample Air Reflections Time (usecs) Receiver Amplitude (dB)

9. Specimen (Meringue) PreparationRaw Materials • 2 Grade-A small egg whites • Cream of Tartar (1/4 t.sp) • Sugar ( 1/3 – ¼ cup) • The cream of tartar is added to the egg-whites • Mixture is beaten at low-speed using a regular egg-beater for ~ 30s and then at high speed for ~35s • Sugar is added, and the mixture is further beaten at high speed for ~80s • The resulting concoction is poured on a pan and placed in the oven for baking (~3 hrs). (cool down period ~ 2 hrs)

10. Results

11. Velocity vs. Aging

12. Transmittance vs. Egg-beating Time **Note that a minimum is obtained at egg-beating time of 175s

13. Velocity vs. Egg-beating Time **Note that the egg-beating time of 175s corresponds an observed velocity of 265 m/s

14. Image depicting Effect of Egg-beating time on Porosity • Egg-beating time- 148s • Velocity-820m/s • Sugar- ¼ cup • Temp – 275C • Baking time-3 hrs

15. Image depicting Effect of Egg-beating time on Porosity • Egg-beating time – 187s • Velocity-237m/s • Sugar – ¼ cup • Temp-275C • Baking time-3hrs

16. Conclusions • It was observed that increase in egg-beating time resulted in • Increase in velocity • Increase in porosity • A minimum value of transmittance was observed at egg-beating time of 175s and this corresponds to the velocity of 265 m/s • The aging of the meringue samples could be monitored by observing the velocity values. As meringue ages, the moisture from it gets absorbed by the ambience • Preliminary data suggests that the cream of tartar has an effect on the velocity values

17. Benefits of NCU • No coupling agent needed • Unlike conventional ultrasonic measurement techniques, NCU does not require water/gel to require a medium of transduction • Non-intrusive • The specimens surfaces could be rough and uneven, and yet, NCU can provide great estimation of the material properties • The NCA-1000 system could be automated in such a way that rapid raster scanning of the specimens could be achieved