1. DMA THERMAL ANALYSIS OF PLANT TISSUE
Jiří Blahovec

2. Thermal Analysis of Materials
… developed out of the scientific study of the changes in the properties of a sample which occur on heating.
Haines, 2002

3. BASIC THERMAL METHODS Differential scanning calorimetry DSC
Differential thermal analysis DTA
Thermomechanical analysis TMA
Dynamic mechanical Analysis DMA
Dielectric thermal analysis DETA
Thermogravimetry TG
… study of changes in structure and mechanisms …

4. HOW TO APPLY THEM TO BIOOBJECTS?

5. SIMPLE POTATO CELLULAR STRUCTURE
Symplast
Apoplast
Cellular walls

6. SCHEME OF CELLULAR MEMBRANE
Polar hydrophilic side
Hydrophobic sides
Lipid Double Layer
symmetrical
Pore – Based on Proteins
source of asymmetry

7. COMPLICATED STRUCTURE caused COMPLICATED THERMAL RESPONSE

8. MECHANICAL PROPERTIES and cell walls

9. POTATO Compression at room temperature
Squeezing out
~ 3 %

10. POTATO Slope analysis
True slopes: I Variable, flaccid tissue II about 3 MPa, quasi-elastic III (1.54±0.13) MPa, sap squeezing out

11. TISSUE RIGIDITY

12. GOOD BASIS FOR DYNAMIC MECHANICAL ANALYSIS (DMA) OF VEGETABLE TISSUE

13. TYPES OF LOADING

14. DMA PARAMETERS
Specimen dimensions: length mm width mm thickness 3 mm Distance between jaws mm Amplitude mm (it corresponds to 3 % quasi-elastic deformation) Frequency Hz Temperature Range oC Heating Rate oC/min Tissues: Potato (cork, pith and side with vascular ring), Carrot
Tests were done in air with 90 % humidity !

15. POTATO The important starch effect

16. STORAGE MODULUS

17. LOSS MODULUS

18. LOSS TANGENT (LM/SM)

19. STORAGE MODULUS (Slope Analysis – 10 replications)

20. LOSS MODULUS (Slope Analysis – 10 replications)

21. LOSS TANGENT (Slope Analysis – 10 replications)

22. POTATO PITH AND CORTEX AT ROOM TEMPERATURE
(a) pith (b) cortex
Starch grains
Protein micelles
Cell wall
Arranged under Karlsson & Eliasson (2003), LWT 36,

23. STARCH CHANGES First Heating
POTATO
STARCH CHANGES First Heating
Arranged under Ratnayake & Jackson (2007) Carbohydrate Polymers 67,
Gelatinization
Tissue DMA Peak

24. POTATO STARCH CHANGES Shear Rheology X-Ray Diffraction
Arranged under Ratnayake & Jackson (2007) Carbohydrate Polymers 67,
Kaur et al. (2002), Food Chemistry 79,
Shear Rheology
X-Ray Diffraction
Partial Crystallinity
Crystallinity (%)
Nearly amorphous 10 45
Partial Crystallinity 45

25. POTATO STARCH CHANGES Swelling
Arranged under Li & Yeh (2001) J. Food Eng. 50,

26. CARROT A representative of standard plant tissue

27. ELASTIC MODULE

28. ELASTIC MODULE (Slope Analysis – 10 replications) Indications of further temperature dependent changes

29. LOSS TANGENT (Slope Analysis – 10 replications) Indications of further temperature dependent changes

30. CONCLUSIONS
Deformation of potato tubers at temperatures higher than 60oC is controlled by starch gelatinization and swelling,
DMA detects gelatinization in state in which the thermally controlled processes detected by DSC are finished,
DMA is able to detect further cell wall changes connected with cell wall semi-permeability

31. THANK FOR YOUR ATTENTION!