Application of low intensity ultrasound to characterise model food systems [Elektronische Ressource] / Qin Wang

Lehrstuhl für Lebensmittelverfahrenstechnik und Molkereitechnologie
der Technischen Universität München





Application of low-intensity ultrasound to characterise the
microstructure of model food systems

Qin Wang

Vollständiger Abdruck der von der Fakultät Wissenschaftszentrum Weihenstephan für
Ernährung, Landnutzung und Umwelt der Technischen Universität München zur Erlangung
des akademischen Grades eines

Doktor-Ingenieurs (Dr.-Ing.)

genehmigten Dissertation.




Vorsitzender: Univ.-Prof. Dr. rer. nat. Thomas Hofmann

Prüfer der Dissertation: 1. Univ.-Prof. Dr.-Ing. Ulrich Kulozik
2. Univ.-Prof. Dr. med. Dr.-Ing. Erich Wintermantel


Die Dissertation wurde am 16.08.2007 bei der Technischen Universität München eingereicht
und durch die Fakultät Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung
und Umwelt am 15.11.2007 angenommen.
I
Acknowledgements

This work was carried out between 2002 and 2007 at the Chair for Food Process Engineering
and Dairy Technology of Technische Universität München.
I am grateful to my supervisor Professor Dr.-Ing. Ulrich Kulozik for providing excellent
research facilities and for his professional expertise and guidance during course of this work.
I am very thankful to Prof. Dr. med. Dr.-Ing. Erich Wintermantel, the second reviewer of this
thesis and to Professor Dr. rer. nat. Thomas Hofmann for taking over the Chair of the
examination board.
Furthermore, I would like to thank Brigitte Härter and Anne Keller for their help with HPLC
analysis and thank Karin Zielonka for her help with total protein content determination. I
would also like to thank Christian Ederer, Franz Fraunhofer and Erich Schneider for the
technical support. Many thanks are going to Sabine Becker, Friederike Schöpflin, Birgit
Weber and Marianne Hager for their help with administrative issues. I also would like to
thank all other colleagues and the personnel of the chair for their support and contribution to
the friendly atmosphere during the progress of this work.
I would like to thank my whole family in China for their spiritual support. Especially I would
like to thank my uncle William Li, who encouraged me to come to study in Germany and
financially supported me in the first year of my study.

Qin Wang






II
Contents

1 Introduction………………………………………………………………………………………..1
2 State of knowledge……………………………4
2.1 Physical fundamentals………………………………………………………………………….4
2.1.1 Generation of Ultrasound………………………………………………………………..4
2.1.2 Measuring methods for ultrasound………………………………………………………5
2.1.2.1 Through transmission…………………………………………………………...5
2.1.2.2 Pulse-Echo technique……………………………………………………………5
2.1.2.3 Interferometric method………………………….7
2.1.2.4 Resonator ……………………………………………..8
2.1.3 Ultrasonic parameters……………………………………………………………………9
2.2 High-resolution ultrasonic measurement devices on the market……………………………...13
2.3 Hydration of sugars……………………………………………………………………………15
2.4 Gelation of hydrocolloids…………………………..16
2.4.1 Carrageenans……………………………………………………………………………16
2.4.2 Gelatine………………………………………………………………………………....20
2.5 Milk gelation…………………………………………………………………………………..21
2.5.1 Rennet gelation of milk………………………………………………………………....21
2.5.2 Acid gelation of milk…………………………………………………………………...23
2.5.3 Caseinomacropeptide…………………………………...26
2.6 Thermal denaturation of proteins……………………………………………………………...27
2.6.1 Whey protein α-lactalbumnin…………………………………………………………..29
2.6.2 Egg proteins…………………………………………….30
2.6.3 Protective effect of sugars on the protein stability……………………………………..34
2.7 Hydrolysis of lactose………………………………………………………………………….35
3 Target of this work……………………………………………………………………………….37
4 Material and methods………………………39
4.1 Analytical methods……………………………………………………………………………39
4.1.1 Ultrasonic measurements using the ResoScan® system……………………………….39
4.1.2 Oscillating rheological measurements……………………………………….41
4.1.3 DSC method……………………………………………………….43
4.1.4 HPLC method……………………………………………………..43
4.1.5 Determination of total protein content……………………………………….44
4.2 Experimental performance…………………………………………………………………….44
4.2.1 Experiments for the determination of the hydration of sugar…………………………..44
4.2.2 Experiments for characterising the gelation behaviours of carrageenanen…………….44 III
4.2.3 Experiments for characterisation of gelatine gelation………………………………….46
4.2.4 Experiments to investigate the rennet gelation………………………………46
4.2.5 Experiments to investigate the acid induced milk gelation…………………………….48
4.2.6 zing CMP gelation………………………………………….49
4.2.7 Experiments to determine the degree aggregation of α-lactalbumin…………………...50
4.2.8 Experiments to characterize the thermal denaturatio