The main campus today

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1 The main campus today 0

2 Faculties at the TU Berlin I II III IV V VI VII Humanities Mathematics and Natural Sciences Process Sciences Electrical Engineering and Computer Sciences Mechanical Engineering and Transport Systems Planning Building-Environment Economics and Management Institutes Biotechnology Energy Management Technical Environmental Protection Food Technology and Food Chemistry Process Engineering Material Science and Material Technology 1

3 The Institute of Food Technology and Food the Faculty of Process Sciences at the TU Berlin Department of Brewing Science Department of Food Biotechnology and Food Process Engineering Department of Food Engineering Department of Food Technology and Food Materials Science Department of Food Chemistry and Analytics Department of Food Chemistry and Toxicology 2

4 the Department of Food Technology and Food Material Science 3

5 the Department of Food Technology and Food Material Science Technology Functionality Structure Composition 4

6 Oat protein as an alternative protein source for semi-solid foods Monika Brückner-Gühmann and Stephan Drusch Department of Food Technology and Food Material Science, Technische Universität Berlin, Germany

7 Semi-solid food Coagulation Thermal Acid ph Protein suspension Foaming Air Interface Agitation Emulsification Protein solution Oil steric electrostatic stabilisation Interface Agitation Protein solution 6

8 Cultured fermented dairy products Fresh milk (1.5 % fat) Addition of OPC, OPI/lactose or SMP Mixing (30 min, 37 C) Heating (20 min, 80 C) Cooling to fermentation temperature (40 C) Addition of starter culture (0.2 U) Mixing (15 min, 40 C) Fermentation (16 h, 40 C) Cooling (4-6 C) Milk yoghurt fortified with Universität Berlin Cold-set after heat treatment Acidification (yoghurt) 7

9 Characterization of the fermentation process Course of storage modulus G and loss modulus G`` during fermentation of milk fortified with OPC 8

10 Influence of oat protein on gel formation assessment of compatibility Course of storage modulus G and ph during fermentation of milk fortified with OPC, OPI/lactose or SMP at 13.8 % dry mass with Lactobacillus delbrückii ssp. Bulgaricus and Streptococcus thermophilus 9

11 Influence of oat protein on products` characteristics Gel firmness obtained by texture analysis of yoghurt made of milk fortified with OPC, OPI/lactose or SMP Water holding capacity (centrifugation method) of yoghurt made of milk fortified with OPC, OPI/lactose or SMP 10

12 Consumer s perceptions: sensory profile 11

13 Continuous Phase Food with interfaces Dispersed Phase Gas Liquid Solid Gas - Aerosol Smoke Liquid Foam (milk foam, whipped cream) Emulsion (mayonnaise, dressing, drink, milk) Dispersion (fermented, acidic beverages) Solid Solid foam (bread) Solid emulsion, gel (cheese, processed meat roducts) Mixtures (chocolate) 15

14 Selected parameter and their influence on solubility Concentration of soluble protein versus ph Protein solubility of an OPC suspension (4% w/v) before and after homogenization (300 bar, 2 cycles) at different ph Solubility of oat proteins Reduced around neutral and slightly acidic ph range Limited use as a functional food ingredient in liquid/semi-solid food matrices 16

15 Interfacial properties of proteins Air or oil Most proteins are surface-active Interface Protein unfolds at interface and decreases interfacial tension 1 1 Diffusion 2 Adsorption 3 conformational changes 4 network formation Water Proteins in dispersions cause lowering of surface tension at the water air interface, thus creating foaming capacity. A lowering of surface tension at the oil/water air interface creates emulsification capacity. SURÓWKA, K. & FIK, M. Studies on the recovery of proteinaceous substances from chicken heads. I. An application of neutrase to the production of protein hydrolysate. Int. J. Food Sci. Technol. 27, 9 20 (1992). Proteins at interfaces schematic presentation of the behavior 17

16 Interfacial properties of oat protein Surface tension [mn/m] of OPC 50, OPC 60 and OPI against oil after 30 min of drop formation Surface tension [mn/m] of OPC 50, OPC 60 and OPI against air after 30 min of drop formation Oat protein is surface-active and able to reduce the surface tension 18

17 Emulsification OPC 5 % Extraction (1 h in 10 mm ph 4 or ph 6 buffer) Centrifugation ( g, 10 min) Protein extract (supernatant) Pre-Emulsification with ultra turrax (72 g extracts, 10 % oil) bc/homogenizer_valve_assembly.png/270px- Homogenizer_valve_assembly.png Emulsification 300 bar, 1 cycle 19

18 Emulsification Z average of diluted emulsions Long-term stability of emulsions (1 week) No differences have been detected for the EAI Problem: low solubility of the OPC and consequently low protein content in the extracts 20

19 Foaming Foaming device DFA 100, Krüss GmbH (left) with brightness distribution of a foam sample (middle), OPC foam and OPC caramell ice cream (right) A: Foaming; B: Foam collapse Number 1 represents the foaming speed, 2 describes the cumulative drainage after 1 min, and 3 gives the liquid proportion at the point of maximum foam hight 21

20 Foaming of oat protein concentrate Foam made of 0.14 % (w/v) OPC at ph 7, foam at the beginning in the DFA (left), brightness profile (middle), foam in the DFA after 1800 s (right) At ph 7: foaming properties comparable to WPI At ph 4: oat protein concentrate poorly foamable Foam made of 0.14 % (w/v) WPI at ph 7, foam at the beginning in the DFA (left), brightness profile (middle), foam in the DFA after 1800 s (right) 22

21 Modification by enzymatic hydrolysis Limited enzymatic hydrolysis with trypsin and alcalase alters peptide profile Alcalase (endoprotease): strong effect on the dimer Trypsin: very specific towards its substrate SDS polyacrylamide gel electrophoresis of 0.14% OPI-, OPA- and OPT- solutions at ph 7 (DH3) Protein solubility [%] of OPI, OPT and OPA at ph

22 Modification: tailored functionality Trypsin hydrolised oat protein has improved foam stability at ph 4 Foam made of 0.14 % (w/v) OPI at ph 4, foam at the beginning in the DFA (left), brightness profile (middle), foam in the DFA after 1800 s (right) Foam made of 0.14 % (w/v) OPT at ph 4, foam at the beginning in the DFA (left), brightness profile (middle), foam in the DFA after 1800 s (right) 24

23 Characterisation of the interfacial film (air/water) OPI: has reduced solubility OPA: has an increased amount of low molecular weight peptides with reduced hydrophilic and hydrophobic patches OPT: forms strong viscoelastic films with strong hydrophobic interactions Dilatational rheology Storage modulus E and loss modulus E of 0.14% OPI-, OPA- and OPT-solutions at ph 7 and ph 4, after 30 min drop film ripening 25

24 Take home message Oat protein has good functional properties and can be used as gelling agent, in foams and emulsions Acidified milk gels: Compatibility of oat protein in the form of OPI with milk proteins is low Strong sedimentation OPC enrichment combines: Nutritional benefits Sustainable use of the by-product of oat processing Improved product quality with respect to syneresis and mouthfeel Foams/emulsions: Oat protein is surface-active but low solubility restricts functional properties Modification by tryptic hydrolysis improves the solubility at ph 4 Tryptic hydrolysates have improved foaming as well as emulsification properties at ph 4 26

25 Acknowledgments & contact The authors thank the German Ministry of Education and Science (BMBF) Projektträger Jülich for the financial support (project no. 031A661). Dr. Monika Brückner-Gühmann Department of Food Technology and Food Material Science Institute of Food Technology and Food Chemistry Technische Universität Berlin