Characterising the influence of milk fat towards an application for extrusion-based 3D-printing of casein−whey protein suspensions via the pH−temperature-route

Research output: Contribution to journalArticlepeer-review


  • Kilian Daffner
  • Lydia Ong
  • Eric Hanssen
  • Sally Gras
  • Tom Mills

Colleges, School and Institutes


This study presents the design and characterisation of casein−whey protein suspensions (8.0/10.0% (w/w) casein and 2.0/2.5% (w/w) whey protein) mixed with dairy fat (1.0, 2.5 and 5.0% (w/w) total fat) processed via the pH−temperature-route in preparation for 3D-printing. Mechanical treatment was applied to significantly decrease the particle size of the milk fat globules and increase surface area, creating small fat globules (<1 μm) covered with proteins, which could act as pseudo protein particles during gelation. Different proteins covered the fat globule surface after mechanical treatment, as a result of differences in the pH adjusted just prior to heating (6.55, 6.9 or 7.1). The protein-fat suspensions appeared similar by transmission electron cryogenic microscopy and the zeta-potential of all particles was unchanged by the heating pH, with a similar charge to the solution (~−20 mV) occurring after acidification (pH 4.8/5.0) at low temperatures (2 °C). A low heating pH (6.55) resulted in increased sol−gel transition temperatures (G՛ = 1 Pa) and a decreased rate of aggregation for protein−fat suspensions. A higher heating pH (6.9 and 7.1) caused an increased rate of aggregation (aggregation rate ≥ 250 Pa/10 K), resulting in materials more promising for application in extrusion-based printing. 3D-printing of formulations into small rectangles, inclusive of a sol−gel transition in a heated nozzle, was conducted to relate the aggregation rate towards printability.

Bibliographic note

Funding Information: This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/N024818/1 ]. This research was supported under Australian Research Council's Industrial Transformation Research Program (ITRP) funding scheme (project number IH120100005). The ARC Dairy Innovation Hub is a collaboration between The University of Melbourne, The University of Queensland and Dairy Innovation Australia Ltd. The authors would like to thank Ian Norton as well as Eddie Pelan for fruitful discussions and Adabelle Ong for help with the SDS-PAGE. The authors would like to thank The Bio21 Molecular Science & Biotechnology Institute at The University of Melbourne for access to equipment. Cryo EM was carried out at the Bio 21 Advanced Microscopy Facility, at The University of Melbourne. We acknowledge Unternehmensgruppe Theo Mueller for gifting the powders.


Original languageEnglish
Article number106642
Number of pages11
JournalFood Hydrocolloids
Early online date16 Feb 2021
Publication statusE-pub ahead of print - 16 Feb 2021


  • Acidified milk gels, Food printing, Heat-induced gelation, Physical properties, Protein−fat suspension