3D printing of textured soft meat analogues : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Palmerston North, New Zealand
Meat analogue is a food product mainly made of plant proteins. It is considered to be a sustainable food, and has gained a lot of interest in the recent years. Hybrid meat is a new type of meat analogue, which mixes plant protein and meat ingredients. It helps meat analogues express similarity with real meat, and also reduces the negative environmental impact. Three-dimensional (3D) printing technology is becoming increasingly popular in food processing. 3D food printing involves modification of food structure, which leads to the creation of soft food. Currently, there is no available research on 3D printing of meat analogues. Therefore, this study was carried out to create plant and animal protein based formulations for 3D printing of hybrid meat analogues with soft texture. This study was divided into three major sections. The first section was pre-printing experiments. Preliminary extrusion trials through a syringe were done using various materials, including different meat, plant protein samples and their combination, to finalize the most suitable material and formulations for further printing test using a 3D printer. Then rheology and forward extrusion tests were carried out on these selected samples to get basic understanding of their potential printability. In the second section, extrusion-based 3D printing was conducted to print various 3D shapes. The third section of the thesis presents the characterization of 3D printed products. From the results of preliminary trials, pea protein isolate (PPI) was selected as the main plant protein source. For 3D printing tests, the addition of 20 % chicken mince paste (dry basis) to PPI based paste achieved better printability and fibre structure. In addition, the printing performance was standardized and was found to be optimal at 1.54 mm nozzle size, 10 mm/s printing speed and 100 % infill density. At these conditions, meat analogues with a layered structure could be designed through 3D printing. Chicken mince and printed meat analogues had a similar moisture content of approximately 70 %. However, the protein content increased with an increase in the amount of chicken in the 3D printed samples. The addition of chicken also hardened the texture of pre-printed products, but the printing process reduced the hardness. This demonstrated that printing is a suitable method to produce a soft meal. The results of light and scanning electron microscopy (LM & SEM) on cooked 3D printed samples showed that addition of chicken to plant protein matrix led to better fibre formation. PPI itself was not able to form any fibres merely by 3D printing and cooking in boiling water. Protein-protein interactions were also studied through the protein solubility test, which indicated that hydrogen bonding was the major bonding to contribute the structure formation in cooked and printed meat analogues. In addition, disulphide bonding was correlated with improved fibrous structures as observed through SEM. This study investigated that meat analogues with softer texture were created through 3D printing. Due to the unique rheological properties of the printing materials, printing could only be carried out properly at a low speed (10 mm/s). High speed led to a poor shape forming capacity. Slight changes in the shape of printed products were observed after cooking however it did not affect their overall 3D structure. Further research is needed to develop an approach for high-speed printing by further optimizing formulation or printing parameters.