3D printing of meat.

TL;DR: A temperature-controlled extruder-type 3D printer built with multi-head system is suggested to suit the required conditions for meat safety and rheological requirements and the elemental aspects affecting the printability and post-processing feasibility of 3D printed meat products.

About: This article is published in Meat Science.The article was published on 2019-07-01 and is currently open access. It has received 136 citations till now. The article focuses on the topics: Meat packing industry.

Summary

Introduction

• AC C EP TE D M AN U SC R IP T 1 Three-dimensional printing (3DP) process stands as a developing technology for food manufacturing, which offers the opportunity to design novel food products with improved nutritional value and sensorial profile.
• This review analyses the potential applications of 3DP technology for meat processing and the elemental aspects affecting the printability and postprocessing feasibility of 3D printed meat products.
• The combination of nutritionally balanced ingredients and novel internal structures may be schemed into a multi-material 3D model that meets special individual needs, such as chewing and swallowing difficulties.
• Furthermore, a temperature-controlled extruder-type 3D printer built with multi-head system is suggested to suit the required conditions for meat safety and rheological requirements.

Contents

• 17 Introduction 1. Only 7.2% in weight of a cattle carcase accounts for cuts that are considered suitable for high-value steaks (Conroy, Drennan, Kenny, & McGee, 2010).
• Based on the additive manufacturing (AM) process, which consists of a layer-by-layer deposition with predetermined thickness to create complex freeform structures (Noorani, 2017), 3DP offers the possibility of manufacturing novel food products with digitalized intricate shapes, inexperienced textures and higher nutritional value, through the combination of different food ingredients and printing methodologies.
• The printability of any food material refers to its ability to be handled and dispensed by a 3D printer into a freeform structure after deposition (Godoi et al., 2016), and is affected by the printing conditions and the rheological properties of the materials (Kim, Bae, & Park, 2017).
• Likewise, Liu et al. (2018a) were able to 3D print chicken, pork and fish in a slurry form with the addition of gelatine solution.

3D Printing process 2.

• Three-dimensional printing, also known as additive manufacturing (AM), is a process that generates freeform structures by introducing a prototype into a computer aided design (CAD) software, which is then converted into a .STL file by a slicing software to be recognised and processed by 3D printers (Noorani, 2017).
• The technology involves a layer-by-layer ACCEPTED MANUSCRIPT AC C EP TE D M AN U SC R IP T 6 deposition with predetermined thickness to create complex three-dimensional objects from different materials used as “inks”, using strictly the necessary amount of material to consolidate the shape of the printed object.
• 3DP offers an alternative technology with sustainability benefits such as reduced demand of raw materials, workforce, energy and transportation (Peng, 2016; Sher & Tutó, 2015).
• Besides waste conversion through the added-value chain, the development of health and well-being products, as well as novel food interactions may be triggered.
• Some of these aspects, as reported in the literature, include but are not limited to the printing machines, methodologies, prototype design and software, food ingredients and additives, processing parameters, and post-processing suitability (Liu, Zhang, Bhandari, & Wang, 2017) applied to each 3D printed food manufacturing process.

2.1 Current application of 3DP in food products

• In the last decade, 3DP technology for food products has increasingly developed through its application to a wide range of food materials.
• Nonetheless, few studies (Lipton et al., 2010; Lipton, Cutler, Nigl, Cohen, & Lipson, 2015; Severini et al., 2016a) have taken into account the post-processing feasibility of the 3D construct for materials such as dough or meat, which require further heat treatment; for instance, its ability to withstand cooking operations without losing the 3D intricate design due to cooking loss/shrinkage.
• In general, there is still an extensive field for research regarding the application of this technology for a broad range of foodstuffs with varying formulations.

2.2 3D Printing of meat

• To date, only a small number of studies account for the printability of fibrous-meat materials, through the assessment of the rheological properties of the meat “ink”, as well as the postdeposition and post-processing properties of the printed object.
• Also, the same slurry was used to print a cube containing celery fluid gel inside.
• Such introductory results in 3D meat printing show how this technology can further generate meat products with complex internal structure, containing on-demand functional ingredients and modified textures for enhanced eating experiences.
• Recently the printability of fish surimi gel was assessed by Wang et al. (2018) using a screw-conveyor extruder type 3D printer.
• Furthermore, the authors evaluated the effect of printer settings on the geometrical precision and dimension of the deposited structures, although no objective comparison was performed among printed structures, such as the post-deposition and postprocessing properties.

2.3 3D Food printers and printing parameters

• The basic components of a 3D food printer stage include a motor-driven print-head and a platform, commonly attached to a stage with Cartesian configuration (Sun, Zhou, Yan, Huang, & Lin, 2018).
• Based on the 3D printing methodology built into the 3D printer, the print-head and platform characteristics may vary.
• Some previous studies on meat and seafood printing focused on the extrusion and printing process (Kouzani et al., 2017; Liu et al., 2018a), post-deposition and post-processing conditions (Lipton et al., 2010), rheological and mechanical properties of the material (Wang et al., 2018), regardless of safety concerns during printing due to the printer’s limitations.
• When a printer is not attached with cooling system, the suitability of the technology for the processing of highly perishable materials like meat is dependent on the initial meat paste temperature and the period of time that the meat paste remains in the cartridge or platform at ambient temperature.

2.4 Printing conditions to enable 3D printing of meat

• Several studies demonstrate the effect of varying printing processing parameters on the printability of food materials and hence, the quality of the final printed objects.
• Similarly, an optimal nozzle height determines the accuracy and dimensions of the printed meat product, and it is suggested to be equivalent to the dimension of the nozzle diameter.
• If the nozzle speed is too high, a thinner stream of meat paste is obtained and dragged, preventing the subsequent binding of layers and producing inaccuracies in the final product since voids remain within the cross-section area, and under deposition may occur.
• Similarly, varying infill percentages will affect the total amount of deposited material in the internal part of the printed structure, affecting the void fraction within the final 3D printed meat product and thus the post-processing conditions.
• The void fraction would determine the cooking conditions for a specific degree of doneness since as more porosity remains within the structure, less heat transfer occurs during cooking, affecting the moisture and fat releases and thus the texture of the cooked meat product.

2.5 Design development

• The in-software design for a determined 3D printed meat product sculpts its nutritional and sensorial profile.
• Even though the rheology of the meat paste may represent a challenge when reproducing such complex patterns, these approaches could provide food consumers with both on-demand nutrition and novel eating experiences.
• As an example, three hypothetical designs (Autodesk, Inc.), such as sausage, steak and beef patty are shown in Figure 8.
• Recombined meats, such as steaks can be 3D printed as a multi-material model from soft meat paste, fat slurry and other food ingredients to approximate the flavours and nutrients of a beefsteak.
• The model is sliced into 2D cross-sectional layers, according to the required design and printing settings (Noorani, 2017).

2.6 3D Printing methodologies suitable for meat materials

• A variety of 3DP methods has been used for food printing, such as extrusion, inkjet printing, binding deposition, and bioprinting (Godoi et al., 2016), which are commonly applied to paste-like materials, liquid-based foods, powder-based foods, and cultured cells, respectively.
• 3D printing of meat products consists of building the desired geometry from a slurry material, which requires controlled temperature below 4 °C, calling for liquid-based methodologies, such as extrusion and/or inkjet printing.
• Among the available extrusion mechanisms (syringe-based, air pressure-driven and screw-based extrusion), air pressure driven extrusion is not recommended for viscous paste materials due to their ease of attaching to the walls of the cartridge (Sun et al., 2018), and thus is not endorsed for 3D printing of meat paste.
• After fusion, the agarose structure is removed and the tissue is subjected to low-frequency stimulation in a bioreactor to maturate meat fibres (Sher et al., 2015).
• First, as a fibrous material, the raw meat needs to be finely comminute into a paste form with controlled particle size to enable the extrusion through the nozzle of mm to micron size.

3.1 Potential viscosity enhancers and binders for printable meat paste

• The viscosity of the paste has to be low enough to flow easily through the nozzle and high enough to maintain the deposited shape (Godoi et al., 2016), and further support the subsequent layers on top.
• To improve the mechanical stability of the paste upon deposition, heat- and cold- set binders are available based on the temperature required for the occurrence of the binding mechanisms that are described below.
• Furthermore, the addition of salts and phosphates is recommended to aid the extraction of salt soluble proteins, such as myofribrillar and some sarcoplasmic (Boles, 2011), and thus increase the binding matrix.
• In general, the addition of different food hydrocolloids to the meat paste can provide modified rheological and mechanical properties through varying binding mechanisms, enhancing its printability and post-processing viability.
• Very few studies refer to the printability of fibrous meat materials, such as pork, turkey, chicken and fish, while no data is available for beef meat.

Declarations of interest 6.

• This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
• Meat Products Handbook - Practical Science and Technology: Woodhead Publishing.
• 3D printing technologies applied for food design: status and prospects.

Highlights

• Multi-material 3D printing allows the production of recombined meats.
• The design of appetizing soft-meat products is viable with 3D printing technology.
• Low temperature-3D printers are needed to process meat products safely.
• The application of heat- and cold-set binders enhances the meat paste rheology.