Researchers from Ewha Womans University’s Department of Food Science and Biotechnology and SuFAB Inc., a company based in South Korea, have developed a 3D printing food ink using Auxenochlorella protothecoides to simulate selected fish texture properties. Rheological measurements, printability tests, and texture profile analysis identified a 36% biomass concentration as the only formulation achieving stable extrusion and dimensional accuracy. The study, published in the LWT journal, examines how material composition and printing parameters define a narrow processing window for successful 3D printing.
Global seafood consumption has been increasing at nearly twice the rate of population growth, according to the UN Food and Agriculture Organization (FAO), contributing to overfishing, biodiversity loss, and exposure to contaminants such as mercury and microplastics. Development of fish analogs has accelerated in response, typically relying on multi-component formulations based on plant proteins and hydrocolloids to reproduce structure and texture. This study instead evaluates A. protothecoides, a white-pigmented microalga containing approximately 65% protein on a dry-matter basis, as a single-ingredient printable matrix. Its pale coloration supports visual alignment with white-fleshed seafood, addressing limitations associated with green microalgae.
Rheological analysis showed that all tested formulations exhibited shear-thinning behavior, enabling flow under applied stress during printing. Increasing biomass concentration reduced the flow index while significantly increasing the consistency index, indicating improved resistance to deformation but reduced flowability. Microstructural analysis using scanning electron microscopy revealed a progressively denser porous network as concentration increased, with pore sizes decreasing from approximately 57 μm to 13 μm. This structural densification reflects increased cross-linking within the material, which contributes to higher viscosity and mechanical strength but limits extrusion at higher concentrations.
Viscoelastic testing further showed that storage modulus (G′) exceeded loss modulus (G″) across all samples, indicating predominantly elastic behavior. Yield stress increased from 25.68 Pa at 32% concentration to 425.22 Pa at 40%, confirming that higher biomass levels improve structural stability after deposition. However, this also narrows the processing window. At lower concentrations (32% and 34%), printed filaments spread due to insufficient elastic resistance. At higher concentrations (38% and 40%), extrusion became unstable or failed due to elevated viscosity and nozzle clogging. Results indicate that printability depends on balancing flow under shear with structural recovery after deposition.
“WC 36% was identified as the practical optimum, providing sufficient post-deposition self-support without exceeding the extrusion limits of the printing system,” the researchers state. Dimensional analysis confirmed zero percent error in both height and width relative to the CAD design at this concentration, while other formulations showed measurable deviations or extrusion failure. Three-interval thixotropy testing further showed that viscosity recovery alone did not predict printability, requiring evaluation alongside extrusion behavior and dimensional fidelity.
Using the optimized formulation, the team assessed how nozzle diameter and infill density influence printed structure. Smaller nozzle diameters produced more uniform filament deposition, while larger diameters reduced feature resolution and introduced rounding at corners. Increasing infill density increased material deposition and reduced internal voids, although gains diminished at higher densities, particularly for larger nozzles where inter-filament gaps limited effective densification. Printed geometries followed CAD designs under optimal conditions, with resolution dependent on parameter selection.
Texture profile analysis compared printed samples with steamed mackerel, flounder, and salmon using hardness and cohesiveness as metrics. Hardness increased with infill density across all nozzle sizes, enabling replication of species-specific targets through different parameter combinations. Mackerel-like hardness was achieved using either a 0.85 mm nozzle at 30% infill or a 0.5 mm nozzle at 60% infill, while flounder and salmon targets were reached using alternative configurations. Cohesiveness showed more limited alignment, with only mackerel values reproduced within the tested range.
Findings establish a relationship between biomass concentration, rheological behavior, and printing performance in microalgae-based systems. Results show that A. protothecoides can function as a standalone material within a narrow processing window, where deviations in concentration lead to filament spreading, under-extrusion, or clogging. The study titled “3D Printing Food Ink Development Using Auxenochlorella protothecoides: Rheology, Printability, and Fish Texture Simulations,” was authored by Jin-Kyu Rhee, Yourim Oh, Eui-Jung Han, and Yurim Ha.
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Featured image shows Printability evaluation of 3D-printed white chlorella (WC) inks at different concentrations. Image via Jin-Kyu Rhee et al., LWT.
