Analysis on the printability and rheological characteristics of bigel inks: Potential in 3D food printing

Abstract

Bigels possess special characteristics that make them optimal for 3D printing applications. In this study, the 3D printability, rheological properties, and microstructure of bigel inks containing 20% (BG1), 30% (BG2), 50% (BG3), 70% (BG4) and 80% (BG5) fractions of beeswax oleogel were investigated. BG5 supported the maximum layer height of 65 mm and yielded the best printing precision. In terms of the extrudability in 3D printing, the value of K increased but n decreased as oleogel fraction increased, which indicated that the viscosity and shearing thinning properties increased. K was 679.38 Pa·sn and n was – 0.19 when the oleogel fraction reached 80%. In addition, confocal laser scanning microscopy showed in BG1 to BG4, oleogel and hydrogel particles aggregated to different degrees after extrusion, but remained unchanged in BG5. These characteristics of BG5 allowed the ink to be extruded from the nozzle smoothly. Recording recoverability, results revealed that as oleogel fraction increased, the recovery time decreased in bigel inks, and BG5 could recover within 2 s after extruding. For self-supportability, as oleogel fraction increased, more needle-like crystals with structures of β′ and β emerged, especially in BG5, which had the largest yield stress (567.71 Pa), complex modulus (G* of 8.35 × 105 Pa), and gel strength (A value of 488.34 × 103 Pa s1/z), indicating that it had the necessary mechanical strength to successfully self-support. These bigel inks suggest a methodology for developing high-oil materials that can be applied in 3D food printing.