Effect of gums on the rheological, microstructural and extrusion printing characteristics of mashed potatoes.

This paper studied the rheological, microstructural and 3D printing characteristics of mashed potatoes (MP) with gums of xanthan (XG), guar (GG), k-carrageenan (KG) and k-carrageenan- xanthan gum blend (KG-XG). Addition of gums increased the viscosity, storage modulus (G'), and loss modulus (G″) of MP except XG. Creep results indicated that self-supporting performance followed decreasing order of KG > KG-XG > GG > contorl > XG. Fourier Transform infrared spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) results well explained the behavior by enhancing hydrogen bonding and constraining water molecules' mobility. KG-MP samples possessed good self-supporting performance but with rough surface and lots of defective points. The parts printed using XG-MP were "fatter" than target objects but with a smooth surface structure. This probably because the excellent extrudability (more fluid-like behavior, tanδ 0.185) but with poor self-supporting ability indicated by lower G' and greater creep strain 0.88%. The printed objects using KG-XG-MP possessed a smooth surface structure (visual appearance), and good printing precision indicated by the lowest dimensional printing deviation for a printed cuboid shape (2.19%, 2.20%, 2% for length, width, height direction, respectively). This was probably because the creaminess effect provided by XG render the printed objects a smooth surface structure, while KG provided MP with sufficient mechanical strength (proper G' and load bearing capacity) to be capable of self-supporting.