I. Ultrasound treatment and addition of CaCl₂ to manipulate the producibility of jelly using a fused deposition modeling 3D printer
The objective of this study was to investigate the effect of ultrasound and alcalase treatments on the formulation requirements for printing jelly using a FDM 3D printer, which include fidelity, shape retention, and extrudability. The jelly formulation to be treated with ultrasound ( 'Formulation A' ) contained gelatin 16% (w/w), sugar 40%, and citric acid 1% and the CaCl₂ was added to jelly formulaion( 'Formulation B' ) consisted of gelatin 10% (w/w), pectin 7%, sugar 30%, and citric acid 1%. The amount of Formulation A and the treatment voltage and time of ultrasound treatment were 1300 g, 700 W, and 30 min, respectively, and CaCl₂ (2% of the pectin). were added. The requirements of jelly printing were fidelity, shape retention, and extrudability and the parameters used to describe the requirements included elastic modulus (G'), loss modulus (G" ), tan δ, shear modulus, yield stress (τ 0), phase angle (δ), and gel strength. Ultrasound treatment increased the G' , shear modulus values, and decreased the phase angle and gel strength values. Addition of CaCl₂ increased G' , G" , shear modulus, τ 0, and gel strength values, and lowered the tan δ, and phase angle values. The results indicate that both ultrasound treatment and addition of CaCl₂ improved the fidelity, shape retention, and extrudability of jelly. The results suggest that ultrasound treatment and addition of CaCl₂ can be used as methods of controlling the requirements of the jelly formulations for FDM 3D printing.
II. Addition of poly-γ-glutamic acid and pH adjustment of cookie dough to manipulate the producibility of cookie dough using a fused deposition modeling 3D printer
Addition of poly-γ-glutamic acid (PGA) and pH adjustment of cookie dough was developed in this study as a method for controlling the rheological properties of cookie dough for successful 3D printing by fused deposition modeling (FDM). Cookie dough consisted of wheat flour (51%, w/w), sugar (20%), water (19%), and olive oil (10%). After adding PGA at concentrations of 1, 2, and 3% of flour content to the dough, the rheological properties of dough were measured. The printing parameters of dough were determined to be G' , G" , shear modulus, tan δ, yield stress (τ 0), phase angle (δ), and hardness. The fidelity, shape retention, and extrudability of the printed object were assessed based on these parameters. When 3D printing dough with varying composition, with the rheological parameter values of dough with excellent fidelity, shape retention, and extrudability were set as the 3D printing parameter values. As the concentration of PGA added increased from 1% to 3%, G' , G" , shear modulus, tan δ, τ 0, δ, and hardness values also increased. Adjusting pH of dough increased G', G'', shear modulus, τ 0, and hardness, and lowered the tan δ and phase angle. Consequently, addition of 1% PGA and pH adjustment of dough enabled successful dough printing by improving fidelity, shape retention, and extrudability of dough. The findings in the study showed the effects of adding PGA and adjusting pH of the dough on the rheological parameters required for 3D printing dough. The findings further confirmed that addition of PGA and pH adjustment of dough could be used as a method for controlling the physical properties of materials for 3D printing of dough.
III. Development of treatment method for enhancing the structural stability in 3D-printed cookie dough
The effect of the vacuum drying and rapid freezing process was evaluated on the changes in the dimensions and hardness of the cookie dough after baking, which was prepared by fused deposition modeling (FDM) 3D printing. Cookie dough consisted of wheat flour (51%, w/w), sugar (20%), water (19%), and olive oil (10%), with or without poly-γ-glutamic acid (PGA) (1% of the flour). Cookie dough was vacuum-dried (60 ℃, ~0.019 MPa) until the moisture content reached 10% or rapidly freezed at -80 ℃ and thawed in an incubator at 25 ℃ after than baked in an oven (180 ℃, 15 min), respectively. The baking reduced the spread ratio of 3D-printed cookie by increasing the height and reducing the diameter while increased the spread ratio of molded cookie by reducing height and increasing diameter. Although the vacuum drying destroyed the shape of the cookie made of manually prepared dough using a mold, 3D-printed cookie maintained the original shape and possessed uniform color. Vacuum drying of 3D-printed cookie dough reduced the baking time by ~6 min, and increased hardness of baked cookies not containing PGA. Freezing altered the dimension of molded dough but did not deform the dough prepared with 3-D printing. The addition of PGA increased the hardness of the cookie prepared with freezed 3-D printed dough. The results showed potential of vacuum drying and rapid freezing as a means to enhance the structural stability of the 3D-printed cookie before baking.