*2.2. Sample Preparation*

Sodium alginate was blended with deionized water to form a 2% (*w*/*v*) solution, and was centrifuged at 19,802× *g*, 20 ◦C for 15 min. SPI was blended with deionized water to form a 12% (*w*/*v*) solution at room temperature and underwent ultrasonic degassing for 20 min. The pH of the SPI solution was determined to be 7.51. The viscosity of the prepared sodium alginate solution and SPI solution was determined to be 2630 and 10,590 cP, respectively, at 20 rpm speed. CaCl2 solution (3% *w*/*v*) was prepared by dissolving CaCl2 in deionized water. Lutein fortified OL (0.5% *w*/*v*) or SO (0.5% *w*/*v*) was added in the SPI solution to form the emulsion by using the high shear mixer (Silverson L4RT, US) at 8000 rpm for 7 min, and the container was placed under the ice bath to prevent the excessive heat. The ratio of the lutein fortified oil to SPI solution was 10:1 (*v*/*v*).

## *2.3. Assembly of Microfluidic Devices*

Assembly of microfluidic devices was performed based on the methods disclosed in a patent (No. 10201906256W). The flow rate was set at 3000 μL/min for sodium alginate solution and 500 μL/min for SPI and lutein-fortified oil emulsion for the co-flow device, while it was set separately at 454.5 μL/min and 45.5 μL/min for the SPI solution and lutein-fortified oil for the combination of co-flow and flow-focusing device (namely combination-flow).

Schematic diagrams of two different microfluidic devices are shown in Figure 1. The co-flow device (Figure 1a) is made up of an inner circular capillary that is fitted in an outer square capillary, with both the inner (SPI and lutein fortified oil emulsion) and outer (sodium alginate) fluids flowing in the same direction. Flow-focusing is similar to the co-flow device, whereby the inner (lutein fortified oil) and outer (SPI) fluids are introduced in opposing directions to each other before exiting through the same capillary. Combination-flow (Figure 1b) consists of the flow-focusing on the left part and co-flow on the right part. The mixture of lutein-fortified oil and SPI is extruded first with flow-focusing and then follows the fate of the co-flow; flowing through the inner capillary with the same direction as sodium alginate, which flows in the outer capillary. The material composition of extrudates are theoretically the same for both two devices. The extruded noodle-like samples were subjected to a CaCl2 bath for 30 min for ionic gelation and were subsequently heated in a deionized water bath (80–85 ◦C) for 6 min for thermal gelation. Afterwards, all noodle samples were kept in water as dehydration may occur due to the diffusion of saturated water vapor at the surface [31]. All the above procedures were done under dull red light to minimize the photodecomposition of lutein.

**Figure 1.** Schematic diagram of microfluidic devices (**a**) Co-flow; (**b**) Combination-flow. SPI: Soy protein isolate. Critical channel diameters are measured in millimeters.
