I own a 3D printer. An FFF type, fused filament fabrication. I am using it for prototyping simple machines for food use. As I said “prototype”. I am switching to food safe materials as soon as I got it working efficiently.
There are several reasons why 3D printed plastics are not suited in food applications.
From my own observation PLA (the common filament) begins to soften at 100 C. Most heat application requires at least that much. The boiling is set to 100C, deviating slightly with place elevation. Sterilization usually heat plus increased pressure. I have the slightest idea of what is gonna happen with plastic if undergone these two forces. Pasteurization require gentler heat. It might be safer, it might be not. When in state of doubt, discard it.
PLA has a bad reputation of absorbing moisture. Other types have more or less the same characteristics. Unless stored in airtight container with desiccator, its usable life for printing is only six months. Maybe shorter in areas of high relative humidity.
My theory is. If used as food container or anything that requires food contact, it might absorb water plus the flavor it carries. Then removal will be next to impossible. Lastly, using with other food items may cause cross contamination.
3D printing filaments come in different colors. Food safety of those are unsure. Even if they use food approved dyes, reaction is uncertain. Every item and process should be tested thoroughly by regulatory agencies.
Crevices and Rough Lines
The rule of cGMP, surfaces should be easy to clean. 3D printed items have rough lines and sometimes crevices. Cleaning them sure is not easy. Food debris clinging to furrows will be carried over to next production batch.
Resin type 3d printing produces a much smoother surface with negligible lines. I have never seen one in close up so I cannot conclude on this.
Strength is another issue. PLA is brittle. It will hamper production when it fails and will likely cause contamination too. There are other impact resistant filament but still not suited because of the several weaknesses stated above.