Ink jet printing can be used to print on the surface of many of today’s most popular edible food items. However, it’s not as simple as simply using your home computer printer to print “Happy Birthday” onto a page of rice paper. That may be fine for mom and the kids, but for commercial use, there are several additional steps and procedures required.
Many of today’s most common foods like cakes, cookies, biscuits, cereals, crackers and others use printing to identify the ingredients or to make the items more attractive. In these cases, a “food grade” ink is required. This assures the buyer that the ink is certified as acceptable and approved for human consumption by the appropriate regulatory agencies.
Even though food grade inks are not certified by the US Food and Drug Administration, they still need to adhere to restrictions relating to “GRAS”, a government guideline that’s short for “generally recognized as safe”.
But manufacturers like to use food grade ink for other reasons. It allows them to properly code their products during the manufacturing process. Often, they will use ultraviolet ink which isn’t visible to consumers but can be tracked by special UV scanners.
In a commercial environment, because there are hundreds if not thousands of continuous printings, a number of concerns need to be addressed:
- The ink must be compatible with the surface of the food medium it’s being used on.
- The ink must have the proper viscosity, resistance from smearing, surface tension, solubility and drying times required.
- A “make-up fluid” needs to be mixed with the ink to replace solvent that evaporates during the printing process so that ink performance is maintained. Another reason this fluid is used is to ensure that the proper chemistry is maintained in the printing fluid.
- It also must be as non-smearing as possible, and have enough viscosity and other attributes to stay together and not run while being printed.
Today there are only a few food grade inks on the market which match all of these requirements. Others may contain harmful substances that could cause health problems if ingested. Often, when the right viscosity isn’t reached, the ink will tend to smear. Ink manufacturers are constantly trying to improve these inks but a final solution has not yet evolved. The process of printing on rice paper and placing the paper on a food surface is often used, but this method requires additional labor and isn’t suitable for many food products because of their varying shapes and sizes.
Food grade ink usually contains one or more food grade dyes plus a food grade glycol, like 1,2-propanediol, in order to print directly on food surfaces. Most of today’s better quality food grade inks for printing are non-toxic.
Another component that is commonly used in food grade ink is glycerin. Glycerin acts as a “co-solvent” which enhances the solvent power of the primary solvent. Dyes can also be added to add or slightly change the original ink color. Finally, food grade ink usually contains additives which act as thickening agents, antimicrobial and buffering agents, antioxidants, surface tension modifiers, and preservatives. A minor percentage of alcohol (isopropanol or ethanol) is also sometimes added.