Edible printing is the process of printing images with edible food colors onto various food products such as candies, cakes, cookies, pastries, and even dinner. The advancements of digital printing technologies along with consumers' demands have stimulated the growth of the edible printing market. One of the fastest growing business sectors is bakery, where photo cakes are getting more and more popular. Inkjet printers with edible ink cartridges are used to print images on a sheet of edible paper called frosting sheet, which is then applied to a cake. With the boom of the edible printing market, print quality becomes more and more important. Consumers would want legible small text and color-accurate photo images. In this study, two test charts were printed on frosting sheets with edible inks and image quality was evaluated.
An Epson Workforce 30 inkjet printer was used to print a gray-scale test chart and a 24-patch ColorChecker test chart on frosting sheets. The printed images were measured with an X-Rite SpectroDensitometer 528. The tints on the printed gray-scale test chart were used to measure dot gains. The 24 color patches on the printed ColorChecker test chart were used to measure L*a*b* values, which were then used to calculate delta E (?E) values. In order to note any changes in quality within a short, realistic time frame, the prints were measured on the day they were printed as well as seven days later after being placed in an airtight, tin foil folder and stored inside a refrigerator.
It is found that fonts of 5 points or smaller were illegible and lines below 1-point thickness became nonuniform. The dot gain curve peaked at 15% for the 40% tint. This could be easily improved by adjusting the calibration curve of the inkjet printer. As for color reproduction, cool colors showed lower ?E values around 5, while warm colors had higher ?E values with patch 15 (red) having the highest ?E value of 46. Creating a printer profile for this specific frosting sheet is needed for color management. However, even a basic IT8.7/3 test chart has 182 color patches, and since it is difficult to measure on a brittle frosting sheet using an automatic measuring table, it would be time-consuming to measure all the patches by hand. Meanwhile, each substrate requires its own printer profile, so color management for edible printing substrates is very challenging. It is also found that one-week storage under low temperature didn't affect the print quality of edible inks, which indicated that they had good resistance to chilling.