The food synthesizer (or food processor) was a common receptacle used aboard 23rd century starships and starbases for synthesizing foods and beverages. An evolution over the older protein resequencer, these food receptacles served as a supplement to the ship's chef and were predecessors to 24th century replicators. Unlike replicators, where food orders were made by voice command, food orders given to food synthesizers were made by program tapes or cards inserted into a slot.
In 2268, while the USS Enterprise was infested with tribbles, it was discovered that they had gotten into the food processors aboard the ship through one of the ship's air vents. (TOS: "The Trouble with Tribbles"; DS9: "Trials and Tribble-ations")
Nurse Chapel offered the surviving children of the Starnes Exploration Party a selection of cards with differing flavors of ice cream to choose from. All they had to do was pick a card and the computer would mix their favorite combination. (TOS: "And the Children Shall Lead")
Upon taking on a contingent of Klingon officers, lead by Kang, aboard the Enterprise, Captain Kirk ordered Johnson to have the food synthesizers programmed to accommodate their guests. (TOS: "Day of the Dove")