The food synthesizer (or food processor) was a common receptacle used aboard 23rd century starships and starbases for synthesizing foods and beverages. Replacing 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 the mid-22nd century, T'Les had a food synthesizer in her home on Vulcan. When T'Les' daughter T'Pol and Charles Tucker III were visiting the residence in 2154, the food synthesizer was broken, so T'Les asked Tucker if he could fix it, but he didn't have an opportunity to reply, due to the arrival of Koss. (ENT: "Home")
A series of food synthesizers were located in the mess hall aboard the Crossfield-class starship Discovery. When Commander Saru offered Michael Burnham some blueberries aboard the Discovery in 2256 and she responded that they tasted different from ones she had eaten in prison, Saru reckoned that was less likely to be "a food synthesizer issue" than a result of the environment she was eating them in, which Burnham casually agreed with. (DIS: "Context Is for Kings")
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")