Raymond Hodgson, 31, assaulted Emma McCormick by squirting the sauce into her face, Carlisle Magistrates' Court heard.
Hodgson said he threw brown sauce at McCormick to show her what saucy 'really meant'.
Prosector Adrien Harris explained to the court the actions of the man.
"Mr Hodgson thought that the book was pornographic, and that she should not read such literature," he said. "The argument continued into the following day, with the two exchanging text messages."
The court was then told how Hodgson went round to McCormick's house, with the bottle of brown sauce, to continue the argument.
Prosecutor Harris added: "She went to close the door and he jammed his foot into the door, slapped her once in the face, and then squirted her with this bottle of sauce."
Hodgson was charged with common assault. He was ordered to pay McCormick £100 compensation and £85 towards prosecution costs.
He also received an imposed curfew from 6pm to 8am and a six-month community order.
The couple are both still in touch with each other.
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