I got yelled at by my boss because I wouldn't serve expired gross mocha syrup

The mocha syrup is good for 24 hours once made. A mocha was made yesterday morning and it went out today at 630am. My boss kept telling me it's fine it's good for 24 hours. I said yeah but this sticker says it went out this morning at 630am. She said no that's just the date and time it was made. I told her it doesn't work that way. When she wasn't looking I dumped the product and made a new one. I refuse to serve old expired product because you don't want to listen to your workers who know more than you do. My boss is new to the company and acts like she knows more than the tenured workers but she doesn't.