Possible Clues:

• Upsetting note: 'This has turned the milk!'
• It's used to curdle milk for cheese
• Wrong note in the stomach (6)
• Cheese-maker's substance
• Substance used in cheesemaking
• Returned note with what you need to make cheese
• Apple for which you'd need to return a note
• Note how it is up to making one sweet
• Substance used to curdle milk in cheese-making
• Return money to jelly-maker