Propionic acid is approved for use as a preservative, but only in limited quantities. Acetic acid (vinegar) is officially classed as a seasoning and there are no restrictions as to how much can be added to food products.
其中「丙酸」是合法的防腐劑，必須限量使用；「乙酸」是調味劑（俗稱的醋酸），可無限量使用。