We all know that a “No Parking” sign must be read carefully to avoid a ticket – the direction of the arrow, time and day of the week listed on the sign make all the difference. The same is true with a kosher certificate. A kosher certificate is filled with important data to verify the kosher status of a particular product. The two most important pieces of information are the Product Name and the expiration date.
The kosher certificate only applies to the item listed on the certificate and only when the item is SEALED in the original packaging.
Once an item is opened, the kashrus is no longer guaranteed. A pre-mix, used in a store, might be kosher certified, but once the mix is put into the stores machines and prepared and served, the kosher status is no longer guaranteed unless the actual store is kosher certified by a reputable agency as well.