Sterile is the inside. Perhaps, this is necessary in the preparation of frozen custard. This however does not transcend to outside when making your order. There are lot's of tasty treats to order. Be it the Razzle Dazzle (Gf's favorite) socked full of raspberries and hot fudge or a "plain Jane" shake with some other yummy ingredient added, Mr. D's has something yummy and cold to cool you down on a hot summer afternoon.