Casamino Acid: This productthis peptone is a complete acid digest of casein and is the key ingredient in Mueller-Hinton agar, an agar typically used for antibiotic susceptibility testing.this peptone is a complete acid digest of casein and is the key ingredient in Mueller-Hinton agar, an agar typically used for antibiotic susceptibility testing.ThisTT is a complete acid digest of casein and the key ingredient in Mueller-Hinton agar, an agra typically used for antibiotic susceptibility testing.