PKU Air20, Green, Citrus Twist, 174 mL Pouch. 100 calories per each 174 mL (5.9 fluid ounce) pouch. PKU Air 20 is a ready to drink, phenylalnine free, protein substitute with a blend of essential and non essential amino acids, carbohydrate, vitamins, minerals and trace elements with DHA. Each pouch provides the equivalent of 20 grams of protein.