Factors Affecting the Determination of Available Lysine in Whey with 2,4,6-Trinitrobenzene Sulfonic Acid

Lactose in cheese whey interferes with the determination of biologically available lysine in whey proteins when the reagent 2,4,6-trinitrobenzene sulfonic acid is employed. Loss of the epsilon-TNP-derivative of lysine is dependent upon the amount of lactose hi the test material. The sample weight chosen for analysis also influences results with this reagent. The larger the sample of either pure protein or carbohydrate containing material, the smaller the amount of available lysine found. By careful selection of experimental conditions and by application of a correction formula for lactose interference, the available lysine in whey protein can be rapidly approximated with the 2,4,6-trinitrobenzene sulfonic acid method. Results compare favorably with those obtained by an established method.