There is no set time; first thing in the morning and last thing at night are both good times. However, the most important time is right after you workout, when muscles are in an anabolic state (15 to 30 minutes after exercise finishes). Protein consumption at this time allows nutrients to be shunted preferentially into protein synthesis rather than energy production or conversion to fat.
Mixing protein with 8 ounces of fruit juice (grape, orange or apple) has been shown to help speed protein delivery to muscles after workouts. The high glycemic carbs from the juice create a release of insulin which acts synergistically with the enzyme glycogen synthetase, speeding protein/peptides and amino acid nitrogen into muscle cells and away from fat cells.
It is important to consume Designer Whey with grape juice [or any high glycemic (sweet) carbohydrate] immediately (15 - 30 mins) after your workout. This is based on scientific research that demonstrates that consuming high glycemic carbohydrates and protein, in combination, increases the rate of muscle glycogen (carbohydrate) synthesis and protein storage after exercise. In other words, the post-workout carbohydrate/protein meal enhances glycogen re-synthesis and protein synthesis. During exercise, your muscle glycogen and amino acid stores become depleted. After exercise, as a result of heightened insulin sensitivity and muscle cell receptor site stimulation, your muscles are primed to receive protein and carbohydrates.