Hi Dina, it depends on how long it sits and the temperture you keep it at.
The first thing that gets lost are the antioxidants. As soon as the food is blended with liquid and air, antioxidants go to work to counter the effects of oxidation which happens from the breaking a part of the plant tissues and them mixing with air and liquid. So you lose a lot of the antioxidant benefits of the foods.
The enzymes that are naturally existing beging breaking dowm the food you blended even further and after about 15 minutes the blast color and texture will change. It will not be as pleasant to drink.
The minerals are not effected however some Vitamins like Vitamin C may begin losing some potency.
It is best to drink as soon as you make the blast. Thee great thing about the NutriBullet is that it is very portable. You can easily take it to work to make blast. And it is inexpensive enough to buy an extra one and just keep it at work.
I hope this helps,
Wally Bishop C.N.C.