When peppercorns are ground into powder, they can quickly lose their flavor and aroma during storage, making them less desirable for use in a sauce. Whole peppercorns, on the other hand, retain their flavor and aroma for much longer. If you crush them or use pre-ground pepper, the sauce will be spicy and distinctively peppery while using whole seeds, the taste is mellow, mild, with only a hint of kick.