Which preservative can extend the shelf life of whole wheat bread above 7 days?

Calcium propionate is a commonly used preservative that can extend the shelf life of whole wheat bread beyond 7 days. It works by inhibiting the growth of mold and certain bacteria, helping to maintain freshness. Other options include vinegar and ascorbic acid, which can also contribute to longer shelf life while improving bread quality. However, calcium propionate is the most widely recognized for this purpose in bread products.