They will keep for about three days. Wrap in moist paper towels for longer storage, up to five days. The flavor may intensify in the refrigerator during the longer five day storage. A member of the cruciferous vegetable family, mustard contains large amounts of beta carotene and vitamin C that are important antioxidants. Although scientists do not fully understand how, these vegetables seem to have cancer-preventive properties.
Mustard greens are also a source of calcium that can be important to lactose intolerant individuals.
Mustard greens also contain a significant amount of iron. Freezing is the best way to preserve an over abundance of mustard greens. Like other vegetables, mustard greens must be blanched before freezing. Blanching is simply the emersion into scalding water then into an ice water bath before freezing. In a blanching pot or large pot with a tight fitting lid, bring 5 quarts of water to a rolling boil.