Sumac, a berry, has been used in the Middle East as a souring agent for centuries. However, according to Wolfert, unlike lemon juice or vinegar, which could accomplish the same thing, “sumac adds another dimension that lemon juice does not,” It also adds a lovely red ting to a dish.
Sumac is sold as dried berries and ground. Please be aware that you need to buy this from a store and must not pick the sumac growing on the roadside in places as some of those varieties are poisonous. Wolfert advises storing the berries in the freezer and the ground sumac in the fridge.
This spice is a fantastic tabletop condiment, to be sprinkled on such dishes as salads, baked chicken, hummus, boiled eggs and more to provide that extra zing. For cooking, Wolfert suggests adding some water to the berries, allowing the mixture to sit for a bit and then draining the berries. Using the sumac water will allow the spice's taste penetrate the dish (as opposed to just adding powdered sumac or sprinkling the sumac as a garnish). Sumac goes well with chicken and fish. Even though lemon or vinegar can't be substituted for it effectively, the reverse substitution -- sumac instead of lemon or vinegar -- can work wonders in kebabs, broiled chicken, fish, stews, salad dressing and more. Sumac can be used during the cooking process and then also sprinkled on top of the final dish.