Meringue powder has a shelf life of up to two years. It mainly consists of dry egg whites, so there are no preservatives to extend the shelf life of this product.
To ensure that meringue powder reaches its maximum shelf life, keep it in a dry space and do not use a spoon that has been used prior to measuring out the powder. Always use a fresh spoon to keep the product from being tainted. If the meringue powder is two years past its expiration date or has an off smell, do not use it and buy a fresh supply.