Dehydrated White Onion Granules Enriched with the goodness of essential vitamins like vitamin B and C, minerals like manganese, calcium, iron and potassium, and a myriad of antioxidants, onion Granules hold high significance in treating a host of ailments including mouth sores, heart problems, headaches, high blood sugar and even cancer. Onion powder is a seasoning made from dehydrated ground onions. This potent-smelling spice is most often used in dry rubs and in marinades to get concentrated onion flavor without the moisture and bulk of the onion bulb itself.