Gravy Mix

Ingredients:

Cornstarch, dhydrated onion, salt, beef fat, autolyzed yeast, sour cream, corn syrup solids, partially hydrogenated vegetable oil (contains one or more of the following: soybean and/or cottonseed), non-fat milk, silicon dioxide, sodium caseinate, maltodextrin, lactose, natural flavor, beet powder, xanthan gum, lactic acid, citric acid, mono and diglycerides, disodium inosinate, disodium guanylate, lactic culture, TBHQ, propylene glycol, sulfiting agents.

Preparation instructions:

Combine gravy mix and 1 cup water in small saucepan. Bring to a boil stirring constantly until smooth and thickened. Reduce heat; simmer 1 minute.

Questions:

What is the function of silicon dioxide? What other ingredients could you use instead? Why do we add propylene glycol? Why do we include sulfiting agents?