Making "White Christmas Pie" for the first time, the recipe calls for beaten egg whites, with cream of tartar and sugar but never says to "cook" it. Is it necessary to cook the egg whites, or is it safe to use them, blended with other ingredients?--Dora
You are right to be concerned about using raw egg whites. The USDA now warns against eating anything made with raw eggs and especially about serving them to infants, young children, older adults, pregnant women, and people with weakened immune systems, since they are the most susceptible to salmonella bacteria. The risk is especially high in something like White Christmas Pie, since it is typically made well ahead of consumption and may be eaten over a period hours or even days.
There are alternatives however. Some cooks have suggested a process for heating the egg whites with water, sugar and cream of tartar over a double boiler until they reach a temperature of 160°F (71°C). I'm not crazy about this method for two reasons -- first because raising the temperature increases the risk of contamination so you need to be sure to heat the entire amount to that temperature and hold it there, and second because there is a chance of actually cooking the eggs if they are over-heated. If done right, however, apparently you can still whip the egg whites as usual.
The other alternatives are the whites of pasteurized in-the-shell eggs and powdered egg whites or meringue powder. The US FDA has approved the pasteurization of whole eggs in their shell. They can be found in some grocery stores and can be used in recipes calling for uncooked eggs. Powdered egg whites are also pasteurized and can be used. They are reconstituted with water following the manufacturer's directions and should whip well for this recipe.
Meringue powder is powdered egg whites already blended with sugar and stabilizers such as gum arabic, as well as flavor and preservatives. Since they already contain sugar and usually vanilla, you will likely need to reduce or completely omit the sugar and vanilla called for in the recipe. It may take a bit of experimenting to find the right amount of sugar and vanilla to use.
In any case, the pie should be kept refrigerated until served.