For crust, in a small mixing bowl combine the crushed graham crackers and melted margarine. Press the mixture onto the bottom of a 9-inch springform pan. Bake in a 325 degree F oven for 5 minutes. Cool the crust.
In a large mixing bowl combine the cream cheese and ricotta cheese. Beat with an electric mixer on medium speed until smooth. Add the yogurt, sugar, flour, lemon juice, and vanilla. Beat on low speed until combined. Add the egg whites or egg product. Beat on low speed just until combined. Pour into the crust. Place the springform pan on a shallow baking pan in the oven.
Bake in a 325 degree F oven for 55 to 65 minutes or until center appears nearly set when gently shaken. Cool for 15 minutes. Loosen crust from the sides of the pan. Cool for 30 minutes more; remove the sides of the pan. Cool completely. Cover and chill cheesecake for 4 to 24 hours. Before serving, top cheesecake with kiwifruit, strawberries, and blueberries. Makes 12 servings.