Disperse Avicel RC-591F into hot water with vigorous agitation and mix until smooth and viscous (5-10 min). Continue heating. Add raspberries, all colorings, sodium benzoate, and potassium sorbate and mix well. Add starch slurry at 190-200 F (88-94 C). Maintain temperature and agitation for 10 min. Product will thicken at this point. Add flavor, citric acid, and sodium citrate. Fill into containers and cool. Deposit on or in pastry. Bake pastry and freeze. Defrost in microwave oven for 2-2.25 min.