2 g of calcium hydroxide are dissolved in 80 cc of hot water having a temperature of 60.degree. C. to prepare a water solution of calcium. 50 g of fibrous soybean protein are added into 150 cc of hot water having a temperature of at 60.degree. C. to prepare a water solution of soybean protein. The water solution of soybean protein is stirred and added 10 g of dried egg, and stirred, then added the water solution of calcium and stirred. 30 g of glucomannan are added into 678 cc of hot water having a temperature of 60.degree. C. to prepare a water solution of glucomannan and stirred to form a jelly-like product. A water solution comprising soybean protein, dried egg and calcium hydroxide is added to the jelly-like product, kneaded and coagulated to form a plate-shaped "Soybean Protein-Glucomannan Jelly". The plate-shaped "Soybean Protein-Glucomannan Jelly" is minced into small pieces, 3 to 9 mm wide and 3 to 9 mm length, heated at a temperature of 110.degree. C. for 40 minutes to denature them. The small pieces are packed in a retort pouch made from a laminated film comprising a polyester film, an adhesive, an aluminum foil, an adhesive and a high density polyethylene film in this order, degassed, sealed by heat-sealing, and put the heat-sealed retort pouch into an autoclave. Then, sterilization is carried out by increasing the temperature of the center of the heat-sealed retort pouch to 120.degree. C. for 4 minutes.