Protein-starch binary molding composition and shaped articles obtained therefor

A method for manufacturing a water-soluble and edible thermoplastic molding composition in the granular form, which comprises:

• heating and mixing at 50.degree. C or more a blend of (A) at least one edible natural unmodified starch, (B) at least one edible natural protein concentrate, (C) an aqueous dispersion of at least one inorganic alkali selected from the group consisting of sodium, potassium and calcium hydroxides, carbonates and bicarbonates, to form a salt of the protein, (D) at least one edible organic low-molecular-weight plasticizer selected from the group consisting of glycerol, ethylene glycol, sorbitol, sorbitan, mannitol, maltitol, hydrogenated starch syrup, and sucrose, and (E) at least one lubricant selected from the group consisting of mono-, di- and tri-esters of the edible polyhydric alcohols set forth in (D) with edible higher fatty acids having at least 10 carbon atoms, phosphoric acid derivatives of said esters and lecithin;
• said starch material containing at least 50% by weight of amylose;
• the weight ratio of said starch material to said protein salt being 30/70 to 70/30;
• the amount of said organic low-molecular-weight plasticizer and that of said lubricant being, respectively, 20 to 60 parts by weight and 1 to 11 parts by weight per 100 parts by weight, in total, of said starch material and said protein salt;
• and the amount of said aqueous dispersion of at least one inorganic alkali being sufficient enough to substantially neutralize said protein;
• while gradually adding further water and
• thereafter granulating the blend and finally adjusting the water content in the composition to 10 to 40% by weight.

A method for manufacturing a water-soluble and edible thermoplastic extrusion-molded article, which comprises:

• heating, mixing and granulating a blend of a starch material, a protein material, water, an organic low-molecular-weight plasticizer and a lubricant to form a thermoplastic molding material;
• introducing the molding material into the heated barrel of an extruder;
• mixing the composition under pressure in the extruder, and
• then extruding the mixed composition through a die;
• and
• finally adjusting the water content in the resulting molded article to 5 to 30% by weight;
• said protein material being at least one edible protein salt selected from the group consisting of edible neutral salts of sodium, potassium and calcium with edible natural protein concentrates;
• said organic low-molecular-weight plasticizer being at least one edible polyhydride alcohol selected from the group consisting of glycerol, ethylene glycol, diethylene glycol, sorbitol, sorbitan, mannitol, maltitol, hydrogenated starch syrup and sucrose;
• said lubricant being at least one member selected from the group consisting of mono-, di- and tri-esters of said edible polyhydric alcohols with edible higher fatty acids having at least 10 carbon atoms, phosphoric acid derivatives of said esters and lecithin;
• said starch material being at least one edible natural unmodified starch, and containing at least 50% by weight of amylose;
• the weight ratio of said starch material to said protein salt being 30/70 to 70/30;
• the water content in the composition being 10 to 40% by weight;
• and the amount of said organic low-molecular-weight polasticizer and that of said lubricant being, respectively, 20 to 60 parts by weight and 1 to 11 parts by weight per 100 parts by weight, in total, of said starch material and said protein salt;
• said heating and mixing being effected at a temperature of 40.degree. C to 160.degree. C, said extruder having a L/D of 20 to 30 and a screw compression ratio of 1.5 to 4.5, the extrusion conditions being such that the barrel under the hopper is cooled with water, the barrel temperature is 90-200.degree. C, the die temperature is 70-120.degree. C, and the barrel internal pressure is 10-150 kg/cm.sup.2.

A method for manufacturing a water-soluble edible thermoplastic injection-molded article, which comprises:

• heating, mixing and granulating a blend of a starch material, a protein material, water, an organic low-molecular-weight plasticizer, and lubricant to form a thermoplastic molding composition in granular form;
• introducing the molding composition into the heated barrel of an injection machine;
• injecting the composition under pressure into a mold maintained at a temperature slightly lower than that of said barrel to fill the mold cavity;
• and
• then adjusting the water content in the resulting molded article to 5 to 30% by weight;
• said starch material being at least one edible natural unmodified starch;
• said protein material being at least one edible protein salt selected from the group consisting of edible neutral salts of sodium, potassium, and calcium with edible natural protein concentrates;
• said organic low-molecular-weight plasticizer being at last one edible polyhydric alcohol selected from the group consisting of glycerol, ethylene glycol, diethylene glycol, sorbitol, sorbitan, mannitol, maltitol, hydrogenated starch syrup, and sucrose;
• said lubricant being at least one member selected from the group consisting of mono-, di- and tri-esters of said edible polyhydric alcohols with edible higher fatty acids having at least 10 carbon atoms, phosphoric acid derivatives of said esters and lecithin;
• said starch material in the molding composition containing at least 50% by weight of amylose;
• the weight ratio of said starch material to said protein salt being 30/70 to 70/30;
• the water content in the molding composition being 10 to 40% by weight;
• the amount of said organic low-molecular-weight plasticizer and that of said lubricant being, respectively, 20 to 60 parts by weight and 1 to 11 parts by weight per 100 parts by weight, in total, of said starch material and said protein salt;
• said heating and mixing being effected at 40.degree.-160.degree. C the injection-molding conditions being such that the barrel temperature is 100-200.degree. C, the mold temperature is up to 80.degree. C, and the injection pressure is 10 kg/cm.sup.2 or more.

A water-soluble and edible thermoplastic film or sheet which comprises a starch material, a protein material, water, an organic low-molecular-weight plasticizer and a lubricant, and has excellent physical properties and post-processability, said starch material being at least one edible natural unmodified starch, said protein material being at least one edible protein salt selected from the group consisting of edible neutral salts of sodium, potassium and calcium with edible natural protein concentrates, said organic low-molecular-weight plasticizer being at least one edible polyhydric alcohol selected from the group consisting of glycerol, ethylene glcyol, diethylene glycol, sorbitol, sorbitan, mannitol, maltitol, hydrogenated starch syrup, and sucrose, said lubricant being at least one member selected from the group consisting of mon-, di- and tri-esters of said edible polyhydric alcohols with edible higher fatty acids having at least 10 carbon atoms, phosphoric acid derivatives of said esters and lecithin, said starch material containing at least 50% by weight of amylose, the weight ratio of said starch material to said protein salt being 30/70 to 70/30, the water content in the film or sheet being 5 to 30% by weight, the amount of said organic low-molecular-weight plasticizer and that of said lubricant being, respectively, 20 to 60 parts by weight and 1 to 11 parts by weight per 100 parts by weight, in total, of said starch material and said protein salt.