GB770089A - Production of amylose films - Google Patents

Abstract

Strong, pliable and transparent amylose films are produced by dissolving at least 5 per cent by weight of a starch carbohydrate, containing at least 50 per cent by weight of amylose, in water at a temperature of at least 120 DEG C. and preferably 140-165 DEG C., cooling the solution to below its boiling point, casting a film from the resulting clear solution on a support having a temperature higher than the gelation temperature of the solution, and afterwards drying and cooling the film on the support and stripping it from the support. The concentration of the amylose solution may be up to about 25 per cent and is preferably 10-20 per cent. The amylose may have an average molecular weight of about 120,000 and is preferably dispersed in water having a pH of about 7, to which up to 0.2 per cent of sodium sulphite may be added. The dispersion may be heated in an autoclave or by passing it through heated tubes for 5-8 minutes, prolonged heating at an unnecessarily high temperature being avoided to minimize degradation of the amylose. The casting temperature is preferably sufficiently high to evaporate part of the water before the solution gels. The drying air may have a temperature of 90-110 DEG C., provided it has a high relative humidity, e.g. between 40 and 80 per cent, at the end of the drying process and during cooling. The amylose should preferably be free from contaminants, e.g. magnesium sulphate introduced during the preparation of the amylose from starch, but should preferably contain 10-20 per cent of amylopectin. A plasticizer such as glycerol or sorbitol may also be present. In the example, an aqueous slurry containing 15 per cent by weight of amylose, 0.05 per cent of sodium sulphite and 5 per cent of glycerol is heated to 160 DEG C. in about 2 minutes and kept at that temperature for about 4 minutes by passing it through heated tubes. The resulting clear solution is cooled to about 95 DEG C., filtered at 95 DEG C., cast on to an endless travelling belt of chromium-plated steel having a temperature of about 85 DEG C. and dried in hot air having a temperature of 100 DEG C. and a relative humidity of about 65 per cent. The film is then cooled while still on the belt in air having a temperature of about 22 DEG C. and a relative humidity of about 100 per cent, and is finally stripped from the belt. The amylose film is suitable for application in the food industries, due to its digestibility.ALSO:Strong, pliable and transparent amylose films are produced by dissolving at least 5 per cent by weight of a starch carbohydrate, containing at least 50 per cent by weight of amylose, in water at a temperature of at least 120 DEG C. and preferably 140 DEG -165 DEG C., cooling the solution to below its boiling point, casting a film from the resulting clear solution on a support having a temperature higher than the gelation temperature of the solution, and afterwards drying and cooling the film on the support and stripping it from the support. The concentration of the amylose solution may be up to about 25 per cent and is preferably 10-20 per cent. The amylose may have an average molecular weight of about 120,000, and is preferably dispersed in water having a pH of about 7, to which up to 0,2 per cent of sodium sulphite may be added. The dispersion may be heated in an autoclave or by passing it through heated tubes for 5-8 minutes, prolonged heating at an unnecessarily high temperature being avoided to minimize degradation of the amylose. The casting temperature is preferably sufficiently high to evaporate part of the water before the solution gels. The drying air may have a temperature of 90 DEG -110 DEG C., provided it has a high relative humidity, e.g. between 40 and 80 per cent, at the end of the drying process and during cooling. The amylose should preferably be free from contaminants, e.g. magnesium sulphate introduced during the preparation of the amylose from starch, but should preferably contain 10-20 per cent of amylopectin. A plasticizer such as glycerol or sorbitol may also be present. In the example, an aqueous slurry containing 15 per cent by weight of amylose, 0,05 of sodium sulphite and 5 per cent of glycerol is heated to 160 DEG C. in about 2 minutes and kept at that temperature for about 4 minutes by passing it through heated tubes. The resulting clear solution is cooled to about 95 DEG C., filtered at 95 DEG C., cast on to an endless travelling belt of chromium-plated steel having a temperature of about 85 DEG C, and dried in hot air having a temperature of 100 DEG C. and a relative humidity of about 65 per cent. The film is then cooled while still on the belt in air having a temperature of about 22 DEG C. and a relative humidity of about 100 per cent, and is finally stripped from the belt. The amylose film is suitable for application in the food industries, due to its digestibility.