GB846614A - A process for the preparation of aqueous gels from amides of polyuronic acids - Google Patents

Abstract

Aqueous gels are prepared by dissolving a polyuronic acid amide, at least half of whose acyl groups are present as carbonamide groups and the remainder substantially as neutralised carboxyl groups, in excess amounts of water in the presence of a lactone of a hydroxy acid or an organic acid anhydride as acid-forming substances. The polyuronic acid amide and the lactone or anhydride may be mixed together, if desired with the addition of further substances, to form compositions which form aqueous gels on addition to water. The term "polyuronic acid" is defined to include cellulose glycollic acid and the preferred amides used are those of alginic acid, pectic acid and cellulose glycollic acid. These amides should contain 0,5 to 1,5 acyl groups per uronic acid unit, about 50-80% of these acyl groups being carbonamide groups and the remainder being neutralised with ammonium ions or monobasic organic or inorganic bases. Preferred acidforming substances are the lactones of sugar acids, such as gluconic acid lactone or mannuronic acid lactone, and glycollic acid anhydride. In forming the aqueous gels generally less than 30 parts by weight of polyuronic acid amide are used per 100 parts by weight of water and 10-100 parts by weight of acid forming substance per 100 parts of amide. Firmer gels are obtained when polyvalent metal ions such as calcium, magnesium or aluminium ions are present in amounts of less than 1% by weight based on the amides. Though the aqueous gels may be formed in the cold, the solution of the gel-forming substances may be accelerated by working at elevated temperatures up to 100 DEG C. The gels prepared may be used for the preparation of culture media for microorganisms, for pharmaceutic and cosmetic preparations and for the preparation of jelly-like foods (see Group VI). Specification 768,309 is referred to.ALSO:Jelly-like foods are prepared without heating by dissolving in excess water or aqueous liquid an amide of a polyuronic acid at least half of whose acyl groups are present as carbonamide groups and the remainder substantially as neutralised carboxyl groups, and a lactone of a hydroxyacid or an organic acid anhydride, together with a content of flavouring. The amides of alginic acid, pectic acid or cellulose glycollic acid may be employed in these preparations. Suitable lactones are gluconic acid lactone or mannuronic acid lactone, and glycollic acid anhydride is a suitable anhydride. The polyuronic acid amide and the lactone or anhydride together with a content of flavouring may be mixed together to form food compositions which, after mixing with some aqueous liquid, e.g. fruit juice, wine or milk or with water itself, provide jelly-like foods of good appearance. These foods may be eaten as such or further processed, for example for the production of ice-cream and similar frozen foods. Examples describe the preparation of chocolate and vanilla puddings with milk powder and whole milk. Specification 768,309 is referred to.