STARCH PRODUCT

Abstract: A highly adsorbent edible pregelatinised starch product is prepared by extruding a starch composition in the presence of a minor amount of water at temperatures of at least 150°C enabling gas-forming additives to be dispensed with. The products have low bulk density and are highly adsorbent, enabling mixtures with liquid products such as lipids to be obtained in powdered form.

Description: This invention relates to the preparation of fat-adsorbent starch, and in particular to a method for preparing such starch by extrusion. Adsorbent starch is a widely used ingredient for food compositions and may be prepared from farinaceous materials such as potato starch, rice starch or wheat or other cereal flour, by heat-drying an aqueous slurry of the material on a heated drum from which it is scraped off by a doctor blade, the starch in the feedstock being pre-gelatinised in the process and the product providing a highly adsorbent, edible carrier for fat or other liquefiable food component. From WO 83 01729 a process is known for the production of dry coating for products like fish fingers and chicken pieces. In this process, ingrédient materials with less than 14% moisture are extruded, using internal temperatures of 160-230°C and pressures of 140-175 bar. The product has a moisture content of 4-10%. From EP 39 957 a process is known for the preparation of expanded starch products. In this process a fast build up of a high pressure (100-500, preferably 200-300 bar) is required in the first part of an extruder. This process is therefore complicated and limited to the use of special apparatus. It is known from Japanese Patent J.51051555 to extrude boiled and crushed waxy milo granules at 120-200°C for use in cake recipes. It is also known from Japanese Patent Specification No. 78019-671 to prepare an additive for processed meat by extruding corn starch with 20 to 40% water and up to 20 parts by weight of sucrose fatty acid ester. In DE 3206751 a process is described for the preparation of expanded pre-gelatinized starch products by extrusion of comminuted or granulated starch or starch-containing material which may be modified by treatment with cross-linking agents. The extrusion is carried out in the presence of 10 to 30% water and a gas-forming agent comprising a metal carbonate with a suitable acid for generating carbon dioxide during the extrusion, e.g. the extrusion is conducted in a screw press under elevated pressure and at a temperature of 140°C and the extrudate is milled. The presence of the gassifying agent is imperative according to this document. However, the use of such an agent will result in undesirable exhaust gases while the product will always contain some undesirable residues of these acids. We have now found an improved process by conducting the extrusion at a temperature of 175 to 200°C, which surprisingly yields product having a bulk density of 20-100 g/l. This process is carried out in the absence of gas forming additives, in particular additives leaving residual metal derivatives in the product. The present invention provides a method for obtaining highly adsorbent, edible powdered carrier material which comprises extruding a mixture of farinaceous vegetable starch with a small amount of water and at a temperature of at least 175°C sufficient to gelatinize starch present in the material and crushing the extruded matter, preferably to an average particle size from 100 to 500 microns. Preferably, the feedstock comprises vegetable starch extracted from seed crops. Cassava and potato starch are also suitable. The composition to be extruded preferably contains less than 10% added water, particularly from 1 to 5% added water. Extrusion is effected at a temperature of 175 to 200°C, at which the starch content of the extrusion mix is gelatinized. The extrusion is effected at a pressure from 10 bar to 100 bar, particularly 20 to 50 bar. Proprietary equipment suitable for the process of the invention consists of a generally cylindrical casing enclosing a pair of parallel, co-rotatable feedscrews, along the length of which the starch is delivered from a hopper at the back of the device, forward to an extrusion plate at the front, the plate being, for example, 5 cm is diameter and furnished with extrusion holes 0.5 cm in diameter. Suitable equipment is manufactured by Werner-Pfeidlerer. Pre-gelatinized starch powder finds a variety of applications in the food industry, particularly as an ingredient which readily adsorbs moisture in cake batters and dough and thereby contributes to maintaining a highly viscous composition in recipes. It is also particularly suitable as a carrier on which fat can be adsorbed, thereby providing a fat in a powdered form which can be readily poured and measured in industrial and also domestic applications, particularly in cake and batter mixes requiring the addition only of water, eggs or milk and containing flour, dried eggs, sugar and other cake or pancake ingredients. The starch products of the present invention exhibit very high surface area and low bulk density characteristics, particularly 20-100 g/l. The present invention therefore also provides a mixture of pre-gelatinized starch having a bulk density of 20-100 g/l on which is preferably adsorbed an edible fat composition in an amount from 20 to 80%, preferably 50-75% by weight of the starch. In such compositions, the fat may comprise liquid or solid food quality oils or fats, or other edible food lipids, e.g. emulsifiers, as generally used in the food industry, including animal, vegetable, and margarine oils, e.g. soya bean oil, palm oil, coconut and other lauric fats, sunflower oil and also hard butters, e.g. sal, shea, cokum and cocoabutter and their fractionated and hydrogenated products. These admixtures are advantageous in that, with the addition of water, the adsorbed fat is immediately available in the resulting dough or batter. In contract, compositions containing spray-dried fats commoly used in similar formulations provide less accessible fat upon immediate addition of water since the fat is encapsulated in the spray-drying process. Other ingredients may be incorporated in the mix to be extruded, particularly nuts or fruit, especially in dried form, to provide culinary variations in cooking compositions. Applications of extruded starch made in accordance with the process of the present invention include use as a fat carrier in culinary mixes, e.g. cake and custard mixes, for emulsifiers, e.g. DATA esters and partial glycerides to prevent caking and to improve the free-flowing properties of these materials and mixtures containing them, and as carriers for non-water-based liquid flavours to provide these in a powdery structure. The extruded products of the invention may also be used as a carrier for fat-encapsulated components, to provide controlled release of active components, for example ascorbic acid, for use in bread mixes and bread improvers. EXAMPLE Twin-screw co-rotating extruders ex Werner and Pfleiderer fitted with extrusion dies 4 mm bore and heaters were supplied with starch and water under conditions given in the accompanying Table in a series of tests and the properties of the extrudate were measured in each and appear in the Table. In a comparison with a commercially available variety of potato starch extruded with ammonium carbonate, the products of the above tests exhibited lower moisture content and greater fat uptake, while the rice starch showed a higher amount of particles greater than 500 microns when milled.

Claims: 1. Process for the preparation of highly adsorbent carrier material by extrusion of a farinaceous vegetable starch-containing composition under pressure at elevated temperatures sufficient to gelatinize the starch in the presence of less than 10 wt.% of added water, based on the whole composition, characterized by the fact that the extrusion is carried out in the absence of gas-forming additives, the extrusion is effected at a pressure of 10-100 bar, and the temperature during the extrusion is 175-200°C, whereas an extruded product with a bulk density of 20-100 g/l is formed, which product is crushed after the extrusion. 2. A powdered culinary composition comprising an extruded pre-gelatinized starch composition with a bulk density of 20-100 g/l as obtainable by the process of Claim 1, characterized by the fact that on the starch composition 20-80 wt.%, by weight of the starch composition, of an edible lipid is adsorbed. 3. Use of highly adsorbent carrier material, consisting of extruded starch with a bulk density of 20-100 g/l as obtainable by the process of Claim 1, characterized by the use of the extruded starch as a carrier for fat and/or emulsifier(s) in culinary mixtures.

Inventors: GEWITZ, PETER, YOELL, RICHARD WILLIAM FLETCHER
Applicants: UNILEVER N.V., UNILEVER PLC
Application year: 1988
Main classification: A23L1
IPC codes: A23L1, C08B30