Composite materials

摘要

1,125,350. Porous food compositions; coffee preparations. NESTLE'S PRODUCTS Ltd. 28 June, 1967 [8 July, 1966 (2)], No. 29950/67. Heading A2B. [Also in Division C3] A composite material comprises a continuous phase consisting essentially of a porous structure of a dry substance, there being included within the pores of the structure at least one further substance, different from the first, which has been dried by lyophilisation "in situ". The composite material is prepared either by adding to a porous material, by absorption or adsorption, at least one second substance different from the porous material and subsequently freezing and lyophilising the mixture, or by freezing and lyophilising a system containing at least one solute dissolved in at least two different diluents. The system may, for example, contain two different solutes dissolved in two diluents which are miscible with each other, or consist of an emulsion containing two solutes dissolved in two immiscible solvents. The absorption or adsorption of the former procedure may be effected by immersing the porous material in a solution of the second substance, by soaking the material by running the solution over its surface, or by exposing the material to a current of saturated vapour. Impregnation and the subsequent lyophilisation may be repeated several times, using new solutions each time in order to obtain multi-component materials of micro-granular structure. The following are mentioned as constituents of the impregnation solution: synthetic resins, therapeutic agents, fertilizers, amino acid salts, vitamins, preservatives, flavourings such as chocolate or fruit extracts, volatile aromatic fractions extracted from coffee, tea or chicory, and artificial aromas. Turning now to the latter procedure, he water and dioxan in a system consisting of a 1% aqueous solution of dextran and a 0.1% solution of polystyrene in dioxan and optionally including mineral salts, sublime simultaneously during lyophilisation to give a porous and finely heterogeneous composite material containing 1 part of polystyrene per 10 parts of dextran in intimate admixture. In a system consisting of a 1% solution of polystyrene in dioxan with a 1% solution of polystyrene in carbon tetrachloride, around 50% of the dioxan still remains unsublimed when all the carbon tetrachloride has been removed. In a system consisting of a 1% solution of dextran in water and a 1% solution of polystyrene in benzene, the water sublimes more sloyly than the benzene. According to the Examples: (1) A 1% solution of polystyrene in carbon tetrachloride is prepared and frozen at -70‹C. in plates 10 mm. thick which are lyophilised in vacuum at -50‹C. These plates are then impregnated with a 2% solution of dextran in water under a moderate vacuum. After freezing at -40‹C. the impregnated plates are lyophilised at - 20‹C. to give a porous composite material of low specific gravity (0.03), having the properties of lyophilised polystyrene and dextran. (2) A foam produced by blowing gaseous carbon dioxide into a concentrated aqueous solution of coffee solids, is frozen at -45‹C. in relatively thin plates which are lyophilised to a dry product having a porous structure. The plates of lyophilised coffee are impregnated with a concentrated solution of the lipidic and aromatic constituents of coffee in carbon tetrachloride or fluorinated hydrocarbon, and the impregnated plates are frozen and lyophilised to give a dry coffee extract in the form of a porous material of specific gravity 0.2-0.3 which contains, in a continuous phase, the soluble constituents of coffee and, in the dispersed phase, the aromatic and lipidic constituents of coffee intimately mixed within the pores of the continuous phase. Alternatively, the porous dry coffee extract may be impregnated at a pressure not below 5.5 kg/cm2 with a solution of lipidic and aromatic constituents of coffee in liquid carbon dioxide and the pressure lowered to induce spontaneous freezing of the diluent and sublimation at atmospheric pressure. (3) Flat porous sticks of lyophilised biscuit mass (prepared from milk powder, egg white, sugar, gelling agent and water) are impregnated with a solution in fluorinated hydrocarbon of either a fatty chocolate preparation or a vegetable protein hydrolysate, and the impregnated sticks are lyophilised. (4) An aroma concentrate obtained by steam stripping roasted and ground coffee is twice extracted with trichlorotrifluoroethane, coffee oil is dissolved in the combined organic phase which is then emulsified in aqueous coffee extract containing 45% of coffee solubles. The emulsion is frozen and ground to a particle size between 0.25 and 2.0 mm., and the particles are lyophilised. (5) a mixture of aqueous coffee extract containing 20% coffee solubles and a dioxan solution of coffee oil and aromatic coffee distillate, is rapidly frozen in the form of a thin film which is then lyophilised.