Milk protein isolate and method for preparing same

#This application is a national stage application filed under 35 USC 371 of International Application No. PCT/FR03/0201 5, filed Jun. 30, 2003, which claims priority from French patent application 02 08234 filed Jul. 2, 2002.

#The subject of the present invention is a novel process for isolating milk proteins, the composition, milk protein isolate or milk protein fraction, resulting therefrom and its applications, in particular its food and pharmaceutical applications.

#Several prior art documents describing the purification of milk proteins are known.

#The subject of the invention is a process for isolating milk proteins from milk or whey comprising the following steps: a) the milk or the whey is sterilized and defatted; b) the milk fraction derived from step a) is passed over a cation-exchange resin conditioned in an elution column; c) the fraction retained on the resin is eluted with an aqueous salt solution; d) the eluate resulting from step c) is desalted, preferably by ultrafiltration and diafiltration, and then sterilized, preferably by microfiltration.

#This process being characterized in that: α) the cation-exchange resin is a resin grafted onto strong acid functional groups; the parameter BV denoting the ratio of the volume of raw material to the volume of wet resin in the column, the parameter SV denoting the ratio of the rate of feeding the column to the volume of wet resin in the column, the parameter LV denoting the ratio of the rate of feeding the column to the section of the column, β) during step b), the binding parameters have the following values: BVf is between 50 and 400, preferably between 80 and 300; SVf is between 2 and 40 h−1; LVf is greater than or equal to 1 m/h and less than or equal to 5 m/h. γ) during step c), the elution parameters have the following values: BVe is between 1.5 and 7; LVe is less than 1 m/h, preferably less than 0.5 m/h.

#It is possible to use as starting material in the process according to the invention either milk or whey, preferably derived from cows. Whey is the residual liquid obtained after extracting the proteins and the fat from milk or milk serum. Three categories of whey can be distinguished. The first two categories are classified according to the acidity of the whey which may be less than or greater than 1.8 g of lactic acid/1: sweet whey, derived from the manufacture of cooked or uncooked pressed cheese (emmenthal, saint-paulin, etc.) and acid whey, derived from casein or other cheeses obtained by mixed or lactic curdling (soft cheeses, fromage frais). The average composition of sweet whey is, as a guide, for 61 g of dry matter content per kg of whey, from 42 to 48 g of lactose, 8 g of proteins, 2 g of fat, 5 to 7 g of minerals, 1 to 5 g of lactic acid and the remainder as minerals and vitamins.