sterilization treatment is clearly demonstrated here b comparative measurements of the viscosities of a composition according to the invention and of those of the three compositions according to the prior art the nutrient composition according to the invention as obtained in example 1 as well as the three compositions a b and c described in example 2 were subjected to a viscosity measurement with the aid of a brookfield viscometer and according to the procedure for using this apparatus the viscosity was measured at a dry matter content of 50 therefore after prior dilution of the composition according to the invention in addition comparative measurements of viscosity were carried out at 55 and 60 dry matter between the composition according to the invention described in example 1 and the composition a described in example 2 ______________________________________ viscosity in millipascal seccomposition at 55 dm at 60 dm______________________________________invention 600 3 400a 13 500 solid appearance______________________________________ these results clearly demonstrate the superiority of the compositions according to the invention in their ability to be concentrated while remaining suitable for industrial use the nutrient composition according to the invention as obtained in example 1 is subjected to a filtration test in comparison with the compositions a b and c described in example 2 this test consists in measuring the time required for 10 ml of the test solution to pass through a filter consisting of an ashless paper disc 150 mm in diameter prolabo reference 08 313 766 the dry matter content of the test solutions is adjusted to 25 g l these solutions are subjected after dilution to sterilization by heat treatment at 120 u00b0 c for 20 minutes their ph corresponds to the natural ph that is to say 4 5 the values.