Abstract:
An enteral composition of protein, glucides, lipids and minerals, which is suitable for tube feeding, employs native micellar casein as the protein. The composition is prepared by obtaining native micellar casein and combining it with the glucides, lipids and minerals. A dispersion of micellar casein may be obtained by microfiltering milk, particularly skim milk, and glucides and minerals are dispersed in the micellar casein retentate obtained, lipids are added to the resulting dispersion and then the mixture is homogenized and sterilized. The microfiltered retentate may be diafiltered for obtaining the dispersion.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an enteral composition containing proteins, glucides and lipids. 
     An enteral composition is a sterilized liquid composition intended for feeding patients incapable of feeding themselves normally. It is administered by a nasal or oral tube leading directly to the digestive system and is supposed to supply three basic nutritive elements, namely proteins, glucides and lipids, in a suitable ratio and in a high calory density. 
     The choice of protein material for these enteral compositions is relatively limited. The majority of proteins are sensitive to heat and coagulate during sterilization. Caseinates are an exception and, accordingly, are widely used in this type of product, occasionally in association with soya proteins. The use of skimmed milk powder as a casein source is not an alternative to caseinates because it contains too much lactose which would lead to an enteral composition of laxative and hyperosmotic character. 
     Two types of caseinates are commonly used, namely sodium or potassium caseinate (Na/K caseinate) and calcium caseinate (Ca caseinate). 
     Na/K caseinate is soluble and has a high viscosity when its concentration exceeds 5%. This high viscosity is a major disadvantage for enteral and particularly nasal nutrition where particularly fine tubes are used. The enteral. Compositions require high concentrations of protein (5 to 10% by weight) to ensure that the calory input is accompanied by balanced protein/glucide/lipid ratios. The viscosity of Na/K caseinate limits its use to compositions containing less than 6 to 7% of protein. 
     Although not soluble, Ca caseinate forms a colloidal dispersion of relatively low viscosity in water. A major disadvantage of Ca caseinate is that it gives rise to the appearance of pronounced foreign tastes in the sterilized products. 
     SUMMARY OF THE INVENTION 
     The object of the present invention was to obviate the disadvantages described above by providing enteral compositions, as defined above, essentially containing native micellar casein as their protein source. 
     The native micellar casein replaces caseinates in enteral nutrition and is advantageous by virtue of enabling preparation of an enteral composition for tube feeding a patient which has a high protein concentration (5% to 10%) and a low viscosity and which has thermal stability to withstand sterilization. 
     The present invention also provides a process for preparing the enteral composition for tube feeding a patient comprising the nutritive elements of proteins, glucides and lipids wherein native micellar casein is obtained and employed as the protein for preparing the composition, the process being further characterized in that a milk, particularly skimmed milk, is microfiltered to isolate a retentate, which optionally is diafiltered, and then glucides and minerals are dispersed in the retentate, lipids are added to the resulting dispersion and the mixture is homogenized and then sterilized. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The native micellar casein employed in accordance with the present invention is obtained from animal milk, such as cow&#39;s milk, goat&#39;s milk or ewe&#39;s milk. It is prepared by microfiltration of the milk. 
     The micellar protein is obtained by microfiltration of milk, optionally followed by diafiltration, on a membrane with a porosity of, for example, 0.1 to 0.2 micrometer. 
    
    
     EXAMPLES 
     Microfiltration selectively concentrates casein without retaining whey proteins, which is thus preferred for reasons of stability to sterilization. 
     Aside from its remarkable properties, the native micellar casein thus prepared has proved to be a protein source particularly suitable for enteral compositions. It does not have any of the disadvantages of the above-mentioned proteins: 
     its nutritional qualities are equivalent or superior to those of the proteins traditionally used, 
     it forms a low-viscosity colloidal dispersion in water which enables it to be used in high concentrations (5 to 10%) without any flow problems in the finest tubes, 
     it shows high thermal stability and thus withstands sterilization, 
     for the same concentration, it gives solutions of lower osmolarity than caseinates, 
     it has no taste whatever and 
     it gives solutions with a whiteness superior to that of caseinates. 
     The invention is illustrated by the following Examples in which parts and percentages are by weight (g per 100 g of liquid composition) unless otherwise indicated. 
     Example 1 
     Preparation of Micellar Casein 
     300 kg of skimmed cow&#39;s milk, pasteurized for 15 s at 72° C., are treated in a microfiltration installation (TECHSEP® module 1S 151) equipped with 3.4 m 2  of membrane M 14 (mean pore diameter approximately 0.15 micrometer) at a temperature of 50° to 55° C. until 200 kg of permeate have been eliminated (which corresponds to concentration by a volume factor of 3). The retentate is then diafiltered with demineralized water by elimination of 500 kg of permeate (corresponding to a diafiltration volume factor of 5). The object of this diafiltration step is to produce the micellar casein with a protein purity of around 85% with less than 1% of residual lactose, based on total dry matter. The retentate is then concentrated to a final volume of 50 to 70 l which guarantees a dry matter content of 18 to 20%. The retentate contains 185 g/kg of total solids with a protein content of 84%, based on total dry matter. Its composition is as follows in g/kg of liquid: 
     Proteins 164 
     Lactose 0.4 
     Ash 15.6 
     Fats 1.3 
     Calcium 6 
     Potassium 0.1 
     Sodium 0.04 
     Phosphorus 1.7 
     Fractionation of the proteins in accordance with Rowland&#39;s scheme (Rowland, 1938; J. Dairy Res. 9, 42-46) shows that, since 96% of the total protein can be precipitated at pH 4.6, the retentate must be casein. Analysis of a dilute dispersion of retentate in a Malvern particle sizer shows that the casein is present in the form of particles with a mean diameter of 300 nanometers (nm) and that the distribution of the particles is relatively uniform (one family only ranging from 100 to 400 nm). This image corresponds exactly to that obtained for skimmed milk which indicates the presence of the micelles characteristic of milk. 
     Preparation of a Composition Intended for Enteral Nutrition 
     2.13 kg of the above retentate containing 19.5% total solids and corresponding to 350 g of proteins are transferred to a stirrer-equipped tank thermostatically controlled to 55° C. The following ingredients are then added to the dispersion in solid form (in g): 
     Maltodextrin MD-02 300 
     Sucrose 150 
     Tri-K citrate H 2  O 20.33 
     MgCl 2  6H 2O  9.21 
     NaCl 5.84 
     After the ingredients have dissolved in the retentate, demineralized water is added to a total weight of 4825 g. At this stage, the pH is checked and, if necessary, adjusted to a value of 6.8. The fatty phase, i.e. 175 g of corn oil containing 2% (based on the oil) of soya lecithin as emulsifier, is then added. The mixture is homogenized in a two-stage homogenizer to 20 MPa in the first stage and then to 5 MPa in the second stage. The emulsion is then sterilized by indirect UHT treatment (heat exchanger) for 20 s at 130° C. or by direct UHT treatment (direct injection of steam) for 5 s at 148° C. or even by sterilization in cans or bags for 6 to 8 mins. at 120° C. 
     Three enteral compositions with the same energy density, i.e., 4.184 kJ/ml (1 kcal/ml) are thus prepared as described above: 
     
         ______________________________________   Ingredient (%)     Composition A     7     Native      Composition B                            Composition C     micellar    7          7Proteins (% p/v)     casein      Ca caseinate                            Na/K caseinate______________________________________Lipids (corn     3.5         3.5        3.5oil)Glucides  9.5         9.5        9.5(maltodextrins/sucrose)Minerals  Ca     0.21        0.2      0.07  K      0.16        0.15     0.18  Na     0.05        0.05     0.06  Mg     0.03        0.03     0.02  P      0.12        0.12     0.07  Cl     0.1         0.1      0.03______________________________________ 
    
     The products obtained after sterilization in cans for 6 minutes at 120° C. are compared for their total protein content, their dynamic viscosity (shear rate 1600 s-1 , ambient temperature), osmolarity and organoleptic properties: 
     
         ______________________________________                                Presence    Proteins Osmolarity  Viscosity                                of foreignComposition    (total), %             mOsm/kgH.sub.2 O                         mPa · s                                tastes______________________________________A        7.56     392         6      NoB        6.81     386         9      YesC        7.38     481         30     Yes______________________________________ 
    
     Composition A (native micellar casein) is clearly distinguished from composition C (Na/K caseinate) by its reduced viscosity and its low osmolarity. It is distinguished from composition B (Ca caseinate) by its viscosity and taste. 
     Example 2 
     An enteral composition with an energy density of 6.276 kJ/ml (1.5 kcal/ml) and 8% (p/v) of proteins is prepared from &#34;low temperature&#34; skimmed milk powder, i.e., skimmed milk dried under controlled thermal conditions. 
     20 kg of low-temperature skimmed milk powder are dispersed in 100 kg of demineralized water at a temperature of 50° to 55° C. This dispersion, which corresponds to twice-concentrated skimmed milk, is microfiltered in the same installation as in Example 1 in the diafiltration mode by passing demineralized water through until 600 kg of permeate have been eliminated. The retentate is then further concentrated to around 60 kg, which represents a dry matter content of 21% with a protein content, based on dry matter, of 82%. 
     To prepare the enteral composition, 2.323 kg of liquid retentate, representing 400 g of total proteins, are mixed at 55° C. with the following ingredients (g): 
     Maltodextrin MD-02 600 
     Sucrose 200 
     Tri-K citrate H 2  O 20.33 
     MgCl 2  6H 2  O 9.21 
     NaCl 5.84 
     After the ingredients have dissolved in the retentate, demineralized water is added to a total weight of the dispersion of 4.7 kg. The pH is then adjusted to 6.8, after which 300 g of fatty phase are introduced, the total weight of the dispersion being 5 kg. After homogenization and sterilization as in Example 1, the product has a dynamic viscosity of 112 mPa.s (shear rate 1600 s-1 , ambient temperature) it is white in appearance, has an agreeable sugary taste and is free from foreign tastes.