Lactose osmotic pressure

Lactulose. 4-O-P -D-Galactopyranosyl-4-D-fmctofuranose [4618-18-2] (Chronolac) (12) may be made from lactose using the method described in Reference 9. It is a synthetic disaccharide that is not hydroly2ed by gastrointestinal enzymes in the small intestine, but is metabolized by colonic bacteria to short-chain organic acids. The increased osmotic pressure of these nonabsorbable organic acids results in an accumulation of fluid in the colon. Lactulose may not be tolerated by patients because of an extremely sweet taste. It frequently produces flatulence and intestinal cramps. 

Ultrafiltration. Membranes are used that are capable of selectively passing large molecules (>500 daltons). Pressures of 0.1—1.4 MPa (<200 psi) are exerted over the solution to overcome the osmotic pressure, while providing an adequate dow through the membrane for use. Ultrafiltration (qv) has been particulady successhil for the separation of whey from cheese. It separates protein from lactose and mineral salts, protein being the concentrate. Ultrafiltration is also used to obtain a protein-rich concentrate of skimmed milk from which cheese is made. The whey protein obtained by ultrafiltration is 50—80% protein which can be spray dried. 

The presumed significance of this control mechanism is to enable mammals to terminate the synthesis of lactose when necessary, i.e. to regulate and control osmotic pressure when there is an influx of NaCl, e.g. during mastitis or in late lactation (lactose and NaCl are major determinants of the osmotic pressure of milk, which is isotonic with blood, the osmotic pressure of which is essentially constant). The ability to control osmotic pressure is sufficiently important to justify an elaborate control mechanism and the wastage of the enzyme modifier. 

Lactose appears to promote the absorption of calcium but this is probably due to a nonspecific increase in intestinal osmotic pressure, an effect common to many sugars and other carbohydrates, rather than a specific effect of lactose. 

Water movement across the vesicle membranes is controlled by osmotic pressure considerations. Since lactose is a major contributor to the osmotic pressure of milk, the concentrations of both soluble and colloidal salts in... 

Being less sweet than other commercial sugars makes lactose useful in processing many foods. It may be added to increase osmotic pressure or viscosity or to improve texture without making the product too... 

Whittier, E. 0. 1933B. Freezing points and osmotic pressures of lactose solutions. J. Phys. Chem. 37, 847-849. 

Aimar et al. [19] noted that in the UF of complex liquids, such as cheese whey, which contains proteins, salts and casein fragments, concentration polarization, and adsorption and cake formation play a role in flux behavior during crossflow filtration. They may induce osmotic pressure in the retentate side since the chemical potential of the solute-rich polarized layer is lower than that of the permeate, and therefore at equilibrium, a positive osmotic pressure develops in the retentate to equal that of the permeate. The smaller the solute, the greater is its contribution to the osmotic pressure of the liquid, so that in milk, lactose and the minerals have the biggest contribution to osmotic pressure. In skim milk or whey, the osmotic pressure is around 7 bar (700 kPa) and this must be exceeded in RO to commence permeation in UF, only the proteins contribute to the osmotic pressure, which increases exponentially with protein concentration [56]. In any case, a TMP greater than the osmotic pressure is required for solvent to flow from the retentate side to the permeate side. This leads to the reduction in the effectiveness of applied TMP as driving force to permeation. 

An alternative to produce low-lactose milk is overexpression of jS-galactosidase in milk. However, the monosachharides produced within the formed milk increases the osmotic pressure within the alveolar lumen, thereby drawing more water and resulting in further dilution of other milk components (Bremel et al., 1989). 

Various ideas have been considered by which lactose promotes its laxative effect. Perhaps the most probable one is that the sugar acts as a hy-dragog and, as such, results in a water purgation. Possibly this is due to slow hydrolysis and absorption of lactose, thus maintaining a high osmotic pressure in the lumen of the intestines. This increases the water content and distends the intestines which, in turn, stimulates peristaltic action. The subject has been extensively reviewed 34) ... 

Glucose is a carbohydrate found in many materials in combined forms such as cellulose, starch, sucrose, lactose, and a,a-trehalose. It is also found in the free state in a number of materials such as honey, grapes, and raisins. Glucose plays an important role in the blood of all animals, where it serves as an immediate source of energy and as a stabilizer of the osmotic pressure of the blood. It further serves as the precursor for the formation of glycogen and fat. 

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