Interaction between casein and vitamin A during food processing.

A particular relation exists between casein micelle and vitamin A. In vitro, large amounts of retinol are fixed to acid casein and its different fractions by hydrophobic bindings. The binding on the hydrophobic amino-acid residues (Trp, Phe) is greatly facilitated by a configurational change in the molecule exposed to physico-chemical parameters: alcalinity and heat treatments. Another amount of retinol is even more strongly fixed by a binding which can only be broken by saponification. Casein plays an important role in stabilizing retinol which does not degrade over time or during heat treatments. In vivo, when the retinol availability is measured by the vitamin A content in the liver, acid casein somewhat increases the retinol efficiency and, even more so, the retinal efficiency. Nevertheless, this favourable action is only observed under particular conditions: balanced diet, casein from milk, etc. For the moment, the animal data cannot be directly linked with the properties of binding appearing in vitro.

Effect of soybean and casein on the vitamin A status in the rat.

With a well-balanced diet containing 1.3 mg of retinol/kg, a limited quantity of acid casein (10%) provokes a maximal efficiency of retinol. At a rate of 5% or 25% of casein, the retinol efficiency is decreased and identical to that of soybean diets. In casein-soybean mixed diets, the variations of retinol efficiency are only imputable to the casein presence. With diets containing 6.5 mg of retinol/kg, the specific effect of casein disappears.

Influence of vitamin A form and protein nature on the retinol status in the rat.

In comparison with soybean proteins, the acid casein increases the blood and liver concentrations of retinol when the diet contains 1 mg of retinol/kg. The effect of the acid casein is more important when the vitamin A is supplied to rats as retinal: with the alcohol form, the amount of liver retinol is 88.7 micrograms; with the aldehyde form, it reaches 137 micrograms.

Galactose metabolism in male and female rats. II. Eye-ball differences.

When rats consumed a well-balanced diet containing 30% lactose or 30% glucose-galactose mixture, the biological composition of the lens was more disturbed in female: the leak of inositol and the accumulation of galactitol were higher than in the male.

Galactose metabolism in male and female rats. I. Blood and urinary differences.

When rats consumed a well-balanced diet containing 30% lactose or 30% glucose-galactose mixture, some differences of metabolic utilization arose between males and females. With lactose, the urinary excretion of lactose, galactose and galactitol was higher in females. With the glucose-galactose mixture, galactosury and galactitolury in males and females increased and were similar; but galactosaemia and galactitolaemia were more important in females.

[Effects of prolonged consumption of lactose or hydrolyzed lactose in the rat. 5. Intestinal metabolism of glucose and galactose]. / Répercussions chez le rat d'une consommation prolongée de lactose ou de lactose hydrolysé. 5. Métabolisme intestinal du glucose et du galactose.

Effect of Prolonged Consumption of Lactose or Hydrolyzed Lactose in Rats.--5. Intestinal Metabolism of Glucose and Galactose. The intestinal metabolism of galactose is different according to the form of ingestion. With a lactose diet (L), the galactose is abundant in intestinal contents (Tab. I), since neither the intestinal flora (Tab. II), nor the epithelial tissue (Tab. III) can easily metabolize the galactose. The glucose disappears more rapidly than the galactose (Tab. I). With a hydrolyzed lactose diet (LH), the intestinal contents of two hexoses are identical (Tab. I). In this case, the enzymic activity of epithelium metabolizes an amount of galactose 6 times as big as with the lactose diet (Tab. III).

[Intestinal absorption of glucose and galactose in the rat determined by blood hexose]. / L'absorption intestinale due glucose et du galactose chez le rat, mesurée par les hexosémies.

Adult rats are used to consume their diet within the space of 30 min. They are sacrified after fasting 2 hours or 30 to 90 min. after the end of meal. Blood sugars are determined. -- The administration of galactose (GAL group) at 40 p. 100 of the diet induces a high postprandial galactosemia (near 600 mg p. 100 ml) without glycemia change: the absorbed galactose is not converted into glucose. -- The consumption of glucose-galactose mixture (G-G group) don't induce postprandial hyperglycemia. However, galactosemia is about 250 mg p. 100 ml. In our conditions, glucose and galactose seem absorbed by two different systems. The galactose absorption would be favoured; otherwise, the absorbed glucose would be partly epimerized into galactose. Galatitolemia goes on 24 hours after the meal but it is not immediately modified by the galactose consumption. The galactosemia and galactitolemia variations are independent one of the others.

[Effect of prolonged consumption of lactose or hydrolyzed lactose in the rat. 2. Digestibility, retention and utilization of lactose components]. / Répercussions chez le rat d'une consommation prolongée de lactose ou de lactose hydrolysé. 2. Digestibilité, rétention et utilisation des contituants du lactose.

Nutritional balances are made with groups of 12 rats Wistar receiving well-balanced diets with 40 p. 100 of sucrose (T), or 40 p. 100 of lactose (L and P), or hydrolyzed lactose (LH and PH). Whey (L) and ultrafiltration permeate (P) are used in crude state or after enzymic industrial lactase hydrolysis (LH and PH). The animals consume diets during eight months. Faeces contain neither lactose nor galactose, but glucose in small quantities. In all urines occurs about 0,5 mg/day of glucose. The lactose diets (L and P) provoke a week lactosury (0,36 p. 100 of ingestion). Galactose and galactitol are abundant in urines: with lactose diets (L and P), the urinary excretion is equal to 4 p. 100 of ingested galactose. In urines of hydrolyzed lactose diets (LH and PH) the excretion reaches 26 p. 100 of ingestion. In this case the excretion is remarkably invariable from third day of eighth month: the urinary galactose corresponds to 23 p. 100 and galactitol to 3 p. 100 of consumed galactose. The urines of lactose diets (L and P) and hydrolyzed lactose diets (LH and PH) contain 100 and 300 mg/day of non sugar reducing substances respectively, i.e. 40 p. 100 of total urinary reducing power. The apparent retention of lactose (L and P) is 95,5 p. 100 and that of the hydrolyzed lactose (LH and PH) is 86 p. 100 after 8 months of experiment but it is estimated that digestive flora consumes 40 p. 100 of dietary lactose (L and P).

[Reactions in the rats from prolonged consumption of lactose or hydrolyzed lactose. 3. Crystalline lens]. / Répercussions chez le rat d'une consommation prolongée de lactose ou de lactose hydrolisé. 3. Etude du cristallin.

Three groups of 15 rats Wistar receive a well-balanced diet with 40 per cent of sucrose (T), lactose (P) or hydrolyzed lactose (PH) in the form of ultrafiltration permeate. After 160 days, no cataract is revealed in the T and P groups. In the PH group, 14 rats reached by cataracts in both eyes: it is slightly developed (PH 2), mildly developed (PH 3) or practically total (PH 4). The inositol disappearance, the high quantity of galactitol, the water and sodium increases are the factors observed before the lens opacification and are responsible for the cataract. Then, during the opacification, soluble proteins, potassium and hydratation of the lens decrease. Galactose 1-P is slowly formed before and during the lens opacification. The lens of the P group (lactose) differ from the control group (T) by the nature and the quantity of hexitols, only.

[Effect of prolonged consumption of lactose or hydrolyzed lactose in rats--nutritive efficiency and anatomical changes (author's transl)]. / Répercussions chez le rat d'une consomation prolongée de lactose ou de lactose hydrolysé. 1. Efficacité alimentaire et répercussions anatomiques.

Growing rats receive for 270 days well-balanced diets with 40 p. 100 of lactose or industrial hydrolyzed lactose. Whey and ultrafiltration permeate are used in crude state or after enzymic lactose hydrolysis. In lactose diets the ingesta and the food efficiency are considerably reduced as well as the growth. The water intake is greatly increased. The dry mater digestibility is not modified by the lactose after an experiment of 7 months. Hydrolyzed lactose provokes all these phenomena but with a weaker intensity. In a zootechnical point of view the lactose hydrolysis reduces the detrimental properties of lactose. After 270 days animals having received lactose show a high hypertrophy of small intestine and caecum tissues as well as a small renal hypertropy (dry matter/100 g of living weight). Hydrolyzed lactose involves the comparable modifications but with a less extent. Numerous facts attributed to lactose molecule are partially imputable to galactose molecule mainly the increase of water consumption. Only the growth of bone tissue (femur) is provoked by the lactose molecule itself and not to its components. When the diet is well-balanced the presence of whey proteins does not seem to modify the lactose effects.