The poor and slow degradation of the antigenic epitopes of whey proteins when pepsin digestion occurs under conditions that prevail in the stomach of infants could be of much importance for the development of cow milk hypersensitivity. The immature gastrointestinal mucosal barrier of infants allows large antigenic fragments of these proteins to pass into the systemic circulation.

Whey protein components were hydrolyzed with Corolase 7092'" (peptidases from Aspergillus strains), pepsin and Corolase PP'" (a mixture of pancreatic enzymes), either individually or in combination, in trials to eliminate protein allergenicity. The hydrolysates were characterized by physico-chemical and by immunological techniques using sera from patients allergic to milk proteins. Enzyme specificity rather than degree of hydrolysis or molecular mass distribution of hydrolysates determined the residual antigenicity of the whey proteins. Ultrafiltration was a prerequisite for obtaining hypoallergenic whey protein hydrolysates.

Whey protein concentrate was hydrolyzed using the technical food-grade enzyme Corolase 7092 in order to abolish the allergenicity of whey proteins. The immunological properties of the hydrolysates were tested in vitro with a human-immunoglobulin E (human-IgE) enzyme-linked immunosorbent assay (ELISA) using sera obtained from children allergic to milk proteins and in vivo with a mouse-rat heterologous passive cutaneous anaphylactic test and an anaphylactic shock test in mice. The protein efficiency ratio, determined in young growing rats, was compared to that of casein. Ultrafiltration of the hydrolysates appeared to be necessary to obtain a hypo-allergenic product. The minimal molecular mass to elicit immunogenicity and allergenicity of whey protein hydrolysates appeared to be between 3,000 and 5,000 Da, so the molecular weight cut-off value of the filters required must be in this range. Although there was no evidence that extensively hydrolyzed whey protein is nutritionally inferior to casein, the slightly bitter taste might reduce food intake.

We tested the hypothesis that increased intakes of calcium and phosphate lower magnesium solubility in the intestinal lumen, causing a decreased magnesium absorption. In in vitro experiments at a constant magnesium concentration, increasing calcium concentrations reduced magnesium solubility. This effect did not occur in the absence of phosphate. Increasing phosphate concentrations decreased the solubility of magnesium in the presence, but not in the absence, of calcium. These results suggest that the formation of an insoluble calcium-magnesium-phosphate complex determines magnesium solubility. To extend this concept to in vivo conditions, rats were fed purified diets containing a constant concentration of magnesium (16.4 mumol/g) but different concentrations of calcium (25, 100 or 175 mumol/g) and phosphate (58, 103 or 161 mumol/g). Increased intakes of calcium decreased magnesium solubility in the ileal lumen and lowered magnesium absorption. The latter result occurred only if the dietary phosphate concentration was at least 103 mumol/g. Increasing dietary phosphate concentrations reduced both magnesium solubility in the ileum and magnesium absorption, but only if the dietary calcium concentration was at least 100 mumol/g. These results support those obtained in vitro. We conclude that increased intakes of calcium and phosphate decrease magnesium absorption by the formation of an insoluble calcium-magnesium-phosphate complex in the intestinal lumen.

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