Effects of heat treatment of cow's milk and whey on the nutritional quality and antigenic properties.

Recent experiments in guinea-pigs suggest that heat treatment applied during the manufacture of baby milk formulae reduces the immunological sensitising capacity of the cow's milk proteins. This immunological benefit must be weighed against possible damage that heat treatment may cause to the nutritional quality of the products. Severe heat treatment of skimmed milk (121 degrees C for 20 min) destroyed all the vitamin B12, about 60% of the thiamin and vitamin B6, 70% of the ascorbic acid, and about 30% of the folate. Available lysine was reduced by 21% and lactulose was formed (166 mg/100 ml). Despite extensive denaturation of the whey proteins the milk retained its capacity to sensitize guinea-pigs for systemic anaphylaxis when administered orally. Animals drinking heated milk also produced circulating antibodies to beta-lactoglobulin and casein, although titres were lower than for unheated milk. Unlike skimmed milk, heat-treated diafiltered whey failed to sensitize guinea-pigs orally. It caused the production of trace levels of antibodies in some of the animals, but these were specific for residual casein. We suggest that it may be possible to produce a non-sensitising baby milk without casein based on heat-denatured whey. The nutritional quality could be preserved by removing low molecular weight nutrients before heat treatment and adding back appropriate quantities later.