Digestibility and allergenicity of casein glycomacropeptide and β-lactoglobulin mixtures

Abstract

Casein glycomacropeptide (CMP) and β-lactoglobulin (β-lg) are present in cheese-whey at concentrations about 20 and 50% respectively. In the last years CMP received increasing attention because of its unique composition and biological activities. On the other hand, it is well known the high allergenicity of β-lg that affects children and adults. So, the aim of this work was to analyze the effect of the interaction between β-lg and CMP on the digestion products and to evaluate the effect of the presence of CMP on the allergenicity of β-lg. CMP, β-lg and CMP:β-Ig mixtures were studied at pH 7.0 and 3.5. The digestion was simulated using an in vitro system in two steps which mimicked digestion in the stomach and duodenum. The digestion products were analyzed by: polyacrylamide gel electrophoresis, HPLC, LC-ESI-ITMS/MS and IgG binding by direct ELISA. The effect of the interaction of 6-lg and CMP on the allergenicity of the digestion products was studied by human IgE binding by inhibition ELlSA with serum samples from children with clinical allergic symptoms to β-lg. No differences were obsewed (by HPLC and electrophoresis) in the digestion products of the mixtures due to the effect of interactions between CMP and P-lg. However, LC-ESI-IT-MS/MS results showed different peptides occurring in the mixtures hydrolysates. Additionally, it was obsewed an important reduction of the allergenicity of P-lg in the presence of CMP. The disappearance of epitopes in the digested mixtures could explain the lower allergenicity obsewed in these systems compared to β-lg. It can be concluded that the presence of CMP in whey products containing p-lg may modify the digestion products helping to reduce the allergenicity of β-lg, as well as providing bioactive properties.