Extraction and characterization of certain food allergen proteins of animal origin

Imene Khafallah, Aissa Boutebb

Abstract

Because they are widely used for human consumption, cow’s milk and hen eggs allergy are of the most commonly implicated causes of food allergic reactions. To characterize allergen proteins of these two products, ovalbumin, conalbumin, lysozyme, ovomucoïde, serum-albumin, β-lactoglobulin, whole caseins, αs1-casein, β-casein and kcasein are extracted, isoelectric points, temperatures denaturation, carbohydrate and protein rates are determined, relationships between different physicochemical parameters are defined, amino acids quantity of protein hydrolysates are demonstrated and relative molecular masses are evaluated. Results reveal the existence of thermoresistant and thermolabile allergen proteins, most of them have an acid isoelectric point and carbohydrate portion and rich in cystein and tyrosin, what assure to the protein a geometric compact structure resistant to the unfolding provoked by heat treatments. All of them are of low relative molecular weight. There is a relationship between carbohydrate rate and temperature denaturation and it is confirmed that glycan fraction protects glycoproteins from thermal denaturation. Trophallergens characterized by an acid isoelectric point, low relative molecular weight, high content of carbohydrate and rich of cystein and tyrosin residues are necessary thermostable. When trophallergens have a basic or near of neutrality isoelectric point, an unimportant content of glycan portion and when they are of low relative molecular weight and poor in cystein and tyrosin, they are necessary thermolabile.