Comparison of extraction conditions for milk and hen's egg allergens
Résumé
The evaluation of recovery rates extracting dried milk and egg powder using eleven different extractants led to approximately similar results for both foods. Compared to the other extraction solutions investigated, "1% Tween 20 and 0.4% Triton X-100" and "4 % SDS" are the most qualified extractants to isolate proteins of hen's egg or milk. Comparing calculated protein recovery rates of egg and milk powder extracts the results clearly indicate that the choice of a suitable extractant is of particular importance. Qualitative investigation of the extracts via LDS - PAGE followed by silver staining as well as immunoblotting confirmed the results of protein quantification. Hence, the immunoblots showed that the used extraction agents had no negative influence onto the antigenicity of the extracted allergenic proteins. In this study, variation of extraction temperature neither led to any benefit in extraction quality nor to degradation. Changing pH did not reveal any tendencies but a progressive protein hydrolysis at strong alkaline. Evaluation of recovery rates as well as results of unspecific and specific staining of the extracts revealed that an extraction duration of one hour is sufficient for an appropriate sample preparation. For investigations with and without food matrix different results were obtained. In summary, wheat starch did not influence the extraction quality within all examined materials and different extractants. In contrast, using fat powder and dry cake mix, respectively, led to different results in extraction procedure. When fat powder and dry cake mix were used as food matrices, some protein recovery rates decreased and some increased depending on the allergen material. These results highlight the fact that suitability of extractant not only depends on allergen properties but furthermore on the matrix the allergen is to extract out of.
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