Rapid, Sensitive, Enzyme-Immunodotting Assay for Detecting Cow Milk Adulteration in Sheep Milk: A Modern Laboratory Project

• Published in: Journal of chemical education 1998-12, Vol.75 (12), p.1618
• Main Authors: Alava, María A, Calvo, Miguel, Inda, Luis A, Razquín, Pedro, Lampreave, Fermín
• Format: Article
• Language: English
• Subjects: Assaying; Biochemistry; Chemistry; Fundamental Concepts; Laboratories; Milk; Organic Chemistry; Protocol Materials; Quality Control; Science education; Sheep; Thinking Skills; Water
• ISSN: 0021-9584; 1938-1328
• DOI: 10.1021/ed075p1618

Specificity, sensitivity, and experimental simplicity make the immunoenzymatic assay suitable for a variety of laboratories dedicated to diverse activities such as research, quality control in food analysis, or clinical biochemistry. In these assays, the antibody that specifically recognizes the antigen is covalently attached to an enzyme. Once the antigen-antibody immunocomplex is formed, the enzymatic reaction gives a colored product that allows the detection of the initial antigen.The aim of this work was the design of a new laboratory project appropriate for use in courses of biochemistry, immunochemistry, or analytical chemistry. The assay described here detects the presence of cow milk in milk of other species. The main application is the detection of cow milk in sheep milk and cheese. Specific proteins, immunoglobulins (IgG) of the fraudulent bovine milk, are specifically recognized and retained by antibodies immobilized on a membrane. The binding of a second antibody covalently attached to horseradish peroxidase (HRP) allows the development of a visible signal. Thus, students can rapidly detect milk adulterations using a specific, sensitive, and safe experimental approach. The experiment allows students to apply their theoretical knowledge, resulting in a stimulating experience of solving a real problem during a 4-hour laboratory period.