This chapter describes technologies and methods widely employed in the development and engineering of antibodies utilized in food diagnostics. Immunoassays have been considered as the golden standard for the simple, high-throughput screening of contaminants from a variety of matrices. Cost-efficiency, in combination with increasingly efficacious tools for obtaining antibodies with high specificity and affinity, has led to the widespread use of immunoassays for the routine detection of various food contaminants. As the quality of the immunoassay is primarily dependent on the binding properties, such as affinity and specificity, of the antibody used to recognize the contaminating compound, it is often feasible to modify these properties to enhance the performance of the assay. The rapid development of directed antibody engineering technologies in the past three decades has facilitated the generation of assays with novel specificity for high-throughput analysis of foodstuffs. More recently, antibodies with novel specificity have been utilized to develop high-performance analytical methods which have expanded the limits of traditional immunoassays, in terms of sensitivity and number of detectable contaminants.