Methods to detect and quantitate spleen added to ground beef

Experiments were conducted to explore the feasibility of employing the storage iron compounds, hemosiderin and ferritin, as indicators for the detection and quantitation of spleen added to ground beef.

Weighed amounts of ground beef and a composite spleen homogenate were combined to yield products with 0, 2.5, 5 and 10 percent spleen. A graded series was prepared at each of three fat levels.

A quantitative procedure based on the organ specificity and insolubility of hemosiderin was tested. The soluble iron forms were removed by saline extraction and centrifugation. Any iron remaining in the residue was assumed to be hemosiderin iron.

The retained iron was extracted by acid hydrolysis and quantitated colorimetrically with ferrozine and by atomic absorption. The residues from unadulterated samples held less than 4 μg Fe/g original sample. Insoluble iron increased linearly (Slope = 4.83) as the level of spleen in the product increased. The fat content of the products had little effect on the quantitation of added spleen.

A qualitative spot test based on the solubility and heat stability of ferritin was investigated. Protein pellets prepared from unadulterated samples maintained a white to grey-white color after Prussian blue iron staining. Pellets from spleen-added samples developed a blue color. The amount and intensity of blue increased as the amount of spleen in the product increased.

A presumptive test was performed by applying Prussian blue directly to the raw products. The spleen-added products developed a blue color.