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L. D. APPLEWHITE, APL Sciences, Inc., P.O. Box 357730, 3610 NW 42nd Terrace, Gainesville, FL 32635

JUSTIFICATION: Sulfites are commonly used as food additives in shrimp processing. Sulfites effectively prevent melanosis and are generally applied immediately post-harvest on both wild and cultured shrimp. A segment of the population is allergic to sulfite residuals on foods and the U.S.FDA regulates its use. The regulation for shrimp states that if sulfites are used in processing and residuals of 10ppm SO₂ remain on the product it must be labeled. To date, there are no rapid, quantitative analyses available to monitor sulfite residuals on treated shrimp.

OBJECTIVE: The objective of this work was to investigate the use of an enzymatic reaction for the determination of sulfite residuals on shrimp.

METHOD: Shrimp were treated with sulfites using customary good manufacturing practices. Untreated shrimp served as the control. Shrimp were homogenized in acetate buffer and the shrimp was allowed to settle. The supernatant was filtered through filter paper. The sulfite residuals in the extracts are measured when the sulfite ions are oxidized to sulfate ions by oxygen in the presence of sulfite oxidase, forming hydrogen peroxide. Hydrogen peroxide is transformed to water by reduced NADH in the presence of NADH peroxidase. NADH is consumed in amounts proportional to the sulfite concentration and is measured spectrophotometrically at 340nm.

RESULTS: The results from three separate trials show that sulfite residuals are readily extracted from shrimp and SO₂ can be calculated from the absorbance of the sample and the blank using the Beer-Lambert equation. The results obtained from the enzymatic method were similar to the A.O.A.C. method +/- 10ppm.

SIGNIFICANCE: Sulfite residuals on shrimp can be quantitatively measured using this enzymatic method. The extraction and analyses can be completed in approximately two hours. This new method gives industry and regulatory agencies a tool to rapidly and quantitatively monitor sulfites remaining on treated shrimp.