Status of Iodine in Milk Preserved with Sodium Metabisulfite and Formaldehyde

Abstract

Fresh raw whole milk labeled in vitro with iodine-131 was preserved with 0.2 to 1.0g of Na2S2O5 per liter of milk at 23–26C. Analyses of portions of milk by ion exchange resin treatment showed quantitative recoveries of 131I up to three days; mold growth and spoilage were observed on the fourth day. The sample with 1.0g of Na2S2O5 showed mold growth but no spoilage up to seven days. Although Na2S2O5 maintained 131I in the reduced state, it had no bactericidal effect and was considered ineffective for preserving milk.Reconstituted powdered milk labeled in vitro with 131I was preserved with formaldehyde and stored for 18 days at 23–26C. Analyses of portions of milk showed 97–100% recoveries of 131I. No xanthine oxidase activity was found in the freshly reconstituted milk, indicating no protein-binding of 131I.Standardizing radionuclide methods for collaborative testing of reconstituted powdered milk labeled in vitro with radio-nuclides and preserved with formaldehyde are satisfactory.