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J AOAC Int. 1995 Jul-Aug;78(4):1097-101.

Enhancement of ethylenethiourea recoveries in food analyses by addition of cysteine hydrochloride.

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U.S. Food and Drug Administration, Kansas City District Office, Lenexa 66285-5905, USA.


The effectiveness of cysteine hydrochloride (Cys-HCl) as a preservative of ethylenethiourea (ETU) in product matrixes and during analysis was studied. ETU recoveries were adversely affected by certain product matrixes when fortified directly into the product. Recoveries in 8 selected food items were 0-92% when analyzed 30 min after fortification and 0-51% when analyzed after 24 h. When Cys-HCl was added to product prior to fortification, recoveries increased to 71-95% even after frozen storage for 2-4 weeks. Cys-HCl was added during analysis of 53 untreated items. Recoveries improved an average of 15% with Cys-HCl. Without Cys-HCl, recoveries were erratic (20-98%), but with Cys-HCl, recoveries were 68-113%. Other antioxidants (sodium sulfite, butylated hydroxyanisole, butylated hydroxytoluene, and vitamins A and C) also were evaluated as ETU preservatives. When lettuce was treated first with sodium sulfite and then fortified with ETU, recoveries averaged 86%; without sodium sulfite, they averaged 1%. The other antioxidants were less effective for preserving ETU in lettuce, giving only 8-46% recoveries. The effect of oxidizers (potassium bromate, sodium hypochlorite, and hydrogen peroxide) on ETU recovery was also determined. Recovery of ETU from a baby food product (pears and pineapple) was 82%; with oxidizers, recoveries were 0-8%.

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