Soybean containing products are widely consumed, thus reliable methods for detection of soy in foods are needed in order to make appropriate risk assessment studies to adequately protect soy allergic patients. Six methods were compared using eight food products with a declared content of soy: a direct sandwich ELISA based on polyclonal rabbit antibody (ab) to raw soy flakes, a commercial and an in-house competitive ELISA both based on ab to denatured, 'renatured' soy protein, an enzyme-allergosorbent test (EAST) inhibition based on two sera from soy allergic patients, histamine release (HR) using basophils passively sensitized with patient serum and a PCR method detecting soy DNA. Eight food products were selected as model foods to test the performance of the methods. There was an overall good agreement between the methods in terms of ranks of soy content but not the quantity. The sandwich ELISA aimed at native soy proteins had the lowest detection limit of 0.05 ppm, but only identified soy in 5/8 products, and generally in lower amounts compared to other methods. The competitive ELISA had a higher detection limit of 21 ppm, but seemed more successful in detecting processed soy. Only HR, EAST inhibition and PCR detected soy in all eight products. In spite of a general good correlation in terms of ranks of soy content, more than a single method may be necessary to confirm the presence of soy in foods.

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The laccase used in the study was produced by submerged fermentation of Aspergillus oryzae, containing a gene originating from Polyporus pinsitus. Laccase is to be employed as a processing aid in the juice industry to make a clear and stable juice. The enzyme was subject to a series of toxicological tests to document its safety in use. It was not mutagenic in the Salmonella typhimurium reverse mutation assay, and it did not cause chromosomal aberrations in cultured human lymphocytes. No evidence of inhalation toxicity or skin and eye irritation was found. Oral administration to rat of up to 10 ml kg(-1) b.w. day(-1) (equivalent to a total organic solids dosage of 676 mg kg(-1) b.w. day(-1) or a laccase dosage of 2601 LACU kg(-1) b.w. day(-1)) for 13 weeks did not cause any adverse effect. The maximum recommended dosage of laccase used for juice applications is 50 LACU l(-1) juice.