Purpose: To accurately detect soya protein in processed foods, we developed a reliable ELISA kit and evaluated the performance of this kit.
Methods: A soya protein-specific sandwich ELISA kit was developed using a special extraction solution (patent pending) and polyclonal antibodies against beta-conglycinin. For standard, soya protein was extracted from defatted soya (Enrei) powder with the extraction solution and the protein content was determined by a 2D Quant kit (GE healthcare).
Results: Our kit was able to detect both raw and heat treated soya protein and the recovery was more than 80%. The kit showed no cross-reactivity to other food ingredients such as peanut, wheat, egg, milk, buckwheat and many kinds of nuts (e.g., almond, cashew, pistachio, walnut, pecan, hazelnut), and low cross-reactivity to some kinds of beans. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.156 microgram/g food and 0.31 microgram/g food, respectively. The recovery of soya protein from model processed foods ranged from 77% to 122% and was higher than other commercial kits. The average intra-assay variation (repeatability) was C.V. 1.0% calculated by measuring in three assay on the same day. The inter-assay variation (reproducibility) was C.V. 2.6% calculated by measuring for three days.
Significance: Our ELISA kit is useful and valuable for detecting soya protein in both non-processed and highly processed foods.