Functional Properties of Soy Protein Enriched with Soybean Isoflavones
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Abstract:
Soy protein enriched with isoflavones was prepared under different heating conditions and its functional characteristics were studied. The insolubility of isoflavones in protein was greatly changed. Soy protein enriched with natural soybean isoflavones (SPIG) and aglycone isoflavones (SPIA) prepared under pH 6.4 and pH 7.0 were selected. Compared with soybean protein isolate (SPI), the foaming abilities of the heated SPI (HSPI), SPIG and SPIA were enhanced after isoflavone was added. When the pH value was 7.0, the foaming ability of SPIG was 165.77 ± 2.90 %, which was stronger than that of the other proteins enriched with isoflavones. However, water holding ability of the soybean proteins decreased after adding isoflavone, and SPIA 6.4 demonstrated the lowest water holding ability. Then, SPI, the mix of soy protein and natural soybean isoflavones and aglycone isoflavones (MixG and MixA), SPIG and SPIA were respectively adopted to make emulsion. The d43 of fresh emulsion was determined; the average droplet size of SPI was 1.35 ± 0.12 μm, while the average droplet size of MixG and MixA was 25.41 ± 1.32 and 24.57 ± 1.73 μm, respectively. After heating, the average droplet size of SPIG and SPIA increased to 38.99 ± 0.89 μm and 34.50 ± 0.48 μm, respectively. The emulsion stability coefficients of SPIG and SPIA under centrifugal condition were relatively low, but the emulsion had better plasticity than the emulsion of SPI. The conclusion derived?from confocal laser scanning photomicrographs (CLSM) was corresponded with d43.
