The poor bioaccessibility of the phenolic compounds of soybeans is a key challenge to developing functional food products. Therefore, a novel hydrophilic food-grade hydroxypropyl methylcellulose (HPMC) polymer was added to soybean to prepare a soybean food composite (SFC), in order to improve the soybean's functionality. The SFC was prepared with soybean (95%) plus HPMC (5%) (w/w) mixes (HSE), as well as 100% soybean extrudate (SE), at 80 °C and 130 °C by a hot melt extrusion (HME) process. A non-extrudate 100% soybean material was considered as a control. It is observed that water solubility was significantly increased (35.18%), and particle size reached to nano-size (171.5 nm) in HSE at 130 °C compared to the control (7.14% and 1166 nm, respectively). The total phenolic, flavonoid, and single isoflavones content, including daidzin, daidzein, glycitein, genistein, and genistin was significantly increased in HSE at 130 °C compared to the control. The antioxidant properties were also significantly increased in HSE at 130 °C compared to the control, measured by 2,2-diphenyl-1 picryl hydrazyl (DPPH), a ferric reducing antioxidant power assay (FRAP), and the phosphomolybdenum method (PPMD). Finally, it is concluded that the HPMC polymer could be used as a novel excipient to develop nanocomposite via HME, in order to improve the functionality of soybean food products.
Keywords: bioaccessibility; hot melt extrusion; isoflavones; phenolic content; polymer; solubility.