**1. Introduction**

Soy isoflavones (SIF), as bioactive substances, are the main secondary metabolites in soybeans. SIF have been found to possess several potential health benefits such as anticancer [1], reducing menopausal syndrome [2], and preventing osteoporosis [3]. Because of their health benefits, SIF have been recommended as a functional ingredient for formulation of healthy foods and pharmaceutical products. However, due to its low solubility in water, poor bioavailability, and high susceptibility to degradation under oxygen, light, and heating conditions [4], the application of SIF in the food industry is limited. Several approaches have been developed to solve these problems. Functional SIF nanoparticles were prepared by antisolvent precipitation method to improve the water dissolution rate [4]. Wang et al. [5] reported that SIF were microencapsulated in gel beads of soybean hull polysaccharides.

Goat milk whey protein has attracted increasing interest in recent years. The major components in goa<sup>t</sup> milk whey protein are β-lactoglobulin (β-LG) and α-lactalbumin ( α-LA), which have excellent emulsifying and foaming properties [6,7]. In recent years, membrane processing technology has been widely used in the dairy industry in an industrial scale due to its low energy consumption, low temperatures, and reduction of environmental contaminants. The goa<sup>t</sup> milk whey protein was

prepared from clarified cheese whey by microfiltration (MF) and ultrafiltration (UF) technology, which has good gelation and emulsifying properties [8]. The emulsifying property of goa<sup>t</sup> milk whey protein can be improved by heat treatments [9]. During heating, the polypeptide chains of protein unfolded, and the sulfhydryl groups were exposed to form polymerized whey proteins (PWP) which can be used as an encapsulating material with improved functional properties [10,11]. Because of the protein surface-active property, PWP has a strong affinity towards different ligands [12]. Information about the application of polymerized goa<sup>t</sup> milk whey protein (PGWP) as a bioactive compound carrier is very limited.

Therefore, the aim of this work was to prepare SIF nanoparticles using PGWP as wall material. The PGWP was prepared directly from goa<sup>t</sup> milk by membrane processing technology and the physicochemical properties of nanoparticles were characterized.

#### **2. Materials and Methods**
