Walnut milk, which is generally produced in the presence of stabilizers by homogenization, is being increasingly consumed by people in China, due to its good nutritional and functional properties. In this study, the mechanism behind the poor dispersion stability of walnut milk without stabilizer has been clarified as caused by heat-induced large aggregate formation from walnut oil bodies and protein. It was found that addition of raw soymilk into walnut milk could result in the stable mixed beverage by homogenization with subsequent heating. This was because raw soymilk played roles on decreasing the particle size of walnut oil bodies during the homogenization, and preventing the large aggregate formation from walnut oil bodies and protein during the subsequent heat treatment. Amino acid analysis showed that the stable mixed beverage contained more lysine than the walnut milk. In addition, the stable mixed beverage had higher levels of protein content (about 2%) than the commercial walnut milk (commonly < 1%) in China. Therefore, this study was meaningful for the convenient and value-added utilization of walnut.Keywords: walnut milk, soymilk, mixed beverage, walnut oil bodies, walnut protein IntroductionWalnut is one of the mostly cultivated tree nuts in the world, including southern Europe, northern Africa, eastern Asia, the USA and western South America (Martinez et al., 2010), and China is the leading producer. It is consumed due to its nutritional, healthy and sensory attributes. It has been reported that walnut exhibits greater antioxidant capacity than any other nuts (Arranz et al., 2008) and its oil has a perfect balance of n-6 and n-3 polyunsaturated fatty acids (4:1) (Simopoulos, 2002). The consumption of walnut can lower plasma total-and low-density lipoprotein cholesterols (Lavedrine et al., 1999;Banel and Hu, 2009), and incidences of cardiovascular diseases (Simopoulos, 2002). In addition, the intake of walnut has been proved to effectively reduce inflammation and improve arterial functions (Ros et al., 2004;Tapsell et al., 2004).The most popular walnut products are made from toasted nuts.However, not many people may be motivated to consume the toasted walnut all the times due to the inconvenience of the shell removal. Therefore, the walnut products, convenient to the consumers, are prioritized by the food industry. Some food scientists have tried to produce walnut-containing meat products (Cofrades et al., 2004;Ayo et al., 2005). Nevertheless, the most popular way is the production of walnut milk beverage (Gharibzahedi et al., 2012;Luo et al., 2010;Yu et al., 2010). But poor dispersion stability of walnut milk is a key limiting factor.Until now, the mechanism behind the poor dispersion stability is unclear. Commonly, homogenization in the presence of various stabilizers (xanthan, sodium carboxymethyle cellulose, monoglyceride, sucrose ester, sodium caseinate, arabian gum and so on) is a well-used strategy to produce stable walnut milk beverage (Gharibzahedi et al., 2012;Luo et al., 2010;Yu et al., 2...