Soybeans are one of the most widely grown crops in the world and provides the largest source of plant protein in the human diet due to its superior nutritional, economical, and functional base. They contain abundant plant-derived proteins, isoflavones, and other high-nutritional value ingredients, such as saponin and phytic acid. Soy protein isolates (SPI) have been widely used as functional ingredients in foods such as meats, sausages, breads, and beverages. Despite its high functionality, the typical grassy and beany off-flavours in SPI remain a major hurdle in expanding the use of SPI in mainstream food applications. The off-flavours associated with SPI have been recognized as beany, bitter, chalky, cardboard, astringent, toasted, nutty, and cereal-like. The volatile off-flavours are related to the oxidation of polyunsaturated fatty acids and several phytochemicals, such as isoflavones, saponins, phenolic acids, etc., and impart bitter and astringent tastes to SPI. Removing the off-flavours and improving the sensory quality of soybean products is a major technical challenge during the processing of soybean foods. For improving product quality, several treatments have been used for the removal or elimination of off-flavours, including physical methods, chemical methods, biological methods, and genetic engineering.