Assessing Compositional Differences in Soy Products and Impacts on Health Claims

In October 1999, the Food and Drug Administration (USA) approved a health claim for soy indicating that consumption of 25 grams of soy protein a day as part of a diet low in saturated fats and cholesterol may help lower the risk of heart disease. Additionally, soy has officially been approved in the UK, Brazil, Malaysia, Japan, Korea, Philippines, Indonesia and South Africa. Some countries have, however, been slower to approve a health claim and are requiring more substantive evidence. Questions of concern include the impact of processing on the efficacity of soy protein, information on the normal and acceptable levels of isoflavones in soy products, efficacy of soy proteins in which isoflavones have been removed versus soy proteins containing isoflavones in respect to relationship with cardiovascular disease risk reduction, feasibility of consumers to take in 25 g of soy protein a day, effect of antinutritional factors (e.g., trypsin inhibitors, phytates, lectins, lysinoalanine), heat resistance of trypsin inhibitors found in soybeans and the specific effects of soy protein alone compared to soy protein within a matrix (e.g., whole soybean foods and foods made from soy protein ingredients). These questions are pertinent as there is a wide variety of soyfoods available on the market with different macro and micro nutrient compositions. Answers to these questions will therefore be useful in identifying the specific conditions required for soyfoods to carry a health claim. Foods prepared from whole soybeans include soymilk and tofu. Soybean derived ingredients include defatted soy flour, soy protein concentrate, soy protein isolate and soy fibre. Soy protein isolates in particular have been very successful commercially and are used extensively today in the production of a large number of foods. Different techniques can be used for making soy protein isolate and the type of processing treatment used can affect the nutrient and physicochemical composition of the isolate (e.g., composition of residual isoflavones, saponins, trypsin inhibitors, phytic acid and minerals). Isoflavones, saponins, trypsin inhibitors and phytic acid are all biologically active molecules and as such variations in their composition can hinder the ability to determine if a reported health benefit is due to the soy protein alone or the presence of these other compounds. The chapter will provide a brief update on some of the reported health benefits of soy components. An overview of some of the major soyfoods and soy ingredients currently