Removing isoflavones from modern soyfood: Why and how?

Abstract

Estrogenic isoflavones were found, in the 1940s, to disrupt ewe reproduction and were identified in soy-consumers' urine in 1982. This led to controversy about their safety, often supported by current Asian diet measurements, but not by historical data. Traditional Asian recipes of soy were tested while assaying soy glycosilated isoflavones. As these compounds are water-soluble, their concentration is reduced by soaking. Pre-cooking or simmering time-dependently reduces the isoflavone:protein ratio in Tofu. Cooking soy-juice for 15 or 60min decreases the isoflavone:protein ratios in Tofu from 6.90 to 3.57 and 1.80, respectively (p<0.001). Traditional Tempeh contains only 18.07% of the original soybean isoflavones (p<0.001). Soy-juice isoflavones were reduced by ultra-filtration (6.54 vs 1.24 isoflavone:protein; p<0.001). Soy-protein and isoflavones are dissociated by water rinsing and prolonged cooking, but these have no equivalent in modern processes. As regards human health, a precise definition of the safety level of isoflavone intake requires additional studies.

Characterization of Soaking Process’ Impact in Common Beans Phenolic Composition: Contribute from the Unexplored Portuguese Germplasm

“…Before the soaking process, only daidzein was identified. As water-soluble compounds, isoflavones are present in the soaking water [72]. Nevertheless, this phenolic compounds’ class only represented 0.02% of the total compounds diffused into water, indicating its low contribution to the soaking water’s phenolic content.…”

Soy Isoflavones

“…This indicates that the historical exposure to isoflavones was probably low in Asia (Barnes 2010). However, some amounts of these compounds remain in the productfor example, in protein extracts, where there is still a small amount of isoflavones (Fernandez-Lopez et al 2016). A database of isoflavone content in unprocessed and processed soy products is available from the US Department of Agriculture (USDA) (Bhagwat and Haytowitz 2015).…”

“…Soybeans did not reach the Americas and Europe until the eighteenth century; the earliest records of their presence there date back to 1765 in Savannah (Georgia, USA), 1739 in Paris, and 1790 in London (at Kew Gardens). It is only in the last century that the human intake of soy and soy-derived products has increased in these Western countries, with industrialized processing that started in the 1940s (Barnes 2010, with references;Fernandez-Lopez et al 2016). Nowadays, these products are mainly used for surrogate food production as a protein source solution for vegetarians because of their high protein content and usefulness in the production of different products such as meat analogues.…”

Effects of isoflavones on breast tissue and the thyroid hormone system in humans: a comprehensive safety evaluation

“…Moreover, even in Asia, nutritional habits as well as food preparation (cooking) and processing techniques of soy beans and products thereof were different in the past, which may also have led to lower intakes than today. For example, traditional soy food preparation was based on soaking, rinsing, and prolonged simmering in water, all of which lead to a depletion of glycosylated isoflavones in the product (Fernandez-Lopez et al 2016 ).…”

“…In contrast, the mean dietary intake is rather high in Asian populations and the exposure is assumed to result from a lifelong consumption of soy food starting early in life (see “ Exposure ”). In addition, there are considerable differences in the global diet composition when comparing Western and Asian populations (Morinaka et al 2013 ), soy intake only accounting for a small proportion of this difference (Morinaka et al 2013 ; Fernandez-Lopez et al 2016 ). A systematic review by Nagata et al ( 2014 ) summarised the data of five cohort studies and six case-control studies with Japanese women.…”