Improved Food-Processing Techniques to Reduce Isoflavones in Soy-Based Foodstuffs

Abstract

Soy is a growing protein source; however, the isoflavones it contains are of concern, as they exhibit estrogenic activities whose toxicological limits might be exceeded. Reducing their concentrations to safe levels while preserving nutritional quality in soy foodstuffs is therefore a matter of public health. The main objective of this paper is to develop at pilot scale a process for isoflavones’ extraction from soybeans, and to show its feasibility and efficiency. The study was conducted by first optimizing the previously obtained laboratory treatment key factors. These data were then transposed to the pilot level. Finally, the process was adjusted to technical constraints which appeared at pilot scale: the mandatory use of drenching and the exploration of granulometry analysis. The involved steps were validated by monitoring the genistein and daidzein content variations through statistical analysis of the data of an ELISA and a Folin–Ciocalteu assay. Additionally, isoflavones’ recovery from treatment waters for their valorisation and the water cleaning by means of filtration, centrifugation and resin adsorption were carried out. The results showed that the most successful pilot treatment developed involved soybean dehulling, drenching, washing and drying and almost halved isoflavones while preserving the main nutritional characteristics. A combination of techniques led to almost complete recovery of isoflavones from process waters.

Traditional and Domestic Cooking Dramatically Reduce Estrogenic Isoflavones in Soy Foods

“…Moreover, using hot water did not bring additional efficiency to the process. These results are consistent with those previously published by Bensaada et al [12]. Although this result might appear to be counterintuitive, it was observed several times by our team during the analysis of water treatments on both soybeans and soy-textured proteins.…”

“…This work also shows that simple water renewals during domestic beans soaking can dramatically reduce estrogenic IFs from subsequent preparations of soy juice or tofu. It appears that treating dehulled beans is more efficient for IFs removal than treating whole beans, as already observed [12]. Similarly, when water rinsing was tested on textured proteins of different sizes, IFs were more efficiently removed from fine or extra-fine proteins than from large or medium-sized ones.…”

“…Regarding the proteins and lipids contents of soy products, they are not significantly reduced after water treatment [12]. Indeed, working on whole beans or dehulled beans allows the soy-cells integrity to be preserved.…”

“…Such treatments applied to beans or dehulled beans have been reported to yield the inactivation of antinutritional factors and the removal of estrogenic IFs while preserving proteins [12], fibers, and polyunsaturated fatty acids (PUFAs) among ω3 and ω6 families [13]. In contrast, modern industrial processes primarily involve physical constraint treatments such as pressing and extrusion, which may lead to some concentration of IFs.…”