Stability of isoflavone phytoestrogens in fermented soymilk with Bifidobacterium animalis Bb12 during storage at different temperatures

Soy isoflavones in fermented soymilk with Bifidobacterium animalis Bb12 were stored at various temperatures (?80, 4, 24.8 and 37 °C) for 8 weeks and the concentration of isoflavones determined weekly using reverse‐phase high‐performance liquid chromatography (RP‐HPLC). The first‐order kinetic model was used to assess the degradation of each isomer at each storage temperature. Soymilk predominantly possesses high concentrations of isoflavone glucosides and very low concentration of bioactive aglycone component. During storage at various temperatures, concentrations of individual isoflavone isomers appeared to be significantly stable (P < 0.01). Interestingly, aglycones showed much smaller degradation constants compared with glucosides at all the storage temperatures studied. Genistein and daidzein were much more stable than glycitein and had almost similar degradation patterns, despite differences in their concentrations in the fermented soymilk. It was, however, observed that 4 °C was the most suitable storage temperature for the product in order to guarantee minimal degradation of bioactive isoflavone aglycones.     

Use of Bacillus subtilis to enrich isoflavone aglycones in fermented natto

BACKGROUND: Natto is a food made by fermenting cooked soybeans with Bacillus subtilis. Soybean isoflavones are reported to provide many health benefits, including oestrogenic effects. However, isoflavone aglycones may be absorbed faster and in higher amounts in the human intestine than their glucosides. This study aimed to investigate the content of isoflavone components in commercial natto products as well as the use of B. subtilis strains to ferment cooked soybeans to produce a high level of isoflavone aglycones in natto. RESULTS: The content and composition of isoflavones in commercial natto products were predominantly (>76%) isoflavone glucosides. Fermentation of cooked soybeans with B. subtilis BCRC 14718 at 37 °C for 48 h was more effective in converting glucosides to aglycones than with other strains of B. subtilis, increasing the proportion of isoflavone aglycones from 12 to 68% of the total isoflavones in the fermented natto. The proportions of the isoflavone aglycones daidzein and genistein in cooked soybeans fermented with B. subtilis BCRC 14718 for 48 h increased from 6 to 54% and from 5 to 13% respectively. CONCLUSION: Bacillus subtilis BCRC 14718 incubated with cooked soybeans produces higher levels of isoflavone aglycones, which may enhance health benefits over traditional fermented natto. Copyright © 2008 Society of Chemical Industry     

青方腐乳发酵过程中大豆异黄酮的转化研究

本文比较了青方、红方、白方和低盐红腐乳中大豆异黄酮组成和含量差异,并对青方腐乳发酵过程中大豆异黄酮含量和构型变化规律进行研究。结果表明,四种类型腐乳中大豆异黄酮基本以苷元形式存在,青方腐乳大豆异黄酮含量明显低于其他类型腐乳,仅为红方腐乳的33.01%,从单一异黄酮来看,大豆苷元和染料木素在四种类型腐乳中的含量明显高于黄豆黄素;青方腐乳发酵过程中大豆异黄酮转化研究发现,白坯中大豆异黄酮以糖苷型为主,染料木苷含量高于大豆苷和黄豆黄苷,前酵过程中糖苷型大豆异黄酮转化为苷元型大豆异黄酮,盐腌过程中糖苷型大豆异黄酮含量有轻微降低,发酵过程中苷元型大豆异黄酮总量在后酵前30 d显著下降,其中大豆苷元可能部分转化为雌马酚,导致青方腐乳大豆异黄酮含量明显低于其他类型腐乳,对其转化物质需进一步鉴定。     

Content composition and antioxidant activity of isoflavones in commercial and homemade soymilk and tofu

BACKGROUND: Isoflavones, found in soymilk and tofu, are one of the phytochemicals in soy‐based products that may promote good health. Homemade tofu and various homemade soymilk samples were made using different soaking, grinding, and cooking methods. The homemade samples were compared to commercial tofu and soymilk for total isoflavone content and composition as well as their antioxidant capacity. All samples were freeze‐dried and extracted with a 58% acetonitrile solution which was subsequently used to determine the isoflavone content by reverse‐phase high‐performance liquid chromatography. The antioxidant activity of extracts was determined using a modified 2,2‐azino‐bis‐(3‐ethylbenzthiazoline‐6‐sulfonic acid) method and total antioxidant capacity was reported as ascorbic acid equivalents. RESULTS: The total isoflavone, aglycone, and antioxidant levels were significantly higher in homemade soymilk and tofu (1571 µg) than in commercial samples. Homemade soymilk made by the extended boiling method yielded the highest total isoflavone (2567 µg) and glucoside (1525 µg) content. A strong positive correlation was observed between the total isoflavone, aglycone conjugates, and genistein series concentration and antioxidant capacity of soymilk. CONCLUSION: Increased moist heating time yielded the highest concentration of total isoflavones as well as aglycone conjugates and the genistein series. Increasing the duration of boiling can increase the isoflavone content of both homemade and commercial soymilk and tofu. Copyright © 2007 Society of Chemical Industry     

The effect of probiotic‐fermented soy milk on enhancing the NO‐mediated vascular relaxation factors

BACKGROUND: Soy milk is one of the common soy‐based foods in Asia. In this study the effects of soy milk fermented with selected probiotics on nitric oxide (NO)‐mediated vascular relaxation factors in cell model systems were investigated. RESULTS: Soy milk fermented with Lactobacillus plantarum TWK10 or Streptococcus thermophilus BCRC 14085 for 48 h showed a greater transformation of glucoside isoflavones to aglycone isoflavones (P < 0.05). An increase in aglycone isoflavones in ethanol extracts from fermented soy milk stimulated NO production and endothelial NO synthase (eNOS) activity in human umbilical vein endothelial cells. It also had a stimulating effect on superoxide anion scavenging and prostaglandin E₂ production. In addition, it enhanced mRNA expression of the E‐prostanoid 4 receptor in rat thoracic aorta smooth muscle cells. Moreover, a small amount of O induced by water extracts from fermented soy milk at low concentration (1 mg mL^?1) increased the content of calcium ions and activated eNOS, thereby promoting NO production and the coupling state of eNOS. CONCLUSION: Soy milk fermented with selected probiotics promotes the relaxation factors of vascular endothelial cells and can be applied in the development of functional foods. © 2012 Society of Chemical Industry     

INFLUENCE OF HEAT TREATMENT AND GRAIN GERMINATION ON THE ISOFLAVONE PROFILE OF SOY MILK

Soy foods have attracted much attention for their possible effects on human health because of their phytochemical content, mainly isoflavones. Twelve forms of isoflavones have been identified in soybeans and soy products. Technological processes like heat treatment or fermentation can change the isoflavone profile of soy products. In this study, the effects of heat treatment and grain germination on isoflavone profile of soy milk prepared from BRS 213 soybean variety were evaluated. Isoflavone forms were separated and quantified by reversed‐phase high‐performance liquid chromatography. Heat treatment by autoclaving for 5 min did not affect the total isoflavone content, but led to a 90% decrease in malonyl forms, whereas β‐glycosides increased by 70%. Autoclaving for 15 min led to a 20% loss of total isoflavones. Germination for 3 days did not change the total isoflavone content, but changed the distribution profile (15% increase of malonyl forms and 30% decrease of β‐glycosides). Germination for 7 days increased the bioavailability of aglycone isoflavones in soy milk by seven times.     

Original article: Thermal dynamic properties of isoflavones during dry heating

Thermal stabilities of major soya isoflavones at different dry‐heating temperatures were determined in this study. The conversion of glucoside isoflavones to aglycone isoflavones was monitored as well. The thermal degradation of the isoflavones: glucoside form daidzin, glycitin, and genistin and aglycone form daidzein, glycitein, and genistein followed first‐order reaction kinetics at heating temperatures 100, 150, and 200 °C. The degradation rate constants of the six isoflavones were not significantly different at 100 °C. However, the constants increased with increasing heating temperature. The half‐life for the glucoside and aglycone isoflavones was from 144 to 169 min and 139 to 176 min at 100 °C, respectively. They decreased rapidly to 15.7–54.7 and 36.0–90.7 min when temperature increased to 150 °C. When heated at 200 °C, they further decreased to 5.8–6.0 and 15.7–21.2 min, respectively. The order of thermal stability from lowest to highest was glycitin < genistin < daidzin < glycitein < genistein < daidzein at temperature below 150 °C. However, their thermal stabilities were not different at 200 °C. The conjugated glucosides were cleaved from the isoflavones to produce their corresponding aglycones when heated at 150 °C or higher. The production of glycitein increased constantly and was the highest among the three aglycone isoflavones.     

Characterization of fermented black soybean natto inoculated with Bacillus natto during fermentation

BACKGROUND: To make nutrients more accessible and further increase biological activity, cooked black soybeans were inoculatedwith Bacillus natto and fermented at 37 °C for 48 h. The changes in physiochemical properties of fermented black soybean natto were investigated. RESULTS: The inoculation procedure significantly increased moisture, viscosity, color, polyphenol compounds and anthocyanin, and significantly decreased hardness after 48 h fermentation. Fibrinolytic and caseinolytic protease, β‐glucosidase activities, TCA‐soluble nitrogen, and ammonia nitrogen contents in the inoculated samples significantly increased as fermentation time increased. Genistin and daidzin concentrations gradually decreased with increased fermentation time. However, genistein and daidzein increased with fermentation time, which reached 316.8 and 305.2 µg g^?1 during 48 h fermentation, respectively. DPPH radical scavenging activities of the fermented black soybeans increased linearly with fermentation time and concentration. Compared with the soaked black soybeans and cooked black soybeans, the fermented black soybeans with B. natto resulted in higher scavenging activity towards DPPH radicals, which correlated well with the content of total phenols (r = 0.9254, P < 0.05) and aglycone isoflavone (r = 0.9861, P < 0.05). CONCLUSION: Black soybean natto fermented by B. natto has the potential to become a functional food because of its high antioxidant activity. Copyright © 2010 Society of Chemical Industry     

Concentration of phytoestrogens in soybeans and soybean products in Korea

Concentrations of total isoflavones in soybean varieties of different origins and soybean products were determined by high performance liquid chromatography. Wild soybeans showed the trend to have more isoflavone content than cultivars or landraces, showing mean value of 1528, 1265 and 1249 mg kg⁻¹, respectively. There were no meaningful differences in the ratio of genistein and daidzein among the modern variety groups. Korean varieties including South Korea and North Korea seemed to have total isoflavone content more than Chinese varieties, although samples of Chinese varieties were limited. In a dried basis of soyfoods, total isoflavone contents were in order of soybean sprout, chungkukjang, soymilk, soybean curd, denjang, kochujang, respectively. Five soybean foods contributed 96% of total genistein and daidzein intake in Korea: soybean sprout, soybean curd, denjang, chungkukjang and soybean seed itself. According to a Korean National Survey Report and our data, the average Korean daily intake of isoflavone from soybean foods can be estimated as 21 mg day⁻¹. © 2000 Society of Chemical Industry     

Sensory properties of soy yoghurts prepared from yellow and black soymilk using Streptococcus infantarius 12 and Weisellia sp. 4

BACKGROUND: Soy yoghurts containing enhanced bioactive isoflavone aglycones were prepared from combinations of yellow (YS) and black soymilk (BS) (YS:BS = 100:0, 70:30, 50:50 and 0:100, v/v) by fermentation with Streptococcus infantarius 12 and Weisellia sp. 4 at 37 °C for 10 h. Sensory properties of the bioactive soy yoghurts were investigated. Furthermore, other characteristics including the contents of isoflavones, viable cell numbers, pH, colour and DPPH radical scavenging activity were investigated. RESULTS: One hundred percent YS yoghurt showed the highest scores of all sensory attributes while 100% BS yoghurt was the lowest for colour and smoothness. The overall acceptability scores were 5.9 and 5.2 for 100% YS and 100% BS yoghurts, respectively (9‐point scale). The L‐values of soy yoghurts decreased as the percentage BS increased, indicating darkening of soy yoghurts. The contents of bioactive isoflavone aglycones (daidzein and genistein) in soy yoghurts remarkably increased (>1300 mg kg^?1) by fermentation. Viable cell numbers and pH of soy yoghurts ranged from 8.4 × 10⁸ to 9.6 × 10⁸ CFU g^?1 and 4.43 to 4.54, respectively. DPPH radical scavenging activity significantly increased as the percentage BS increased (P < 0.05). CONCLUSION: One hundred percent YS yoghurt was better for overall sensory properties while 100% BS yogurt was more bioactive in terms of the isoflavone aglycone contents and DPPH radical scavenging activity compared to other yoghurts. Copyright © 2008 Society of Chemical Industry     

Effect of free or protein-associated soy isoflavones on the antioxidant status in rats

BACKGROUND: The objective of this study was to investigate the effect of chronic ingestion of free and protein‐associated soy isoflavones on the antioxidant status in male Wistar rats. Free isoflavone (iso), protein‐associated soy isoflavone (iso + prot) and soy protein (prot) extracts were administered for 30 days by gavage to the rats at a dosage of 1 mg aglycone isoflavones per 200 g body weight, adjusted daily, and the prot group was given the same concentration of soy protein received by the iso + prot group. Antioxidant capacity of plasma, thiobarbituric acid‐reactive substance (TBARS) and glutathione (GSH) levels and catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities in plasma, erythrocytes and tissues and gene expression levels in liver and kidney were evaluated. RESULTS: Chronic ingestion of free but not of protein‐associated soy isoflavones nor of solely soy protein increased plasma antioxidant capacity and GPx activity in erythrocytes. Soy protein increased CAT activity and gene expression in liver. SOD activity in erythrocytes was increased by all treatments. CONCLUSION: The overall results confirm that dietary soy isoflavones have a positive effect on antioxidant status, enhancing antioxidant capacity of plasma and antioxidant enzymes in various tissues, but the effects are dependent on the form of administration and on a complex mechanism of antioxidant status balance on the organism. Copyright © 2010 Society of Chemical Industry     

A new ultra-high pressure liquid chromatography method for the determination of total isoflavone aglycones after enzymatic hydrolysis: Application to analyze isoflavone levels in soybean cultivars

Since only isoflavone aglycones are considered to be bioactive, the determination of total aglycones that are released from conjugated isoflavones after hydrolytic treatment may facilitate an objective alternative for quantifying isoflavone contents in soy products. Given this major benefit, a new ultra-high pressure liquid chromatography (UV-UPLC?) method was developed for the fast and reliable determination of total aglycones in soybeans (daidzein, glycitein, and genistein) after enzymatic hydrolysis applying helix pomatia digestive juice. Capitalizing on the enhanced performance of UPLC?, aglycones were separated within 3 min only, with a total runtime of 8 min till the next injection. Thus, especially compared to HPLC protocols, UPLC? proved to be superior due to significantly shorter runtimes and accordingly increasing sample throughput. Additionally, regarding the performed validation (linearity, precision, recovery, selectivity, and robustness), the established method proved to be suitable for quantifying total aglycones in soybeans. Moreover, method applicability was demonstrated by analyzing 23 commercial soybean cultivars for their isoflavone contents. Cumulative aglycone levels ranged from 100 to 255 mg per 100 g, hence implying an average ratio of 52%, 41%, and 7% of total isoflavones for genistein, daidzein and glycitein, respectively. However, for some soybeans, other distinct aglycone distributions were observed as well.     

Change in isoflavone concentration of soybean (Glycine max L.) seeds at different growth stages

This study was conducted to determine the fluctuating levels of isoflavone in soybean (Glycine max L.) seeds of six varieties at different development stages. The average concentration of total isoflavone in the fully matured seed was 669 µg g^?1, whereas those in the seeds of the R5 (beginning), R6 (green full‐sized) and R7 (onset of physiological maturity) stages were 145, 296 and 611 µg g^?1, respectively. Sowonkong variety was highest in total isoflavone content of the fully matured and the R7 seed among all the varieties. In all six varieties, total isoflavone levels at the R7 stage were higher than those of R5 and R6 stages. Total isoflavone concentrations rapidly increased as growth stages transitioned from R5 to R7, as indicated by a positive correlation (r = 0.80***) between the total isoflavone and growth stages. Overall, total isoflavone levels were similar between R7 and the full maturity stages. Of the various isoflavone derivatives, acetylglucoside and aglycon were not significantly correlated with total isoflavone concentrations. However, glucoside (r = 0.97***), malonylglucoside (r = 0.99***), TGIN (genistein + genistin + malonylgenistin + acetylgenistin, r = 0.93***) and TDIN (daidzein + daidzin + malonyldaidzin + acetyldaidzin, r = 0.99***) were very highly correlated with total isoflavone concentrations. As a result, they constituted most of the total isoflavones in the soybean seeds at R5, R6, R7, and full maturity stages. Copyright © 2007 Society of Chemical Industry     

Ripening temperature affects the content and distribution of isoflavones in sufu,a fermented soybean curd

Sufu, a fermented soybean curd, was prepared by ripening the salted tofu cubes in the Aspergillus oryzae‐fermented rice–soybean koji mash at 25, 35 or 45 °C for a period of 16 days. It showed that the 16‐day ripened sufu contains less total isoflavone content (629.29–739.68 μg g^?1 dried matter) than the salted tofu before ripening (942.59 μg g^?1 dried matter). Regardless of ripening temperature, ripening causes a major reduction in the content of β‐glucoside and malonylglucoside isoflavones along with a significant increase of aglycone isoflavone content. These changes were enhanced as the ripening period extended. Among the various treatments examined, sufu ripened at 45 °C showed the greatest increase in aglycone content coupled with the greatest decrease in malonylglucosides. The distribution of malonylglucosides decreased from an initial 40.32% in the tofu cube to 9.78% after 16 days of ripening at 45 °C. Meanwhile, the distribution of aglycone increased from 13.17% to 39.88%.     

Phenolic Antioxidants of Soy Protein Hydrolyzates

Soy protein hydrolyzate (SPH) was investigated to identify the phenolic compounds responsible for antioxidant activity. Three isoflavones–genistein, daidzein, and glycitein–were found in SPH. These are the same isoflavones that have been identified in raw soybeans. No isoflavone glycosides were found in SPH. The phenolic acids found in SPH were caffeic, ferulic, p-coumaric, syringic, vanillic, gentisic, and p-hydroxybenzoic acids. The compounds were identified by TLC, GLC and UV spectra. The isoflavones were confirmed by their mass spectra.     

Content and Profile of Isoflavones in Soy-Based Foods as a Function of the Production Process

Soy has been traditionally incorporated in diet as processed foods, such as soymilk, tofu, miso, tempeh, etc., and the consumption is commonly associated with a reduction of the development of chronic diseases due to their antioxidant, anti-inflammatory, and anti-allergic properties, among others. Many of the health benefits of soy have been attributed to isoflavones. They comprise a group of naturally occurring flavonoids consisting of heterocyclic phenols. Soy contains three types of isoflavones in four chemical forms: the aglycones daidzein, genistein, and glycitein; the β-glucosides daidzin, genistin, and glycitin; their 6″-O-malonyl-β-glucosides (6OMalGlc); and their 6″-O-acetyl-β-glucosides (6OAcGlc) conjugates. Industrial processing methods of soy-based food products commonly lead to the loss of isoflavones through removal of undesirable fractions. On the other hand, isoflavones can be transformed into different conjugates, which may have significant effects on the food texture and on the bioavailability and pharmacokinetics of the isoflavones. This article reviews the effect of a number of soybean processing treatments on the isoflavone content and profile. The preparation and manufacturing of different soy-based food and food ingredients, fermented and non-fermented, has been analyzed in terms of content and distribution of the three major isoflavone derivatives, daidzein, genistein, and glycitein, and their respective conjugates.     

Isoflavone profiles,phenol content,and antioxidant activity of soybean seeds as influenced by cultivar and growing location in Ohio

Isoflavone levels and isoflavone chemical composition in soybeans vary between planting locations although the exact factors which control isoflavone biosynthesis are unclear. We compared levels of 12 isoflavones in soybean seeds of six cultivars grown in four different locations in Ohio in 2002 as determined by high‐performance liquid chromatography. Antioxidant activity contained in plant‐based foods can improve food oxidative stability and phenolics and isoflavones have proven active in food systems. Radical scavenging activity was assessed using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical. Total phenolics (TPCs) were determined by using Folin–Ciocalteu reagent. Total isoflavones (TIs) varied five‐fold (1573–7710 nmol g^?1) between seeds from the various location–cultivar combinations. One location (Wooster, Ohio) produced seeds containing half the isoflavones as the other locations tested apparently due to poor growing conditions. The cultivars could be divided into two groups based on TI, one having approximately 50% more isoflavones. Surprisingly, across the entire data set, with increasing TI, the proportion of isoflavones accounted for by the daidzein family increased due primarily to malonyl daidzin. DPPH scavenging did not differ significantly by location or cultivar (P > 0.05) and did not correlate with TPC or TI. Profiling soybean isoflavones could help elucidate how isoflavone biosynthesis is regulated and lead to better disease resistance of soybean crops and soy foods with greater health benefits. Copyright © 2007 Society of Chemical Industry     

Transformation of isoflavone phytoestrogens during the fermentation of soymilk with lactic acid bacteria and bifidobacteria

In the present study, soymilk is fermented with lactic acid bacteria (Streptococcus thermophilus BCRC 14085, Lactobacillus acidophilus BCRC 14079) and bifidobacteria (Bifidobacterium infantis BCRC 14633, B. longum B6) individually, and in combination. The change in the content of various isoflavones (aglycones, glucoside, acetyl- and malonyl-glucosides) and the beta-glucosidase activity in soymilk during fermentation is investigated. It is observed that fermented soymilk contains a lower total isoflavone content (81.94-86.61 microg/ml) than soymilk without fermentation (87.61 microg/ml). Regardless of starter organism employed, fermentation causes a major reduction in the contents of glucoside, malonylglucoside and acetylglucoside isoflavones along with a significant increase of aglycone isoflavones content. The level of change in the content of various isoflavones and beta-glucosidase activity after fermentation varies with the starter organism. Among all the fermented soymilks tested, soymilk fermented with S. thermophilus showed the highest beta-glucosidase activity and the greatest increase in the contents of aglycones. The percentage of daidzein, genistein and glycitein to total isoflavone content in S. thermophilus-fermented soymilk increases from an initial 14.24%, 6.89% and 2.45%, respectively, to 36.20%, 28.80% and 12.44% after 24h of fermentation. Finally, the increase of aglycones and decrease of glucoside isoflavones during fermentation coincides with the increase of beta-glucosidase activity observed in fermented soymilk.     

Bioavailability of soy isoflavones in rats Part I: application of accurate methodology for studying the effects of gender and source of isoflavones

There are limited and controversial reports about the effects of gender and source of isoflavones on their bioavailability. Moreover, several previous studies have not used appropriate methodology to determine the bioavailability of soy isoflavones, which requires comparing the area under the plasma concentration-time curve after both oral and intravenous injection (IV) administration. Therefore, the present study was conducted to determine the bioavailability of isoflavones from different sources following both oral and IV administration in male and female rats. Three sources of isoflavones; Novasoy (a commercial supplement), a mixture of synthetic aglycones (daidzein, genistein and glycitein) and a mixture of synthetic glucosides (daidzin, genistin and glycitin) were tested. Following administration, blood samples were collected at several time points (0, 10, 30 min and 1, 2, 8, 24, 48 h post oral gavage and 0, 10, 30, 45 min and 1, 2, 3, 4, 8 h post-IV dosing) and plasma isoflavones were measured by LC/MS. Bioavailability values for daidzein, genistein and glycitein were significantly (p <0.05) higher (up to sevenfold) in Novasoy and the glucoside forms of isoflavones compared with those of the aglycone forms. Moreover, significant (p <0.05) gender differences in the bioavailability of 7-hydroxyl-3-(4'-hydroxyphenyl)-chroman (a metabolite of daidzein), glycitein and daidzein were observed for Novasoy, with higher values in male rats. In summary, the source of isoflavones and the sex of rats had significant effects on isoflavone bioavailability.     

Urinary isoflavone excretion in Korean adults: comparisons of fermented soybean paste and unfermented soy flour

BACKGROUND: This study compared the 24 h urinary excretion of isoflavone algycones after the consumption of fermented soybean paste or unfermented soy flour in a population of healthy Koreans (four males and five females). An equivalent amount (20 mg) of total isoflavone was consumed as either 52 g of soybean paste or 12.2 g of soy flour in a randomised, crossover trial consisting of two single‐time‐point feedings and having 3 day run‐in and washout periods between feedings. RESULTS: Analysis of starting materials indicated that daidzein (1.4%) and genistein (1.4%) constituted a smaller proportion of the total isoflavones in soy flour as compared with soybean paste (55.3% daidzein and 45.7% genistein). Free and glycosidic forms of isoflavones differed significantly between the two soy products. Levels of β‐glycosides as well as total glycosides (β‐glycosides, malonyl and acetyl forms) were two‐fold higher in soy flour as compared with soybean paste. Malonyl forms predominated in soy flour. CONCLUSIONS: The consumption of soybean paste resulted in significantly higher urinary excretion of both daidzein and genistein as compared with soy flour (P < 0.05 and P < 0.01 respectively). Copyright © 2007 Society of Chemical Industry