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     

Effects of the β‐glycosidase reaction on bio‐conversion of isoflavones and quality during tofu processing

BACKGROUND: Isoflavones are the most common group of phytoestrogens which are present in significantly large amounts in soybean and soy products such as tofu. Isoflavones occur naturally in glycoside forms having lower bioavailability than their aglycone forms. β‐Glycosidase acts as a bio‐catalyst for the conversion of isoflavone glycosides to isoflavone aglycones, raising the bioavailability of isoflavones; therefore, it can be used to improve the quality of tofu. We need to establish process conditions for the optimal outcome of the enzyme reaction in tofu. RESULTS: By using the β‐glycosidase (0.02% w/v) reaction at 55 °C for 30 min, a maximum 84.5% conversion of isoflavone glycoside to isoflavone aglycone was obtained. The enzyme reaction caused no significant effects on the sensory acceptability of soft tofu. The hardness of enzyme‐treated hard tofu increased with the coagulant amount whereas prolonged heating resulted in decrease of hardness. Incorporation of enzyme reaction before the coagulation process during soft tofu processing provided a sufficient bio‐conversion of isoflavones at optimal conditions. CONCLUSION: β‐Glycosidase can be effectively used for the bioconversion of isoflavones in soft tofu manufacturing process at optimal reaction conditions before the onset of coagulation process. Copyright © 2010 Society of Chemical Industry     

加热预处理对大豆胚芽风味及其异黄酮存在形式的影响

大豆胚芽含有大量异黄酮化合物,天然异黄酮存在形式主要丙二酰型糖苷,此类异黄酮化合物是大豆胚芽的苦涩、豆腥味的主要呈味物质。研究显示采用加热处理可较大程度地降低大豆胚芽的苦涩味,从而改善胚芽的风味。采用HPLC分析显示,加热处理可使丙二酰型异黄酮糖苷转换为乙酰型糖苷,甚至糖苷化合物,后者的呈味显著低于丙二酰型异黄酮糖苷化合物。     

Functional attributes of soybean seeds and products,with reference to isoflavone content and antioxidant activity

The concentrations of isoflavones, especially daidzein and genistein, were determined by high performance liquid chromatography in 4 soybean cultivars and 26 soybean products. The total isoflavone content of the soybean cultivars was in the range of 525–986 mg per kg, and for soy products it was 32.9–795 mg per kg. Amongst the soybean products, the isoflavone content decreased in the order: soy sprouts, soy seeds, soy flour, soy milk, soy meals and soy sauce. Significant differences in the concentration of genistein and daidzein were observed between the commercial soy products and also within the soybean cultivars. The antioxidant activity of soybean and soy products correlated well with total phenolic content (TPC) and total isoflavones (TI), whereas TPC showed higher correlation with TI.     

Skim milk powder supplementation affects lactose utilization, microbial survival and biotransformation of isoflavone glycosides to isoflavone aglycones in soymilk by Lactobacillus

Four probiotic bacteria, Lactobacillus acidophilus 4461, L. acidophilus 4962, Lactobacillus casei 290 and L. casei 2607, were used for fermentation of soymilk (SM) prepared from soy protein isolate (SPI) supplemented with skim milk powder (SMP) (SSM). Soymilk and reconstituted skim milk (RSM) were used as controls. Lactose utilization in SSM by these probiotic organisms ranged from 14.97 to 18.15mg/ml, compared to 14.12-16.06mg/ml for RSM. The pH in SSM dropped to 4.07-4.29 compared to 6.15-6.36 for SM and 4.10-4.96 for RSM. The microbial viable counts were also significantly enhanced by up to 0.98logCFU/ml by the supplementation of SMP to SM. The biotransformation level of isoflavone glycosides (IG) to isoflavone aglycones (IA) in SSM ranged from 81.4% to 85.1%, which was 13.9-19.0% higher than that for SM, after 24h of incubation. Most of IG in SSM was completely converted to IA, except malonyl glycitin and malonyl genistin. At the end of the incubation, IA comprised up to 76.8% of total isoflavones in SSM.     

Soybean isoflavones: Efficacy of extraction conditions and effect of food type on extractability

Soy isoflavones are phytochemicals of intense interest due to their association with a variety of health protective effects. Analytical techniques to identify and quantify these compounds vary in accuracy, reproducibility and sensitivity. In this study, solvent extraction efficiencies, and the effect of replicate extractions, and sonication on the isoflavone content of two soy products (high and low protein content) were evaluated. The later study was conducted to determine the effect of protein content on isoflavone extractability. Repeated extractions (up to five sequential extractions) of soy meal sample increased the total concentration of isoflavones by 74%, 69% and 65%, using acetonitrile–HCl, methanol and ethanol. The increment for soy protein isolate was 147%, 103% and 105%, respectively. Sonication of both samples in the three solvents for 15 min extracted as much isoflavones as the total of the five sequential extractions. These results strongly indicates that, a one step extraction without sonication can markedly under-estimate the concentration of isoflavones in foods, and that protein content of foods may have a marked impact on isoflavone extractability.     

Critical Issues in R&D of Soy Isoflavone-enriched Foods and Dietary Supplements

ABSTRACT: Increasing consumer awareness of soy as a healthy food ingredient has led to a tremendous growth in sales of soy isoflavone‐enriched foods and dietary supplements in the past 3 y. Because of their weak estrogenic activity, isoflavones are believed to have preventive effects for several hormone‐dependent diseases. This article discusses some critical issues to be considered in any R&D program of novel soy and isoflavone products for the healthy‐food market, such as (1) Which isoflavone compounds should be in the product? (2) Which individual isoflavones are the most beneficial ones? (3) Can certain isoflavone groups be targeted to specific disease prevention goals? (4) Are there any safety concerns in isoflavone consumption? (5) How are isoflavones affected by thermal processing and storage? (6) How should isoflavones be analyzed? These questions may affect the choice of isoflavone source, processing conditions, quality control procedures, and marketing considerations.     

Preparation and characterisation of isoflavone aglycone‐rich calcium‐binding soy protein hydrolysates

Isoflavone aglycone‐rich calcium‐binding soy protein hydrolysates were prepared by subcritical water treatment and subsequent protease hydrolysis. Contaminated β‐glucosidase in the Protease M preparation could effectively convert glycosides into aglycones. Compared with Alcalase hydrolysates, Protease M hydrolysates exhibited higher molecular weight (>5000 Da) and more hydrophobic characteristics because of its weaker proteolytic activity. The antioxidant activity of Protease M hydrolysates was obviously improved. Initial increased DPPH and ABTS radical scavenging rate of Protease M hydrolysates may be ascribed to the conversion of isoflavones (<30 min) and a gradual release of antioxidant peptides. In the later hydrolysis, a gradual exposure of isoflavones involved in the interior of heat‐induced protein aggregates was mainly responsible for further improved antioxidant activities. Higher calcium‐binding capacity (up to 7.86%) with lower yield of peptide–calcium complex was observed for Protease M hydrolysates. These results could help researchers to develop a feasible protocol for producing nutrient‐enhanced soy protein hydrolysates.     

β-GLUCOSIDASE ACTIVITY AND ISOFLAVONE CONTENT IN GERMINATED SOYBEAN RADICLES AND COTYLEDONS

Seeds of BRS 213 soybean cultivar were germinated for 72 h at 25c. Samples were collected and analyzed every 6 h during germination. β‐glucosidase activity increased 3.3‐fold in radicles and 2.3‐fold in cotyledons. In the radicles, there was a significant decrease in total isoflavone content (6.3‐fold), while for malonyl forms, daidzin and glycitin, there was a decrease of 5.0‐ to 10.0‐fold. Daidzein did not vary significantly during germination, while genistein and glycitein were detected at some germination times. In the cotyledons, there was an increase in total isoflavone content (2.4‐fold), malonylgenistin (2.6‐fold) and 3.3‐fold increases for malonyldaidzin. Genistin and daidzin did not vary significantly during germination and genistein was only detected 0 and 6 h after incubation.     

Characterization of Isoflavones in Membrane-processed Soy Protein Concentrate

ABSTRACT: Aqueous soy flour solutions (5% w/w) were treated for 3 h at 45 to 50 °C with Crystalzyme®, without enzyme at 45 to 50 °C, or blanched at 80 °C. Solutions were ultra‐ and dia‐filtered to produce membrane soy concentrates (MSC). Total isoflavones of MSCs were 3.02 mg/g, 3.12 mg/g, or 3.42 mg/g, respectively, on a dry weight basis. Membrane processing contributed to approximately 18, 15, or 8% decreases, respectively, in total isoflavones of MSCs compared with soy flour (3.71mg/g). This represents at least an 82% recovery. There was no significant difference in total isoflavone content in any MSC, however the profile of isoflavones as glucosides or aglycones changed with treatment conditions.     

Evaluation of isoflavone content and antioxidant activity of soy-wheat pasta

The purposes of this work were to determine isoflavones profile and antioxidant activity of two soy flours and spaghetti produced from semolina blended with increasing amount of these flours. Defatted and toasted soy flour (DSF and TSF, respectively) showed different isoflavone profiles though glucosides were the most abundant isoflavone forms in both the meals. The pasta-making procedure determined an increase of the aglycone forms that was at least 37 and 21% in TSF and DSF pasta, respectively. Cooking operations induced severe decreases of the isoflavone content (the losses ranged from 60.44 to104.91 mg kg⁻¹ for TSF pasta and from 85.41 to 469.33 mg kg⁻¹ for DSF pasta). The results of the antioxidant activity were quite different as a function of the methods applied but they resulted generally well correlated with the isoflavone contents of the samples. Cooking induced significant decreases of the antioxidant activity in almost all samples. This result appears well correlated with the decrease of the total isoflavone content and the presence of antioxidant activity in the cooking water.     

Profiling and quantification of isoflavones in soymilk from soy protein isolate using extracted ion chromatography and positive ion fragmentation techniques

Dietary supplements on soy based foods and beverages are increasingly gaining prominence all over the world. In this study, liquid chromatography coupled with positive electrospray ionisation tandem mass spectrometry (LC-ESI-MS) and diode array detection was used for the quantitation and characterisation of isoflavones in fermented and unfermented soymilk made from soy protein isolate SUPRO 590. Bifidobacterium animalis ssp. lactis Bb12 was used for the fermentation of soymilk. The isoflavones were found to produce characteristic radical ions as well as molecules of H₂O, CO₂, a sugar unit, and an alcohol through collision-induced fragmentation. Product ion fragments revealed unique fragmentation pathways for each isoflavone compound. Characteristic fragmentation of different isoflavones were unequivocally identified and differentiated. The occurrence of aldehydes such as pentanal, ethanal and methanal was shown to be specifically linked with isoflavone aglycones, daidzein, genistein and glycitein, respectively. Main glycosides such as genistin, daidzin and glycitin as well as the acetyl-, and malonyl forms also showed respective aglycone ions in their spectra fragmentation. Thus positive ion fragmentation was important in the absolute confirmation of isoflavones and to reveal the occurrence of other related compounds such as aldehydes in soymilk.     

Effects of extraction temperature,ionic strength and contact time on efficiency of bis(2‐ethylhexyl) sodium sulfosuccinate (AOT) reverse micellar backward extraction of soy protein and isoflavones from soy flour

BACKGROUND: Soy protein enriched with isoflavones has been linked to various disease‐preventing and health‐promoting activities owing to the antihypertensive, hypocholesterolaemic, antiobesity and antioxidative properties of isoflavones. The isoflavone profiles of soy‐based products are known to be highly dependent on the various chemical and physical treatments to which the products have been subjected. The aim of this research was to increase the efficiency of backward extraction of soy protein and isoflavones from bis(2‐ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles by studying the effects of extraction temperature, ionic strength of the aqueous stripping solution and contact time on the amounts of soy protein and isoflavones backward extracted from an AOT/H₂O/isooctane reverse micellar system. RESULTS: By modifying the extraction temperature, ionic strength and contact time, 47.0–60.2% of protein, 43.3–68.4% of daidzin, 43.8–74.6% of genistin, 39.0–88.8% of glycitin, 20.8–92.6% of malonyl genistin, 20.2–52.0% of malonyl glycitin, 32.7–75.6% of acetyl genistin, 49.7–76.8% of daidzein and 19.6–38.1% of genistein present in the AOT reverse micellar solution were backward extracted into the aqueous stripping phase. Statistical analysis showed that there were significant linear and interactive effects of temperature and contact time on the backward extraction of daidzin, genistin, glycitin and daidzein. Significant linear and interactive effects of ionic strength and contact time were found in the backward extraction of daidzin and genistin. The backward extraction of genistein was only influenced by contact time and its interaction with temperature. CONCLUSION: This study showed the potential of reverse micelles as a protocol for extracting isoflavones from soy samples for analytical purposes. By modifying the extraction temperature, contact time and ionic strength, soy protein enriched with daidzin, genistin, daidzein and genistein could be produced from soy flour. The results represent an important contribution to current knowledge on utilising reverse micellar extraction in food technology. Copyright © 2007 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。     

弱碱水解丙二酰基型大豆异黄酮的研究

本实验采用碱法将丙二酰基大豆异黄酮水解为葡萄糖苷型大豆异黄酮。通过正交实验得到最佳碱水解条件为:PH=11.0,水解温度65℃,水解时间1h。水解前样品中大豆异黄酮的含量分别是:D:16.12%,G:14.49%,MD:33.62%,MG:35.77%,水解后样品中大豆异黄酮的含量分别是:D:46.86%,G:47.34%,MG:5.80%,MD:nd。     

中国大豆制品中异黄酮含量测定和分析研究

对中国几种有代表性的大豆制品进行了异黄酮含量测定。测定结果表明 :中国的大豆制品中含有一定量的异黄酮 ,其中非发酵制品中的异黄酮只有极少量以游离形式存在 ,大部分以 β 葡萄糖苷的形式存在 ,主要是黄豆苷 (daidzin)和染料木素 (genistin) ;而在发酵大豆制品中 ,由于酶的作用 ,部分黄豆苷和染料木素转化成黄豆苷原 (daidzein)和染料木因 (genis tein) ,因此 ,游离态的异黄酮比例增加。中国大豆制品中异黄酮含量随大豆品种和加工工艺而异 ,含量范围在 1 1 2 82～ 1 871 6 1 μg/ g ,这个结果表明中国的大豆制品对人体的健康具有重要作用。     

萌芽-低温打浆技术制备高苷元类异黄酮豆乳粉

在传统湿法工艺技术制备豆乳粉的基础上,以萌芽大豆为原料,对热烫后的大豆进行低温打浆处理,提高豆乳粉苷元类异黄酮含量。在单因素试验基础上,采用响应面法对萌芽-低温打浆制备高苷元型异黄酮豆乳粉工艺进行优化,确定最优萌芽-低温打浆的工艺参数为萌芽温度25?℃、萌芽时间75?h、浆液pH?6.0、打浆温度57?℃、打浆时间3.5?h,响应值苷元类异黄酮含量有最优值,为6.43?mg/g。利用高效液相色谱测定豆乳粉中异黄酮种类及含量,结果发现萌芽-低温打浆可显著提高豆乳粉中总异黄酮含量及苷元类异黄酮含量（P＜0.05）,与传统湿法工艺相比,其异黄酮总含量及苷元类异黄酮含量分别增加了1.09?倍和9.37?倍。     

Chromatographic fingerprints and quantitative analysis of isoflavones in Tofu-type soybeans

Tofu-type soybeans can differ from conventional soy varieties in seed size, seed composition, flavour and nutrition. Using HPLC coupled with ESI-MS and PDA detection, a total of 19 isoflavones were detected and identified from Tofu-type soybean seeds, more than previously reported forms from many other soybeans. An HPLC/UV fingerprint study was performed for qualitative evaluation, which enabled the isoflavone profile of Tofu-type soybeans to be characterised and differentiated from other vegetative soybeans by similarity comparison. To meet the frequent quantitative application for isoflavone contents, a simple, precise and reliable method using HCl hydrolysis during sample extraction and LC/UV for the detection was developed and validated to quantitate total isoflavones in soybeans, and then applied to determine the total isoflavone contents of different Tofu-type soy varieties grown in different field locations over two growing seasons. A range of total isoflavone contents for Tofu-type soybeans was established to confirm the use of this analytical approach for quality control applications.     

Efficacy of isoflavones in relieving vasomotor menopausal symptoms – A systematic review

This review assessed the efficacy of isoflavone supplements to reduce vasomotor symptoms in menopausal women by reviewing all published randomized controlled trials. Systematic literature searches were carried out in 70 databases. Randomized and placebo controlled studies were included if they investigated the treatment of isoflavone supplements derived from soy or red clover on vasomotor symptoms in peri‐ or postmenopausal women for at least 12 wks. Data were analyzed concerning outcome and methodological quality of the study. Twenty‐three trials met the inclusion criteria, thereof 17 investigated soy isoflavones and 6 red clover isoflavones. Without exception, selected trials examining the effect of red clover isoflavones were already assessed in several meta‐analyses and were therefore excluded from this evaluation. As the soy isoflavone studies were very heterogeneous concerning interventions and outcome measures, meta‐analysis could not be performed and trials were systematically assessed in a structured approach. Included soy isoflavone studies had numerous quality deficiencies and did not consistently show a reduction of flushes after treatment with soy isoflavones. Therefore, there is no conclusive evidence, but only some indication of a benefit of soy isoflavones on hot flush frequency or severity.