Traditional Soy Foods Research Articles

In vitro DIAAS of Swiss soybean cultivars using the INFOGEST model: Increase in protein quality from soybean to soymilk and tofu

To support the transition towards more sustainable and healthy diets, viable alternatives to foods of animal origin need to be identified. Many plant-based protein sources are currently marketed with claims of minimal environmental impact, but very limited consideration has been given to their protein quality and bioavailable mineral content considering the fact that animal-based foods are typically the primary source of both in Western diets. In this study, traditionally consumed soy foods (cooked soybeans, soymilk, tofu) from different Swiss soybean cultivars were nutritionally characterized and the in vitro digestibility of individual amino acids and total protein were assessed using an in vitro model based on the static INFOGEST protocol; the protein quality was evaluated using the in vitro digestible indispensable amino acid score (DIAAS). The results reveal an increase in total protein in vitro digestibility across the traditional soy food production value chain: 52.1–62.7% for cooked soybeans, 84.1–90.6% for soymilk, and 94.9–98.4% for tofu. Protein quality, determined using the recommended amino acid pattern for 0.5–3 years old, was “low” (no claim) for cooked soybeans (DIAAS < 60), while soymilk (DIAAS = 78–88) and tofu products (DIAAS = 79–91) were of similar “good” protein quality, with considerably higher DIAAS values than those of cooked soybeans (P < 0.001). The iron and zinc contents in soy foods were substantial, but high molar ratios of phytic acid (PA) to iron (PA/Fe; >8) and PA to zinc (PA/Zn; >15) indicate a possible strong inhibition of iron and zinc bioavailability. Based on the DIAAS results, soymilk and tofu would be suitable plant-based alternatives to animal-based foods, while future efforts should focus on optimizing soybean preparation to overcome the negative effects of the plant tissue matrix as well as processing steps to reduce mineral absorption inhibiting substances.

Nutritional Health Perspective of Natto: A Critical Review.

Natto, a traditional soy food fermented by Bacillus subtilis, is made by steaming or cooking soaked soybean seeds, inoculating them with the bacteria, and then letting them sit for an incubation period. Natto soya has grown popular because of its nutritional importance and health advantages. As a result, farmers have more opportunities, thanks to the natto soybean market. For the natto soybean market to remain stable and grow, improved soybean cultivars with enhanced natto quality traits are essential. Natto's high-quality attributes are influenced by the bacteria strain, processing parameters, and soybean variety. Natto has a specific flavor and aroma with a slimy, sticky consistency. Natto possesses various therapeutic potentials and contains a range of essential nutrients and bioactive compounds, i.e., nattokinase, soybean isoflavone, γ-polyglutamic acid, vitamin K2, and biogenic amines. Bacterial species, processing conditions, and cultivars of soybean determine the quality characteristics of natto. Natto food is higher in menaquinone-7 and contains 100 times more menaquinone-7 than most cheeses. The present review highlights the production technology, microbiology, nutritional composition, and therapeutic potentials of natto.

Development of instant vegetarian cream soup from tempeh powder to increase antioxidant capacities

Tempeh is an Indonesian traditional soyfood made by Rhizopus spp. fermentation. Tempeh has been well known as a vegetarian-friendly food and has been processed into various derived food products. This study aimed to develop an instant vegetarian cream soup from tempeh powder. The addition of tempeh powder was expected to increase the product’s antioxidant activity without compromising its physicochemical properties as an instant product. The five different formulations of cream soups containing 0–30% tempeh powder were analysed for their physicochemical properties (dissolving time, density, viscosity, colour, pH), antioxidant capacity (total phenolic content, total flavonoid content, DPPH radical scavenging activity, reducing power, and ferrous ion chelating ability), and hedonic test. Soup cream made with more tempeh power had a higher dissolving time, but lower viscosity, lightness value, and pH value. However, their antioxidant activities also increased with the increase of tempeh powder added. From the hedonic analysis, the formulation with 15% tempeh powder showed the highest hedonic rate and therefore, was chosen as the best formulation. In conclusion, the addition of tempeh powder did not only give a better consumer acceptance but also higher antioxidant activities.

Extending the cDNA microarray detection system to evaluate genetically modified soybean and traditional soy foods

Aggravating controversies of GM (genetically modified) foods on the social, ethical and health aspects have lead to efficient and reliable detection systems to safeguard homogeneity of foods and address legal disputes. Improvising on the existing detection systems, the present investigation demonstrates the advantages of using cDNA microarray as a detection system for GM food. We have extended the study for the detection of genetic modification in commercial GM soybean seeds and in home-made traditional foods derived from these seeds, such as tofu and dried tofu. We looked for common T-DNA regions such as CaMV35S promoter, NOS or 35S terminators, nptII, hph or pat selection marker genes, GUS or GFP marker genes. We also searched for specific traits such as Bt11, T25, CP4EPSPS and four plant internal control genes (invertase, legumin, tubulin, actin gene). Results indicate that our microarray detection system can identify GM soybean seeds as well as processed food made from these seeds, with 100% accuracy. Transformation events identified in the GM soybean seeds were also visible in the processed foods, thereby confirming the accuracy and reproducibility of this procedure to even processed foods. We believe that with more popularity if the cDNA microarray detection system will soon be implemented as a diagnostic kit.

Improvement of soybean cultivars for natto production through the selection of seed morphological and physiological characteristics and seed compositions: A review

AbstractNatto, a traditional soyfood fermented by Bacillus subtilis (natto), is prepared by steaming/cooking of soaked soybean seeds followed by inoculation with the bacteria and incubation. Natto soybean has increased in popularity due to its nutritional value and health benefits. Thus, the natto soybean market provides additional opportunities for farmers. The development of soybean cultivars with improved natto quality characteristics is crucial for maintaining and increasing the natto soybean market. Good‐quality characteristics of natto are determined by soybean cultivar, processing conditions and bacteria strain. Natto quality evaluation generally determined by sensory panels is time consuming. Therefore, indirect selection for natto quality based on seed traits is preferred. Seed morphological and physiological characteristics and seed compositions play an important role in producing natto of good quality. In this review, we have summarized natto processing conditions, natto quality characteristics, seed traits involved in natto quality and their genetic variation, as well as the genetic diversity in food‐grade soybean germplasms and B. subtilis strains. Information presented will be helpful for natto soybean cultivar development and natto manufacture.

A short review of health benefits and nutritional values of mung bean in sustainable agriculture

Mung beans, also known as Lu Dou, are one of the traditional soy foods consumed mainly in East Asia, especially by Chinese and Japanese. It has been used both as nutritional food and herbal medicine. Mung is a valuable plant for sustainable agriculture due to its ability to use atmospheric nitrogen. Because of energy crises and high mineral fertilizer prices cultivation of legumes become one of the most promising strategies for sustainable agriculture. The factors determining the efficiency of symbiotic process are the genetic constitution of the host plant and bacteria, environment, and technological inputs (inoculums, fertilizers and pesticides). Inoculation of mung bean with Bradyrhizobium enhanced nodulation, and results in increasing of shoot biomass and grain yield. The legume residues are also a good source of mineral nitrogen for the succeeding crops. Mungbean is rich in easily digestible protein, it also contains vitamin A, B1, B2, C, niacin, folate, iron, calcium, and zinc. Nutrition therapy on the basis of traditional Chinese medicine (TCM) is quite effective at treating common diseases. The most important health benefits of mung beans are anti-oxidant effects, antifungal and antimicrobial activity, anti-inflammatory activity, activity against diabetes, hypertension and cancer. Mung bean clears heat, detoxifies, reduces swelling, promotes urination, quenches thirst, aids edema in the lower limbs. It is recommended for conjunctivitis, diabetes, dysentery, summer heat, heatstroke, dehydration, edema and food poisoning.

Evaluation of Natto Soybean for Agronomic and Seed Quality Traits

Natto is a traditional Japanese soyfood, but little information is available on how agronomic and seed physical quality traits affect natto quality. The objective of this study was to evaluate agronomic and seed physical quality traits of natto varieties of soybean [Glycine max (L.) Merr.], including genotype and environmental effects, as well the heritability and correlations among those traits. During two years, 15 natto genotypes were grown, with three replications, in three Arkansas locations (Keiser, Rohwer, and Stuttgart) and were analyzed for agronomic and seed physical quality traits. Genotype affected all of the traits except for yield. Superior natto varieties (ARK1, ARK2, and ARK3) matured later and produced smaller and softer seeds than the other natto varieties. All of the traits had high heritability (>0.60). Varieties with larger seeds had significantly higher yield than varieties with smaller seeds. Because small-seeded varieties with quality attributes are desirable for natto production, breeding for small-seeded, high-yielding genotypes will continue to be a challenge.

Fibrinolytic Activities of Bacillus Species Isolated from Traditional Fermented Soyfoods

Fibrinolytic Activities of Bacillus Species Isolated from Traditional Fermented Soyfoods

Regulation of the immune response by soybean isoflavones

Soybeans are rich in immuno-modulatory isoflavones such as genistein, daidzein, and glycitein. These isoflavones are well-known antioxidants, chemopreventive and anti-inflammatory agents. Several epidemiological studies suggest that consumption of traditional soy food containing isoflavones is associated with reduced prevalence of chronic health disorders. Isoflavones are considered to be phytoestrogens because of their ability to bind to estrogen receptors. The literature is extensive on the chemistry, bio-availability, and bio-activity of isoflavones. However, their effects on immune response are yet to be fully understood, but are beginning to be appreciated. We review the role of isoflavones in regulation of the immune response and their potential clinical applications in immune-dysfunction. Special emphasis will be made regarding in vivo studies including humans and animal model systems.

Changes of isoflavone profiles in Cheonggukjang with Lentinus edodes

Cheonggukjang, a traditional soy food, was prepared with addition of Lentinus edodes powder at 0, 5, and 10% (w/w), and the distribution of isoflavones were analyzed by high performance liquid chromatography during fermentation for 48 h. β-Glucosidase activity and changes in succinyl genistin and succinyl daidzin were monitored. β-Glucosidase activity in cheonggukjang with 5 and 10% (w/w) L. edodes powder were significantly higher than those in control samples (p <0.05). Total isoflavones in 48-h fermented cheonggukjang with 0, 5, and 10% (w/w) L. edodes powder were 4.88, 4.26, and 3.99 μmole/g, respectively. Aglycones of isoflavones in cheonggukjang with 5 and 10% (w/w) L. edodes powder were 27.61 and 24.76% for 24 h and 28.2 and 38.74% for 48 h, whereas those in control samples were 5.50 and 21.11% for 24 and 48 h, respectively. Succinyl daidzin and succinyl genistin in L. edodes powder-added cheonggukjang were significantly lower than those of control samples (p <0.05), implying that β-glucosidase activity from L. edodes negatively affected the formation of succinyl derivatives.

Nutritional Aspects of Second Generation Soy Foods

Samples of 15 second generation soy-based products (n = 3), commercially available, were analyzed for their protein and isoflavone contents and in vitro antioxidant activity, by means of the Folin-Ciocalteu reducing ability, DPPH radical scavenging capacity, and oxygen radical absorbance capacity. Isoflavone identification and quantification were performed by high-performance liquid chromatography. Products containing soy and/or soy-based ingredients represent important sources of protein in addition to the low fat amounts. However, a large variation in isoflavone content and in vitro antioxidant capacity was observed. The isoflavone content varied from 2.4 to 18.1 mg/100 g (FW), and soy kibe and soy sausage presented the highest amounts. Chocolate had the highest antioxidant capacity, but this fact was probably associated with the addition of cocoa liquor, a well-known source of polyphenolics. This study showed that the soy-based foods do not present a significant content of isoflavones when compared with the grain, and their in vitro antioxidant capacity is not related with these compounds but rather to the presence of other phenolics and synthetic antioxidants, such as sodium erythorbate. However, they may represent alternative sources and provide soy protein, isoflavones, and vegetable fat for those who are not ready to eat traditional soy foods.

Whole Versus the Piecemeal Approach to Evaluating Soy

Soy has been singled out for attention among other legumes as a valuable source of nutrients, phytochemicals, and bioactive compounds. Early epidemiological studies established that whole soy and traditional soy foods were implicated in health-protective effects in Asian populations. The same benefits attributable to soy have not been consistently proven in Western populations that, for various reasons, opt to consume more processed soy foods or various soy components. Soy researchers continue to isolate soy components in search of identifying its salubrious components and whole soy remains relatively underinvestigated despite what we know of the health benefits it may confer to those regularly consuming it. Various dietary guidelines advocate the regular consumption of legumes that tend not to be included in our diets in sufficient quantities. This paper highlights the possibility that whole soy may have a more unique effect on health than a select soy component(s). It explores the rationale for focusing research on whole soy in an attempt to understand it better rather than trying to replicate the health benefits by targeting various soy components, which has been plagued by inconsistent results.

Insights Gained from 20 Years of Soy Research ,

Soyfoods have long been recognized for their high-protein and low-saturated fat content, but over the past 20 y an impressive amount of soy-related research has evaluated the role of these foods in reducing chronic disease risk. Much of this research has been undertaken because the soybean is essentially a unique dietary source of isoflavones, a group of chemicals classified as phytoestrogens. The estrogen-like properties of isoflavones have also raised concern, however, that soyfoods might exert adverse effects in some individuals. There is intriguing animal and epidemiologic evidence indicating that modest amounts of soy consumed during childhood and/or adolescence reduces breast cancer risk. Evidence also suggests that soy reduces prostate cancer risk and inhibits prostate tumor metastasis, but additional clinical support for the chemopreventive effects of soyfoods is needed. Soy protein is modestly hypocholesterolemic and there is suggestive epidemiologic evidence that soyfoods lower risk of coronary heart disease (CHD) independent of effects on cholesterol. In clinical studies, soy favorably affects multiple CHD risk factors; however, with the exception of improved endothelial function, the data are too limited and/or inconsistent to allow definitive conclusions to be made. In regard to bone health, although recent clinical data have not supported the skeletal benefits of isoflavones, 2 large prospective epidemiologic studies found soy intake is associated with marked reductions in fracture risk. Soybean isoflavones also modestly alleviate hot flashes in menopausal women. Finally, other than allergic reactions, there is almost no credible evidence to suggest traditional soyfoods exert clinically relevant adverse effects in healthy individuals when consumed in amounts consistent with Asian intake.

Investigating the Optimal Soy Protein and Isoflavone Intakes for Women: A Perspective

Traditional soyfoods have been consumed for centuries throughout much of East Asia and, recently, these foods have also become popular in the West. Soyfoods and specific soybean components, such as the protein and isoflavones, have attracted attention for their possible health benefits. Isoflavones are classified as phytoestrogens and have been postulated to be natural alternatives to hormone therapy for menopausal women. To provide guidance on optimal soy intake, this article evaluates Asian soy consumption and both clinical and Asian epidemiologic studies that examined the relationship between soy intake and a variety of health outcomes. On the basis of these data and the standard principles of dietary practice the author suggests that optimal soy protein and isoflavone intakes are 15-20 g/day and 50-90 mg/day, respectively. In addition, an intake of 25 g/day soy protein can be specifically used as the recommendation for cholesterol reduction.

Validation of a Soy Questionnaire with Repeated Dietary Recalls and Urinary Isoflavone Assessments Over One Year

This study assessed the validity and reliability of a 12-item soy questionnaire designed for use in cancer prevention research. The questionnaire measures soy intake over the past year. Subjects were 199 healthy 35- to 46-yr-old premenopausal women participating in an ongoing soy intervention study. Soy questionnaire estimates of isoflavone intake over 1 yr were compared with individual and combined estimates from two reference measures covering the same period: three or four repeated 24-h recalls and one or two repeated urine analyses. The sensitivity and specificity of the soy questionnaire in classifying high vs. low exposure (high exposure = soy intervention group membership) were comparable with 24-h recalls and were superior to urine analyses (sensitivity = 94.8%, 97.9%, and 71.1%; specificity = 95.1%, 97.1%, and 90.3% for the soy questionnaire, 24-h recalls, and urine analyses, respectively). Soy questionnaire isoflavone estimates were highly correlated with the combination of the two reference measures for the entire study population. Its brevity, ease of administration, and good measurement properties over a 1-yr period make the soy questionnaire well suited to the needs of researchers who wish to identify high and low consumers of soy foods, especially in populations who consume traditional Asian soy foods.

Phytoestrogen Supplement Use by Women

Phytoestrogens are weak estrogens found concentrated in soybeans. Americans consume phytoestrogens primarily in traditional soy foods, soymilk and isolated soy protein added during food processing or consumed as a beverage. Extracted phytoestrogens are also marketed in numerous forms as dietary supplements regulated under the Dietary Supplement Health and Education Act. Consumers of phytoestrogen supplements tend to be peri- and postmenopausal women looking for an alternative to hormone therapy. Although there are no approved health claims for phytoestrogens at this time, numerous claims are being made regarding benefits to heart, bone, breast and general menopausal health. The data supporting these claims are generally not strong. The strongest data show that phytoestrogens reduce the number and intensity of hot flashes, although the reduction is a modest 10-20%. The studies showing cholesterol lowering have used soy protein rather than phytoestrogen extracts. The soy protein appears to be required for this effect, although phytoestrogen extracts may have other beneficial effects on the cardiovascular system. The data on bone metabolism are suggestive of possible benefits whereas the effects on the breast are the most poorly understood. Although most animal studies have shown cancer-preventive effects, a few recent studies suggest that soy phytoestrogens may stimulate breast cancer cell growth under certain circumstances. Before recommendations regarding phytoestrogen supplements can be safely made, we must have more information on the effects of the extracts on bone, heart and breast health. Until safety with respect to breast cancer is established, phytoestrogen supplements should not be recommended, particularly for women at high risk of breast cancer.

Phytoestrogen and breast cancer prevention

The incidence rate of breast cancer varies worldwide, with the rate of Japanese and other Asian women only being a third to a half of that for Caucasian women. Recent research has suggested that consumption of phytoestrogen-rich foods may reduce breast-cancer risk. Most epidemiologic studies have involved Asian populations and some studies have shown a substantial reduction in breast-cancer risk (17-73%) in these populations. These results were also observed in countries where the level of consumption of traditional soy foods is low.

Phytoestrogen consumption and breast cancer risk in a multiethnic population: the Bay Area Breast Cancer Study.

Research on the relation between phytoestrogens and breast cancer risk has been limited in scope. Most epidemiologic studies have involved Asian women and have examined the effects of traditional soy foods (e.g., tofu), soy protein, or urinary excretion of phytoestrogens. The present study extends this research by examining the effects of a spectrum of phytoestrogenic compounds on breast cancer risk in non-Asian US women. African-American, Latina, and White women aged 35-79 years, who were diagnosed with breast cancer between 1995 and 1998, were compared with women selected from the general population via random digit dialing. Interviews were conducted with 1,326 cases and 1,657 controls. Usual intake of specific phytoestrogenic compounds was assessed via a food frequency questionnaire and a newly developed nutrient database. Phytoestrogen intake was not associated with breast cancer risk (odds ratio = 1.0, 95% confidence interval: 0.80, 1.3 for the highest vs. lowest quartile). Results were similar for pre- and postmenopausal women, for women in each ethnic group, and for all seven phytoestrogenic compounds studied. Phytoestrogens appear to have little effect on breast cancer risk at the levels commonly consumed by non-Asian US women: an average intake equivalent to less than one serving of tofu per week.

Estimated dietary isoflavone intake of Korean population based on National Nutrition Survey

The dietary isoflavone intake of the Korean population was estimated based on data from the Korean National Nutrition Survey conducted in 1995, which included 3224 male and 3475 female subjects with a wide age range. Data on the isoflavone content of soybeans and their products were collected from a literature survey of Korean journals. This information was then screened based on the methodological validity, compared with values reported in international journals, and an average value adopted for each food. Thereafter, the total isoflavone intake per capita was estimated as 14.88 mg/d, which was attributed to genistein (7.32 mg), daidzein (5.81 mg), and glycitein (1.75 mg). Soybeans and three traditional soy foods (tofu, soybean paste, soybean sprouts) contributed to more than 94% of the total isoflavone intake of the Korean population. Slight differences in the isoflavone intake level and pattern were observed between the various residential areas. The rural and urban isoflavone intakes were estimated at 15.18 and 14.85 mg per capita, respectively. Rural residents were more dependent on soybeans than processed soy products for their isoflavone intake, while urban residents extracted more isoflavones from tofu, compared to their rural counterparts. The total isoflavone intake reported in this study may be underestimated, as other products containing soyflour and soy protein were not accounted for.

Effects of soy foods on ovarian function in premenopausal women.

It has been proposed that the high intake of soy foods among Asians may partly explain their lower rates of breast cancer, perhaps by lowering endogenous oestrogen levels, although this has been inadequately studied. Twenty healthy cycling premenopausal women (ten Asians and ten non-Asians) participated in a 7-month soy intervention study which was designed to investigate the effect of supplementation on ovarian function. Asian soy foods (tofu, soymilk, green soybean peas) in the amount of approximately 32 mg of isoflavones per day were added to the women's diets for three menstrual cycles. The women's baseline (two cycles) serum hormone levels were compared to levels during soy intervention (three cycles) and levels after intervention (two cycles). During the entire study period, subjects provided almost daily overnight urine samples and blood specimens during specified days of their menstrual cycles. The day of urinary luteinizing hormone (LH) peak was used as a marker for the day of ovulation. Knowledge of day of ovulation allowed comparison of hormone measurements at baseline to those obtained during intervention and recovery cycles with standardization of day of cycle. Soy intervention was associated with a statistically significant reduction in serum luteal oestradiol level (–9.3%, P< 0.05), but there were no significant changes in follicular phase oestradiol, follicular or luteal phase progesterone, sex hormone-binding globulin or menstrual cycle length. This significant reduction in luteal phase oestradiol was, however, observed only among Asian (–17.4%) but not among non-Asian (–1.2%) participants; urinary excretion of isoflavones was higher among Asians than non-Asians (29.2 vs 17.1 μmol day−1, P = 0.16) during the intervention period. Thus, supplementation using traditional soy foods reduced serum oestradiol levels among Asian participants in this study. Differences in the type of soy products (i.e. traditional soy foods versus soy protein products), amount of isoflavones, and race/ethnicity of participants may have contributed to the divergent results. Larger soy intervention studies designed specifically to include participants of different race/ethnicities and using both traditional soy foods and soy protein products providing comparable doses of isoflavones are needed to definitively determine the effect of soy on ovarian function. © 2000 Cancer Research Campaign