Discovery of an S-equol rich food stinky tofu, a traditional fermented soy product in Taiwan

Characterisation of the Aroma Profile and Dynamic Changes in the Flavour of Stinky Tofu during Storage

Stinky tofu is a traditional Chinese food with wide consumption in China. Nevertheless, the dynamic changes in the flavour of stinky tofu during storage have yet to be investigated. In this study, the flavour changes of stinky tofu over six different storage periods were comprehensively analysed through sensory, electronic nose and gas chromatography-mass spectrometry (GC-MS) analyses. The results of the sensory and electronic nose analyses confirmed the changes in the flavour of stinky tofu across different storage periods. In the GC-MS analysis, 60 volatile compounds were detected during storage, and the odour activity values indicated that 29 of these 60 compounds significantly contributed to the aroma profile. During storage, the alcohol concentration of the stinky tofu gradually decreased while the acid and ester concentrations increased. According to a partial least squares analysis, 2-phenylethyl acetate, 2-phenylethyl propanoate, p-cresol, and phenylethyl alcohol, which were detected after 10 days of storage, promoting the release of an overripe apple-like odour from the stinky tofu. Findings regarding the flavour changes and characteristics of stinky tofu during different storage periods can provide a potential reference for recognising the quality of these products.

The state of plant-based food development and its prospects in the Indonesia market

Innovations in food biotechnology reflect the increasing demand for healthy food and the change in conventional dietary patterns to plant-based diets, encouraging the development of functional products and opening new perspectives for industry interests. In addition, the development of vegetable-based products is supported by several studies that state that plant-based diets help reduce the risk of diseases, reduce stress, and even help maintain healthy body weight, making this diet a promising development for the future. The industry mainly uses fermentation techniques to obtain plant-based foodstuffs. However, fermentation is just one method that can develop probiotic products. Other methods include high moisture extrusion cooking and applying shear cells, for instance, for developing vegetable meats. This article summarizes trends and shifts in eating preferences, the response of the respective industry, and the future potential of plant-based products.

Red clover-rich grassland increases equol concentration in eggs from free-range laying hens

1. The aim of this study was to evaluate the production of equol (4',7-isoflavandiol; a bacterial polyphenol metabolite which is an isoflavandiol oestrogen metabolised from daidzein from plants) enriched eggs from free-range hens fed different pasture species. Four species were tested: red clover, white clover, ryegrass and chicory.2. The study was conducted from June to September 2017 on eight free range, outdoor areas, each containing fifteen laying hens and sown with a single pasture species3. Precursors of equol (daidzein, formononetin) were analysed every fortnight from the fresh pasture cover in each area, as well as equol and daidzein levels in eggs.4. Daidzein and formononetin concentrations in the fresh pasture samples differed significantly according to species (P < 0.001), whereby red clover had the highest concentrations of daidzein and formononetin (85 and 996 µg/g DM, respectively).5. Equol concentration in eggs differed according to pasture species (P < 0.001). Equol concentrations reached about 1,200 ng/g DM in eggs from hens with access to red clover. These eggs can represent a valuable source of equol in the human diet.

A Systematic Review of the Effects of Equol (Soy Metabolite) on Breast Cancer

Equol is a soy isoflavone metabolite that can be produced by intestinal bacteria. It is lipophilic and resembles natural oestrogens with an affinity to oestrogen receptors. This review is focused on how equol affects breast cancer, as evidenced by in vivo and in vitro studies. Equol is considered chemoprotective in specific endocrine-related pathologies, such as breast cancer, prostate cancer, cardiovascular diseases, and menopausal symptoms. In humans, not everyone can produce equol from gut metabolism. It is postulated that equol producers benefit more than non-equol producers for all the endocrine-related effects. Equol exists in two enantiomers of R-equol and S-equol. Earlier studies, however, did not specify which enantiomer was being used. This review considers equol's type and concentration variations, pathways affected, and its outcome in in vivo and in vitro studies.

Lactobacillus intestinalis efficiently produces equol from daidzein and chungkookjang, short-term fermented soybeans

Equol improves menopausal symptoms and it is synthesized from daidzein, one of the isoflavonoids in soybeans, by the bacteria in the large intestines of some people. The purpose of this study was to isolate equol-producing bacteria using daidzein from the intestinal microflora and to produce equol-containing chungkookjang (short-term fermented soybean). Equol-producing bacteria from the feces of Sprague-Dawley female rats were isolated using media containing daidzein. The isolated bacteria were cultured in thioglycollate media and equol production was identified through thin-layer chromatography and ultraperformance liquid chromatography-mass spectrometry. The bacteria were identified by 16S rRNA sequencing. The rate of equol production in different concentrations of daidzein was assessed. The expression of genes that code for enzymes associated with the production of equol from daidzein was detected through reverse transcription quantitative PCR. The bacterium we isolated was Lactobacillus intestinalis (LC096206.1, 99%). L. intestinalis was found to express daidzein reductase, dihydrodaidzein reductase, and tetrahydrodaidzein reductase, the enzymes involved in producing equol from daidzein. The conversion rate of equol from daidzein was highest (29.5%) using 200 μM daidzein for 48 h of incubation. When chungkookjang fermented with Bacillus amyloquencies SRCM100001 was incubated with L. intestinalis, 0.32 ± 0.04 mg equol/g chungkookjang was produced. In conclusion, L. intestinalis efficiently produces equol from not only daidzein but also in chungkookjang.

Equol Decreases Hot Flashes in Postmenopausal Women: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Soy isoflavones may benefit some, but not all, menopausal women, and the ability of the women to produce equol may be the major determinant of effectiveness. We assessed the efficacy of soy isoflavones and equol for alleviating menopausal symptoms, especially vasomotor symptoms, in postmenopausal women who were equol producers and nonproducers by using systematic review and meta-analysis of randomized clinical trials (RCTs). We searched 12 English, Korean, and Chinese language scientific and medical databases. We selected all available RCTs that assessed the effect of equol, either equol itself or soy isoflavone in equol producers, on menopausal symptoms in peri- or postmenopausal women. The primary outcome was the effect on hot flashes. The severity of hot flashes was determined by the scores, and sensitivity and risk of bias analyses were conducted. Other outcomes of the review, but not meta-analysis, included depression and adverse events. Six studies (779 total subjects) met all criteria for the systematic review, 5 of those could be included in the meta-analysis (728 total subjects). Two studies included in the meta-analysis reported no statistically significant benefits of equol; the other three did report significant benefits of equol. Meta-analysis revealed a significant benefit of equol for lowering hot flash scores and revealed a generally low risk of bias. In conclusion, this study found that supplementing equol to equol nonproducers significantly lowered the incidence and/or severity of hot flashes in menopausal women.

GC-MS Characterization of Volatile Flavor Compounds in Stinky Tofu Brine by Optimization of Headspace Solid-Phase Microextraction Conditions

This study optimized the headspace solid phase microextraction (HS-SPME) conditions for the analysis of the volatile flavor compounds of Chinese south stinky tofu brine by gas chromatography-mass spectrometry (GC-MS). The optimum HS-SPME conditions established were as follows: polar column CD-WAX, white 85 μm polyella extractor, extraction temperature 60 °C, equilibrium time 20 min, extraction time 40 min. Under these conditions, a total of 63 volatile flavor compounds in five stinky tofu brines were identified. The offensive odor of the stinky tofu may be derived from some of the volatile flavor compounds such as phenol, p-cresol, 3-methylindole, indole, acetic acid, propionic acid, isobutyric acid, n-butyric acid and 3-methylbutanoic acid. The volatile flavor substances data was examined by principal component analysis (PCA) to visualize the response patterns in the feature space of principal components (PC). PCA analysis results revealed that the Chengshifu brine (STB1) and Baise jingdian brine (STB4) are similar in PC 1, 2, and 3, and the two brines have a similar flavor. Results also indicate that the Huogongdian brine (STB2) and Wangcheng brine (STB3) can be grouped in the same class as they are similar in PC 3. However, PC 1, 2, and 3 of the Luojia brine (STB5) and other brands of brine are different as is the flavor.

Flavonoid metabolism: the interaction of metabolites and gut microbiota

Several dietary flavonoids exhibit anti-oxidative, anti-inflammatory, and anti-osteoporotic activities relevant to prevention of chronic diseases, including lifestyle-related diseases. Dietary flavonoids (glycoside forms) are enzymatically hydrolyzed and absorbed in the intestine, and are conjugated to their glucuronide/sulfate forms by phase II enzymes in epithelial cells and the liver. The intestinal microbiota plays an important role in the metabolism of flavonoids found in foods. Some specific products of bacterial transformation, such as ring-fission products and reduced metabolites, exhibit enhanced properties. Studies on the metabolism of flavonoids by the intestinal microbiota are crucial for understanding the role of these compounds and their impact on our health. This review focused on the metabolic pathways, bioavailability, and physiological role of flavonoids, especially metabolites of quercetin and isoflavone produced by the intestinal microbiota.

Skin aging and oxidative stress: Equol's anti-aging effects via biochemical and molecular mechanisms

Oxygen in biology is essential for life. It comes at a cost during normal cellular function, where reactive oxygen species (ROS) are generated by oxidative metabolism. Human skin exposed to solar ultra-violet radiation (UVR) dramatically increases ROS production/oxidative stress. It is important to understand the characteristics of human skin and how chronological (intrinsic) aging and photo-aging (extrinsic aging) occur via the impact of ROS production by cascade signaling pathways. The goal is to oppose or neutralize ROS insults to maintain good dermal health. Botanicals, as active ingredients, represent one of the largest categories used in dermatology and cosmeceuticals to combat skin aging. An emerging botanical is equol, a polyphenolic/isoflavonoid molecule found in plants and food products and via gastrointestinal metabolism from precursor compounds. Introductory sections cover oxygen, free radicals (ROS), oxidative stress, antioxidants, human skin aging, cellular/molecular ROS events in skin, steroid enzymes/receptors/hormonal actions and genetic factors in aging skin. The main focus of this review covers the characteristics of equol (phytoestrogenic, antioxidant and enhancement of extracellular matrix properties) to reduce skin aging along with its anti-aging skin influences via reducing oxidative stress cascade events by a variety of biochemical/molecular actions and mechanisms to enhance human dermal health.

S-equol: a potential nonhormonal agent for menopause-related symptom relief

Many women suffering from vasomotor symptoms (VMS) are now seeking nonpharmaceutical treatments for symptom relief. Recently, S-equol, an intestinal bacterial metabolite of the soybean isoflavone daidzein has received attention for its ability to alleviate VMS and provide other important health benefits to menopausal women. S-equol is found in very few foods and only in traces. About 50% of Asians and 25% of non-Asians host the intestinal bacteria that convert daidzein into S-equol. Clinical trials that evaluated the efficacy of an S-equol-containing product found that VMS were alleviated but these trials were limited in scope and primarily involved Japanese women for whom hot flashes are a minor complaint. The only trial in the United States evaluating hot flashes found symptoms were significantly reduced by S-equol, but the study lacked a placebo group, although it did include a positive control. The daily dose of S-equol used in most trials was 10 mg, and because the half-life of S-equol is 7-10 hours, to maximize efficacy, it was taken twice daily. Subanalysis of epidemiologic studies suggests that equol producers are more likely to benefit from soyfood consumption than nonproducers with respect to both cardiovascular disease and osteoporosis, although the data are inconsistent. The limited safety data for S-equol do not suggest cause for concern, especially with regard to its effects on breast and endometrial tissue. Further studies are needed before definitive conclusions of its effectiveness for VMS can be made, but the preliminary evidence warrants clinicians discussing the potential of S-equol for the alleviation of VMS with patients.

The role of colonic bacteria in the metabolism of the natural isoflavone daidzin to equol

Isoflavones are found in leguminous plants, especially soybeans. They have a structural similarity to natural estrogens, which enables them to bind to estrogen receptors and elicit biological activities similar to natural estrogens. They have been suggested to be beneficial for the prevention and therapy of hormone-dependent diseases. After soy products are consumed, the bacteria of the intestinal microflora metabolize isoflavones to metabolites with altered absorption, bioavailability, and estrogenic characteristics. Variations in the effect of soy products have been correlated with the isoflavone metabolites found in plasma and urine samples of the individuals consuming soy products. The beneficial effects of the soy isoflavone daidzin, the glycoside of daidzein, have been reported in individuals producing equol, a reduction product of daidzein produced by specific colonic bacteria in individuals called equol producers. These individuals comprise 30% and 60% of populations consuming Western and soy-rich Asian diets, respectively. Since the higher percentage of equol producers in populations consuming soy-rich diets is correlated with a lower incidence of hormone-dependent diseases, considerable efforts have been made to detect the specific colonic bacteria involved in the metabolism of daidzein to the more estrogenic compound, equol, which should facilitate the investigation of the metabolic activities related to this compound.

A survey of equol contents in Chinese stinky tofu with emphasis on the effects of cooking methods

The equol contents of 32 samples of Chinese stinky tofu from different manufacturers in China mainland were determined. The results showed that 15 samples of raw stinky tofu contained substantial amounts of equol (1.16 ± 1.69 mg/100 g, wet basis), in which sample c-4 elicited the highest equol of 6.65 mg/100 g, whereas significantly lower equol contents were found in 17 fried samples (0.15 ± 0.14 mg/100 g, wet basis). A significant strong correlation between equol contents and the amino nitrogen contents (p < 0.01, Pearson correlation coefficient 0.725) was observed which indicated the eqoul content was associated with the fermentation extent. Cooking methods influenced the equol contents. Microwaving and frying tofu rapped with starch paste improved the equol contents, whereas deep frying, stir frying, and stewing had negative effects. The study demonstrated stinky tofu served as a good equol dietary source. Extensive fermentation and delicate cooking approaches were necessary for a high-equol final product.

Isolation and characterization of novel S-equol-producing bacteria from brines of stinky tofu, a traditional fermented soy food in Taiwan

Six strains capable of transforming daidzein to S-equol were isolated from the fermented brines of stinky tofu purchased in Taiwan. Daidzein was completely converted into S-equol within 24h of incubation in five strains. All the strains were gram-positive, rod-shaped, obligately anaerobic, non-motile, and non-spore-forming. In a phylogenetic analysis based on 16S rRNA gene sequences, the strains distributed into three groups in the family Coriobacteriaceae. SNR40-432 (Group I) showed 98.6% 16S rRNA gene similarity and 48-49% DNA-DNA relatedness with Paraeggerthella hongkongensis HKU10(T), suggesting the possibility that SNR40-432 represents a new species in the genus Paraeggerthella. SNR48-44 (Group II) and SNR44-10, SNR45-571, SNR46-41, SNR48-350 (Group III) showed a maximum of 92.2 and 92.1% 16S rRNA gene similarities with Eggerthella sinensis HKU14(T) and Eggerthella lenta JCM9979(T), respectively, which denotes that each group may represent a novel genus and species in the family Coriobacteriaceae. This is the first report isolating equol-producing bacteria from food.