The effects of processing techniques on the distribution of isoflavones were investigated by manufacturing tempeh, soymilk, tofu, and protein isolate. The manufacturing steps causing significant losses (p < 0.05) of isoflavones were as follows:  soaking (12%) and heat processing (49%) in tempeh production; coagulation (44%) in tofu processing; and alkaline extraction (53%) in soy protein isolate production. In the production of tempeh, soymilk, and tofu, malonyldaidzin and malonylgenistin decreased after soaking and cooking. Concomitantly, acetyldaidzin and acetylgenistin were generated during heat processing. After fermentation, daidzein and genistein concentrations increased in tempeh, apparently as a result of fungal enzymatic hydrolysis. In protein isolate processing, alkaline extraction caused the generation of daidzein and genistein, probably through alkaline hydrolysis. Keywords: Isoflavones; mass balance; soy protein isolate; tempeh; soymilk; tofu

Soybean isoflavones have been proposed to be anticarcinogenic, but their effective doses have not been established. To study their bioavailability, seven women consumed 3.4, 6.9, or 10.3 mumol isoflavones/kg body wt in soymilk in each of three meals of a liquid diet on one of three feeding days that were separated by 2-wk washout periods. Subjects were randomly assigned to doses in a cross-over design. Plasma, urine and fecal isoflavones were measured by reverse phase HPLC. In two subjects, fecal isoflavone recovery was 10-20 times that in the other five subjects. Average 48-h urinary recoveries of ingested daidzein and genistein were 16 +/- 4 and 10 +/- 4%, respectively, at all three doses among the five subjects excreting only small amounts of isoflavones in feces, whereas urinary recoveries of daidzein and genistein in the two subjects who excreted large amounts of fecal isoflavones were 32 +/- 5 and 37 +/- 6%, respectively. Urinary isoflavone excretion was nearly zero in all subjects at 48 h after dosing. Average plasma concentration of genistein at 24 h after the breakfast isoflavone dose in subjects excreting large amounts of fecal isoflavones was significantly greater by 2.5-fold than in subjects who excreted small amounts of fecal isoflavones (P < 0.05). In vitro anaerobic incubation of isoflavones with human feces showed that intestinal half-life of daidzein and genistein may be as little as 7.5 and 3.3 h, respectively. These data suggest that human isoflavone bioavailability depends upon the relative ability of gut microflora to degrade these compounds.

Soybean isoflavones are proposed to be anticarcinogenic, but their effective doses have not been established. To study the bioavailability of soybean isoflavones for humans, 12 young adult women received single doses of 0.7, 1.3 and 2.0 mg isoflavones/kg body wt in soybean milk as part of a liquid diet. Plasma, urine and fecal isoflavones were measured by reverse-phase HPLC. Average 24-h urinary recoveries of daidzein and genistein were approximately 21% and 9%, respectively, at all three doses. Urinary recovery of daidzein was significantly greater than that of genistein (P < 0.001). Total fecal excretion of isoflavones was only 1-2% of the ingested amount. Plasma total isoflavone concentration was significantly increased to 4.4 +/- 2.5 mumol/L at 6.5 h after a dose of 2.0 mg/kg. The plasma concentrations of daidzein and genisten were approximately equal. Twenty-four hours after dosing, both plasma and urine isoflavone concentrations were nearly nil. Although soybean milk isoflavones seem to be 85% degraded in the intestine, the bioavailability, especially of daidzein, may be sufficient to exert some health-protective effects.

To characterize bioavailability of soybean isoflavones, proposed anticarcinogenic food components, eight women, ages 20-41 y, were fed 0.9 mg isoflavones/kg body wt from soymilk at 0730, 1230 and 1730 h for 1 d. Subjects consumed three background diets in random order: a diet prepared for them (basic foods diet) or a self-selected diet at the specified times, or a self-selected diet eaten ad libitum. In a second study, women were fed single isoflavone doses of 0.8-1.4 mg/kg in breakfast casseroles containing tofu, tempeh, cooked soybeans or texturized vegetable protein. Both studies were conducted in randomized, cross-over designs. Plasma, urine and fecal isoflavones were measured by reverse-phase HPLC. After consumption of background diets, 48-h urinary recovery of daidzein (D) was 26-27%, and of genistein (G), 18-20% of the dose given with each diet. At 24 h after consumption of different background diets, plasma D and G concentrations were similar (1.4 +/- 0.7 mmol/L) and were not affected by diet selection. Urinary recoveries of D over 24 h from the various soy foods were 38-51%, and of G, 9-16% of the dose given. In both studies, urinary recovery of D was significantly greater than that of G. Only a few percentage of the total isoflavone dose was recovered in feces, probably due to bacterial breakdown of these compounds. Therefore, isoflavone bioavailability may not be affected by choice of background diet or food source of isoflavones.

When obtained form a usual diet, a food component that sustains or enhances physiological functions and/or prevents diseases is a nutrient. Isoflavones, tocotrienols, and carotenoids are candidate nutrients which may be of health benefit to humans by inhibiting cancer development and reducing risk of atherosclerosis. The amounts of some of these candidate nutrients in food are known. A carotenoid data base has been developed. Isoflavone content of soy foods ranges from 0.1 mg/g (soymilk) to 2.5 mg/g (soy protein isolate). Human bioavailability studies have also been performed with these candidate nutrients. For example, in young adult females fed a single meal containing soy milk, isoflavones were cleared from urine within 24 h after feeding, with about 15-20% of the total dose accounted for in urine and feces. The two major soy isoflavones, genistein and daidzein, differ in bioavailability, with daidzein being more readily excreted in urine. Isoflavones, tocotrienols, and carotenoids meet several criteria for classification as nutrients. But after appropriate animal testing, food analyses, and availability studies have been performed, human health-protective efficacy must be proven in long-term feeding trials, in order for potential health-enhancing food components to be classified as nutrients.

The absorption of some dietary components may be inhibited by dietary fiber. To study the effect of dietary fiber on the bioavailability of Isoflavones, seven healthy women were randomly assigned in a crossover design to a control diet containing 15 g dietary fiber or a wheat fiber-supplemented diet containing 40 g dietary fiber, both fed with a single dose of 0.9 mg isoflavones/kg body weight from tofu or texturized vegetable protein (TVP). The fiber-rich diet produced 55% lower plasma genistein at 24 h after soy dosing (P < 0.05) and reduced total urinary genistein by 20% (P < 0.03). Urinary daidzein was not significantly related to fiber intake. Highly insoluble, dietary wheat fiber reduced the absorption of genistein probably by its bulking effect and hydrophobic binding to this compound. Urinary genistein was greater by 23% after tofu than after TVP consumption (P < 0.02), but the percentage of ingested genistein recovered in urine was not affected by soy product intake. The higher urinary genistein after tofu consumption compared with TVP was apparently due to differences in amount of genistein between these soy foods, not the different forms of genistein present in these two soy food products.

(1,3)-β-D-Glucans with (1,6)-β-D-glucosyl branches are bioactive polysaccharides in fruiting bodies and mycelia of Ganoderma lucidum, a mushroom used in traditional Chinese medicine. Submerged cultivation of mycelium is one of the more efficient means of generating polysaccharides from this fungus. Twelve mycelium samples examined in this study demonstrated the quantitative and qualitative molecular characteristics of soluble (1,3;1,6)-β-D-glucans. It was observed that the concentration of soluble (1,3;1,6)-β-D-glucan varied substantially from 1.3 to 79.9 mg/dL. (1,3;1,6)-β-D-Glucans also preserved their molecular characteristics with degrees of branching (DB) of 0.21-0.36 and molecular masses of 10(5)-10(6) g/mol for those samples with substantial quantities of β-D-glucan. Using the high aggregating tendency of these molecules, (1,3;1,6)-β-D-glucans were successfully purified via fractional precipitation with 35% (v/v) ethanol. (1,3;1,6)-β-D-Glucan was proposed as a putative bioactive marker for immunomodulation because it was the most abundant polysaccharide in G. lucidum mycelium products to stimulate macrophage RAW 264.7 cells to release TNF-α.

Fucose is one of important residues of recognition pattern for many immune cells. In this study, we characterized bioactive fucose-containing acidic polysaccharides from submerged fermentation of Agaricus blazei Murill. We obtained the polysaccharides through a cell-based activity-guided strategy, and used carbohydrate recognition monoclonal antibodies based Enzyme-Linked Immuno Sorbent Assay (ELISA) along with methylation and NMR analyses to investigate the structural characteristics of the polysaccharides. The polysaccharides had Mw of 3.5 × 10 Da. The major sugars were l-fucose, l-arabinose, d-galactose, d-xylose, and d-galacturonic acid in the molar ratio of 6.4, 15.5, 28.5, 14.7, and 25.0% with a small amount of d-glucose, d-mannose, l-rhamnose, and d-glucuronic acid. Results indicated that the bioactive polysaccharides consisted of a (1,4)-Galp and (1,4)-GalAp back bone; (1,2)-Xyl and (1,2)-Rha might also comprise backbone or constitute side chain; linkage (1,5)-Ara and terminal fucosyl residues were also involved in the polysaccharides. Regarding bioactivity, removal of the terminal l-fucosyl residues reduced the TNF-α cytokine stimulating activity of the polysaccharides in a RAW 264.7 macrophage cell-line test, whereas NF-κB and TLR4 affected the polysaccharide-induced TNF-α production.