Fisheries Science 62(3), 454-461 (1996)

Dietary Fiber Content, Water-holding Capacity and Binding Capacity of Seaweeds

Takeshi Suzuki, Yasufumi Ohsugi, Yumiko Yoshie, Takaaki Shirai, and Toshiyuki Hirano

Department of Food Science and Technology, Tokyo University of Fisheries, Konan, Minato, Tokyo 108, Japan (Received September 20, 1995)

Dietary fiber content, water-holding capacity, and binding of artificial colors, vitamin, and cholate were studied for 12 species of green, brown, and red algae. Hijiki contained higher soluble dietary fiber and some specimens of wakame had the highest amount of insoluble dietary fiber. High water-holding capacity of wakame seemed to be characteristic, ranging from 19 to 44 g/g dry seaweed. When samples were immersed in acid water to simulate the gastric pH condition, almost all water-holding capacity of seaweeds decreased. Settling volume in water was similar to water-holding capacity, and wakame had the higher values. Susabi-nori, suji-aonori, and some specimens of wakame showed a higher capacity to bind amaranth than other seaweeds. Erythrosine and rose Bengal bound by many seaweeds were higher than amaranth. Wakame sporophyll and hijiki showed the highest percent binding (42.7-45.6%) for thiamin, but Mitsuishi-kombu and susabi-nori showed the lowest binding (8.3-10.6%). Binding of sodi um cholate by susabi-nori was the highest (12.6-15.5%); over twice that bound by another seaweeds ex cept suji-aonori (9.7%). However Mitsuishi-kombu, ma-kombu and one hijiki had a lower binding capacity (0-2.6%).

Key words: dietary fiber, seaweeds, water-holding capacity, sodium cholate, thiamin, amaranth, erythrosine, rose Bengal

Dietary fiber is thought to be an important food compo nent resistant to hydrolysis by the enzymes of the human Materials and Methods digestive tract1) From a nutritional viewpoint, dietary fiber's resistance to digestion provides bulk to feces, holds Materials water, acts as a site for ion exchange, and binds organic Twelve specimens of seaweeds were purchased in a local molecules.2) Dietary fiber contents in seaweeds were sum super market in Tokyo. Green alga: dried suji-aonori marized in the standard tables of food composition in (green laver) Enteromorpha prolifera grown in Kochi; Japan,) but only total dietary fiber contents are listed in brown algae: dried ma-kombu (Japanese sea tangle, kelp) those tables. Both soluble and insoluble dietary fibers were Laminaria japonica grown in Hokkaido, dried Mitsuishi known to have different physiological responses, and the kombu (kelp) Laminaria angustata grown in Hokkaido, type of dietary fibers consumed seemed to have an impact steamed and dried hijiki Hizikia fusiformis grown in on the physiological responses for human.4) In our previ Chiba (hijiki (C)) and Mie (hijiki (M)), dried (with ash) ous paper,5) we reported the effect of sodium alginates, wakame Undaria pinnatifida grown in Tokushima which is the main component of brown algae, on (wakame (T)), boiled and salted wakame grown in Iwate cholesterol levels and digestive organs of high-cholesterol (wakame (I)), Aichi (wakame (A)), and Ehime (wakame fed rats, and these physiological effects were thought to be (E)), and wakame sporophyll grown in Miyagi; and red related the physicochemical properties of dietary fiber like alga: minced and dried susabi-nori (purple laver) Por water-holding capacity.2) The ability to increase fecal bile phyra yezoensis grown in Chiba (susabi-nori (C)) and acid excretion has been correlated to the plasma Hyogo (susabi-nori (H)). Salted specimens, wakame, were cholesterol-lowering effect of certain dietary fibers.1) Dieta washed by water and wakame and wakame sporophyll ry fiber is known to induce a number of physiological were freeze-dried. Dried samples were pulverized by a grin effects, depending upon the physical and chemical proper der (SK-M1OR, Kyoritsu Riko Co., Tokyo) and passed ties of the individual fiber sources.1) Adsorption of nutri through a 30-mesh screen. tionally important substances such as minerals and vita mins was thought to have adverse effects of dietary fiber. Dietary Fiber This research reports the content of soluble and insoluble Soluble and insoluble dietary fibers were determined ac dietary fibers and the water-holding capacity in seaweeds. cording to an enzymatic-gravimetric method,) which has Also we report the physiological characteristics of dietary been approved as the legal or recommended procedure for fibers, such as in vitro binding of artificial colors, vitamin, food analysis. However this method was modified here by and bile acid with seaweeds. using pancreatin,7,8) because almost all seaweeds contain lit- Properties of Dietary Fiber in Seaweeds 455

tie protein and no starch. The procedure consists of follow 200 mg of samples in centrifuge tubes, 20 ml of 1 mmol/1 ing steps: (1) Boiling 0.5 g of sample powder with 30 ml of thiamin hydrochloride in 1 / 15 mol/ 1 phosphate buffer so water for 5 min. (2) Incubation with 20 ml of 2% pancrea lution at pH 6.0 was added, and the tubes were incubated tin and 30 ml of phosphate buffer at pH 6.8 in the presence at 37?C for 1 h with shaking. After centrifuging at of NaCl (10 mmol/ 1) for 24 hat 40?C. (3) Water insoluble 9,000 x g for 10 min, the concentration of thiamin in super dietary fiber was filtered off by a glass fiber filter (GA-100, natant was measured colorimetrically at 267 nm, Final Advantec Toyo Inc., Tokyo), washed twice with 20 ml of pHs of sample solution were pH 6.0•}0.1. 95% ethanol and 10 ml of acetone, and dried at 105?C. (4) Water soluble dietary fiber was precipitated from the Binding of Bile Salt filtrate using 4 volumes of ethanol and recovered by filtra Binding of sodium cholate to seaweeds was carried out tion in the same way as for insoluble fiber. (5) All samples according to the method of Calvert and Yeates.14) To 200 analyzed were assayed in duplicate and one of the dupli mg of samples in centrifuge tubes, 20 ml of 2.5 mmol/I so cates was used to determine protein content by Kjeldahl dium cholate in 1 / 15 mol/ l phosphate buffer solution at method, while the other was used to determine ash content pH 8.0 was added, and the tubes were incubated at 37?C in the fiber precipitate. (6) The final corrected values for for 2 h with shaking. After centrifuging at 9,000 x g for 10 dietary fiber were calculated by subtracting the weights of min, the concentration of cholate in supernatant was meas ash and protein from the dietary fiber precipitate. ured by enzymatic colorimetry using a bile acid test Wako kit (TBA 431-15001, Wako Pure Chemical Industries, Ltd. Water-holding Capacity Tokyo). Final pHs of sample solution were pH 7.7•}0.1. Water-holding capacity of seaweeds was measured by the modified centrifugation method of McConnell et al.9) Results and Discussion To 200 mg of samples in centrifuge tubes, 20 ml of water were added and the tubes were shaken in a shaking culture Dietary Fiber bath for 24 h at 37?C. After centrifuging at 14,000 x g for The soluble, insoluble, and total dietary fiber contents 10 min, the supernatant was discarded and the weight of of six green, brown, and red algae are shown in Table 1. residue was measured. Final pHs of sample solution Results are expressed as g of fibers per 100 g of dry weight soaked in water were 6.4•}0.6. On the other hand, samples of seaweeds. The soluble dietary fiber levels in hijiki were were immersed in water adjusted to pH 2 by hydrochloric higher than other seaweeds, and they ranged from 22.1 to acid for 30 min to simulate the gastric pH condition. Final 25.6 g. Mitsuishi-kombu, susabi-nori (H), and wakame pHs of sample solution were pH 1.9•}0.2. (A) were found to contain relatively small amounts of solu ble fiber (7.2-7.9 g). On the other hand, wakame (I) and Settling Volume wakame (A) contained the highest amount of the insoluble Settling volume of seaweeds in water was analyzed using dietary fiber (58 g). Susabi-nori (C), suji-aonori, ma the method based on Middleton and Byers.10)To 200 mg kombu, and Mitsuishi-kombu showed a relatively low con of samples in cylinders, 20 ml of water were added, and centration of insoluble fiber (15.6-28.0 g). Therefore, the the sample and water were vigorously stirred. The cylin total dietary fiber levels in the seaweeds ranged from 26.4 ders were left to stand for 24 h at 37?C, and settling to 69.6 g, and hijiki and wakame (except wakame (E)) volume was measured. When air bubbles appeared, the retained high concentration of fibers (more than 60 g). As cylinder was placed in a vacuum desiccator and evacuated for the percent soluble dietary fiber against total dietary for 30 min. On the other hand, samples were immersed in fiber, susabi-nori (C) was the highest (40.9%), and hijiki acid water mentioned above for 30 min to simulate the gas tric pH condition. Final pHs of sample solution were analogous to the case of water-holding capacity. Table 1. Dietary fiber contents of seaweeds (g/ 100 g dry weight) Bindinz of Artificial Colors Binding of artificial food red colors to seaweeds was car ried out according to the method of Takeda and Kiriya ma.11) To 200 mg of samples in centrifuge tubes, 20 m/ of 50

ƒÊ g/I(ppm) amaranth (red No. 2), erythrosine (red No. 3), or rose Bengal (red No. 105) in 1 / 15 mol / 1 phosphate buffer solution at pH 6.0 were added, and the tubes were incubated at 37?C for 24 h with shaking. After centrifug ing at 9,000 x g for 10 min, the concentrations of amaranth, erythrosine, and rose Bengal in supernatant were measured colorimetrically at 522, 526, and 548 nm, re spectively. Final pHs of sample solution were pH 6.0•}0.1.

Binding of Vitamin Binding of thiamin (vitamin B1) to seaweeds was carried out according to the method of Omaye et al.12) This was a modified method to measure the binding of bile salts.13) To 456 Suzuki et al.

and suji-aonori followed. High water-holding capacity of wakame seemed to be Ikegami et al.15) and Sumimoto et al.16) determined the characteristic, ranging from 19 to 44 g/g dry seaweed, and total dietary fiber in various foods including seaweeds by especially wakame (I) (38.6 g) and wakame (A) (44.4 g) the enzymatic-gravimetric method, and the latter data showed the maximum capacity (Fig. 1). When samples were referred to the standard tables of food composition were immersed in acid water to simulate the gastric pH con in Japan.3) The results of seaweed dietary fibers (Table 1) dition, water-holding capacity of seaweeds decreased ex were nearly the same except wakame in which our data cept suji-aonori and susabi-nori (H). In the case of were higher than the others. Also Mori et al.17) reported wakame (A), water-holding capacity was drastically total dietary fiber contents in seven species of seaweeds by decreased to nearly 20% (Fig. 1). some other analytical methods; however, Mori18) stated As shown in Fig. 2, settling volume in water is similar to neutral detergent fiber method was not adequate for dieta water-holding capacity, and wakame (I) and wakame (A) ry fiber determination of seaweeds, because seaweeds con had the highest values (100 ml/g dry seaweed), followed tained indigestible polysaccharides which are soluble in by wakame (E) (52 ml) and wakame (T) (45 ml), just like neutral detergent. water-holding capacity. A relationship between water There is very little information available on the distribu holding capacity and settling volume was very high tion of soluble and insoluble dietary fibers in seaweeds. As fr=0.961. for susabi-nori, we reported the contents of both soluble Takeda and Kiriyama11) studied physical properties of and insoluble dietary fibers in dried nori which was culti dietary fiber prepared from roots of edible burdock, and vated in eight main prefectures such as Chiba and Hyogo, they stated there was a close parallel (r=0.96) between harvested in January and March, and classified by prices at water-holding capacity and settling volume in water of auction,19) and also in dried nori of several culture places several fractions prepared from the samples. The terms in Korea.20) There were many differences in soluble and in water holding capacity, water binding capacity, and water soluble dietary fiber contents among the samples cultivat hydration capacity, have been used interchangeably in the ed in Japan, ranging from 3.1 to 32.4 g/ 100 g and from literature to refer to the ability of dietary fiber to hold 14.6 to 38.9 g/ 100 g, respectively. For hijiki, seasonal vari water under specific conditions.2) The major factors affect ation in the soluble and insoluble dietary fibers was found, ing water holding capacity were particle size, pH, and ion and the molecular weight of major components in soluble ic strength.2) Parrott and Thrall22) reported that Avicel and fiber gradually increased.21 Both soluble and insoluble die Alphacel samples showed a maximum water-holding tary fibers were known to have different physiological capacity at pH 7.33 with a two-fold reduction in an acidic responses, and the type of dietary fibers consumed seemed condition of pH 2.69, peanut hull fibers had a high water to have an impact on the physiological responses for hu holding capacity in an acid medium and a decline in the man.4) Therefore it is necessary to determine the contents capacity with increasing pH values, and the brans showed of both soluble and insoluble dietary fibers. no significant difference in the capacity due to pH. In our experiment, wakame (A) showed the significant difference Water-holding Capacity and Settling Volume in water-holding capacity, and the capacity at pH 6.4 was Water-holding capacity and settling volume in water are five times as much as that at pH 1.9; however, no marked shown in Figs. I and 2, respectively. difference was found in susabi-nori (C) (Fig. 1). These

Fig. 1. Water-holding capacity of seaweeds. Properties of Dietary Fiber in Seaweeds 457

Fig. 2. Settling volume of seaweeds.

results indicate the water-holding capacity was closely not such a significant correlation between water-holding related to the components of dietary fibers. capacity and uronic acid contents. Therefore further McConnell et al.9) investigated the water-holding capaci research is needed to understand the characteristics of sea ty of fruit and vegetables which were dried to a powder weed dietary fibers. (acetone-extracted residues), and reported that lettuce, car rot, cucumber, celery, and aubergine had the greatest Binding of Artificial Color water-holding capacity, ranging from 17.3 to 23.7 g Percentages of amaranth, erythrosine, and rose Bengal water/g acetone dried powder, whereas maize, oatmeal, bound to seaweeds are shown in Figs. 3, 4, and 5, respec potato, banana, and wheat bran had the least, ranging tively. Susabi-nori, suji-aonori, wakame (A), and wakame from 1.5 to 2.9. Selvendran et al.23) classified these (I) showed a higher capacity to bind amaranth (19.3 products in (1) organs poor in intracellular starch like 25.8%) than other 7 specimens of seaweeds (7.1-12.2%) vegetables from lettuce to aubergine, (2) organs rich in (Fig. 3). The lowest amount of erythrosine was bound by starch like potato and banana, and (3) wheat bran, which hijiki (M) (22.9%), and the percentage increased in the ord contains relatively little starch compared to maize and oat er, hijiki (C) (37.4%), Mitsuishi-kombu (44.4%), and ma meal. They stated that water-holding capacity of the ace kombu (52.1%) (Fig. 4). The erythrosine bound by the tone dried powder was very much influenced by the remaining seaweeds was high (67.1-93.8 %) (Fig. 4). In the presence of contaminating starch, and organs which were case of rose Bengal, hijiki (M) bound less color (53.8%) relatively free of starch and had similar amount of fibers than another substances, followed by Mitsuishi-kombu, had comparable water-holding capacity. In the case of sea susabi-nori (H), and hijiki (C) (73.5-75.1%), and all of weeds, starch is not such an important component. other seaweeds showed the higher binding capacity (more Stephan and Cummings24) studied water-holding proper than 80 %) (Fig. 5). From these results, greater binding of ties of 17 dietary fiber preparations, mainly food materials artificial colors was seen in wakame (A) and wakame (I), and gel-forming polysaccharides using a centrifugation and suji-aonori, and relatively less binding was observed technique and a dialysis bag method, and they found no in hijiki and Mitsuishi-kombu. value could be obtained by centrifugation for most of the Adsorption of amaranth to seaweeds was lower in com gel-forming polysaccharides because they did not cen parison with another artificial colors. Amaranth belongs trifuge down. Of there materials pectin, sodium carbox to the azo compounds, and erythrosine and rose Bengal be ymethyl cellulose, and A carrageenan had the greatest long to the xanthene compounds which were less water-holding capacity, ranging from 41.3 to 56.2 g hydrophilic than the azo compounds. These difference water/g dry material, but bran, bagasse, and potato pulp may be caused by the chemical character of each color. had the lowest water-holding, ranging from 4.2 to 7.0 g A large amount of amaranth is known to retard the water/g dry material. Also they reported that water growth of rats, but various plant dietary fibers had the uptake was related to uronic acid content (r=0.87) and in beneficial effects on the response of rats to 5% dose of creased by a smaller particle size in the food materials. Sea amaranth in a diet.26) Takeda and Kiriyama11) reported that weeds were known to have many kinds of polycarbohy acid-detergent fiber prepared from burdock dietary fiber drates containing uronic acid and sulfate.25) In this experi absorbed the highest amount of amaranth just like activat ment we also analyzed uronic acid content, but there was ed charcoal, but cellulose powder and another dietary 458 Suzuki et al.

Fig. 3. Binding of amaranth with seaweeds.

Fig. 4. Binding of erythrosine with seaweeds.

fibers prepared from burdock absorbed only a small Correlations between water-holding capacity and bind amount. They also stated settling volume in water seemed ing of food colors such as amaranth, erythrosine, and rose to be the most important factor under their specific ex Bengal were r=0.723, 0.704, and 0.708, respectively, and perimental condition, though all physical properties were also correlations between settling volume in water and interrelated among the various aspects of nutritional func binding of food colors were r = 0.751, 0.806, and 0.761, re tions. However in their study on particle size of dietary spectively. These data indicated the absorption of food fiber, protective activity of dietary fibers was roughly cor colors by seaweed dietary fiber was influenced to some ex related with their value of settling volume in water.27) tent by water-holding capacity. These results suggest that the bulk forming capacity of die Although the ability of some fibers to bind toxic com tary fibers determined by settling volume (in vitro) should pounds has not been extensively studied, it has been be altered after enzymatic digestion, and the altered set proposed as a protective mechanism of the fibers against tling value in the gastrointestinal tract (in vivo) determines gastrointestinal cancers.1) its effectiveness.27) However, there were few reports on the binding of the other two colors, erythrosine and rose Ben Binding of Vitamin gal, with dietary fibers.28) Figure 6 shows the percent binding thiamin. Wakame Properties of Dietary Fiber in Seaweeds 459

Fig. 5. Binding of rose Bengal with seaweeds .

Fig. 6. Binding of thiamin with seaweeds.

sporophyll and hijiki showed the highest percent binding binding capacity (30%) to thiamin in saline solution, fol (42.7-45.6%) for thiamin, followed by wakame (I), lowed by hard red spring and soft white winter wheat wakame (A), and wakame (E) (16.9-20.4%). Meanwhile brans. Loss of ascorbic acid was statistically related to the Mitsuishi-kombu and susabi-nori showed the lowest bind concentration of the fiber sources. However the relation ing (8.3-10.6%) . ship between pH and thiamin interactions with dietary Binding of thiamin was not clearly related to water-hold fiber varied according to the sources of fiber. Also Omaye ing capacity and settling volume in water (r=0.501 and et al.29) reported adsorption of fat soluble vitamins, such 0.520, respectively) , when compared with food colors. as vitamin D (cholecalciferol) and E (ƒ¿a-tocopherol), by the Omaye et al. 12)studied in vitro interaction of water solu same dietary fibers. When incubated in saline solution, ble vitamins (ascorbic acid and thiamin) with wheat brans , most of vitamin D trapped to fibers, but the addition of pectin, and cellulose, and citrus pectin had relatively high bile salt increased the free vitamin. These tendency was 460 Suzuki et al.

Fig. 7. Binding of sodium cholate with seaweeds.

found for the adsorption of vitamin E. tary fiber components, many in vitro studies have It appears that vitamins bound to fibers or some other confirmed and following results were observed: lignin had carbohydrates in foods are not as available as the vitamin the strongest binding capacity of the dietary fiber compo given in pure form, and carotene in carrots, niacin in nents, hemicellulose appeared to absorb bile acids very cereals, and thiamin in bread are examples of this.30) poorly, and cellulose had virtually no binding capacity.2) Potential ability of dietary fiber is the reduction of the In these in vitro experiments, the conditions were highly ar risk factor of certain diseases; however, there may be the tificial because the media did not contain any other lipids. possibility of some adverse effects associated with the in When various dietary fibers were incubated with mixed take of high amounts of dietary fibers. The effect of dieta micelles containing a certain amount of bile acids, ry fiber on micronutrient absorption such as vitamins and cholesterol, and phosphatidylcholine, results agreed with minerals was widely studied.2) When compared to the level the simple studies.2) of data on mineral availability, little is known about the Also in vivo studies have been active in the area of dieta effect of dietary fiber on vitamin availability. It is necessa ry fiber-induced changes in fecal excretion and the profile ry to study the adverse effects of dietary fibers. of bile acids.") Direct binding or sequestering of bile acid by dietary fiber in the bowel lumen appears to be of nutri Binding of Sodium Cholate tional importance because, first, diverts cholesterol which Figure 7 shows the percentage of sodium cholate bound is synthesized in the liver from lipoprotein cholesterol into to seaweeds. Binding of cholate by susabi-nori was the de novo synthesis of bile acids, and second, bound bile highest (12.6-15.5%); over twice that bound by another acids would be unavailable for micelle formation which is seaweeds except suji-aonori (9.7%). Sodium cholate was an important role of bile acids.2) not absorbed to hijiki (M), and ma-kombu and Mitsuishi There is very little information available on interactions kombu had a lower binding capacity (1.5-2.6%). between seaweed dietary fibers and organic substances Correlations between binding of sodium cholate, any such as toxic substances, nutrients, and bile salts. We are water-holding capacity and settling volume in water were investigating the binding of sodium taurocholate with die r=0.598 and 0.549, respectively. An adequate correlatioi tary fiber in seaweeds. was not estimated from the results. This work was supported, in part, by a Centennial The binding of bile acids to certain dietary fibers has Research Fund of Tokyo University of Fisheries. been widely studied. Eastwood and Hamilton") published the first report of bile acid binding to dietary fibers and References they found the binding was the strongest in low pH, and was decreased by increased polarity of the bile acid. The 1) B. 0. Schneeman: Physical and chemical properties, methods of binding increased as the pH decreased; however, this analysis, and physiological effects. Food Technol., 40(2), 104-110 result was complicated by the precipitation of cholic acid (1986). 2) M. L. Dreher: Handbook of Dietary Fiber. Marcel Dekker, New (pK 5.0) at pHs below 4.23) Taurocholic acid differs from York, 1987, pp. 1-468. cholic acid in having a sulfonic acid group which confers 3) Resources Council, Science and Technology Agency: Standard on it higher acidity (pK 1.5) and solubility.23) As for the die- Tables of Food Composition in Japan, Dietary Fiber. Printing Properties of Dietary Fiber in Seaweeds 461

Bureau, the Ministry of Finance, Tokyo. 1992, pp. 42-43 (in 166 (1982). Japanese). 19) Y. Yoshie, T. Suzuki, T. Shirai, and T. Hirano: Dietary fiber and 4) B. O. Schneeman: Soluble vs insoluble fiber-Different physiological minerals in dried nori of various culture locations and prices. responses. Food Technol., 41(2), 81-82 (1987). Nippon Suisan Gakkaishi, 59, 1763-1767 (1993)(in Japanese with 5) T. Suzuki, K. Nakai, Y. Yoshie, T. Shirai, and T. Hirano: Effect of English abstract). sodium alginates rich in guluronic and mannuronic acids on 20) Y. Yoshie, T. Suzuki, T. Shirai, T. Hirano, and E.-H. Lee: Dietary cholesterol levels and digestive organs of high-cholesterol-fed rats. fiber, minerals, free amino acids and fatty acid compositions in Nippon Suisan Gakkaishi, 59, 545-551 (1993). dried nori of several culture places in Korea. J. Tokyo Univ. Fish. 6) L. Prosky, N.-G. Asp, T. F. Schweizer, J. W. DeVries, and 1. (Tokyo Suisandai Kenpo), 80, 197-203 (1993) (in Japanese with En Furda: Determination of insssoluuuuuuuble,soluble and total dietary fiber in glish abstract). foods and food products: Intercollaborative study. J. Assoc. Off. 21) T. Suzuki, K. Nakai, Y. Yoshie, T. Shirai, and T. Hirano: Seasonal Anal. Chem., 71, 1017-1023 (1988). variation of the dietary fiber content and molecular weight of solu 7) S. Plaami, M. Saastamoinen, and J. Kumpulainen: Effect of variety ble dietary fiber in brown alga, hijiki. Nippon Suisan Gakkaishi, of environment on dietary fiber content of winter rye in Finland. J. 59, 1633 (1993). Cereal Sci., 10, 209-215 (1989). 22) M. E. Parrott and B. E. Thrall: Functional properties of various 8) T. Suzuki, K. Nakai, Y. Yoshie, T. Shirai, and T. Hirano: Diges fibers: Physical Properties. J. Food Sci., 43, 759-763, 766 (1978). tibility of dietary fiber in brown alga, kombu, by rats. Nippon Sui 23) R. R. Selvendran, B. J. H. Stevens, and M. S. Du Pont: Dietary san Gakkaishi, 59, 879-884 (1993). fiber: Chemistry, analysis, and properties. in "Advances in Food 9) A. A. McConnell, M. A. Eastwood, and W. D. Mitchell: Physical Research, Vol 31" (ed. by C. O. Chichester, E. M. Mrak, and B. S. characteristics of vegetable foodstuffs that could influence bowel Schweieert). Academic Press. San Diego. 1987. no. 117-209. function. J. Sci. Food Agric., 25, 1457-1464 (1974). 24) A. M. Stephen and J. H. Cummings: Water-holding by dietary fiber 10) H. E. Middleton and H. G. Byers: The settling volume of soils. Soil in vitro and its relationship to faecal output in man. Gut, 20, 722 Sci., 37, 15-27 (1934). 729(1979). 11) H. Takeda and S. Kiriyama: Correlation between the physical prop 25) P. S. O'Colla: Mucilages. in "Physiology and Biochemistry of Al erties of dietary fibers and their protective activity against amaranth gae" (ed. by R. A. Lewin), Academic Press, New York and toxicity in rats. J. Nutr., 109, 388-396 (1979). London, 1962, pp. 337-356. 12) S. T. Omaye, F. I. Chow, and A. A. Betschart: In vitro interaction 26) B. H. Ershoff and E. W. Thurston: Effect of diet on amaranth of 1-14C-ascorbic acid and 2-14C-thiamin with dietary fiber. Cereal (FD&C Red No. 2) toxicity in the rat. J. Nutr., 104, 937-942 (1974). Chem., 59, 440-443 (1982). 27) H. Takeda and S. Kiriyama: Effect of particle size of dietary fiber 13) D. Kritchevsky and J. A. Story: Binding of bile salts in vitro by on its settling volume in water and protective activity against non-nutritive fiber. J. Nutr., 104, 458-462 (1974). amaranth (food red No. 2) toxicity in rats. Nippon Nogeikagaku 14) G. D. Calvert and R. A. Yeates: Adsorption of bile salts by soya kaishi (J. Agric. Chem. Soc. Jpn.), 65, 171-176 (1991) (in Japanese bean flour, wheat bran, lucerne (Medicago sativa), sawdust and lig with English abstract). nin; the effect of saponins and other plant constituents. Brit. J. 28) J. Tsujita, H. Takeda, K. Ebihara, and S. Kiriyama: Comparison Nutr., 47, 45-52 (1982). of protective activity of dietary fiber against the toxicities of various 15) S. Ikegami, F. Tsuchihashi, B.-S. Moon, M. Miyake, Y. Ueno, E food colors in rats. Nutr. Rep. Int., 20, 635-642 (1979). . Nishide, K. Nakamura, and S. Innami: Determination of total dieta 29) S. T. Omaye, F. I. Chow, and A. A. Betschart: In vitro interactions ry fiber in foods and food products by the enzymatic gravimetric between dietary fiber and 14C-vitamin D or 14C-vitamin E. J. Food method. Nippon Eiyo Shokuryo Gakkaishi (J. Jpn. Soc. Nuir. Sci., 48, 260-261 (1983). Food Sci.), 41, 239-243 (1988) (in Japanese with English abstract). 30) J. L. Kelsay: Effects of fiber on vitamin bioavailability. in "Dietary 16) T. Sumimoto, T. Nishimune, T. Yakushiji, T. Ichikawa, S. Fiber-Chemistry, Physiology, and Health Effects" (ed. by D. Kojima, M. Doguchi, T. Kawamura, M. Kawai, T. Kamiki, K. Kritchevsky, C. Bonfield and J. W. Anderson), Plenum Press, New Tanaka, N. Kawabata, and N. Kunita: Determination of dietary York, 1990, pp. 129-135. fiber in foods by an enzymatic-gravimetric method. Syokuhin 30) G. V. Vahouny, R. Tombes, M. M. Cassidy, D. Kritchevsky, and Eiseigaku Zasshi (J. Food Hyg. Soc. Jpn.), 30, 417-424 (1989) (in L. L. Gallo: Dietary fiber. V. Binding of bile salts, phospholipids Japanese with English abstract). and cholesterol from mixed micelles by bile acid sequestrants and 17) B. Mori, K. Kusima, and T. Iwasaki: Dietary fiber in seaweeds. Nip dietary fibers. Lipids, 15, 1012-1018 (1980). pon Nogeikagaku Kaishi (J. Agric. Chem. Soc. Jpn.), 55, 787-791 31) M. Eastwood and D. Hamilton: Studies on the adsorption of bile (1981) (in Japanese with English abstract). salts to non-absorbed components of the diets. Biochim. Biophys. 18) B. Mori: Contents of dietary fiber in some Japanese foods and the Acta,salts to152, non-absorbed 165-173 (1968).31)(1968).componentsM.Eastwood andD. Hamilton: Studiesof the ondiets. the Biochim.adsorption Biophys.of bile amount ingested through Japanese meals. Nutr. Rep. Int., 26, 159