The Soy Protein Research Committee(Japan)
MEASURMENT OF SOY-PROTEIN GELATION USING A PROGRAM CONTROLLED VISCOMETER
Fumio YAMAUCHI, Jun-ichiro UMEYA and Kazuo SHIBASAKI
Department of Food Chemistry, Faculty of Agriculture, Tohoku University.
Nutr. Sci. Soy Protein, Jpn. 2, 4-7, 1981.
The apparent viscosities of commercial flour, glycinin (11S), É¿-conglycinin (7S) and acid-precipitated protein of soybean suspending systems and their heated gels were investigated using a modified coaxial cylinder viscometer. A hybrid program was established: (i) cyclic temperature test (20Å®90Å®20Åé) under constant rate of shear and (ii) cyclic shearing test (48.7Å®243.7Å®48.7 sec-1)under isothermal conditions and at actual temperature. The viscosities of the soy protein suspending system (12%, wt/vol) gradually decreased with increasing temperature to about 70Åé.
Thereafter, characteristic behavior of commercial soy proteins depended upon the usage of them. The apparent viscosity of 7S globulin increased considerably, and reverse hysteresis loops were found 70 and 80Åé in heating period. However, the viscosity of 11S globulin remained almost unchanged under the different temperatures.
PREPARATION AND SOME CHARACTERISTICS OF SOY PROTEIN FROM RAW SOYBEAN AND SOY PROTEIN ISOLATE
Masao KANAMORI and Yuuji DOI
Department of Agricultural Chemistry, Kyoto Prefectural University
Nutr. Sci. Soy Protein, Jpn. 2, 8-13, 1981.
Proteins from raw soybean or Fujipro R were fractionated by Sephacryl S-200 gel filtration with phosphate buffer, pH7.6 (I=0.5), to six fractions (R-I to R-VI or F-I to F-VI). F-I, F-Il and F-IV corresponded to 11S, 7S and 2S proteins, respectively. Trypsin inhibitory activity of the extract from Fujipro R was lost by pepsin treatment, while that from raw soybean was maintained. Proteins from Fujipro R were stable to heating. Half amount of each fraction precipitated by calcium ion, but bovine É»-casein prevents from precipitating.
DETERMINATION OF OFF-FLAVOUR COMPOUNDS ABSORBED IN SOY PROTEIN ISOLATE
Masao FUJIMAKI and Seiichi HONMA
Department of Food and Nutrition, Ochanomizu University
Nutr. Sci. Soy Protein, Jpn. 2, 14-18, 1981.
This study was undertaken to determine flavour compounds in soy protein isolate and to investigate the mechanism in absorption of the flavour compounds to protein.
Soy protein isolate, Fujipro R was brought into fractions with aqueous and 0.01N sodium hydroxide extractions. For the combined form of flavour compound, fractionated proteins were hydrolyzed with Bioprase and extracted with ethyl ether. For the free form, proteins were incubated without Bioprase and treated similarly. The ether extract was applied for gas chromatography to determine n-hexanol and n-hexanal.
Hexanol in the combined form was found both in the residues of aqueous and sodium hydroxide extractions, 25% and 30% of the total hexanol respectively. Most of hexanol in other fractions was found in the free form.
In the alkaline extraction hexanal in the combined form was hardly detected in the protein fractions, and most of hexanal was in the free form. The amount of hexanal per gram of protein was almost similar level in every protein fraction. In the aqueous extraction 20% of total hexanal was found in the cryosoluble protein, and hexanal in other fractions was found in the free form. The total amount of hexanal per protein was found to be the greatest, 0.7 mg in the cryoprecipitated protein.
This protein isolate contained 44-46 ng hexanol per gram of protein and 18-23 mg hexanal. It shows that the quantity of hexanal was more than its threshold value in the case of 1 gram intake.
THE FORMATION OF MACROPEPTIDES AND THE DISTRIBUTION OF CALCIUM-FORMS IN THE SMALL INTESTINE OF RATS GIVEN A DIET CONTAINING SOY PROTEIN ISOLATE
Hiroshi NAITO and Tadashi NOGUCHI
Department of Agricultural Chemistry, The University of Tokyo
Nutr. Sci. Soy Protein, Jpn. 2, 19-22, 1981.
Slight but definite amount of macropeptides in the small intestine was formed shortly after feeding a diet containing soy protein isolate (Fujipro R, SPI).
In the similar experimental condition that the rats meal-fed a 20% SPI diet for 1.5hr, the amount of soluble Ca as well as of soluble P in the intestinal lumen, was much less than the rats given casein, and also was slightly but significantly less than the rats given amino acid mixture simulating casein or egg albumin.
In contrast, the amount of insoluble Ca was the highest in SPI group.
These results suggest that the feeding soy protein isolate may little favor the stimulation in Ca absorption in distal portion of small intestine where passive type of transport occurs. The relation of the formation of macropeptides to the process that insoluble Ca-phosphate complex grows in the lumen was not elucidated, since there seemed to be another possibility that the presence of the small amount of organic phosphorus may also aggravate the solubilization of Ca salts.
IMPROVEMANT OF THE ESSENTIAL AMINO ACID PATTERN OF SOY PROTEIN ISOLATE BY ENZYMATIC MODIFICATIONÅFPROCEDURES FOR THE IMPLEMENTATION AND EVALUATION OF THE PRODUCTS
Soichi ARAI
Department of Agricultural Chemistry, The University of Tokyo
Nutr. Sci. Soy Protein, Jpn. 2, 23-26, 1981.
The classical plastein reaction can be modified to a novel one-step process [J. Agric. Food Chem., 27, 52 (1979) ] which, particularly when papain is used as its catalyzer, permits covalent attachment of amino acids in a simpler manner. This process was implemented to enhance the sulfur amino acid level of soy protein isolate (SPI), with formation of a product having an expected level of covalently attached L-methionine.
A product (P11) with a methionine level of 11% on weight basis was used as a nitrogen source of a diet for a feeding test with rats. Analysis of their small-intestinal content showed that oligopeptides predominated over free amino acids during 1-4 hr after feeding. Despite that, efficient entry of free amino acids, including free methionine, into the portal blood resulted over the same period of time after feeding. This indicates that the covalently attached methionine in P11 is well bioavailable.
A possibility thus exists that the enzymatically modified product such as P11 could be used as a new type ingredient for methionine supplementation to SPI or others.
EFFECT OF SOY PROTEIN ISOLATE ON LIPID METABOLISM
Kiyoshi ASHIDA
Department of Food Science, Sugiyama-Jogakuen University
Nutr. Sci. Soy Protein, Jpn. 2, 27-30, 1981.
Five experiments were conducted to study the effect of age, length of time on diet and some dietary components on the hypocholesterolemic function of soy protein in male Wistar rats fed 15% protein and 15% hydrogenated oil diets. In experiments 1 and 2, there were no differences in plasma cholesterol among soy protein and casein when 4-week-old rats were fed a diet containing animal hydrogenated oil without salt mixture or a diet containing vegetable hydrogenated oil with salt mixture for 2 weeks. In experiment 3, when 5-week-old rats were fed diet containing animal oil or vegetable oil with or without salt mixture for 3 weeks, plasma cholesterol level was significantly lower on the soy protein diet than on the casein diet. Experiment 4 used 6-week-old rats to study the effect of length of time on the diet containing vegetable oil and salt mixture. Plasma cholesterol level was significantly lower when length of time on diet was increased from 2 weeks to 5 weeks. In experiment 5, 6-week-old rats and 9-week-old rats were used to study the effect of age and length of time on diet. Plasma cholesterol level of 6-week-old rats fed for 6 weeks was significantly lower than that of 9-week-old rats fed 3 weeks. These results clearly show that the reduced cholesterol content observed in plasma of rats fed soy protein can be attributed to length of time on diet, not age. In addition, feeding rats the soy protein diet for 2 weeks led to a reduction in plasma triglyceride content which was shown in all cases of experiments, 3, 4 and 5.
CLINICAL EXPERIENCES WITH SOYBEAN PROTEIN SUBSTITUTED DIET ON THE PLASMA LIPIDS
Emiko MIYAZIMA, Shizue TAKEYAMA, Norio TADA,
Toshitsugu ISHIKAWA, Haruo NAKAMURA
Jikei Uniersity School of Medicine
Nutr. Sci. Soy Protein, Jpn. 2, 31-36, 1981.
Twelve cases were subjected to take soybean protein substituted diet for 6 weeks according to cross-over design.
The composition of diet was in the following:
total energy (kcal) : 1750-1970 fiber (g) : 4-5
protein (g) : 73-74 P/S ratio : 2.1-0.8
fat (g) : 41-59 cholesterol (mg) : 357-377
carbohydrate (g) : 272-285
Total animal protein was substituted with soybean protein amounted about 37g.
Total cholesterol decreased on soybean protein diet about 13.7% after 3 weeks which was statistically significant. LDL-cholesterol decreased significantly about 13.5% during the soybean protein diet. Triglyceride did not show any significant changes about 12.5% on the soybean protein diet. Apo-AI remained unchanged during the experimental period. Thus, HDL-C/AI ratio tended to decrease on the soybean protein diet, which was not significant.
In this experiment, we concluded that the soybean protein diet lowered LDL-cholesterol mainly and also decreased HDL-cholesterol without changing AI level.
EFFECT OF SOY PROTEIN ISOLATE ON THE CHOLESTEROL AND TRIGLYCERIDE LEVELS IN LIVER AND SERUM OF RATS
Hiroyasu FUKUBA, Osamu IGARASHI and Rie MORI
Institute of Environmental Science for Human Life, Ochanomizu University
Nutr. Sci. Soy Protein, Jpn. 2, 37-40, 1981.
Serum and liver cholesterol levels are known to be affected by kinds of feeding protein, especially soy protein has a decreasing effect on those levels. One of these effects is assumed to be coming from the difference of amino acid composition of the protein. We noticed the difference of arginine levels in soy protein isolate and casein, the latter having lower level than the former. Rats were fed the diet supplemented with cholesterol at 1% level for 2 weeks. In Exp. 1 the protein level was kept at 20%, whereas in Exp. 2 12%. The following results were obtained.
1) Soy protein isolate decreased the growth rate comparing with casein diet. It might be caused with diarrhea by soy protein isolate.
2) At normal protein level in diet, significant effect of soy protein isolate was not observed in serum lipids. But, at lower protein level, soy protein isolate significantly decreased total and free cholesterol levels in serum and increased HDL-cholesterol level in serum than casein diets.
3) In liver of normal protein group, arginine supplementation decreased significantly triglyceride level and tended to decrease total cholesterol level. Similar effect of arginine was observed in low protein diet, but not significantly.
THE EFFECTS OF PROTEIN NUTRITION ON EXOGENOUS HYPERCHOLESTEROLEMIA
Hisashi OZASA and Takehiko TANAKA
Department of Nutrition and Pysiological Chemistry, Osaka University Medical School
Nutr. Sci. Soy Protein, Jpn. 2, 41-44, 1981.
There are many researches reporting interrelationships between plasma cholesterol levels and dietary fats. However, the effects of dietary protein on cholesterol metabolism has not been elucidated yet. In this report, it is described that plasma cholesterol levels increased after oral loading of cholesterol and bile acid to rats, and this high level is remarkably changed under various conditions of protein nutrition. The plasma levels of cholesterol clearly increased in the animals fed on low protein diet (5%) compared to that on high protein diet (40%). The mechanism of this phenomenon has not yet been elucidated and, so far tested, is not due to changes in intestinal cholesterol absorption.
The differences in dietary protein quality also showed remarkable effects on exogenous hypercholesterolemia. Proteins giving higher biological values showed more increasing effect on plasma cholesterol levels. However, differences in plasma cholesterol levels between animals fed on low protein diets and high protein diets are much more distinguishable in the animals fed on higher quality protein.
HYPOCHOLESTEROLEMIC EFFECT OF SOY PROTEIN ISOLATE IN RATS
Michihiro SUGANO and Yasuo NAGATA
Laboratory of Nutrition Chemistry, Kyusyu University
Nutr. Sci. Soy Protein, Jpn. 2, 45- 51, 1981.
The effect on serum cholesterol of soybean protein isolate compared with casein was studied in male Wistar rats. When cholesterol free diets were fed, the amino acid mixture simulating soy protein exerted a same extent of the cholesterol-lowering action as soy protein itself. The concentration of liver cholesterol was also clearly low in rats fed soy protein, but the difference disappeared when the amino acid mixture served as a nitrogen source. Addition of lysine to soy protein or arginine to casein did not modify their intrinsic effects on the serum cholesterol level. In rats fed vegetable protein or its amino acid mixture, both HDL- and VLDL + LDL-cholesterol decreased proportionately. The serum concentration of apoA-I decreased, while apoB increased. Soy protein significantly enhanced fecal excretion of neutral and acidic steroids and this was not the case with the amino acid mixture, indicating that the hypocholesterolemic action of soy protein is not ascribed solely to the increased steroid output. When diets containing cholesterol were fed, both soy protein and its amino acid mixture were hypocholesterolemic; there was a marked reduction of VLDL + LDL-cholesterol without influencing HDL-cholesterol levels. The concentration of serum apoA-I and apoB was decreased. It is likely that the difference in the amino acid composition between soy protein and casein is exclusively responsible for the different response of serum cholesterol.
COMPARISON OF NUTRITIVE VALUES BETWEEN SOY PROTEIN ISOLATE AND OTHER SOY PROTEINS
Tetsuzo TAKAHASHI, Shigeji MURAMATSU and Yuriko SHIBAHARA
Institute of Health and Sport Science, The University of Tsukuba
Nutr. Sci. Soy Protein, Jpn. 2, 52-57, 1981.
Two animal experiments were conducted to compare the nutritive values among soy protein isolate (Fujipro R), full fat soy powder, full fat soy milk powder (Hiproton) and casein. Full fat soy powder was prepared by the following way: Soybean was boiled at 120Åé in an autoclave, then ground down and freeze-dried into powder.
True digestibility of Fujipro R, full fat soy powder, Hiproton and casein was respectively 94.2%, 84.4%, 90.1% and 95.3% in the first experiment and 92.9%, 85.1%, 89.4% and 94.3% in the second experiment. PER of Fujipro R, full fat soy powder, Hiproton and casein was respectively 3.38, 2.96, 2.27 and 4.09 in the first experiment and 2.62, 2.26, 2.04 and 3.39 in the second experiment. NPR of Fujipro R, full fat soy powder, Hiproton and casein was respectively 3.87, 3.48, 2.78 and 4.47 in the first experiment and 3.22, 2.92, 2.64 and 3.96 in the second experiment. It was suggested that the difference in PER and NPR between soy protein isolate and full fat soy powder was mainly due to the different digestibility.
Nutritive value of soy protein isolate (Supro 620) was compared with that of full fat soy milk powder (Hiproton) by the nitrogen balance method using two healthy university students as the subjects.
It was concluded that there was no difference between soy protein isolate and full fat soy milk powder in the nutritive value.
EVALUATION OF NUTRITIVE VALUE OF SOY PROTEIN ISOLATE USING HEPATIC ORNITHINE DECARBOXYLASE ACTIVITY AS A MARKER
Shin-ichi HAYASHI, Yasuko MURAKAMI, Yoshiko HARA and Tamio NOGUCHI
Department of Nutrition, Jikei University School of Medicine
Nutr. Sci. Soy Protein, Jpn. 2, 58-61, 1981.
We attempted to demonstrate whether hepatic ornithine decarboxylase (ODC) activity of rats could be a good marker for the nutritive value of dietary proteins by comparing casein and soy protein isolate. In some disagreement with last year's results, soy protein isolate gave ODC activity not significantly different from that given by casein either in liver or in kidneys. Methionine supplementation did not show any stimulatory effect. It was concluded that, in contrast to proteins of very low nutritive value such as zein, gelatin or hemoglobin, soy protein isolate is as good as casein in inducing ODC activity, although it has lower nutritive value than casein. Feeding of zein or hemoglobin was found to be followed in 3 to 4 hours by a marked decrease in plasma concentrations of their limiting amino acids, namely tryptophan and lysine or isoleucine, respectively. In contrast to this, feeding of soy protein isolate was followed in 5 hours by 30% rise in plasma concentration of methionine. Since dietary induction of ODC is a rapid process completing in several hours it may be most affected by plasma amino acid concentrations during several hours after feeding. This seems to explain the discrepancy between ODC induction by and nutritive value of soy protein isolate.
NUTRITIVE VALUE OF SOY PROTEIN ISOLATE DETERMINED BY SLOPE RATIO ASSAY IN GROWING RATS
Goro INOUE, Kyoichi KISHI and Ikuko YAGI
Department of Nutrition, School of Medicine The University of Tokusima
Nutr. Sci. Soy Protein, Jpn. 2, 62-66, 1981.
Soybean protein is deficient in sulfur-containing amino acids but its quality is superior to that of cereal grain protein. Although raw soybean contains toxic factors which lower its nutritive value, heat treatment and isolation of the protein largelye liminate or diminish natural toxicants. In this study the utilization of soy protein isolate (SPI) was evaluated at graded levels of intake and relative nutritive value of SPI to lactalbumin and casein was determined.
Male rats of the Wistar strain were fed 0, 3, 7, 10, 15, 20 or 30% SPI diet ad libitum for three weeks. Nitrogen balance was observed during the last three days of the experiment. Body weight gain and carcass N were measured. The utilization of SPI was evaluated from body weight gain, N balane and carcass N in relation to SPI N intake.
PER and NPR of SPI were 2.42 and 3.43, respectively at 10% protein level. NPU estimated by N balance method agreed well with carcass N method and was 52-54.The similar value was obtained by the slope of the regression equation relating N balance or carcass N to N intake. The relative nutritive values of SPI to lactalbumin and casein were 63-72% and 75-78%, respectively. The quality of SPI supplemented with 3% L-methionine was comparable to casein, and that of whey protein of soybean was similar to lactalbumin.
EFFICIENCY OF UTILIZATION SOY PROTEIN ISOLATE SUPPLEMENTED WITH L-METHIONINE L-THREONINE IN PREGNANT RATS
Yoshiaki NIIYAMA and Sadaichi SAKAMOTO
Department of Nutrition, School of Medicine, The University of Tokusima
Nutr. Sci. Soy Protein, Jpn. 2, 67-71, 1981.
Pregnant rats of the Sprague-Dawley strain, weighing about 190g, were fed a 10% soy protein isolate (SPI) diet added 0.3%, 0.4% or 0.5% L-methionine or 0.4% L-methionine and 0.25% L-threonine for 21 days. NPUs of the respective dietary proteins were calculated by nitrogen balance and slaughter methods. At term, animals were autopsied and free amino acid concentration in plasma was determined. Nonpregnant rats were used as the control. Pregnant rats consumed about 340g of the SPI diet during 21-day period and gained about 80g of their body weight. Although food consumptions of the 0.3% to 0.5% methionine added groups of rats were only slightly more than those for SPI diet group, body weight gains for the former were significantly larger than those for the latter, indicating that the supplementation with methionine to the SPI diet improved the dietary utilization. Addition of methionine with threonine resulted in less food intake and comparative weight gain as compared to those for when only methionine was supplemented. Regardless of the amino acid supplementation, growth of the reproductive organs was similar. NPU of the 10% SPI diet was 43 and 37 in pregnant and nonpregnant rats, respectively. Addition of 0.3% to 0.5% L-methionine caused a marked improvement of utilization efficiency of SPI. NPU was further improved by the supplementation of methionine with threonine and it was comparative to that for whole egg protein. Free amino acid concentration in plasma of the pregnant rats did not change by the supplementation of limiting amino acids.
THE EFFECT OF SUPPLEMENTING SOY PROTEIN ISOLATE WITH GLUTEN AND CASEIN ON NUTRITIONAL VALUES IN GROWING RAT
Hideo KOISHI 1, Toyoko OKUDA 1, Reiko TAMURA 1, Yoshiko HATTORI 1, Naemi KAJIWARA 2 and Kuniko MIYATA 2
1 Department of Food and Nutrition, Faculty of the Science of Living, Osaka City University
2 Department of Home Economics, Kobe Women's College
Nutr. Sci. Soy Protein, Jpn. 2, 72-76, 1981.
The effect of supplementing soy protein isolate (SPI), "Fujipro R", with gluten and casein was investigated by feeding rats.
Male rats of the Sprague-Dawley strain, weighing about 80g, were fed ad libitum on wheat gluten (A), casein (B), SPI (C), gluten plus SPI (D), casein plus SPI (E), and gluten plus casein plus SPI (F) as protein sources for 5 or 8 weeks. The level of protein was 6% (0.96 gN/100g diet), and diets (D), (E) and (F) were mixed, so that the amount of nitrogen for each source was equal.
Mean weight gain in the group of male rats fed on SPI (C) was signifiranfly higher than that of the group of rats fed on wheat gluten (A), and significantly lower than that of the group of rats fed on casein (B). Gluten plus SPI (D) did not affect food intake and nitrogen balance, but contributed to weight gain of rats and improved nitrogen efficiency significantly more than SPI (C) alone.
In the group of rats fed on casein plus SPI (E), no such effect could be observed, but the combination of SPI with gluten and casein simultaneously, improved weight gain, food intake and nitrogen balance in rats more than (C), (D), and (E), and achieved better results than casein (B).
It was presumed that, although nutritional values of SPI were lower than those of casein, the former's nutritional values can be improved by supplementing the SPI with gluten or gluten plus casein.
However, in blood status, lipid pattern of erythrocyte and plasma amino acid concentration, there was no significant difference between (B)-(F), and in the groups of rats fed on (D) and (F), significantly higher weight gain than in those fed on (C) was observed. The reason for the above phenomena could not be explained from these results.
LIMITING AMINO ACIDS OF SOY PROTEIN ISOLATE AND THEIR SUPPLEMENTARY EFFECTS (Part 2)
Michio YAMAGUCHI, Masako IWAYA and Motoyoshi MIYAZAKI
National Institute of Nutrition
Nutr. Sci. Soy Protein, Jpn. 2, 77-81, 1981.
In the first experiment, the nutritive values of the soy protein isolate (SPI) each additionally supplemented with its limiting amino acids and all other essential amino acids were examined comparing with those of whole egg protein and casein in growing rats. Some serum components relating to protein and lipid metabolism were also examined.
The supplement of methionine (Met) and threonine (Thr) to SPI improved the body weight gain, protein efficiency ratio (PER) and biological value nearly upto the values of whole egg protein. But, further improvement was not observed by additional supplement of lysine (Lys) and other essential amino acids. The data on serum albumin, A/G ratio, urea-N, leucine aminopeptidase and the total- and HDL-cholesterols gave favourable results to the Met and Thr supplement group on the whole.
In the second experiment, the supplemental effects of Met and Thr to SPI were also examined in adult rats. The body weight change, nitrogen balance, serumÅ@leucineÅ@aminopeptidase and the total- and HDL-cholesterols were improved upto around the values of whole egg protein. The albuinin, A/G ratio and urea-N, whose values of SPI itself were similar to those of whole egg protein and casein, remained unchanged.
SUPPLEMENTAL EFFECT OF METHIONINE AND CYSTINE TO DIETS CONTAINING SOYBEAN OR A SOY PROTEIN ISOLATE
Akira YOSHIDA, Hidehiko YOKOGOSHI and Kyoko KAWAI
Department of Agricultural Chemistry, Nagoya University
Nutr. Sci. Soy Protein, Jpn. 2, 82-85, 1981.
It has been reported that the supplementation of cystine to a diet containing raw soybean protein stimulates the growth of rats whereas the similar supplementation of cystine to a diet containing the soy protein isolate is not effective. We assumed the difference would be due to the presence of trypsin inhibitor which stimulates the excretion of trypsin and chymotrypsin and produces pancreatic hypertrophy. We compared the supplemental effects of methionine and cystine to diets containing raw soybean, heated soybean or a soy protein isolate.
Male young rats of the Wistar strain weighing about 90 g were used. Experimental diets contained 10% of protein as raw soybean, heated soybean or soy protein isolate (Fujipro R). Supplementation of 0.3% of methionine to these diets stimulated the growth significantly only when the basal diet contained the raw soybean. Pancreas weights of rats fed the raw soybean diets were also significantly higher than those fed the heated soybean diets or soy protein isolate. Liver polysome patterns were improved by the supplementation of the S-amino acids. In the group of rats fed the raw soybean diet, cystine supplementation was more effective than methionine supplementation.
In the next experiments, rats were previously injected with 35S-methionine and then fed either the raw soybean diet or the heated soybean diet. Feces were collected for the first 3 days and 35S contents were determined. The group of raw soybean diet excreted more 35S in feces than the group of heated soybean diet.
These results indicate the supplementation of cystine is effective only when the soybean protein contained trypsin inhibitor and excreted more S-amino acid, especially cystine as pancreatic proteases.
CAMPARATIVE STUDIES ON THE GOITROGENIC ACTIVITIES OF DEFATTED SOYBEAN AND SOYBEAN PROTEIN ISOLATE
Shuichi KIMURA and Hiroyuki ODAKA
Department of Food Chemistry, Faculty of Agriculture, Tohoku University
Nutr. Sci. Soy Protein, Jpn. 2, 86-90, 1981.
In a previous study, we demonstrated that soybean contains goitrogenic substances which affect thyroid function and that some of those elements are sapogenols and isoflavonoids.
The present study is undertaken to examine the goitrogenic activity of soy protein isolate compared with defatted soybean. It is expected that the goitrogenic substances may be removed by the process of purification ftom soybean.
Furthermore, this study is undertaken to determine the mechanism of action of plasma cholesterol-lowering via thyroid function.
An enlargement of the thyroid was observed in mice fed on defatted soybean but much less enlargement was seen in mice fed on soy protein isolate.
Addition of iodine to the diets exerted a hypocholesterolemic effect, mainly on the low density lipoprotein (LDL) - cholesterol of plasma. On the other hand, it was observed that a diet containing soy protein isolate produces lower plama cholesterol than that of defatted soybean, however, casein produces an even lower plasma cholesterol. The total plasma cholesterol among the various dietary regiments seems to depend on high density lipoprotein (HDL) - cholesterol.
INTERRELATION OF IRON UTILIZATION AND DIETARY PROTEIN AND STARCH SOURCES
Shiro GOTO, Kazuharu SUZUKI and Yusuke KANKE
Department of Nutrition, Tokyo University of Agriculture
Nutr. Sci. Soy Protein, Jpn. 2, 91-95, 1981
Present studies were performed to investigate the influence of dietary protein (casein and soy protein isolate: SPI; Fujipro R), starch (corn starch and tapioka) and iron levels on the iron and copper utilization, using 48 male albino rats of the Wistar strain, averaging 50g in the initial body weight.
1) On the iron utilization, moderate iron intake showed the higher iron retention compared with the low iron intake in rats fed each diet, however, in SPI + Tapioka fed rats there was no connection with iron intake level.
2) On the copper utilization, the rats fed low iron diet showed a tendency of increasing copper retention in all groups.
3) The rats fed low iron diet showed the low iron concentration in liver and indicated the high hepatic copper concentration in reversely.
4) SPI fed group had no effect of dietary iron level on the hemoglobin value.
The soy protein protein reserch(Japan)