The Soy Protein Research Committee(Japan)

LIPID IN THE SOY PROTEIN ISOLATE WITH BEANY FLAVOUR COMPOUNDS

Seiichi HOMMA, Ko AIDA and Masao FUJIMAKI

Department of Nutrition and Food Science, Ochanomizu University

Nutr. Sci. Soy protein, Jpn. 6, 7-10, 1985.

Soy protein isolate (Fujipro R) and defatted soy meal were enzymatically hydrolyzed and extracted with ether and n-butanol successively. The lipid contents of the soy protein isolate and the defatted soybean meal were 3.07% and 3.33%, respectively. Nonpolar lipids and polar lipids, such as glycolipid and phospholipid, in enzymatic hydrolyzates were extracted with ether and n-butanol, respectively. The column chromatography of the extracted lipids on silicic acid revealed that the ratio of neutral lipid, glycolipid and phospholipid in the soy protein isolate was 25.6, 38.9 and 35.5%, respectively. That of the defatted soy meal was 12.7, 53.5 and 33.8%, respectively. According to the TLC analysis of the phospholipid fraction the contents of phosphatidyl ethanolamine and phosphatidyl choline in the soy protein isolate were 29.2 and 70.7 mg%, respectively. Those in the defatted soybean meal were 5.3 and 57.7 mg%, respectively and two unknown phospholipids were determined and the amounts were 23.3 and 0.9 mg%. Most lipid found in the defatted soy meal seems to he transferred into the soy protein isolate with processing. Compared with the defatted soy meal, the increases of beany flavour compounds and the formation of unknown phospholipids in the soy protein isolate suggest that trace amounts of these lipids found in the soy products are potentially the precursors of beany flavour compounds during storage.

UREOGENESIS-ENHANCING ACTIVITY OF SMALL INTESTINAL CONTENTS OF RATS FED SPI DIET

Hiroshi NAITO, Tai-ichiro SEKI and Tadashi NOGUCHI

Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy protein, Jpn. 6, 11-14, 1985.

The acid-soluble fraction of small intestinal contents of rats, which were fed 20% SPI diet, was prepared. The fraction was partially purified by Dowex 50 W Å~ 4 chromatography and Sephadex G-25 gel filtration. The preparation obtained by this procedure showed an activity to enhance ureogenesis of primary cultured hepatocytes of rats in the presence or absence of glucagon in the medium.

INCREASE IN EMULSIFICATION ACTIVITY AND CALCIUM FORTIFICATION IN SOY PROTEIN BY USING SOY LECITHIN-SOY PROTEIN COMPLEX

Makoto KITO ¹, Hiroshi NARITA ¹, Motohiko HIROTSUKA ² and Hitoshi TANIGUCHI ²

¹ Research Institute for Food Science, Kyoto University
² Fuji oil Company

Nutr. Sci. Soy protein, Jpn. 6, 15-20, 1985.

Soy proteins were associated with soy lecithin. Soy protein isolate (SPI), 7S and 11S proteins complexed with lecithin were similarly affected by ethanol treatment to increase emulsification activity. By this procedure, the conformation of these proteins was changed resulting in aggregation. Though emulsification activity of the lecithin-SPI complex was apparently increased by boiling for 1 min, this treatment only caused the 11S protein component to aggregate resulting in better emulsification activity, regardless of whether it was complexed with lecithin or not. The increase in emulsification activity caused by ethanol treatment was not affected by NaCl, whereas the increase by heat treatment was reduced by NaCl. It seems likely that ethanol and heat treatments change the conformation of soy proteins in different ways. Calcium ion was enveloped with a membrane system before addition to soy protein to prevent soy protein from being coagulated and precipitated by calcium ion. Soy lecithin was first sonicated in calcium salt solution to envelop the calcium ion with a liposomal structure composed of lecithin. Then, the calcium-lecithin liposomes were added to soy protein solution. Precipitation and coagulation were not observed in this soy protein-lecithin liposome system containing 60 mM Ca2+. By this method, it was possible to prepare calcium fortified soy milk containing more calcium (120 mg/100 g) than in cow's milk. These results suggest that this calcium-lecithin liposome system is useful for calcium fortification of soy milk.

STUDY ON QUANTITATION OF SOYBEAN PROTEIN ADDED TO THE PROCESSED MEAT PRODUCTSÅFISOLATION AND IDENTIFICATION OF A SPECIFIC PENTAPEPTIDE IN 11S GLOBULIN OF SOYBEAN PROTEIN

Kyoden YASUMOTO, Hiroshi TODOROKI and Tetsuya SUZUKI

Research Institute for Food Science, Kyoto University

Nutr. Sci. Soy protein, Jpn. 6, 21-27, 1985.

With recent progress in food processing techniques vegetable proteins such as soybean protein, wheat gluten have been getting familiar to be used as binder, emulsifier and extender, and for the purpose of improving texture quality, and nutrition improvement. This paper describes a preliminary study conducted to quantitate soybean protein added to the processed foods of animal origin for the purpose of establishing a standard procedure which can be profitably used in quality control of the processed products. Conventional immunochemical method of using 11S globulin antisera was found not to work for the quantitation of soybean protein contained in the heat processed food materials. The pentapeptide called "SP-1", specific to 11S globulin, was chosen as the target in immunochemical analysis. However, its amino acid sequence as well as its isolation procedure have been remained to be established. So, as the first step improved method was devised for the isolation of the "SP-1" peptide from 11S globulin; a combination of chromatographic procedure including SP-Toyopearl ion exchange chromatography, gel permeation chromatography, and reverse-phase partition chromatography in FPLC system. By using DABITC method the amino acid sequence of Ser-Gln-Gln-Ala-Arg was given for in "SP-1" peptide, which was conjugated with bovine serum albumin.

GASTROINTESTINAL DIGESTION OF SOYBEAN PROTEIN (Part 2)

Kazuo IWAI and Tohru FUSHIKI

Faculty of Agriculture, Kyoto University

Nutr. Sci. Soy protein, Jpn. 6, 28-31, 1985.

An attempt was made to use the disappearance of soybean 11S globulin antigen as an index for the analysis of its digestion process in vivo. At one hour after force-administration of 11S globulin to rats, only 10% of native antigen was detected in the gastrointestinal tract. By comparison of 11S globulin antigen contents with phenol red, a nonabsorbable marker, almost 11S globulin antigen was disappeared from the stomach. The native 11S globulin antigen free from denaturation in the stomach, remained its antigen in the ileum without digestion. While, spontaneous feeding of 11S globulin gave slightly different results. Its 11S antigen contents in stomach was larger than that of force-feeding. But 11S globulin antigen in small intestine of spontaneously fed rats was much smaller than that of force-fed rats. From previous findings, the denaturation of 11S globulin was a rate-limiting step in its digestion process. Thus, it suggested that the denaturation of 11S globulin in stomach is the most important step for its digestion, and spontaneous feeding is more intense than force-administration in denaturation of 11S globulin in stomach.

EFFECT OF CHRONIC FOOD RESTRICTION AND CHRONIC FEEDING OF SOY PROTEIN ISOLATE ON THE ADVANCE OF SENESCENCE IN THE SENESCENCE ACCELERATED MOUSE (SAM)

Atsuko KOHNO, Makiko UMEZAWA and Toshio TAKEDA

Department of Pathology, Chest Disease Research Institute, Kyoto University

Nutr. Sci. Soy protein, Jpn. 6, 32-37, 1985.

A murine model of accelerated senescence, the Senescence Accelerated Mouse (SAM), consisting of senescence-prone (SAM-P) series and senescence-resistant (SAM-R) series was recently developed in our laboratory. Judging from the ageing characteristics such as changes in grading score with advancing age, life span, ageing dynamics and autopsy findings, the ageing pattern in this model seems to be due to an accelerated senescence rather than to a premature ageing. The present studies were undertaken to observe the effect of quantity and quality of food on advance of senescence using SAM. 1) The effects of chronic restriction on grading score of senescence, deposition of senile amyloid (ASSAM), mean life span ad tenth decile were investigated. The grading score of SAM-P/1 was significantly improved in the 40% food restricted group. In SAM-P/1 liver, skin and testis, the severity of amyloid deposition was significantly less in the 40% restricted group. A definite tendency to prolong mean life span and tenth decile was observed in the 40% restricted group. These results suggest that 40% food restriction modulates the advance of senescence in these mice. 2)The effects of soy protein on grading score of senescence, incidence of thymoma and survival were investigated. The experimental groups consisted of soybean group (fed soybean as protein source) and casein group (fed casein as protein source). The grading scores of SAM-R/1, SAM-P/1 and SAM-P/7 were not significantly different between casein and soybean groups. There were no differences in the incidence of thymoma of SAM-P/7 between two groups. A tendency of increased survival was observed in soybean groups of SAM-R/1, SAM-P/1 and SAM-P/7. The detailed studies on the effect of soy protein on the deposition of senile amyloid, mean life span. tenth decile and immunological functions are now under investigation.

THE EFFECTS OF SOYBEAN PROTEIN ON CELL-MEDIATED IMMUNITY IN RATS

Satoru MORIGUCHI, Masamichi TOBA and Yasuo KISHINO

Department of Nutrition, School of Medicine, The University of Tokushima

Nutr. Sci. Soy protein, Jpn. 6, 38-44. 1985.

This experiment was carried out to elucidate the influence of dietary protein upon proliferation of thymocytes or splenocytes of rats following in vitro incubation with mitogens (PHA, Con A and LPS). Rats fed diets containing 20% casein or soybean protein showed a well growth and their body weights were about 180 g at the end of the experiments. On the other hand, rats fed 5% protein diets showed less gains of body weight than those of 20% protein groups. The gains of body weight were almost nothing in 5% soybean protein group throughout this experiment. Furthermore, histological studies found the less cellularity and/or atrophy in thymus and spleen of rats fed diets containing 5% casein and soybean proteins. Those histological changes were restored following the supplement of 0.3% methionine to 5% soybean protein diet. The responses of splenocytes and thymocytes against mitogens did differ in the cultures with Con A. In thymocytes the response to Con A was higher in 5% soybean group or methionine supplemented group compared with that of 5% casein group. In splenocytes the response to Con A was higher in casein group than other groups. Interleukin-1 production from alveolar macrophages (AM) showed a high value in 5% soybean protein group, but that of other groups was almost similar. These observations suggest that cell-mediated immunity in rats is comparatively maintained, even when fed on 5% level of soybean protein with supplement of methionine.

EFFECT OF SOY PROTEIN ISOLATE, CASEIN AND EGG WHITE ON CALCIUM UTILIZATION IN GROWING RATS

Yoshiaki NIIYAMA, Sadaichi SAKAMOTO and Kazuhiro UENISHI

Department of Nutrition, School of Medicine, The University of Tokushima

Nutr. Sci. Soy protein, Jpn. 6, 45-50, 1985.

Effects of different sources of protein and calcium on calcium utilization in growing rats were investigated by a balance method. Rats of the Wistar strain, weighing about 90 g, were fed on one of the six diets containing SPI, casein or egg white as a protein source and crystalline CaCO3 or egg shell as a calcium source for 3 weeks. Levels of protein and calcium in the diets were 20% and 0.6%, respectively. L-Methionine was supplemented to casein and SPI diets at levels of 0.3% and 0.6%, respectively. Food consumption of rats receiving SPI diet with pure CaCO3 was less than that of rats on casein diet with CaCO3. However, food intakes were comparable in both protein diet groups when egg shell was used as the calcium source. Rats fed on egg white diets showed least food intake among three protein diet groups, regardless of dietary calcium sources. Although calcium intakes of the respective groups of animals were varied appreciably from 1550 to 2250 mg/21 days in proportion to their food intakes, differences in calcium retention among the groups were relatively slight and the rats retained about 1000 to 1100 mg of calcium during the period. This is partly due to increased absorption in animals showing less calcium intake. Calcium absorption rates of pure CaCO3 in casein, SPI and egg white diets were 52, 56 and 67%, respectively and those of egg shell were 54, 59 and 70%, respectively. Reasons why calcium in egg shell was efficiently utilized are obscure. Average calcium contents in femur of respective diet groups of animals were identical, however, significant correlations between absorbed calcium and retained calcium and between retained calcium and calcium contents in femur were observed.

NUTRITIONAL EFFECTS OF SOY PROTEIN ISOLATE ON LIVER GLUTATHIONE CONCENTRATION AND É¡-GLUTAMYLTRANSPEPTIDASE ACTIVITY OF ADULT RATS

Misako TANIGUCHI

Department of Food and Nutrition, Nakamura Gakuen College

Nutr. Sci. Soy protein, Jpn. 6, 51-53, 1985.

By feeding a 10% SPI diet, the liver glutathione content decreased in adult male rats as well as in weanling rats. However, liver É¡-glutatmyltranspeptidase activity of adult rats was not affected by 10% SPI diet in contrast with weanling rats in which liver É¡-glutamyltranspeptidase activity increased with concomitant decrease in liver glutathione content. When weanling rats were fed on 10% SPI diet for 3 weeks, the half life of liver glutathione became shorten than that of rats fed on the laboratory chow. These results indicated that glutathione catabolism was accelerated by 10% SPI feeding in order to meet amino acid requirement, especially of cysteine, However, SPI feeding for adult rats did not affect glutathione catabolism, and nutritional value of SPI was high for adult rats, in the view of S-containing amino acid contents.

EFFECTS OF DIETARY PROTEINS ON LIPOGENIC ENZYME INDUCTION IN RAT LIVER

Nobuko IRITANI ¹, Kimiko NAGASHIMA ¹, Hitomi FUKUDA ¹, Akihiko KATSURADA ¹ and Takehiko TANAKA ²

¹ Tezukayama Gakuin College
² Osaka University Medical Scholl

Nutr. Sci. Soy protein, Jpn. 6, 54-57, 1985.

When fasted rats were fed fat-free/varied protein diets for 3 days, the activities of liver glucose-6-phosphate dehydrogenase, malic enzyme, acetyl - CoA carboxylase and fatty acid synthetase were markedly lower in rats fed soybean protein or gluten than in those fed casein or fish protein. The inductions of the lipogenic enzymes appear to be suppressed with plant proteins in comparison with animal proteins. As malic enzyme mRNA activity was not low in the soybean protein-fed animals, the translation of malic enzyme appears to be suppressed by dietary soybean protein. In the soybean protein group compared with the casein group, the incorporation of tritiated water into liver fatty acids after the injection was significantly lower. The triglyceride levels in plasma and especially in liver were also lower in the soybean and gluten groups than in the casein and fish groups. In addition, when dietary soybean protein was replaced with amino acids, the lowering effects on the lipogenic enzyme inductions were reduced but still partially found. Thus, some mechanisms ascribed to the protein itself as well as to the amino acid composition seem to cause these effects.

EFFECTS OF FEEDING SOY PROTEIN ISOLATE AND ITS PROTEOLYTIC DIGESTS ON CHOLESTEROL LEVEL IN RAT SERUM AND HEPATIC AND SMALL INTESTINAL FUNCTIONS

Hiroshi DOI ¹, Kimikazu IWAMI ¹, Fumio IBUKI ¹ and Masao KANAMORI ²

¹ Faculty of Agriculture, Kyoto Prefectural University
² Department of Food and Nutrition, Mukogawa Women's University

Nutr. Sci. Soy protein, Jpn. 6, 58-62, 1985.

Growing rats of the Wistar strain were fed ad libitum diets containing casein and soy protein isolate (SPI) and its peptic (SPI-P) and tryptic digests (SPI-T) as protein sources for one month, followed by measurements of serum cholesterol and triglyceride levels and activities several enzymes such as glutamate-pyruvate transaminase, leucine aminopeptidase, alkaline phosphatase, choline esterase and É¡-glutamyltransferase. Body weight gains of rats fed the SPI- and its proteolytic digest-based diets were significantly lower than those of rats fed the casein-based diet, but there were no differences in liver, small intestine and caecum weight (g/100 g of body weight). No differences were observed for the levels of such enzymes as above. Feeding SPI and its proteolytic digests caused a significant decrease in the serum cholesterol level as compared with feeding casein; feeding SPI-P was the most effective in hypocholesterolemic action. A possible mechanism of the action was discussed.

NUTRITIONAL CHARACTERISTICS OF SOY PROTEIN ISOLATE IN CHOLESTEROL METABOLISM

Akira YOSHIDA and Yoshifumi OKUMURA

School of Agriculture, Nagoya University

Nutr. Sci. Soy protein, Jpn. 6, 63-67, 1985.

Effect of dietary soy protein isolate on serum level of cholesterol was compared with casein, rice protein, wheat gluten and corn gluten with or without cholesterol or PCB. We previously reported the hypercholesterolemic effect of several xenobiotics such as PCB and DDT. This type of hypercholesterolemia is quite different from that due to dietary addition of cholesterol because of the hypercholesterogenic effect of these xenobiotics, and would be a new model of dietary hypercholesterolemia. Serum level of cholesterol in rats fed a 15% soy protein isolate was significantly lower than that of rats fed a casein or rice protein diet. Rice protein diet group showed rather higher serum level of cholesterol than casein diet group. In the presence of 1% of cholesterol or 300 ppm of PCB in diet also showed the similar results. When dietary protein was wheat gluten or corn gluten, serum level of cholesterol was lower than casein diet group. only when cholesterol was added to the diets. If PCB was added to the diet, serum level of cholesterol in rats fed wheat gluten or corn gluten was not different from that of casein diet group. Thus rice protein and wheat gluten showed different effects on serum cholesterol. However, when rats were fed a 90% rice diet or 90% wheat diet, serum level of cholesterol was the same even with or without dietary addition of cholesterol or PCB. In all cases of the present experimental conditions, dietary soy protein was hypocholesterolemic as compared with casein, and wheat gluten and corn gluten were hypocholesterolemic only when cholesterol was added to the diet.

EFFECT OF SUCCINYLATION OF SOY PROTEIN ISOLATE (SPI) AND CASEIN ON PLASMA CHOLESTEROL CONCENTRATION IN RATS

Shigeru SAEKI and Shuhachi KIRIYAMA

Faculty of Agriculture, Hokkaido University

Nutr. Sci. Soy protein, Jpn. 6, 68-75, 1985.

Plasma cholesterol concentration (p-chol) of rats fed a 20% casein diet for 10 days was significantly higher than that of rats fed a soy protein isolate (SPI) diet. Three days after crossing - over of their respective diets, p-chol of each group reached the same level as that of its previous counterpart. When fed a 2% succinylated casein (2% SC) or SPI (2% SS) diet, p-chol level was unchanged in spite of slightly but significantly lowered digestibilities. When the degree of succinylation was increased up to 10% (10% SC or 10% SS), growth rate of rats decreased. The addition of 1% lysine hydrochloride (Lys) to these diets completely improved growth. The addition of Lys to a 10% SS diet significantly increased p-chol above SPI-fed group, but yet it was significantly lower than casein-fed group. Feeding of a 10% SC diet significantly reduced p-chol only after 7 days, but Lys supplementation to this diet induced complete return of p-chol to that of casein-fed group. The addition of cholestyramine (2% and 4% of diet) to a casein or SPI diet had no effect on p-chol. Only when a casein diet was supplemented with 4% cholestyramine, p-chol progressively increased after a small fall for 2 days. From these and previous results in our laboratory, we conclude that the hypocholesterolemic effect of SPI is independent of bile acid binding activity of its undigested residues in the intestinal lumen.

HYPOCHOLESTEROLEMIC EFFECT OF SOY PROTEIN ISOLATE IN RATS (VI )

Michihiro SUGANO and Kazunari TANAKA

Kyushu University School of Agriculture

Nutr. Sci. Soy protein, Jpn. 6, 76-79, 1985

The effect of the Arg/Lys ratio on cholesterol metabolism was studied in male rats given semipurified diets containing isolated soybean protein or casein. Lys or Arg was supplemented to vegetable or animal proteins to make the Arg/Lys ratio in these proteins identical. After 30 days of feeding, rats were received Åm14CÅn cholesterol intravenously and Åm3HÅn cholesterol orally. Amino acid supplementation caused a trend toward reducing serum cholesterol concentration. Analysis of die-away curve ofÅm14CÅn cholesterol revealed independence of several parameters of cholesterol kinetics to the Arg/Lys ratio, except a slight reduction of the slowly exchangeable pool (pool B) after the addition of Lys to soybean protein. Cholesterol absorption measured by the dual isotope serum ratio method was unmodified by adding amino acids, and the excretion of intravenous and oral cholesterol into feces was essentially the same. The rate of biliary cholesterol and bile acid output was apparently uninfluenced by the amino acid supplementation. These results indicate that the effect of the Arg/Lys ratio of dietary protein on the cholesterol metabolism is not demonstrable when it was changed by adding these amino acids in contrast to the case of intact proteins with the different ratios.

EFFECTS OF DIETARY PROTEINS ON GASTROINTESTINAL TRANSIT TIME, FECAL STEROL EXCRETION, AND PLASMA CHOLESTEROL LEVEL IN THE RAT

Shin-ichi HAYASHI, Yoshiko FUJITA, Junko YAMASHITA and Yasuko MURAKAMI

Department of Nutrition, The Jikei University School of Medicine

Nutr. Sci. Soy protein, Jpn. 6, 80-84, 1985.

1. Dietary soy protein isolate (SPI) suppressed plasma cholesterol level of rats compared with casein. When mixed with casein, SPI showed stronger plasma-cholesterol-suppressing effect than wheat gluten or zein did. 2. 50% Casein moderately suppressed plasma cholesterol level of rats compared with 25% casein. 3. At various protein contents, SPI increased fecal excretion of neutral sterols compared with casein. When mixed with casein, SPI caused more excretion of fecal neutral sterols than wheat gluten or zein did. 4. SPI caused a significant reduction in gastrointestinal transit time (T1/2) compared with casein. 5. These results suggested that SPI suppressed plasma cholesterol level by accelerating fecal excretion of sterols, owing to its characteristic digestibility.

PRODUCTION AND NUTRITIONAL QUALITY OF AN OLIGOPEPTIDE MIXTURE PRODUCED FROM SOY PROTEIN ISOLATE

Soichi ARAI ¹ and Hiroko KIMURA <sup>2

1</sup>Faculty of Agriculture, The University of Tokyo
²Kagawa Nutrition College

Nutr. Sci. Soy protein, Jpn. 6, 85-87, 1985.

A method for producing an oligopeptide mixture (OPM) from soy protein isolate (SPI) by treatment with papain and trypsin has been proposed in our previous paper [Nutr. Sci. Soy Protein, Jpn), 4, 22-25 (1983)Ån. In the present work we attempted to replace trypsin with prolyl endopeptidase (EC 3. 4. 21. 26) of Flavobacterium origin, in order to produce an OPM having no significant amounts of free amino acids. SPI was treated first with papain as described in the previous paper and secondly with prolyl endopeptidase. The product was dialyzed to obtain an oligopeptide fraction as a diffusate. The non-diffusible fraction was submitted again to the prolyl endopeptidase treatment to obtain an oligopeptide fraction in a similar manner. These two fractions were pooled prior to lyophilization to produce an OPM. Gel filtration analysis showed that the average molecular weight of the OPM approximated 800 daltons, with no appreciable amounts of lower - and higher molecular weight species. The amino acid composition of the OPM resembled that of the SPI used as material. Feeding tests with rats are under way to verify a superior nutritional effect of the OPM compared to SPI as well as to a free amino acid mixture simulating the OPM.

NUTRITIVE VALUE OF SOY PROTEIN ISOLATE AND EFFECT OF METHIONINE SUPPLEMENTATION IN HUMAN ADULTS

Kyoichi KISHI ¹, Midori MAEGAWA ¹, Shigeru YAMAMOTO ¹, Fujiko SHIZUKA ¹ and Goro INOUE ²

¹ Department of Nutrition, School of Medicine, The University of Tokushima
² Department of Physiology, Hyogo College of Medicine

Nutr. Sci. Soy protein, Jpn. 6, 88-95, 1985.

The present study is a continuation of previous report (Nutr. Sci. Soy Protein, Jpn. 5, 88-93, 1984) which showed no effect of methionine supplementation to soy protein isolate (SPI) in healthy adult men. In the first experiment, five young men received a SPI diet at N intake of 75 mg N/kg/day with or without 1.0% L-methionine supplementation for 10 days. In the second and similar experiment, five young women received 1% methionine supplemented and unsupplemented SPI diets (90 mg N/kg/day). No differences in N balance, digestibility or biological value were observed between supplemented and unsupplemented SPI diets in experiments 1 and 2. In the third experiment, five young men received either SPI diet or mixed protein diet of soy and egg (ratio of 7/3 by N) at N intake of 90 mg N/kg/day for 10 days each. There was no significant difference between two diet groups for N balance. From regression analysis of N balance to N intake, the slopes were 0.637 and 0.506 and the intakes to maintain N equilibrium were 93.4 and 104.5 mg N/kg/day in men for unsupplemented and methionine enriched SPI, respectively. From these and previous studies it is clear that methionine supplementation to well-processed SPI is unnecessary for adult human subjects in short-term N balance studies.

EFFECT OF SUPPLEMENTING METHIONINE TO SOY PROTEIN ISOLATE ON THE PROTEIN UTILIZATION IN MALE ADULT HUMANS (2nd Report)

Tetsuo TAKAHASHI and Tetsuzo YAMADA

Institute of Health and Sports Sciences, University of Tsukuba

Nutr. Sci. Soy protein, Jpn. 6, 96-102, 1985.

The effect of supplementing 1.0 or 1.5% of L-methionine to soy protein isolate on the protein utilization was examined by nitrogen balance method in five healthy young men under the condition of nitrogen intake level of 75 mg/kg/day. The nitrogen balance was improved by addition of 1.0% of methionine in four of five subjects, and on an average the tendency of improved nitrogen balance due to methionine supplementation was observed (p< 0.1). However, no supplemental effect was shown by addition of 1.5% of methionine because of large individual variation. When 1.0% of methionine was supplemented, there was a tendency that the degree of improvement of nitrogen balance was proportional to the degree of negative nitrogen balance in the control (non-supplement) period.

SUPPLEMENTARY EFFECT OF METHIONINE ON THE UTILIZATION OF SOY PROTEIN ISOLATE IN HUMAN ADULTS (2nd Report)

Kayoko KANEKO and Goro KOIKE

Kagawa Nutrition College

Nutr. Sci. Soy protein, Jpn. 6, 103-107, 1985.

Supplementary effect of L-methionine on the utilization of SPI was evaluated in six young women by the nitrogen balance method at protein intake level of 0.3 g/kg/day. Subjects were given SPI in the first experimental period and SPI supplemented with 1% methionine in the second period immediately after a menstruation as the sole source of protein. After one day on protein free diet, each subject received a conventional low protein, diet for three days, then the following seven days a semisynthetic low protein, diet containing SPI or SPI supplemented with methionine in each experimental period, respectively. Energy intake was approximately maintenance level of 35.3Å}4.5 kcal/kg/day. Nitrogen balances in SPI period and methionine supplemented period were both negative, and there was no significant difference between two values. Blood analysis was carried out before and after SPI period and after methionine supplemented period. Urinary creatinine, urea and ammonia excretions were not markedly affected by the methionine supplementation.

NUTRITIVE EFFECTS OF L-METHIONINE SUPPLEMENT TO THE SOY PROTEIN ISOLATE IN HUMAN BODY : ON THE CASE OF LOW PROTEIN LEVEL

Hideo KOISHI, Toyoko OKUDA, Hiroko MIYOSHI and Yukiko OI

Faculty of the Science of living, Osaka City University

Nutr. Sci. Soy protein, Jpn. 6, 108-112, 1985.

Nutritive effects of L-methionine supplement to the soy protein isolate (SPI) were examined on 5 male adult human subjects. They were given a protein free diet for one day and then were given a low protein SPI diet containing 76 mg N/kg body weight/day for 10 days. After three days of this experiment, again they were given the protein free diet for one day and then were given the SPI diet containing 76 mg N/kg/day with L-methionine at a level of 1.5% of protein in the SPI diet for 10 days. There were no significant differences between the SPI diet and the SPI + Met diet on availability of food energy or plasma concentration of cholesterol. On the SPI + Met diet the nitrogen balances were improved significantly and plasma albumin concentration increased. Also the concentration of the urea in plasma decreased on the methionine supplementation.

INFLUENCE OF SOY PROTEIN ISOLATE UPON GLUCOSE TOLERANCE IN MAN

Seiki NAMBU ¹, Masayuki MATSUSHITA ¹, Hideki KOH ¹, Shigeki FUJII ¹,Yasuko NISHIOHEDA ¹, Motoo Tsushima ¹,Teruaki NARIKAWA ², Michio FURUSAWA ² and Tadao NAKANO ²

¹ Division of Atherosclerosis and Metabolism, Department of Internal Medicine, National Cardiovascular Center
² Division of Nutritional Education, National Cardiovascular Center

Nutr. Sci. Soy protein, Jpn. 6, 113-116, 1985

Preliminary study has been carried out to determine whether the amount of dietary intake of soy protein isolate (SPI) affects the glucose-tolerance of NIDDM (non-insulin dependent diabetes mellitus) or not. Four hospitalized patients with NIDDM controlled by energy-restricted diet were chosen. The daily SPI-diet contained 1000 kcal of energy and 73 g of protein including 15 g of SPI or 1500 kcal of energy and 82 g of protein including 30 g of SPI. Each of them was given for one week and compared with recently reported 8 cases with diet controlled NIDDM whose dietary prescription was 1000 kcal of energy and 73 g of protein including 30 g of SPI. In 2 cases with controlled NIDDM, 30 g of SPI in 1500 kcal/day resulted in 12.3% increase in the sum of plasma glucose from 90 minutes to 180 minutes (áîglucose) in 75 g oral glucose tolerance test. The increment of glucose was slightly higher than that in the same amount of SPI in 1000 kcal/day. On the other hand, in the 2 cases with controlled NIDDM 15 g of SPI in 1000 kcal/day resulted in 20.9% decrease in áîglucose. In this preliminary study we suggest that 30 g of SPI in diet might be excess for a control of NIDDM and it will be necessary to investigate further the nutritional quality of SPI in dietary control of NIDDM.

The soy protein protein reserch(Japan)