Effects Of Soy Protein Isolate Research Articles

Mammary Gland Morphology and Gene Expression Differ in Female Rats Treated with 17β-Estradiol or Fed Soy Protein Isolate

Soy foods have been suggested to have both positive health benefits and potentially adverse effects as a result of their content of phytoestrogens. However, studies on the estrogenicity of soy foods are lacking. Here we directly compared the effects of soy protein isolate (SPI), the protein in soy infant formula, with those of 17β-estradiol (E2), on global gene expression profiles and morphology in the female rat mammary gland. Rats were fed AIN-93G diets containing casein or SPI beginning on postnatal d 30. Rats were ovariectomized on postnatal d 50 and treated with 5 μg/kg/d E2 or vehicle for 14 d. Microarray analysis revealed that E2 treatment altered expression of 780 genes more than or equal to 2-fold (P < 0.05), whereas SPI feeding altered expression of only 53 genes more than or equal to 2-fold. Moreover, the groups had only 10 genes in common to increase more than or equal to 2-fold. The combination of SPI feeding and E2 altered expression of 422 genes and reversed E2 effects on many mRNAs, including those involved in the c-myc signaling pathway, cyclin D1, and Ki67. ERα binding to its response element on the Tie-2/Tek and progesterone receptor promoters was increased by E2, but not SPI, and this promoter binding was suppressed by the combination of E2 + SPI for the Tie-2/Tek promoter but increased for the progesterone receptor promoter (P < 0.05). SPI reduced the ratio of epithelial to fat pad area and E2 + SPI reduced both epithelial and fat pad area (P < 0.05). These data suggest that SPI is only minimally estrogenic in the rat mammary gland even in the absence of endogenous estrogens.

Hepatoprotective effects of soy protein isolate against dimethylnitrosamine-induced acute liver injury in Sprague Dawley rat

Diseases and injuries impose oxidative stress on different organs and systems of the body. This study was conducted to investigate the hepatoprotective effects of soy protein isolate against acute liver toxicity induced by dimethylnitrosamine (DMNA). Forty-eight Sprague Dawley rats were randomly divided into three groups. Groups A and B consumed a casein containing diet and the Group C received a soy protein isolate (SPI) containing diet for 18 days. Group A was then given an intra-peritoneal saline injection and continued on a casein diet for another 4 days before being killed. Each animal from groups B and C was given a single intra-peritoneal injection of DMNA (30 mg/kg) on the 18th day of the study. All groups continued their diets for 4 days before their sacrifice. The serum ALT decreased and albumin increased significantly in rats fed 20 % SPI containing diet (P < 0.05). Histological results showed that SPI improved DMNA-induced alteration in the liver structure. Morphological and biochemical data suggest that soy protein isolate containing diet decreased DMNA-induced liver damage.

Hepatoprotective effects of soy protein isolate against dimethylnitrosamine-induced acute liver injury in Sprague Dawley rat

Hepatoprotective effects of soy protein isolate against dimethylnitrosamine-induced acute liver injury in Sprague Dawley rat

Effects of Soy Protein Isolate Feeding on Severe Kidney Damage in DOCA Salt-Treated Obese Zucker Rats

This study assessed the effects of soy protein isolate (SPI) on severe kidney damage in deoxycorticosterone acetate (DOCA) salt-treated obese Zucker rats. These rats underwent heminephrectomy and were fed either casein or SPI diet for 12 weeks. From weeks 8 to 10 of the experiment, kidney damage was induced by biweekly injection of 25 mg/kg DOCA and administration of 0.5% NaCl (w/v) ad libitum. Urinary protein and N-acetyl-β-d-glucosaminidase excretions of SPI rats were much lower than those of casein rats at weeks 1 (p < 0.01) and 2 (p < 0.05) after DOCA treatment. Abnormal mineral excretions induced by DOCA treatment in casein rats were hardly detected in SPI rats. Severe atrophy of tubular epithelium and some flattened/detached renal tubules were also observed in casein rats, but not in SPI rats. These results indicate that consecutive treatment of SPI protects against renal dysfunction, particularly tubulointerstitial nephritis, in DOCA salt-treated obese Zucker rats.

적소두단백질(Red Bean Protein)과 Transglutaminase를 첨가한 돈육 근원섬유 단백질의 물성 증진 효과

본 연구는 TGase 첨가에 따른 근원섬유 단백질과 비육류 단백질인 적소두단백질 또는 대두단백질간의 상호작용을 비교 평가하기 위해 수행되었다. 실험 1에서는 비육류 단백질 함량에 따른 물성 변화를 평가하였으며 실험 2에서는 TGase 반응시간에 따른 최적 조건을 평가하였다. 가열수율은 비육류 단백질을 첨가한 처리구에서 유의적으로 증가하였으며 특히 적소두단백질 1%을 첨가하였을 때 가장 높은 가열수율을 나타내었다(p<0.05). 반면에 겔 강도 및 점성도는 근원섬유 단백질 단독 처리구와 비육류 단백질을 첨가한 처리구와 비교하였을 때 유의적으로 차이가 나타나지 않았다(p>0.05). 또한 전기영동 결과는 가열 전 TGase 첨가 후 4시간 반응시켰을 때는 모든 처리구에서 변화를 보이지 않았지만(실험1), TGase 첨가 후 10시간 반응시킨 모든 처리구에서는 biopolymer 밴드가 나타났다(실험2). 또한 TGase 반응시간에 따른 겔 강도는 10시간째에 유의적으로 증가하였다(p<0.05). 하지만 10시간의 반응시간은 배양시간이 너무 길어 산업적으로 이용하기 부적합 하기 때문에 TGase함량을 0.5%로 증가시켜 효소와 단백질간의 최적 반응시간을 평가하고 비육류 단백질과의 상호작용을 통한 물성을 증진시키는 연구가 앞으로 필요할 것으로 사료된다. The effects of soy protein isolate (SPI) and red bean protein isolate (RBPI) on gelling properties of pork myofibrillar protein (MP) in the presence of microbial transglutaminase (MTG) were studied at 0.45 M NaCl. MP paste was incubated with MTG (0.1%) at various levels (0.1, 0.3, 0.5, and 1%) of SPI and RBPI before incubating at <TEX>$4^{\circ}C$</TEX> for 4 h. The rheological property results showed that MP gel shear stress increased with increasing RBPI concentration. Cooking yield (CY) of the MP gel increased with increasing RBPI and SPI, whereas gel strength (GS) was not affected by adding RBPI or SPI. Thus, effects of incubation time (0, 4, 8, 10, and 12 h) were measured at 0.1% SPI and RBPI. GS values of the MP gel at 10 and 12 h were similar and were higher than those of the others. CY values were highest when RBPI (0.1%) was added, regardless of incubation time. The protein patterns indicated that incubating the MP with MTG for 10 h resulted in protein crosslinking between MP and RBPI or SPI. Based on these results, RBPI and SPI could be used as an ingredient to increase textural properties and cooking yield of meat protein gel.

Effects of soy protein isolate and egg white solids on the physicochemical properties of gluten-free bread

Gluten-free formulations are often supplemented with proteins to improve their quality. To determine the effects of alternative proteins on a hydroxypropyl methylcellulose (HPMC)-treated gluten-free dough system, soy protein isolate was added at 1%, 2% and 3% while egg white solids were investigated at 5%, 10% and 15%. The formulated doughs were analysed using thermoanalytic and rheological techniques to determine the role of water and subsequent flow behaviour upon hydrocolloid addition. The baked loaves were measured for specific loaf volume and tensile strength to determine bread quality. The addition of soy protein isolate and egg white solids (5% and 10%) reduced dough stability by suppressing HPMC functionality, reducing available water, weakening HPMC interactions with the starch matrix and reducing foam stability. At 15% addition, egg white solids became the primary protein scaffolding in the dough and overcame negative interactions with HPMC, improving the loaf volume. However, this formulation may need further optimisation to meet full consumer acceptability.

Quality characteristics of light pork burgers fortified with soy protein isolate

Effect of soy protein isolate (SPI) (0.5 to 3%, w/w) on physical, chemical, sensory, and microstructure properties of light pork burgers containing added water incorporated with 0.7% mixed gum (konjac/gellan gum= 3:1) was carried out. Increasing of SPI levels resulted in significantly (p<0.05) higher cooking yield, lower reduction in diameter, and darker color of light pork burgers in relation to the control. Textural characteristics including cohesiveness, springiness, and chewiness significantly increased (p<0.05) with increasing of SPI up to 2% level; however, decreased these parameters were evident at 3% SPI used. Sensory results indicated that the 2% SPI light formulation showed significantly higher (p<0.05) scores for texture and juiciness than those of the control. The product was considered nutritious and provided the reduction of fat and total caloric content about 62.3 and 43.1% of the full-fat product, respectively.

Soy Protein Reduces Serum LDL Cholesterol and the LDL Cholesterol:HDL Cholesterol and Apolipoprotein B:Apolipoprotein A-I Ratios in Adults with Type 2 Diabetes1–3

Type 2 diabetes is highly prevalent in North America and is associated with increased risk of cardiovascular disease (CVD). Evidence supports a role for soy protein in the reduction of serum lipids related to CVD risk; however, few studies have focused on adults with type 2 diabetes who are not on lipid-lowering medications and/or do not have diabetic complications. The purpose of this study was to determine the effect of soy protein isolate (SPI) consumption on serum lipids in adults with diet-controlled type 2 diabetes. Using a double-blind, randomized, crossover, placebo-controlled intervention study design, adults with diet-controlled type 2 diabetes (n = 29) consumed SPI (80 mg/d aglycone isoflavones) or milk protein isolate (MPI) for 57 d each separated by a 28-d washout period. Twenty-four–hour urine samples were collected on d 54–56 of each treatment for analysis of isoflavones and blood was collected on d 1 and 57 of each treatment and analyzed for serum lipids and apolipoproteins. SPI consumption increased urinary isoflavones compared with MPI. SPI consumption reduced serum LDL cholesterol (P = 0.04), LDL cholesterol:HDL cholesterol (P = 0.02), and apolipoprotein B:apolipoprotein A-I (P = 0.05) compared with MPI. SPI did not affect serum total cholesterol, HDL cholesterol, triacylglycerol, apolipoprotein B, or apolipoprotein A-I. These data demonstrate that consumption of soy protein can modulate some serum lipids in a direction beneficial for CVD risk in adults with type 2 diabetes.

Effect of soy protein isolate on the thermal, mechanical and morphological properties of poly ( ɛ-caprolactone) and corn starch blends

The development of biodegradable polymers is considered to be a good alternative to decrease the volume of the plastic waste disposed into the environment every year. The use of natural polymers as raw materials to develop polymer blends and composites has increased the demand for renewable sources such as starch and soy protein. In this work, the authors prepared and characterized the thermal, mechanical and morphological properties of blends based on poly ( ɛ-caprolactone) and modified corn starch, with added soy protein isolate (SPI) and sorbitol. All samples were processed by extrusion in a single-screw extruder and hot pressing. It was observed that the addition of modified corn starch and SPI were responsible for the reduction of thermal and mechanical properties of the materials, compared to pristine PCL. However, with increasing amounts of SPI and the reduction of starch incorporated into the samples, their properties tend to recover. The insertion of soy protein isolate in the formulations was done with the aim of balancing the C/ N ratio of the blend, which plays a key role in the biodegradation process of these materials.

Effects of soy protein isolate on bone mineral density and physical performance indices in postmenopausal women-a 2-year randomized, double-blind, placebo-controlled trial

Postmenopausal decreases in body composition, physical performance, and bone mass have been shown to be reversed by estrogen, but given the concerns regarding its use, women are looking for alternatives such as soy isoflavones. Most studies on the effects of soy on bone mineral density (BMD) in postmenopausal women have been short-term, that is, 3 to 6 months, and failed to provide conclusive evidence. There is no evidence of its effects on physical performance. The aim of the present study was to investigate the effects of soy plus isoflavones on BMD and physical performance in postmenopausal women. This was a 2-year randomized controlled trial. A total of 203 healthy postmenopausal women were given either 25 g of soy protein without isoflavones, 25 g of soy protein with 90 mg of isoflavones, or 25 g of milk protein (casein and whey) as a control agent for 24 months. Women were followed every 6 months with BMD and physical performance measurements for 2 years. Primary analysis was intent-to-treat analysis. Analysis of variance, chi and Fisher's exact tests, and analysis of covariance were used. There was a significant decrease in the BMD of the lumbar spine and femoral neck in those who completed the study in all groups. Soy isoflavones prevented major bone loss from baseline at the femoral trochanter with no between-group significance. Physical performance measurements decreased in all the groups. : Twenty-five grams of soy protein with 90 mg of isoflavones has no added benefit in preventing bone loss or improving physical performance.

Effect of soy protein isolate on quality of light pork sausages containing konjac flour

The effect of soy protein isolate (SPI) on quality characteristics of light pork sausages (10% fat) containing konjac flour was investigated. Three formulations which replaced for pork meat with SPI ranging 1 to 2% levels were studied for their physical and sensory properties. Incorporation of 2% SPI level significantly increased (p < 0.05) moisture content and cooking yield, while decreased purge loss of the sausages in relation to the control. Also, the sausages were less red and more yellow when the addition of SPI was not less than 1.5% level. Sensory results indicated that some quality attributes of light sausages such as juiciness and firmness can be improved by the addition of SPI. Both 2% SPI and control light sausages were darker and firmer and microbiologically safe after storage at 4-5°C for 4 weeks.

Effects of soy protein isolate and moderate exercise on bone turnover and bone mineral density in postmenopausal women

The aim of this study was to assess the independent and additive effects of soy protein isolate (SPI) and moderate-intensity exercise (EX) on bone turnover and bone mineral density (BMD). This study used a placebo-controlled, double-blind (soy), randomized 2 (SPI vs milk protein isolate [MPI]) x 2 (EX vs no EX) design. Sixty-one postmenopausal women were randomized, and 43 (62 +/- 5 y) completed the 9-month intervention (SPI, n = 10; MPI, n = 12; SPI + EX, n = 11; MPI + EX, n = 10). Serum C-terminal cross-linked telopeptides of type I collagen and serum bone-specific alkaline phosphatase were measured as markers of bone resorption and formation, respectively. BMD was measured by dual-energy x-ray absorptiometry. At 9 months, SPI reduced serum C-terminal cross-linked telopeptides (-13.3% +/- 15.3% vs -1.5% +/- 21.0%; P = 0.02) and serum bone-specific alkaline phosphatase (-4.7% +/- 14.7% vs 6.5% +/- 17.7%; P = 0.02) compared to milk protein isolate. EX attenuated the reduction in serum C-terminal cross-linked telopeptides (-1.9% +/- 21.6% vs -12.4% +/- 15.3%; P = 0.04); however, no EX effects were apparent in serum bone-specific alkaline phosphatase at 9 months (2.8% +/- 16.1% vs -1.0% +/- 18.3%; P = 0.28). Neither SPI nor EX affected BMD at any site; however, change in BMD was related to change in fat mass (r = 0.40, P < 0.05). In postmenopausal women (1) SPI reduces bone turnover with no impact on BMD over 9 months; (2) moderate-intensity endurance exercise training did not favorably alter bone turnover and had no impact on BMD; and (3) there were no additive effects of soy and exercise on bone turnover or BMD.

Effect of soy protein isolate on glycemic control in adults with type 2 diabetes

Effect of soy protein isolate on glycemic control in adults with type 2 diabetes

Effect of soy protein isolate on serum lipids in adults with type 2 diabetes

Effect of soy protein isolate on serum lipids in adults with type 2 diabetes

Effects of soy protein isolate, acid-hydrolysed vegetable protein and glucose on the volatile components of extruded wheat starch

The volatile components produced in wheat starch containing 1% soy protein isolate (SPI), and wheat starch/1% SPI combined with 1% glucose, 1% acid-hydrolysed vegetable protein (aHVP), or 1% glucose and 1% aHVP, extruded under different processing conditions (temperatures of 150 or 180 °C and moisture content of 16% or 20%), were identified by gas chromatography–mass spectrometry (GC–MS). Gas chromatography olfactometry (GCO) was used to assess the odour intensity of volatile components present in the starch/glucose/SPI and starch/glucose/SPI/aHVP extrudates obtained at 180 °C. In total, 94 compounds were identified in the eight extrudates. The smallest number (31) was found in the extrudate of the starch/glucose/SPI feedstock processed at 150 °C and the largest (64) in the extrudate of the starch/SPI feedstock processed at 180 °C. Lipid degradation products, such as alkanals, 2-alkanones, 2-alkenals and 2,4-alkadienals, were present in all extrudates in significant quantities. Strecker aldehydes were also present in all extrudates; however, in those extrudates containing aHVP, these compounds were quantitatively the dominant components. Maillard reaction products, such as pyrroles, pyrazines and oxazoles, were mainly found in extrudates containing aHVP whereas sulphur-containing aliphatic compounds were found in all extrudates. The production of the Maillard reaction products and sulphur-containing compounds was favoured by extrusion at 180 °C. Sensory analyses showed that each of the eight extrudates had different odours, and that the extrudates containing both glucose and aHVP possessed the highest overall odour intensity. In addition, SPI was found to have a modifying effect on the volatile content and odour of extrudates also containing glucose and aHVP.

The Science of Soy: What Do We Really Know?

A stroll through nearly any American grocery store or pharmacy yields ample proof of the soybean’s increasing role in the U.S. diet. Food packaging offers statements about products’ soy content and the purported associated health benefits. Products such as tofu, soy milk, soy-based infant formula, and meatless “texturized vegetable protein” burgers are widely available. Shelves of dietary supplements and nutraceuticals are stocked with isoflavones, naturally occurring estrogenic compounds found in soy. The general impression is one of certainty that both soy and soy isoflavones deliver many health benefits, including prevention of cardiovascular disease, cancer, and osteoporosis, as well as treatment of menopausal symptoms. The science is less absolute, however, and still evolving. Soy provides a complete source of dietary protein, meaning that, unlike most plant proteins, it contains all the essential amino acids. According to the American Soybean Association, 3.14 billion bushels (85.5 million metric tons) of soybeans were harvested in the United States in 2004. Approximately half of the harvest was exported, and most of the remainder was crushed to produce oil and protein meal for domestic use. An April 2006 report from the USDA Economic Research Service indicates that only a small amount of whole soybeans are used to produce soy foods, and just 2% of soy protein meal is used for human consumption; the rest is used for animal feed. The Soyfoods Association of North America reports that U.S. sales of soy foods reached $3.9 billion in 2003, continuing an 11-year trend of 15% average annual increases. According to the United Soybean Board’s 2004–2005 Consumer Attitudes About Nutrition report, 25% of Americans consume soy foods or beverages at least once per week, and 74% view soy products as healthy. Nevertheless, Americans as a whole still consume very little soy protein. Based on 2003 data from the UN Food and Agriculture Organization, per-capita soy protein consumption is less than 1 gram (g) per day in most European and North American countries, although certain subpopulations such as vegetarians, Asian immigrants, and infants fed soy-based formula consume more. The Japanese, on the other hand, consume an average 8.7 g of soy protein per day; Koreans, 6.2–9.6 g; Indonesians, 7.4 g; and the Chinese, 3.4 g. Traditional soy foods include tofu, which is produced by pureeing cooked soybeans and precipitating the solids, and miso and tempeh, which are made by fermenting soybeans with grains. “Second generation” soy products involve chemical extractions and other processing, and include soy protein isolate and soy flour. These products become primary ingredients in items such as meatless burgers, dietary protein supplements, and infant formula, and are also used as nonnutritive additives to improve the characteristics of processed foods.

Diets containing soy protein isolate or the soy isoflavone genistein suppress p53‐mediated activation of the colon DNA damage response pathway in azoxymethane (AOM)‐treated rats

We examined effects of soy protein isolate (SPI) and genistein (GEN) on acute activation of the DNA damage response pathway (detected as increased phospho-p53-ser15) and apoptosis (TUNEL) in male Sprague-Dawley rat colon, after administration of the colon carcinogen AOM. Rats were fed AIN93G diets containing as sole protein source casein (CAS), SPI or CAS + GEN (0.25g/kg). Colons were obtained just prior to and at 1 and 4 days post-AOM. Mid-points of proximal and distal colon were analyzed. Prior to AOM, there were only few phospho-p53-ser15 positive crypt cells in proximal colon (~0.3 cells/crypt) and none in distal colon of all diet groups. At day 1 post-AOM, increased numbers of phospho-p53-ser15 positive cells were observed in crypts of proximal and distal colon, relative to no-AOM control rats (P<0.05). In all groups at 4 days post-AOM, the numbers of phospho-p53-ser15 positive crypt cells were lower than for day 1, but higher than for no-AOM. SPI and GEN rats had fewer phospho-p53-ser15 positive cells in proximal and distal colon at day 1 relative to CAS (30–40% lower, P<0.05). TUNEL results generally followed the same temporal pattern. At day 1 post-AOM, circulating insulin concentrations were reduced by SPI and GEN. Results suggest that SPI and GEN promote a physiological state in the colon which is more resistant to AOM-induced DNA damage and which may involve reduced insulin action. Supported by USDA 6251-51000-004-01S.

Effects of batters containing different protein types on the quality of deep-fat-fried chicken nuggets

The effects of soy protein isolate (SPI), whey protein isolate (WPI) and egg albumen (EA) on the quality of deep-fat-fried chicken nuggets were studied. Batter without protein addition was used as a control. Batter pickup and moisture content, oil content, texture, porosity and colour of the nuggets were determined for 3, 6, 9 and 12 min of frying at 180 °C. Additionally, the rheological properties of batters were studied. SPI (3%) provided the highest apparent viscosity and coating pickup. All the batters showed shear-thinning behaviour except EA-added batter. Addition of different proteins to the batter formulation decreased the oil content of the final product. EA reduced the oil content of chicken nuggets significantly but yielded softer products. WPI (3%) was found to be the most effective ingredient on improving quality parameters of deep-fat-fried chicken nuggets. WPI (3%) added batters provided the hardest and crunchiest product with the darkest colour and also significantly reduced the oil content of the fried nuggets.

Ethanol washing does not attenuate the hypocholesterolemic potential of soy protein

Objective A feeding study in rats investigated the principal active component for the hypocholesterolemic effect of soy protein isolate (SPI) by comparing the effect before and after ethanol washing. Methods Five-week-old male Sprague-Dawley rats were fed cholesterol-enriched AIN-93G diets containing 20% casein (CAS), 20% SPI, 20% ethanol-washed SPI (EWS), 18.4% EWS plus 1.6% ethanol extract (EE), or 20% CAS plus 1.6% EE for 2 wk. Results Plasma cholesterol concentrations in rats fed EWS and SPI were comparable and were significantly lower than those in rats fed CAS. The addition of EE to EWS and CAS did not influence plasma cholesterol level. Fecal steroid excretion of the three SPI groups was higher than that of the two CAS groups. The addition of EE to EWS and CAS showed a tendency to increase acidic steroid and decrease neutral steroid. Conclusions In this experiment which used identifiable protein preparations, a significant fraction of the cholesterol-lowering effect of SPI in rats was attributed to its protein component but not to the ethanol-extractable minor constituents including isoflavones.

Soy Isoflavone Intake Lowers Serum LDL Cholesterol: A Meta-Analysis of 8 Randomized Controlled Trials in Humans

Clinical trials have noted hypocholesterolemic effects of soy protein intake, but the components responsible are not known. This meta-analysis of 8 randomized controlled trials was conducted to more precisely evaluate the effects of isoflavones on blood LDL cholesterol concentration independently of soy protein level. PubMed was searched for English-language "randomized controlled trial" articles published from 1966 to 2003 that described the effects of soy protein isolate (SPI) intake with measured isoflavone levels on blood lipids in humans using the search terms "soy protein," "isoflavones," and "cholesterol." From 31 articles identified by the search, 8 articles (with 10 low vs. high isoflavone comparisons) were selected for the meta-analysis. Subjects in each comparison consumed similar dietary fat, cholesterol, and fiber; the reported body weight of subjects did not change significantly during treatment. Serum LDL cholesterol concentration in subjects who consumed SPI (mean 50 g/d) with high isoflavone content (mean intake 96 mg/d) decreased by 0.15 mmol/L (95% CI: 0.08 to 0.23 mmol/L; P < 0.0001) compared with those who consumed the same SPI level with low isoflavone content (mean intake 6 mg/d). Decreases in serum LDL cholesterol concentration in hypercholesterolemic and normocholesterolemic subjects were 0.18 mmol/L (95% CI: 0.01 to 0.35 mmol/L; P = 0.03) and 0.14 mmol/L (95% CI: 0.06, 0.23 mmol/L; P = 0.0008), respectively. With identical soy protein intake, high isoflavone intake led to significantly greater decreases in serum LDL cholesterol than low isoflavone intake, demonstrating that isoflavones have LDL cholesterol-lowering effects independent of soy protein.