The health effects of soy: A reference guide for health professionals

Soymilk yogurt prepared using Pediococcus pentosaceus TOKAI 759m ameliorates cognitive function through gut microbiota modulation in high-fat diet mice

Recent studies have confirmed that obesity leads to neuroinflammation and cognitive decline. This study aimed to examine whether soymilk yogurt prepared using Pediococcus pentosaceus TOKAI 759m could prevent cognitive decline and neuroinflammation progression in mice fed a high-fat diet (HFD). C57BL/6NJcl male mice were grouped according to the following dietary interventions and monitored for 15 weeks: (1) normal control diet, (2) HFD, (3) HFD with soymilk (SM), (4) HFD with soymilk yogurt (SY), and (5) HFD with bacterial cells of the starter strain (BC). The levels of inflammatory cytokines in serum and hippocampus were measured. Compared to the HFD group, the SY group scored higher in the novel object recognition test and exhibited lower levels of Interleukin-6 (IL-6) and Tumor Necrosis Factor (TNF)-α in the hippocampus. However, the SM and BC groups did not show these significant changes. Proteomic analysis of the hippocampus revealed three enriched protein clusters in the SY group: synaptic proteins, glycolysis, and mitochondrial ATP formation. Fecal samples were also collected to measure the proportion of gut microbiota using 16S rRNA analysis. Interestingly, the proportion of butyrate-producing bacteria, such as Clostridium and Akkermansia, tended to be higher in the SY group than in the HFD group. An additional in vitro study revealed that the components of SY, such as daidzein, genistein, and adenine, could decrease inflammatory cytokine levels in microglial cells. In conclusion, soymilk yogurt prepared using P. pentosaceus TOKAI 759m may modulate gut microbiota and prevent neuroinflammation, thereby leading to a possible improvement in cognitive function.

How phytochemicals influence reproductive outcomes in women receiving assisted reproductive techniques: a systematic review

CONTEXT

Over the past few years, there has been an increasing amount of scholarly literature suggesting a connection between the nutritional status of pregnant mothers and early fetal development, as well as the long-term health consequences of their offspring. Multiple studies have documented that alterations in dietary patterns prior to conception have the potential to affect the initial stages of embryonic development.

OBJECTIVES

The aim of this study was to perform a comprehensive review of the research pertaining to the correlation between phytochemicals ( specifically, polyphenols, carotenoids and phytoestrogens) and assisted reproductive technology (ART).

DATA SOURCES

PubMed, Scopus, Web of Science, and Clinical Trials databases were searched from January 1978 to March 2023.

STUDY SELECTION

This study comprised observational, randomized controlled, and cohort studies that examined the effects of phytochemicals on ART results. The study's outcomes encompass live birth rate, clinical pregnancy, and ongoing pregnancy.

DATA EXTRACTION

The assessment of study quality was conducted by 2 researchers, independently, using the Quality Criteria Checklist for Primary Research.

RESULTS

A total of 13 studies were included, of which there were 5 randomized controlled studies, 1 nonrandomized controlled study, 6 prospective cohort studies, and 1 retrospective cohort study.

CONCLUSION

This research focused on investigating the impact of phytochemicals on ART and has highlighted a dearth of articles addressing that topic. Collaboration among patients, physicians, and nutritionists is crucial for doing novel research.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023426332.

Discovery and Verification of Soybean Sprouting Selection Based on Quality Across Various Origins and Varieties: Varietal Effects on Sprouted Soybean Quality

Research on soybean nutrition is crucial for Chinese agriculture and public health, as soybean sprouting enhances its nutritional value. However, the relationships between grain quality and soybean varieties are not yet fully understood. In this study, the quality of 49 soybean cultivars from 15 different origins was evaluated through multiple correlation analysis. Differences were observed based on their geographical origin, with Shandong Chongwen showing higher calcium and isoflavone levels than the others. A correlation was found between protein content and soybean daidzein (0.561***), as well as genistein (0.597***). Additionally, sprouting was shown to improve soybean nutrition. Among six high-nutrient soybean varieties, increased levels of protein, minerals, and isoflavones were observed during germination. Phytic acid and oligosaccharide levels decreased by 64.7% and 94.5%, respectively, while saponin increased by 106.0%, indicating changes in antinutritional factors. The experiment establishes a clear relationship between soybean nutrients and the tested variables, highlighting the impact of germination on soybean quality and nutrient content.

Lipidomics of coconut, almond and soybean milks - Detailed analysis of polar lipids and comparison with bovine milk

In this work, the lipidomic analysis on polar components of almond, coconut, and soy beverages was performed by liquid chromatography quadrupole time-of-flight mass spectrometry. A comparison with bovine milk was also performed. A total of 30 subclasses of polar lipids, belonging mainly to glycerophospholipids and sphingolipids, and a total of 572 molecular species were identified. Coconut showed various kinds of sphingolipids, belonging to hexosylceramides and sulfatides. Soy is particularly rich in molecular species of phospholipids. Fatty acids with chain length from 16 to 18 were the most common in almond. Numerous species of sphingomyelins were found in bovine milk, differently from plant-based beverages. Furthermore, a principal component analysis based on the polar lipid data was applied to discriminate samples, with 21 molecular species identified as biomarkers. This research opens interesting perspectives on vegetable beverages as bovine milk alternatives, especially in vegetarian and vegan diets.

Characteristics of soybean (Glycine max) protein hydrolysate by bromelain and its effect on inflammation and kidney disorders in gentamicin-induced male Wistar rats

Objectives

Soybeans have various positive effects on health, including anti-inflammatory and preventing kidney damage. There is concern regarding the phytoestrogen content due to the high isoflavone content in soybeans. Various forms of soybean processing have been tried; in this study, the hydrolysis method will be used to obtain the active substance Arginine-Glycine-Aspartate (RGD) tripeptide in soybean protein hydrolyzed by bromelain (SPHB). The research aimed to determine the characteristics and influence of SPHB on kidney function, inflammation, body weight, and estrogen in male Wistar rats induced by gentamicin.

Materials and Methods

Soybeans (Glycine max) are hydrolyzed using the proteolytic enzyme Bromelain from pineapples. The proteomics was investigated using Liquid-Chromatography Mass Spectroscopy Tandem (LC-MS/MS). SPHB in three doses would be tested for 28 days on male Wistar rats induced by gentamicin. The parameters measured were body weight, high-sensitive cell reactive protein (hs-CRP) levels, urea, creatinine, and estrogen levels.

Results

SPHB has a low molecular weight (LMW) of 10 kDa and contains RGD in the lunasin sequence. SPHB showed no effect on body weight (P>0.05). The impact of SPHB on hs-CRP, urea, and creatinine showed differences significantly from the positive control, especially SPHB at a dose of 112 mg/day (P<0.01). Meanwhile, SPHB has almost no effect on estrogen levels.

Conclusion

The administration of SPHB with LMW and contains lunasin showed decreased inflammation and kidney function parameters but did not affect body weight and estrogen levels in induced gentamicin Wistar rats.

Redefining Protein Quality: Integrating Health Outcomes and Environmental Impacts in the Plant-Animal Protein Debate

There is an ongoing debate about the relative merits of plant-based versus animal-based protein sources in terms of human health outcomes and environmental impacts. This viewpoint article reviews and synthesizes the current evidence comparing plant and animal protein sources on measures of human health like cardiovascular disease, cancer, and mortality risk, as well as environmental factors like greenhouse gas emissions, water use, and land requirements. Overall, greater consumption of plant protein sources like legumes, nuts, seeds, and whole grains is associated with reduced risks of cardiovascular diseases, some cancers, and mortality, especially compared to red and processed meats. Crucially, these health benefits align with the dramatically lower environmental footprints of plant proteins across measures like emissions, water use, and land use. However, evidence is mixed for some health outcomes, and more research is still needed. While blanket recommendations should be avoided, the convergence of health and environmental advantages suggests future dietary guidance should emphasize shifting toward more plant-based protein sources. However, evaluations must consider specific foods rather than broad categorizations. New protein production methods like precision fermentation may also reduce environmental impacts while maintaining adequate nutrition.

A Mendelian Randomization Study about Causal Associations between Tofu Consumption and Stroke as well as Related Subtypes

OBJECTIVE

Consuming soy in the diet is beneficial for health, and tofu possess the richest source of dietary soy. However, the specific association with stroke and related subtypes remains controversial. In this study, the genetic causal relationship among tofu and stroke as well as the subtypes was investigated by utilizing the data in a number of genome-wide association study (GWAS) based on population.

METHODS

The tofu intake GWAS analysis is derived from the Medical Research Council (MRC) Integrative Epidemiology Unit at the University of Bristol (MRC-IEU) Consortium. The two-sample Mendelian randomization (MR) study was carried out, utilizing multiple analysis methods to analyze the associations with stroke and related subtypes. The sensitivity, heterogeneity, and potential pleiotropy could be investigated by multiple analysis method.

RESULTS

We found that tofu intake had no causal relationship with stroke. However, in stroke subtype, there is a causal relationship among tofu intake with the risk of intracerebral hemorrhage (ICH) (odds ratio, OR = 1.24 × 10-5, 95% CI: 1.54 × 10-8-9.95 × 10-3, p = 9.300 × 10-4), while tofu intake does not affect the risk of ischemic stroke (OR = 1.07 × 10-1, 95% CI: 3.84 × 10-4-2.97 × 101, p = 4.362 × 10-1) and subarachnoid hemorrhage (SAH) (OR = 3.33 × 10-3, 95% CI: 1.79 × 10-6-6.18, p = 1.373 × 10-1). Both the Mendelian randomization PRESSO (MR-PRESSO) global test and Cochran's Q test did not detect any sensitivity and heterogeneity.

CONCLUSIONS

While tofu consumption is associated with a higher risk of ICH, it does not show a significant relationship with ischemic stroke or SAH. The varying effects of tofu on different stroke subtypes underscore the need for considering potential confounding dietary and lifestyle factors in future studies.

Protein and Amino Acid Adequacy and Food Consumption by Processing Level in Vegans in Brazil

Importance

Major concerns regarding individuals who adhere to a vegan diet are whether they meet protein and essential amino acid recommendations and how reliant they are on ultraprocessed foods.

Objectives

To investigate whether individuals who adhere to a vegan diet meet protein and essential amino acid recommendations and, as secondary objectives, to determine ultraprocessed food intake and potential factors associated with inadequate protein intake in this population.

Design, Setting, and Participants

This cross-sectional survey study was conducted between September 2021 and January 2023 in Brazil among male and female adults (aged 18 years or older) who adhered to a vegan diet recruited from social media platforms.

Exposure

Adherence to a vegan diet and unprocessed and minimally processed foods and ultraprocessed food consumption.

Main Outcomes and Measures

Protein and essential amino acid intake and food consumption by processing level were assessed using a 1-day food diary. Nutrient adequacy ratios were calculated by dividing nutrient intake by its recommendation (using scores truncated at 1) for each participant and then finding the mean across participants for each nutrient. The mean adequacy ratio was the mean of all nutrient adequacy ratios.

Results

Of 1014 participants who completed the survey, 774 individuals (median [IQR] age, 29 [24-35] years; 637 female [82.3%]) were confirmed as adhering to a vegan diet and provided adequate food recalls, among whom 558 individuals reported body weight and so had relative protein and amino acid intake values available. The median (IQR) body mass index (calculated as weight in kilograms divided by height in meters squared) of participants was 22.6 (20.3-24.8). The nutrient adequacy ratio of protein was 0.93 (95% CI, 0.91-0.94); for essential amino acids, ratios ranged from 0.90 (95% CI, 0.89-0.92) for lysine to 0.98 (95% CI, 0.97-0.99) for phenylalanine and tyrosine. The mean adequacy ratio for protein and all amino acids was 0.95 (95% CI, 0.94-0.96). The median intake level was 66.5% (95% CI, 65.0%-67.9%) of total energy intake for unprocessed and minimally processed food and 13.2% (95% CI, 12.4%-14.4%) of total energy intake for ultraprocessed food. Adjusted logistic regression models showed that consuming protein supplements (odds ratio [OR], 0.06 [95% CI 0.02-0.14]; P < .001) or textured soy protein (OR, 0.32 [95% CI, 0.17-0.59]; P < .001) was associated with decreased odds of inadequate protein intake. Higher ultraprocessed food intake levels were also associated with decreased odds of inadequate protein intake (eg, fourth vs first quartile of intake: OR, 0.16 [95% CI, 0.07-0.33]; P < .001), and higher unprocessed and minimally processed protein intake levels were associated with increased odds of inadequate protein intake (eg, fourth vs first quartile of intake: OR, 12.42 [95% CI, 5.56-29.51]; P < .001).

Conclusions and Relevance

In this study, most individuals who adhered to a vegan diet attained protein and essential amino acid intake recommendations, largely based their diet of unprocessed and minimally processed food, and had a significantly lower proportion of ultraprocessed food intake compared with previous reports. Participants consuming less ultraprocessed food were more likely to have inadequate protein intake, suggesting a significant reliance on ultraprocessed proteins for this population.

Fine-tuning of mononuclear phagocytes for improved inflammatory responses: role of soybean-derived immunomodulatory compounds

The concept of inflammation encompasses beneficial and detrimental aspects, which are referred to as infectious and sterile inflammations, respectively. Infectious inflammation plays a crucial role in host defense, whereas sterile inflammation encompasses allergic, autoimmune, and lifestyle-related diseases, leading to detrimental effects. Dendritic cells and macrophages, both of which are representative mononuclear phagocytes (MNPs), are essential for initiating immune responses, suggesting that the regulation of MNPs limits excessive inflammation. In this context, dietary components with immunomodulatory properties have been identified. Among them, soybean-derived compounds, including isoflavones, saponins, flavonoids, and bioactive peptides, act directly on MNPs to fine-tune immune responses. Notably, some soybean-derived compounds have demonstrated the ability to alleviate the symptom of allergy and autoimmunity in mouse models. In this review, we introduce and summarize the roles of soybean-derived compounds on MNP-mediated inflammatory responses. Understanding the mechanism by which soybean-derived molecules regulate MNPs could provide valuable insights for designing safe immunomodulators.

Safety assessment of a proprietary fermented soybean solution, Symbiota®, as an ingredient for use in foods and dietary supplements: Non-clinical studies and a randomized trial

A safety evaluation was performed of Symbiota®, which is made by a proprietary anaerobic fermentation process of soybean with multistrains of probiotics and a yeast. The battery of genotoxicity studies showed that Symbiota® has no genotoxic effects. Safety and tolerability were further assessed by acute or repeated dose 28- and 90-day rodent studies, and no alterations in clinical observations, ophthalmological examination, blood chemistry, urinalysis, or hematology were observed between the control group and the different dosing groups (1.5, 5, and 15 mL/kg/day). There were no adverse effects on specific tissues or organs in terms of weight and histopathology. Importantly, the Symbiota® treatment did not perturb hormones and other endocrine-related endpoints. Of note, the No-Observed-Adverse-Effect-Level was determined to be 15 mL/kg/day in rats. Moreover, a randomized, double-blind, placebo-controlled clinical trial was recently conducted with healthy volunteers who consumed 8 mL/day of placebo or Symbiota® for 8 weeks. Only mild adverse events were reported in both groups, and the blood chemistry and blood cell profiles were also similar between the two groups. In summary, this study concluded that the oral consumption of Symbiota® at 8 mL/day by the general population does not pose any human health concerns.

Profiling of Metabolites in a Fermented Soy Dietary Supplement Reinforces its Role in the Management of Intestinal Inflammation

SCOPE

Gastro-AD (GAD) is a soy flour derived product that undergoes an industrial fermentation with Lactobacillus delbrueckii R0187 and has demonstrated clinical effects in gastroesophageal reflux and peptic ulcer symptom resolution. The aim of this study is to describe and link GAD's metabolomic profile to plausible mechanisms that manifest and explain the documented clinical outcomes.

METHODS AND RESULTS

1H NMR spectroscopy with multivariate statistical analysis is used to characterize the prefermented soy flour and GAD products. The acquired spectra are screened using various resources and the molecular assignments are confirmed using total correlation spectroscopy (TOCSY). Peaks corresponding to different metabolites are integrated and compared between the two products for relative changes. HPLC and GC are used to quantify some specific molecules. NMR analyses demonstrate significant changes in the composition of various assigned bioactive moieties. HPLC and GC analysis demonstrate deglycation of isoflavones after fermentation, resulting in estrogenically active secondary metabolites that have been previously shown to help to reduce inflammation.

CONCLUSION

The identification of bioactive molecules, such as genistein and SCFAs, capable of modulating anti-inflammatory signaling cascades in the stomach's gastric and neuroendocrine tissues can explain the reported biological effects in GAD and is supported by in vivo data.

Soy-derived isoflavones as chemo-preventive agents targeting multiple signalling pathways for cancer prevention and therapy

The chemopreventive and chemotherapeutic properties of soy and soy-derived compounds, especially isoflavones, have been extensively studied in recent years. However, in contrast to their anticancer effects, such as cell growth inhibition, cell cycle arrest and apoptosis induction, isoflavones have also been found to promote the growth of cancer cells. Therefore, the aim of this comprehensive review article is to present the current state of knowledge regarding the molecular mechanisms by which soy-derived isoflavones target multiple cellular signalling pathways in cancer cells. Our findings indicate that soy-derived isoflavones act as, among other things, potent modulators of HOX transcript antisense RNA (HOTAIR)/SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 (SMARCB1), vascular endothelial growth factor (VEGF)/C-X-C motif chemokine ligand 12 (CXCL12)/C-X-C motif chemokine receptor type 4 (CXCR4), 17-β-oestradiol (E2)/oestrogen receptor-α (ERα)/neuroglobin (NGB) and sonic hedgehog signalling pathways, epigenetic modulatory agents (i.a. miR-155, miR-34a and miR-10a-5p) and cancer stem cells and epithelial-to-mesenchymal transition inhibitors. The paper also discusses the latest epidemiological studies and clinical trials and provides an insight into recent extensive research on the chemo-preventive and therapeutic potential of soy-derived isoflavones.

Probiotics: Health benefits, food application, and colonization in the human gastrointestinal tract

Probiotics have become increasingly popular over the past two decades due to the continuously expanding scientific evidence indicating their beneficial effects on human health. Therefore, they have been applied in the food industry to produce functional food, which plays a significant role in human health and reduces disease risk. However, maintaining the viability of probiotics and targeting the successful delivery to the gastrointestinal tract remain two challenging tasks in food applications. Specifically, this paper reviews the potentially beneficial properties of probiotics, highlighting the use and challenges of probiotics in food application and the associated health benefits. Of foremost importance, this paper also explores the potential underlying molecular mechanisms of the enhanced effect of probiotics on gastrointestinal epithelial cells, including a discussion on various surface adhesion‐related proteins on the probiotic cell surface that facilitate colonization.

Effects of Isoflavonoid and Vitamin D Synergism on Bone Mineral Density-A Systematic and Critical Review

Phytoestrogens are non-steroidal plant compounds, which bind to α and β estrogen receptors, thereby causing specific effects. The best-known group of phytoestrogens are flavonoids, including isoflavonoids-genistein and daidzein. They play a role in the metabolism of bone tissue, improving its density and preventing bone loss, which contributes to reducing the risk of fractures. Vitamin D is found in the form of cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) and is traditionally recognized as a regulator of bone metabolism. The aim of this review was to evaluate the synergistic effect of isoflavonoids and vitamin D on bone mineral density (BMD). The MEDLINE (PubMed), Scopus and Cochrane databases were searched independently by two authors. The search strategy included controlled vocabulary and keywords. Reference publications did not provide consistent data regarding the synergistic effect of isoflavonoids on BMD. Some studies demonstrated a positive synergistic effect of these compounds, whereas in others, the authors did not observe any significant differences. Therefore, further research on the synergism of isoflavonoids and vitamin D may contribute to a significant progress in the prevention and treatment of osteoporosis.

Lactose malabsorption and intolerance: What is the correct management in older adults?

Lactose malabsorption is a very common condition due to intestinal lactase deficiency. Post weaning, a genetically programmed and irreversible reduction of lactase activity occurs in the majority of the world's population. Lactose malabsorption does not necessarily result in gastrointestinal symptoms, i.e. lactose intolerance, which occurs in approximately one third of those with lactase deficiency. In the absence of well-established guidelines, the common therapeutic approach tends to exclude milk and dairy products from the diet. However, this strategy may have serious nutritional disadvantages. Mainly in particular categories, such as the older adults, the approach to lactose malabsorption may deserve careful considerations. Milk and dairy products are an important supply of a wide range of nutrients that contribute to meet the nutritional needs in different life stages. Dietary composition can significantly impact the mechanisms leading to age-related loss of bone mineral density, skeletal muscle mass or function and overall risk of sarcopenia. Moreover, in the latest years, different lines of evidence have highlighted an association between dairy intake and prevention of chronic diseases as well as all-cause mortality. The aim of this opinion paper is to provide an overview of lactose malabsorption and intolerance in the older adults and their implications in clinical practice.

An Updated Review of Soy-Derived Beverages: Nutrition, Processing, and Bioactivity

The global market for plant-based drinks is experiencing rapid growth driven by consumer demand for more sustainable diets, including vegetarian and vegan options. Soy beverages in particular are gaining popularity among individuals with lactose intolerance and milk protein allergies. They are considered an excellent source of high-quality protein, vitamin B, unsaturated fatty acids, and beneficial phytochemicals such as phytosterols, soy lecithins, and isoflavones. This review presents a comprehensive market survey of fifty-two soy beverages available in Spain and other European countries. The predominant category among those evaluated was calcium and vitamin-fortified drinks, accounting for 60% of the market. This reflects the need to address the nutritional gap compared to cow's milk and meet essential dietary requirements. The review covers the technological aspects of industrial soy milk production, including both traditional methods and innovative processing techniques. Additionally, it analyzes multiple studies and meta-analyses, presenting compelling evidence for the positive effects of soy beverages on various aspects of health. The review specifically examines the contributions of different components found in soy beverages, such as isoflavones, proteins, fiber, and oligosaccharides. Moreover, it explores controversial aspects of soy consumption, including its potential implications for growth, puberty, fertility, feminization, and the thyroid gland.

Microbial Metabolism of the Soy Isoflavones Daidzein and Genistein in Postmenopausal Women: Human Intervention Study Reveals New Metabotypes

BACKGROUND

Soy isoflavones belong to the group of phytoestrogens and are associated with beneficial health effects but are also discussed to have adverse effects. Isoflavones are intensively metabolized by the gut microbiota leading to metabolites with altered estrogenic potency. The population is classified into different isoflavone metabotypes based on individual metabolite profiles. So far, this classification was based on the capacity to metabolize daidzein and did not reflect genistein metabolism. We investigated the microbial metabolite profile of isoflavones considering daidzein and genistein.

METHODS

Isoflavones and metabolites were quantified in the urine of postmenopausal women receiving a soy isoflavone extract for 12 weeks. Based on these data, women were clustered in different isoflavone metabotypes. Further, the estrogenic potency of these metabotypes was estimated.

RESULTS

Based on the excreted urinary amounts of isoflavones and metabolites, the metabolite profiles could be calculated, resulting in 5 metabotypes applying a hierarchical cluster analysis. The metabotypes differed in part strongly regarding their metabolite profile and their estimated estrogenic potency.

Soy Consumption and the Risk of Type 2 Diabetes and Cardiovascular Diseases: A Systematic Review and Meta-Analysis

Soy is rich in plant protein, isoflavones, and polyunsaturated fatty acids. To clarify the associations between soy intake and type 2 diabetes (T2D) and cardiovascular diseases (CVDs) events, we performed a meta-analysis and review. A total of 1963 studies met the inclusion criteria, and 29 articles with 16,521 T2D and 54,213 CVDs events were identified by the eligibility criteria. During a follow-up of 2.5–24 years, the risk of T2D, CVDs, coronary heart disease, and stroke in participants with the highest soy consumption decreased by 17% (total relative risk (TRR) = 0.83, 95% CI: 0.74–0.93), 13% (TRR = 0.87, 95% CI: 0.81–0.94), 21% (TRR = 0.79, 95% CI: 0.71–0.88), and 12% (TRR = 0.88, 95% CI: 0.79–0.99), respectively, compared to the lowest sot consumption. A daily intake of 26.7 g of tofu reduced CVDs risk by 18% (TRR = 0.82, 95% CI: 0.74–0.92) and 11.1 g of natto lowered the risk of CVDs by 17% (TRR = 0.83, 95% CI: 0.78–0.89), especially stroke. This meta-analysis demonstrated that soy consumption was negatively associated with the risks of T2D and CVDs and a specific quantity of soy products was the most beneficial for the prevention of T2D and CVDs. This study has been registered on PROSPERO (registration number: CRD42022360504).

Evaluation of a low-resource soy protein production method and its products

Introduction

One key approach to achieve zero hunger in Sub-Saharan Africa (SSA) is to develop sustainable, affordable, and green technologies to process nutritious food products from locally available sources. Soybeans are an inexpensive source of high-quality protein that may help reduce undernutrition, but it is underutilized for human consumption. This research evaluated the feasibility of a low-cost method developed initially at the United States Department of Agriculture to produce soy protein concentrate (SPC) from mechanically pressed soy cake and thus create a more valuable ingredient to improve protein intake in SSA.

Methods

The method was initially tested in the bench scale to assess process parameters. Raw ingredients comprised defatted soy flour (DSF), defatted toasted soy flour (DTSF), low-fat soy flour 1 (LFSF1; 8% oil), and LFSF2 (13% oil). Flours were mixed with water (1:10 w/v) at two temperatures (22 or 60°C) for two durations (30 or 60 min). After centrifugation, supernatants were decanted, and pellets were dried at 60°C for 2.5 h. Larger batches (350 g) of LFSF1 were used to examine the scalability of this method. At this level, protein, oil, crude fiber, ash, and phytic acid contents were measured. Thiobarbituric acid reactive substances (TBARS), hexanal concentration and peroxide value were measured in SPC and oil to evaluate oxidative status. Amino acid profiles, in vitro protein digestibility, and protein digestibility corrected amino acid score (PDCAAS) were determined to assess protein quality.

Results

Bench scale results showed accumulation of protein (1.5-fold higher) and reduction of oxidative markers and phytic acid to almost half their initial values. Similarly, the large-scale production trials showed high batch-to-batch replicability and 1.3-fold protein increase from initial material (48%). The SPC also showed reductions in peroxide value (53%), TBARS (75%), and hexanal (32%) from the starting material. SPC's in vitro protein digestibility was higher than the starting material.

Conclusion

The proposed low-resource method results in an SPC with improved nutritional quality, higher oxidative stability, and lower antinutrient content, which enhances its use in food-to-food fortification for human consumption and is thus amenable to address protein quantity and quality gaps among vulnerable populations in SSA.