Allergenic Proteins in Soybean: Processing and Reduction of P34 Allergenicity

The structure-function relationships and techno-functions of β-conglycinin

β-conglycinin (β-CG) is a prominent storage protein belonging to the globulin family in soybean (Glycine max) seeds. Along with other soybean proteins, it serves as an important source of essential amino acids and high-quality nutrition. However, the digestibility and nutritional value of β-CG are key factors affecting the nutritional profile of soy-based foods. The heterotrimeric, secondary, and quaternary structures of β-CG, particularly the spatial arrangement of its α, α', and β subunits, influence its functional properties. Considering these aspects, β-CG emerges as a significant protein with diverse applications in the food and health sectors. Therefore, this review explores β-CG's composition, structure, function, health implications, and industrial uses. Salient discussions are presented on its molecular structure, nutrition, digestibility, allergenicity, and techno-functions including emulsification, solubility, gelling, and structure-function complexities. Overall, the multifaceted potential of β-CG in the healthcare sector and the food industry is evident.

Combined Effects of Lactic Acid Bacteria and Protease on the Fermentation Quality and Microbial Community during 50 Kg Soybean Meal Fermentation Simulating Actual Production Scale

The improvement in the utilization rate and nutritional value of soybean meal (SBM) represents a significant challenge in the feed industry. This study conducted a 50 kg SBM fermentation based on the 300 g small-scale fermentation of SBM in early laboratory research, to explore the combined effects of lactic acid bacteria (LAB) and acid protease on fermentation quality, chemical composition, microbial population, and macromolecular protein degradation during fermentation and aerobic exposure of SBM in simulated actual production. The results demonstrated that the increase in crude protein content and reduction in crude fiber content were considerably more pronounced after fermentation for 30 days (d) and subsequent aerobic exposure, compared to 3 d. It is also noteworthy that the treated group exhibited a greater degree of macromolecular protein degradation relative to the control and 30 d of fermentation relative to 3 d. Furthermore, after 30 d of fermentation, adding LAB and protease significantly inhibited the growth of undesired microbes including coliform bacteria and aerobic bacteria. In the mixed group, the microbial diversity decreased significantly, and Firmicutes replaced Cyanobacteria for bacteria in both groups' fermentation.

Benefits of Soybean in the Era of Precision Medicine: A Review of Clinical Evidence

Soybean (Glycine max) is an important ingredient of cuisines worldwide. While there is a wealth of evidence that soybean could be a good source of macronutrients and phytochemicals with health-promoting effects, concerns regarding adverse effects have been raised. In this work, we reviewed the current clinical evidence focusing on the benefits and risks of soybean ingredients. In breast, prostate, colorectal, ovarian, and lung cancer, epidemiological studies showed an inverse association between soybean food intake and cancer risks. Soybean intake was inversely correlated with risks of type 2 diabetes mellitus (T2DM), and soy isoflavones ameliorated osteoporosis and hot flashes. Notably, soybean was one of the dietary protein sources that may reduce the risk of breast cancer and T2DM. However, soybean had adverse effects on certain types of drug treatment and caused allergies. In sum, this work provides useful considerations for planning clinical soybean research and selecting dietary protein sources for human health.

Alpha-ketoglutaric acid mitigates the detrimental effects of soy antigenic protein on the intestinal health and growth performance of Mirror carp Cyprinus carpio

The study investigated the alleviated effects of Alpha-ketoglutaric acid (AKG) on the intestinal health of mirror carp (Cyprinus carpio Songpu) caused by soy antigenic protein. The diets were formulated from fishmeal (CON), 50% soybean meal (SBM), the mixture of glycinin and β-conglycinin (11 + 7S) and adding 1% AKG in the 11 + 7S (AKG). Carp (~ 4 g) in triplicate (30 fish per tank) was fed to apparent satiation thrice a day for six weeks. Compared with CON, SBM treatment resulted in significantly poor growth performance (P < 0.05), whereas 11 + 7S and AKG treatments were not significantly different from CON (P > 0.05). Gene expression of tumor necrosis factor (TNF-α) and interleukin-1 β (IL-1β) in proximal intestines (PI) and distal intestines (DI) were increased (P < 0.05), and transforming growth factor (TGF-β) in PI and middle intestines (MI) was decreased (P < 0.05) in both SBM and 11 + 7S. The caspase-3 in DI increased in SBM (P < 0.05) and the caspase-3 and caspase-9 in DI increased in 11 + 7S (P < 0.05); conversely, TGF-β in PI and MI was increased, TNF-α and IL-1β in the MI, caspase-3, and caspase-9 in DI was decreased in AKG (P < 0.05). The TOR (target of rapamycin) in PI and MI, ACC in PI, MI and DI was decreased in SBM (P < 0.05), the AMPK in the PI and DI, TOR in PI, MI and DI, ACC in PI and DI, 4E-BP in DI was reduced in 11 + 7S (P < 0.05). AMPK in the PI and DI, ACC in the PI and MI, TOR in PI, MI, and DI, 4E-BP in PI and DI was recovered by AKG supplementation (P < 0.05). Lipids and lipid-like metabolism, organic acids and derivatives metabolism increased in AKG dietary treatment. In conclusion, AKG reduces the expression of intestinal inflammation and apoptosis pathway and changes glycerophospholipid metabolism and sphingolipid metabolism in the intestine of fish.

Nuclei-induced formation of amyloid fibrils in whey protein: Effects of enzyme hydrolysis on the ability of nuclei to induce fibril formation

Homogeneous and secondary nuclei (HN and SN) are aggregates formed at different stages of whey protein isolate (WPI) self-assembly. More fibrils can form when HN/SN are added as nuclei than when WPI self-assembles. We evaluated the effect of hydrolysis treatment on fibril-induction ability of nuclei derived from WPI, and investigated the relationship between induction ability and nuclear structure. Hydrolyzed SN-induced 9.47% more WPI fibrils than unhydrolyzed SN-induced. Infrared spectroscopy, X-ray diffraction analysis, and atomic force microscopy were used to examine the structural changes in hydrolyzed nuclei and the fibrils induced using these nuclei. We concluded that hydrolysis treatment led to a looser inter-β-sheet packaging in nuclei by increasing the inter-β-sheet distance. The inter-β-sheet distance of cross-β structure was a key determinant of fibril-induction ability of nuclei, which could be enhanced when inter-β-sheet structure was moderately loose. This research may provide a theoretical basis for the mechanism of nuclei-induced WPI fibrillation.

In Situ Proteomic Analysis of Herbicide-Resistant Soybean and Hybrid Seeds via Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging

Transgenic soybean is the commercial crop with the largest cultivation area worldwide. During transgenic soybean cultivation, exogenous genes may be transferred to wild relatives through gene flow, posing unpredictable ecological risks. Accordingly, an environmental risk assessment should focus on fitness changes and underlying mechanisms in hybrids between transgenic and wild soybeans (Glycine soja). Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) was used for in situ detection and imaging of protein changes in the seeds of transgenic herbicide-resistant soybean harboring epsps and pat genes, non-transgenic soybean, wild soybean, and their F₂ hybrid. Protein data clearly distinguished wild soybeans, while the F₂ seeds had protein characteristics of both parents and were distinguished from wild soybean seeds. Using UPLC-Q-TOF-MS, 22 differentially expressed proteins (DEPs) were identified, including 13 specific to wild soybean. Sucrose synthase and stress response-related DEPs were differentially expressed in parental and offspring. Differences in these may underpin the greater adaptability of the latter. MSI revealed DEP distribution in transgenic, wild, and F₂ seeds. Identifying DEPs related to fitness may elucidate mechanisms underlying fitness differences among the studied varieties. Our study shows that MALDI-MSI has the potential to become a visual method for transgenic soybean analysis.

Effects of high-pressure homogenization on physicochemical and functional properties of enzymatic hydrolyzed soybean protein concentrate

This paper investigates the effect on the physicochemical and functional properties of soybean protein concentrate (SPC) by using Alcalase protease and high-pressure homogenization (HPH) (0, 20, 40, 60, 80, and 100 MPa) for the combined modification. The results showed that the degree of hydrolysis of SPC was 4.1% and the antigen protein was degraded after Alcalase hydrolysis, when the homogenization pressure (HP) was 6 0Mpa, the particle size of the SPC was the smallest, the zate potential absolute value up to 33.45 mV, the secondary structure has the lowest β-sheet content, the highest random coil content, and the highest surface hydrophobicity (H0), the size of protein fragments on the microstructure surface is the smallest, the lowest denaturation temperature (T d ) and enthalpy (△H) are 72.59°C and 1.35 J/g, the highest solubility is 80.54%, and the highest water and oil holding capacities are 7.73 g/g and 6.51 g/g, respectively. The best emulsifying activity and emulsifying stability were 43.46 m2/g and 190.35 min, the most even distribution of emulsion droplets. This indicates that the HPH treatment destroys the structure of enzymatic hydrolyzed SPC, changes its physicochemical properties, and improves its functional properties. In this study, SPC was modified by HPH and enzyme combined treatment, in order to improve the functionality and application range of SPC, and provide a theoretical basis for its high-value utilization in the food field.

Hydrolysis of Soybean Milk Protein by Papain: Antioxidant, Anti-Angiotensin, Antigenic and Digestibility Perspectives

The objective of the investigation was to understand the biochemical activities of hydrolysate of soybean milk protein (SMP). Hydrolysis was carried out by different concentrations of papain (0.008 g·L⁻¹, 0.016 g·L⁻¹, 0.032 g·L⁻¹ and 0.064 g·L⁻¹). The antioxidant capacity was measured by the ferric-reducing ability of plasma (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assays. The anti-angiotensin activity of hydrolysate was measured by the recombinant angiotensin converting enzyme and substrate Abz-FRK(Dnp)-P. The contributions of the Kunitz trypsin inhibitor (KTI) and Bowman–Birk inhibitor (BBI) on antigenicity, and the in vitro digestion of papain-hydrolyzed SMP were studied. Rabbit polyclonal anti-KTI and anti-BBI antibodies together with peroxidase-labelled goat anti-Rb IgG secondary antibody were used to identify the antigenicity of KTI and BBI in unhydrolyzed and papain-hydrolyzed SMP. The antioxidant capacity and anti-angiotensin activity of SMP were increased after the papain hydrolysis of SMP. The KTI- and BBI-specific antigenicity were reduced in SMP by increasing the concentration of papain. However, there was interaction between papain-hydrolyzed SMP and trypsin in native gel, while interaction with chymotrypsin was absent. The interaction between trypsin and SMP was reduced due to the hydrolysis of papain in a concentration-dependent manner. According to the in vitro gastrointestinal digestion simulation protocol (Infogest), the digestibility of SMP was not statistically increased.

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

Soy is a hotly debated and widely discussed topic in the field of nutrition. However, health practitioners may be ill-equipped to counsel clients and patients about the use of soyfoods because of the enormous, and often contradictory, amount of research that has been published over the past 30 years. As interest in plant-based diets increases, there will be increased pressure for practitioners to gain a working knowledge of this area. The purpose of this review is to provide concise literature summaries (400-500 words) along with a short perspective on the current state of knowledge of a wide range of topics related to soy, from the cholesterol-lowering effects of soy protein to the impact of isoflavones on breast cancer risk. In addition to the literature summaries, general background information on soyfoods, soy protein, and isoflavones is provided. This analysis can serve as a tool for health professionals to be used when discussing soyfoods with their clients and patients.

Establishment of DAS-ELISA for the detection of antigenic changes in glycinin after heat processing

In this study, a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) method was established to detect the antigenic changes of thermally processed products containing glycinin. The proposed DAS-ELISA method used heat-treated antigen-absorbing antiserum as the coating antibody, and horseradish peroxidase (HRP)-labeled rabbit anti-glycinin polyclonal antibody as the detection antibody. The specificity test results which were obtained using the proposed method indicated that good specificity had been achieved. The cut-off value was 0.388, and the LOD was determined to be 19.53 ng/mL. The coefficient of variation was less than 5.25% (intra-day) and 9.50% (inter-day). In this study's milk powder addition test, the recovery rate of the glycinin ranged between 83.65% and 90.13%. The established DAS-ELISA method was also used to detect soybean thermal processing products, such as soy sauce, steamed fish and soy sauce, soybean paste, beef sauce, soy milk powder, and tofu. The results showed that the OD450 values of the aforementioned products were lower than the OD450 values of the glycinin in defatted soybean flour. Therefore, it was indicated that the above products has undergone different degrees of thermal processing. In other words, the majority of the epitopes of glycinin in the products had been destroyed by the thermal processing and could not be combined with heat-treated antigen-absorbing antiserum.

Role of selenium in IgE mediated soybean allergy development

Food allergy is a pathological immune reaction triggered by normal innocuous dietary proteins. Soybean is widely used in many food products and has long been recognized as a source of high-quality proteins. However, soybean is listed as one of the 8 most significant food allergens. The prevalence of soybean allergy is increasing worldwide and impacts the quality of life of patients. Currently, the only strategy to manage food allergy relies on strict avoidance of the offending food. Nutritional supplementation is a new prevention strategy which is currently under evaluation. Selenium (Se), as one of the essential micronutrients for humans and animals, carries out biological effects through its incorporation into selenoproteins. The use of interventions with micronutrients, like Se, might be an interesting new approach. In this review we describe the involvement of Se in a variety of processes, including maintaining immune homeostasis, preventing free radical damage, and modulating the gut microbiome, all of which may contribute to in both the prevention and treatment of food allergy. Se interventions could be an interesting new approach for future treatment strategies to manage soybean allergy, and food allergy in general, and could help to improve the quality of life for food allergic patients.

Soybean allergy: characteristics, mechanisms, detection and its reduction through novel food processing techniques

Human beings have consumed soybean as an excellent food source for thousand years due to its rich protein, fatty acids, minerals, and fibers. However, soybeans were recognized as one of the big eight allergens resulting in allergic symptoms and even could lead to death. With the increasing demand for soybean products, the challenges caused by soybean allergy need to be solved urgently. This review detailly described the pathogenesis and clinical characteristics of soybean allergy, and also the advantages and disadvantages of four different diagnostic methods were summarized. The major soybean allergens and their structures were summarized. Three types of soybean allergy including Type I, III, and IV, which could trigger allergic reactions were reported in this review. Summary in four different diagnostic methods showed that double-blind, placebo-controlled food challenge is recognized as a gold standard for diagnosing soybean allergy. Three types of processing techniques in reducing soybean allergy were discussed, and the results concluded that some novel food processing techniques such as ultrasound, cold-plasma treatment, showed potential application in the reduction of soybean allergenicity. Further, some suggestions regarding the management and treatment of food allergies were addressed in this review.

Soy Protein: Molecular Structure Revisited and Recent Advances in Processing Technologies

Rising health concerns and increasing obesity levels in human society have led some consumers to cut back on animal protein consumption and switch to plant-based proteins as an alternative. Soy protein is a versatile protein supplement and contains well-balanced amino acids, making it comparable to animal protein. With sufficient processing and modification, the quality of soy protein can be improved above that of animal-derived proteins, if desired. The modern food industry is undergoing a dynamic change, with advanced processing technologies that can produce a multitude of foods and ingredients with functional properties from soy proteins, providing consumers with a wide variety of foods. This review highlights recent progress in soy protein processing technologies. Using the current literature, the processing-induced structural changes in soy protein are also explored. Furthermore, the molecular structure of soy protein, particularly the crystal structures of β-conglycinin and glycinin, is comprehensively revisited.

Antigenic activity and epitope analysis of β-conglycinin hydrolyzed by pepsin

BACKGROUND

Soybean is among the 'big eight' allergenic foods, and β-conglycinin, the main antigenic protein of soybean, has high levels of antigenic activity. Why the antigenic activity of soybean β-conglycinin is not eliminated by enzymatic hydrolysis is not clear. In this study, changes in the molecular composition and antigenicity of β-conglycinin hydrolyzed by pepsin were analyzed and it was determined whether complete sequential epitopes exist in the resulting hydrolysates. The nature and antigenic activity of protein subunits obtained after β-conglycinin hydrolysis were also assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and competitive enzyme-linked immunosorbent assay, respectively.

RESULTS

The residual antigenic activity of β-conglycinin was 52%, α'- and α-subunits completely disappeared, the 49 kDa fraction partially disappeared, and peptides measuring 27 and 23 kDa were newly formed after 60 min of enzymatic hydrolysis. Prolonged enzymatic hydrolysis did not result in remarkable changes in these peptides; thus, the peptides show some resistance to enzymatic hydrolysis. The amino acid sequences of the peptide chains were analyzed by matrix-assisted laser desorption / ionization-time of flight mass spectrometry and aligned with the related sequences in the corresponding protein and antigen databases. Ten complete sequential epitopes were identified in the residual 49 kDa fraction, of these epitopes, two were from α-subunits and eight were from β-subunits.

CONCLUSION

The presence of complete sequential epitopes in hydrolysates obtained from the enzymatic hydrolysis of soybean is an important reason for the incomplete disappearance of the antigenic activity of β-conglycinin. © 2020 Society of Chemical Industry.

Study on Effect of Extraction Techniques and Seed Coat on Proteomic Distribution and Cheese Production from Soybean Milk

Soybean-based food products are a major source of protein. In the present study, proteins in soybean milk from seeds of the cultivar Bunya (Glycine max) were extracted using the cheesecloth and the centrifuge methods. The milk was produced through mechanical crushing of both whole and split seeds in water. Following separation by either the cheesecloth or centrifuge, proteins were isolated from the soybean milk by using thiourea/urea solubilisation and then separated them using two-dimensional polyacrylamide gel electrophoresis. The isolated proteins were identified by mass spectrometry. A total of 97 spots were identified including 49 that displayed different abundances. Of the two separation techniques, centrifuge separation gave higher protein extraction and more intense protein spots than cheesecloth separation. Eleven of the β-subunits of β-conglycinin, three of the α-subunits of β-conglycinin, and four of the mutant glycinin showed different levels of abundances between separation techniques, which might be related to subsequent cheese quality. Notably, split-seed soybean milk has less allergenic proteins with four α-subunits of β-conglycinin compared to whole-seed milk with eight of those proteins. The sensory evaluation showed that the cheese produced from split-soybean milk received higher consumer preferences compared to that of whole seed, which could be explained by their proteomic differences. The demonstrated reference map for whole and split-seed soybean milk could be further utilized in the research related to soybean cheesemaking.

Enhancing online protein isolation as intact species from soy flour samples by actively modulated two-dimensional liquid chromatography (2D-LC)

In this study, an enhanced fully automated approach is described for the protein isolation from soy flour samples by two-dimensional liquid chromatography with active modulation interface. The use of two multi-port switching valves is proposed to on-line connect the first to the second dimension column, thus overcoming the problems associated with the re-mixing effects and incompatibility of eluent composition and pH. A 5-cm long C4 analytical column installed in the interface device allows to focus the proteins coming from the first column (size exclusion chromatography), before their selective elution in the second column (reversed-phase). A trap washing step was included in the total workflow, as a desalting step to remove buffer residues from the eluent of the first column and to enhance the chromatographic performances of the second column. The experimental conditions were optimized by analyses of mixed standard solutions of bovine serum albumin, glucose oxidase, immunoglobulin A, thyroglobulin and myoglobin. Then, the optimized 2D-LC method was applied to the protein analysis in extracts of soy flour, known worldwide as one of the major food allergen sources, with the final aim to recovery sufficient protein amounts for the molecular characterization and the assessment of the pattern of allergenic components.

Soy Preparations Are Potentially Dangerous Factors in the Course of a Food Allergy

The special properties of soy preparations make them common additives for food production and can be dangerous for sensitive individuals. Our aim was to check consumers’ awareness of potential risks of soy preparations added to numerous food products, depending on respondents’ education, and to evaluate immunoreactive properties of chosen soy preparations. A personal questionnaire was used. Respondents (n = 251) were aged 23–28 years old, lived in Poland, and were graduates or students in their last year of food technology, medicine, and university of technology. The slot blot and Western blotting methods were used to mark immunoreactivity of soy preparations. It was shown that most respondents often or usually read labels of food products they buy. The surveyed indicated protein is the allergenic component in soy. Almost half of them were of the opinion that hydrolysis removes the allergenic properties of soy. Most of the medical students surveyed thought that people allergic to soy may consume products that contain soy preparations. The analytical results indicated that soy preparation contained protein fractions that were immunoreactive with sera of allergenic patients. It was proven that preparations, even hydrolysates, contain immunoreactive proteins that may be the source of hidden allergens, even though they are not recognized as dangerous by well-educated respondents.

Food protein amyloid fibrils: Origin, structure, formation, characterization, applications and health implications

Amyloid fibrils have traditionally been considered only as pathological aggregates in human neurodegenerative diseases, but it is increasingly becoming clear that the propensity to form amyloid fibrils is a generic property for all proteins, including food proteins. Differently from the pathological amyloid fibrils, those derived from food proteins can be used as advanced materials in biomedicine, tissue engineering, environmental science, nanotechnology, material science as well as in food science, owing to a combination of highly desirable feature such as extreme aspect ratios, outstanding stiffness and a broad availability of functional groups on their surfaces. In food science, protein fibrillization is progressively recognized as an appealing strategy to broaden and improve food protein functionality. This review article discusses the various classes of reported food protein amyloid fibrils and their formation conditions. It furthermore considers amyloid fibrils in a broad context, from their structural characterization to their forming mechanisms and ensued physical properties, emphasizing their applications in food-related fields. Finally, the biological fate and the potential toxicity mechanisms of food amyloid fibrils are discussed, and an experimental protocol for their health safety validation is proposed in the concluding part of the review.

Scientific Papers and Patents on Substances with Unproven Effects. Part 2

Several examples are discussed in this review, where substances without proven effects were proposed for practical use within the scope of evidence-based medicines. The following is discussed here: generalizations of the hormesis concept and its use in support of homeopathy; phytoestrogens and soy products potentially having feminizing effects; glycosaminoglycans for the treatment of osteoarthritis and possibilities of their replacement by diet modifications; flavonoids recommended for the treatment of chronic venous insufficiency and varicose veins; acetylcysteine as a mucolytic agent and its questionable efficiency especially by an oral intake; stem cells and cell therapies. In conclusion, placebo therapies can be beneficial and ethically justifiable but it is not a sufficient reason to publish biased information. Importantly, placebo must be devoid of adverse effects, otherwise, it is named pseudo-placebo. Therapeutic methods with unproven effects should be tested in high-quality research shielded from the funding bias. Some issues discussed in this review are not entirely clear, and the arguments provided here can initiate a constructive discussion.

Combining 2-DE immunoblots and mass spectrometry to identify putative soybean (Glycine max) allergens

Soybean is recognized as a commonly allergenic food, but the identity of important allergens is not well studied. Recently, some global regulatory agencies started requiring quantitative analysis of individual allergens, including unproven allergens, as part of the risk assessment for genetically engineered (GE) soybeans. We sought to identify soybean proteins that bind IgE from any of 10 individual soybean-sensitized subjects. Soybean IgE binding proteins were identified by 2-DE immunoblots using sera from four soy-allergic and plasma from six soy-sensitized human subjects. Corresponding spots were excised from stained gels, digested, and analyzed using a quadrupole TOF Synapt G2-S tandem mass spectrometer. Results showed the major IgE binding proteins were subunits of either β-conglycinin (Gly m 5) or glycinin (Gly m 6). Soybean Kunitz trypsin inhibitor (SKTI) was a significant IgE binding protein for four subjects. Soybean agglutinin, seed biotinylated protein (SBP) of 65 kDa, late embryogenesis protein (LEP), and sucrose-binding protein were identified as IgE binding only for soy-sensitized subjects. We conclude that the major soybean allergens are isoforms of Gly m 5, Gly m 6, and possibly SKTI and that requirements for quantitative measurement of proteins that are not clear allergens is not relevant to safety.

Evaluation of the efficiency of three extraction conditions for the immunochemical detection of allergenic soy proteins in different food matrices

BACKGROUND

Recent studies have shown the need to improve soy allergen extraction using different extraction conditions to ensure more accurate results in allergen detection. This study investigated some of these extraction conditions to confirm that these methods, especially ultrasound-assisted extraction (UAE) and the use of Laemmli buffer instead of the conventional extraction with phosphate-buffered saline (PBS), could be helpful in improving the extraction step in allergen detection.

RESULTS

Higher total soluble protein was obtained in all samples extracted with Laemmli buffer alone and in combination with ultrasound. For immunochemical detection of soy proteins by enzyme-linked immunosorbent assay (ELISA), comparable detection was observed in extracts from all extraction conditions in all commercial samples with the exception of table cracker and veggie burger, where significantly higher detection was seen in extracts from Laemmli buffer only. For the dry mix and cookie samples, the degree of soy protein detection with ELISA varied among the different extraction conditions, but overall, extraction with only Laemmli buffer showed higher detection.

CONCLUSION

Laemmli buffer with conventional extraction and UAE may be better alternatives or additional extraction methods in soy allergen detection. Different food matrices performed differently (whether it was for the recovery of total proteins or detection by ELISA) under different extraction conditions. © 2017 Society of Chemical Industry.

Lupine allergen detecting capability and cross-reactivity of related legumes by ELISA

Lupine belongs to the genus Lupinus and includes three species commonly consumed by humans. The Lupinus genus is closely related to other legumes, such as peanuts, soya, chickpeas, peas, lentils and beans. However, the consumption of lupine (and related legumes) can cause severe allergenic reactions. Therefore, reliable analytical detection methods are required for the analysis of food samples. In this study three commercially available ELISA test kits were analyzed for the detection capability of three common lupine species, as well as cross-reactivity to related legumes. All three ELISA test kits could detect the lupine species, though with different sensitivities. Cross-reactivity varied for the ELISA test kits and all showed some cross-reactivity to related legume samples analyzed.

High hydrostatic pressure (HHP) effects on antigenicity and structural properties of soybean β-conglycinin

In this study, the effect of high hydrostatic pressure (HHP) on antigenicity, free sulfhydryl group (SH) content, hydrophobicity (Ho), fluorescence intensity and circular dichroism data of soybean β-conglycinin was studied. The antigenicity of soybean β-conglycinin was decreased significantly at pressures 200-400 MPa. The antigenicity inhibition rate of β-conglycinin declined from 92.72 to 55.15%, after being treated at 400 MPa for 15 min. Results indicated that free sulphydryl (SH) groups and surface Ho of β-conglycinin were significantly increased at pressures 200-400 MPa and 5-15 min, whereas these properties decreased at the treatments above 400 MPa and 15 min. The maximum fluorescence intensity was noticed at 400 MPa and 15 min. The circular dichroism data analysis revealed that the amount of β-turns and unordered structure significantly increased, while the content of α-helix1 and β-strand1 noticeably decreased. These results provide evidence that HHP-induced the structural modification of β-conglycinin and could alter the antigenicity of β-conglycinin.

Soymilk fermentation by Enterococcus faecalis VB43 leads to reduction in the immunoreactivity of allergenic proteins β-conglycinin (7S) and glycinin (11S)

Food allergies represent a serious problem affecting human health and soy proteins rank among the most allergenic proteins from food origin. The proteolytic enzymes produced by lactic acid bacteria (LAB) can hydrolyse the major allergens present in soybean, reducing their immunoreactivity. Many studies have reported the ability of LAB to ferment soy-based products; while the majority of them focus on the improvement of the sensory characteristics and functionality of soy proteins, a lack of information about the role of lactic fermentation in the reduction of immunoreactivity of these proteins exists. The aim of the present study was to evaluate the capability of the proteolytic strain Enterococcus faecalis VB43 to hydrolyse the main allergenic proteins present in soymilk and to determine the immunoreactivity of the obtained hydrolysates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) results of fermented soymilk demonstrated complete hydrolysis of the β-subunit from β-conglycinin and the acidic polypeptide from glycinin. Reversed phase high performance liquid chromatography (RP-HPLC) analysis of the peptides released after hydrolysis revealed the appearance of new peptides and the disappearance of non-hydrolysed proteins, indicating extensive hydrolysis of the substrate. Results from competitive enzyme-linked immunosorbent assay (ELISA) tests clearly indicated a reduction in the immunoreactivity (more than one logarithmic unit) in the fermented sample as compared to the non-fermented control. Our results suggest that the soymilk fermented by E. faecalis VB43 may induce lower allergic responses in sensitive individuals. The strain E. faecalis VB43 may be considered as an excellent candidate to efficiently reduce the immunoreactivity of soymilk proteins.

The structural properties and antigenicity of soybean glycinin by glycation with xylose

BACKGROUND

Soybean glycinin is considered a major allergenic protein, and glycation is widely used to reduce the allergenic potential of present allergens. Glycation of soybean glycinin with xylose at 55 °C for different lengths of time was investigated. The extent of Maillard reaction was reflected through the content changing of free amino groups, color analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Alteration in the structural properties of glycinin was characterized by Fourier transform infrared spectroscopy, and antigenicity was evaluated by indirect competitive enzyme-linked immunosorbent assay.

RESULTS

The changes in the color of glycinin-xylose samples and the reduction of free amino group content in proteins indicated that the Maillard reaction occurred. The degree of glycation increased in glycated samples with the increase in reaction time. Glycation induced the changes in the secondary structure of glycinin and the ordered structure of proteins increased during the glycation reaction. The antigenicity of glycinin was reduced with the increase in reaction time. After glycation for 12 h, the antigenicity of glycinin declined about 18% compared with native glycinin.

CONCLUSION

The application of glycation may be an efficient method to reduce the antigenicity of soybean glycinin. © 2016 Society of Chemical Industry.

Mass Spectrometric Analysis of N-Glycoforms of Soybean Allergenic Glycoproteins Separated by SDS-PAGE

Glycosylation of many proteins has been revealed to be closely related with food allergies, and screening and structural analysis of related glycoproteins and glycoallergens are essential for studies in this field. Herein, we describe detailed N-glycoform analysis of all glycoprotein fractions of soybean protein isolate (SPI) separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to disclose structural features of the glycan moieties of more soybean glycoproteins. SPI was fractionated by SDS-PAGE, and the generated protein bands were recovered and subjected to in-gel N-glycan release and labeling using a one-pot method newly developed by our group, followed by detailed analysis by electrospray ionization mass spectrometry (ESI-MS) and online hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HILIC-ESI-MS/MS). As a result, we found seven bands mainly containing oligomannose-type glycans; two mainly contain core α1,3-fucosylated glycans, and six have no glycans. This study is the first report that discovers core α1,3-fucosylated N-glycans in bands 1, 2, and 6 and discloses bands 3, 4, 5, and 7 as glycoproteins and their N-glycoforms. Therefore, it can expand our knowledge about soybean protein glycosylation and provide significant structural reference for research of soybean allergens.

Identification and characterization of DC-SIGN-binding glycoproteins in allergenic foods

BACKGROUND

DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin) is a C-type lectin receptor expressed on macrophages and dendritic cells. DC-SIGN has high affinity for fucosylated glycans in several plant glycoproteins and pathogens. DC-SIGN is thought to be crucial for the development of allergic sensitization. However, the precise role of DC-SIGN in food allergy pathogenesis is not yet understood.

OBJECTIVE

We sought to characterize DC-SIGN-binding glycoproteins in a panel of allergenic and non-allergenic foods.

METHODS

Fluorescent-labeled peanut and soy extracts were used to test protein binding to human monocyte-derived dendritic cells (DCs) by flow cytometry. DC-SIGN-blocking assays were performed by incubating DCs with food extracts followed by staining with anti-DC-SIGN antibody. Using a DC-SIGN-Fc chimera, food extracts were tested for binding by ELISA and autoradiography. IgE immunoblotting was performed with pooled sera from food-allergic subjects. DC activation and maturation were assessed by flow cytometry.

RESULTS AND CONCLUSIONS

We demonstrate that peanut agglutinin, a minor peanut allergen, is a novel ligand for DC-SIGN. Peanut agglutinin activates DCs to induce the expression of costimulatory molecules in vitro. We present a comprehensive report on the characterization of DC-SIGN-binding proteins in common allergenic foods such as peanut, soy, tree nuts, egg, and milk. Foods that rarely induce allergy, such as pine nuts, chickpea, and corn, showed no binding to DC-SIGN. Several DC-SIGN-binding proteins show reactivity in serum IgE immunoblots. We have also identified novel non-IgE-binding proteins that interact with DC-SIGN; these proteins may be important for regulating immune responses to these foods.

Danshen enhanced the estrogenic effects of Qing E formula in ovariectomized rats

BACKGROUND

Menopause is characterized by a decrease in life quality due to the appearance of uncomfortable symptoms. Nowadays, Understanding menopause-associated pathophysiology and developing new strategies to improve the treatment of menopausal-associated symptoms is an important issue. Our study was to evaluate the synergistic effects of Danshen (salvia miltiorrhiza bunge) and the phytoestrogenic effects of 3 modified Qing E formulas, to explore a better formula for menopausal disorders.

METHODS

100 rats were randomized into 5 groups: Sham (Sham operation group), OVX (model group of ovariectomized rat), BDL (group with low concentration of Qing E Formula), BDH (group with high concentration of Qing E Formula) and BDD (group with high concentration of Qing E Formula Plus Danshen), receiving vehicle and extract of different modified Qing E formula respectively. The food intake, body weight, uterus weight, blood levels of triglycerides (TG), total cholesterol (TC) and cholesterol fractions were assessed. The mammary glands and uterus were morphologically analyzed. The bone density of tibias were measured by peripheral quantitative computed tomography (pQCT). Additionally, luciferase induction assays were performed in Hela cells with the mixtures derived from Qing E formula plus Danshen (BDD).

RESULTS

Qing E formula plus Danshen significantly increased the uterus wet weight, enhanced the thickness of uterine wall, endometrial epithelium and glandular epithelium, improved trabecular bone and total density evidently, reduced the levels of low density lipoprotein cholesterol (LDL-C) and TG, possessed notable estrogen receptor beta (ERβ) and estrogen receptor alpha (ERα) agonist activity.

CONCLUSION

Qing E formula plus Danshen exerted more evident estrogen-like effects, thus it has a potential therapeutic use to treat menopausal disorders.

Extent and Mode of Action of Cationic Legume Proteins against Listeria monocytogenes and Salmonella Enteritidis

The methylated soybean protein and methylated chickpea protein (MSP and MCP) with isoelectric points around pI 8 were prepared by esterifying 83 % of their free carboxyl groups and tested for their interactions with Listeria monocytogenes and Salmonella Enteritidis. The two substances exhibited a concentration-dependent inhibitory action against the two studied bacteria with a minimum inhibitory concentration of about 100 μg/mL. The IC50 % of the two proteins against L. monocytogenes (17 μg/mL) was comparable to penicillin but comparatively much lower (15 μg/mL) than that of penicillin (85 μg/mL) against S. Enteritidis. The two proteins could inhibit the growth of L. monocytogenes and S. Enteritidis by about 97 and 91 %, respectively, after 6-12 h of incubation at 37 °C. The constituting subunits of MSP (methylated 11S and methylated 7S) were both responsible for its antimicrobial action. Transmission electron microscopy of the protein-treated bacteria showed various signs of cellular deformation. The cationic proteins can electrostatically and hydrophobically interact with cell wall and cell membrane, producing large pores, pore channels and cell wall and cell membrane disintegration, engendering higher cell permeability leading finally to cell emptiness, lysis and death.

Enzymatic treatment of soy protein isolates: effects on the potential allergenicity, technofunctionality, and sensory properties

Soybean allergy is of great concern and continues to challenge both consumer and food industry. The present study investigates the enzyme‐assisted reduction in major soybean allergens in soy protein isolate using different food‐grade proteases, while maintaining or improving the sensory attributes and technofunctional properties. SDS‐PAGE analyses showed that hydrolysis with Alcalase, Pepsin, and Papain was most effective in the degradation of the major soybean allergens with proteolytic activities of 100%, 100%, and 95.9%, respectively. In the course of hydrolysis, the degree of hydrolysis increased, and Alcalase showed the highest degree of hydrolysis (13%) among the proteases tested. DSC analysis confirmed the degradation of major soybean allergens. The sensory experiments conducted by a panel of 10 panelists considered the overall improved sensory properties as well as the bitterness of the individual hydrolysates. In particular, Flavourzyme and Papain were attractive due to a less pronounced bitter taste and improved sensory profile (smell, taste, mouthfeeling). Technofunctional properties showed a good solubility at pH 7.0 and 4.0, emulsifying capacity up to 760 mL g⁻¹ (Flavourzyme) as well as improved oil‐binding capacities, while the water‐binding properties were generally decreased. Increased foaming activity for all proteases up to 3582% (Pepsin) was observed, whereas lower foaming stability and density were found. The hydrolysates could potentially be used as hypoallergenic ingredients in a variety of food products due to their improved technofunctional properties and a pleasant taste.

Analysis using fluorescence labeling and mass spectrometry of disulfide-mediated interactions of soy protein when heated

It is well-known that disulfide-mediated interactions are important when soy protein is heated, in which soy proteins are dissociated and rearranged to some new forms. In this study, the disulfide bond (SS) linked polymer, which was composed of the acidic (A) polypeptides of glycinin, basic (B) polypeptides of glycinin, and a small amount of α' and α of β-conglycinin, was formed as the major product, accompanied by the formation of SS-linked dimer of B and monomer of A as minor products. The role of sulfhydryl (SH) of different subunits/polypeptides for forming intermolecular SS was investigated. The SH of B in glycinin (Cys298 of G1, Cys289 of G2, Cys440 of G4) was transformed into SS in polymer identified by mass spectrometry analysis. The SH content of polymer was lower than that of glycinin and β-conglycinin subunits when heated. The SH content of B in polymer was lower than that in glycinin subunit, and both of them were decreased by heating. The SH content of A in polymer was increased and higher than that of B in polymer and A in glycinin subunit when heated. These results indicated that the SH of B in glycinin subunit was subjected to not only SH oxidation but also SH-SS exchange (with SS of A) for forming intermolecular SS of polymer. The SH oxidation and SH-SS exchange were proven by the change of SH content for the first time. The SH of B was suggested to be reactive for forming intermolecular SS of polymer.