High hydrostatic pressure effects on immunoreactivity and nutritional quality of soybean products

A study on the structure-functionality relationship of Solenaia oleivora protein under high-intensity ultrasonication processing

Solenaia oleivora is a valuable freshwater mussel endemic to China with a high content of high-quality proteins, but the lack of structural information and limited functionality of Solenaia oleivora proteins constrained their application in the food industry. This study investigates the changes in structural characteristics and functionality of Solenaia oleivora protein under ultrasound processing at power from 200 to 600 W. The ultrasound treatment caused increased contents of β-turn and α-helix, and the exposure of interior hydrophobic groups, resulting in the increased hydrophobicity by around 3 folds. The ultrasound treatment could significantly decrease particle size and increase surface charges of Solenaia oleivora proteins, facilitating the increase of hydrosolubility from 10.2% to 81.7%. These structural changes and increased hydrosolubility contributed to the enhancement of emulsifying and foaming properties, and in vitro digestibility. The results suggested that the ultrasound-treated Solenaia oleivora proteins possessed the potential as an alternative protein in food applications.

Effects of High Hydrostatic Pressure on the Distribution of Oligosaccharides, Pinitol, Soysapapogenol A, and Fatty Acids in Soybean

The effects of high hydrostatic pressure (HHP) treatment (100-600 MPa for 10-60 min) and thermal treatment (boiling for 10-60 min) on oligosaccharides, pinitol, and soyasapogenol A as taste ingredients in soybean (Glycine max (L.) Merr.) (cv. Yukihomare) were evaluated. Additionally, soybean-derived fatty acids such as α-linolenic acid, linoleic acid, oleic acid, palmitic acid, and stearic acid in pressurized soybeans were quantitatively analyzed. Sucrose, stachyose, and raffinose concentrations were decreased in all tested pressure and time combinations; however, pinitol concentrations were increased by specific pressure and time combinations at 100-400 MPa for 10-60 min. While the soyasapogenol A content in boiled soybeans decreased with increasing boiling time, that of pressurized soybeans was altered by specific pressure and time combinations. At the lower pressure and shorter time combinations, the essential fatty acids such as α-linolenic acid and linoleic acid showed higher contents. Stearic acid and oleic acid contents of pressurized soybeans increased at mild pressure levels (300-500 MPa). In contrast, the combination of higher pressure and longer time results in lower essential fatty acid contents. Non-thermal-pressurized soybeans have the potential to be a high-value food source with better taste due to the enrichment of low molecular weight components such as pinitol, free amino acids, and the reduction of isoflavones and Group A soyasapogenol.

Structural Characterization and Properties of Modified Soybean Meal Protein via Solid-State Fermentation by Bacillus subtilis

Soybean meal (SBM) is a high-quality vegetable protein, whose application is greatly limited due to its high molecular weight and anti-nutritional properties. The aim of this study was to modify the protein of soybean meal via solid-state fermentation of Bacillus subtilis. The fermentation conditions were optimized as, finally, the best process parameters were obtained, namely fermentation temperature of 37 °C, inoculum amount of 12%, time of 47 h, and material-liquid ratio of 1:0.58, which improved the content of acid-soluble protein. To explore the utilization of modified SBM as a food ingredient, the protein structure and properties were investigated. Compared to SBM, the protein secondary structure of fermented soybean meal (FSBM) from the optimal process decreased by 8.3% for α-helix content, increased by 3.08% for β-sheet, increased by 2.71% for β-turn, and increased by 2.51% for random coil. SDS-PAGE patterns showed that its 25-250 KDa bands appeared to be significantly attenuated, with multiple newborn peptide bands smaller than 25 KDa. The analysis of particle size and zeta potential showed that fermentation reduced the average particle size and increased the absolute value of zeta potential. It was visualized by SEM and CLSM maps that the macromolecular proteins in FSBM were broken down into fragmented pieces with a folded and porous surface structure. Fermentation increased the solubility, decreased the hydrophobicity, increased the free sulfhydryl content, decreased the antigenicity, improved the protein properties of SBM, and promoted further processing and production of FSBM as a food ingredient.

The Differences in Protein Degradation and Sensitization Reduction of Mangoes between Juices and Pieces Fermentation

Given the allergic reaction caused by mangoes, nonthermal food technologies for allergenicity reduction are urgently desired. This study aimed to assess the impact of kombucha fermentation on the allergenicity of mangoes. The total proteins, soluble proteins, peptides, amino acid nitrogen, the SDS-PAGE profiles of the protein extracts, and immunoreactivity of the sediment and supernatant were measured in two fermentation systems (juices and pieces fermentation). Throughout the fermentation, the pH decreased from about 4.6 to about 3.6, and the dissolved oxygen reduced about 50% on average. However, the protein degradation and sensitization reduction of mangoes were different between the two fermentation systems. In juices fermentation, there was a drop in proteins and peptides but an increase in amino acids, due to the conversion of proteins and peptides into amino acids both in the supernatant and sediment. The allergenicity decreased both in the solid and liquid phases of juices fermentation. In pieces fermentation, proteins and peptides were decreased in the solid phase but increased in the liquid phase. This was due to the fact that proteins and peptides were partly transported into the culture liquid, resulting in a decrease of allergenicity in fruit pieces and an increase in culture liquid. The principal component analysis results showed that the fermentation type had significant effects on the protein degradation and sensitization reduction, while mango variety had no significant effect. These results demonstrate that kombucha fermentation can reduce the allergenicity of mangoes, and it is more effective in juices fermentation than in pieces fermentation. The present study provides a theoretical basis for developing hypoallergenic mango products.

Effect of ultrahigh-pressure treatment on the structure and allergenicity of peach allergenic proteins

Peach is a common plant-derived allergenic food and ultrahigh-pressure treatment is often used in peach products. In our study, an in-depth analysis of the structural and allergenicity changes of peach allergenic proteins after UHP treatment was performed by spectroscopy, mass spectrometry combined with serology and cytology. The results indicated that UHP treatment could reduce the content of peach soluble proteins and cause changes in secondary and tertiary structures. In addition, more hydrophobic residues were exposed and proteins tended to polymerize after UHP-treatment. The results of immunological assays showed that UHP treatment could reduce the IgE binding capacity of peach proteins and affect the ability of basophil degranulation, the upregulation of some cytokines may contribute to the reduction of peach protein allergenicity. Notably, UHP treatment may lead to the masking of some digestion sites in Pru p 3 epitopes, thus impeding human digestion and increasing the potential risk of allergenicity.

Effect of processing treatments on the allergenicity of nuts and legumes: A meta-analysis

The effective food processing to reduce nuts and legumes allergenicity could not be easily and directly concluded from reading a few published reports. Therefore, we conducted a meta-analysis to investigate this issue. A literature search was conducted in eight electronic databases from January 2000 to June 11, 2021. The primary outcome of interest was the allergenicity of processed nuts or legumes determined by enzyme-linked immunosorbent assay from in vitro studies. Data with the standardized mean difference (SMD) of 95% confidence interval (CI) were pooled using a random-effect model by RevMan 5.4 software. Heterogeneity was assessed using Cochran's Q (P_Q ) and I² tests. The search strategy identified 18,793 articles. However, only 61 studies met the inclusion criteria and were included in this meta-analysis. There were 21 and 15 types of respective single and combined food processing treatments analyzed for their effects on reducing allergenicity. In single processing treatment, the extrusion and fermentation had the largest reduction in allergenicity, considering their SMD value, that is, -20.19 (95% CI: -22.22 to -18.17; the certainty of evidence: moderate) and -20.8 (95% CI: -24.10 to -17.50; the certainty of evidence: moderate), respectively. Whereas in the combination, the treatment of fermentation followed by proteolytic hydrolysis showed the most significant reduction (SMD: -53.34; 95% CI: -70.18 to -36.5) and the evidence quality of this treatment was considered moderate. In conclusion, these three food processing methods showed a desirable impact in reducing nuts or legumes allergenicity. PRACTICAL APPLICATION: Nuts and legumes play an essential role as protein sources in food consumption worldwide, but they usually contain allergens. Our study has investigated the food processing methods that effectively reduce their allergenicity by meta-analysis. The result gives valuable information for further laboratory investigation on allergens and can be used by food industries in providing foods from nuts and legumes with lower allergenicity.

Impact of Non-Thermal Technologies on the Quality of Nuts: A Review

Nuts are widely consumed worldwide, mainly due to their characteristic flavor and texture, ease of consumption, and their functional properties. In addition, consumers increasingly demand natural or slightly processed foods with high quality. Consequently, non-thermal treatments are a viable alternative to thermal treatments used to guarantee safety and long shelf life, which produce undesirable changes that affect the sensory quality of nuts. Non-thermal treatments can achieve results similar to those of the traditional (thermal) ones in terms of food safety, while ensuring minimal loss of bioactive compounds and sensory properties, thus obtaining a product as similar as possible to the fresh one. This article focuses on a review of the main non-thermal treatments currently available for nuts (cold plasma, high pressure, irradiation, pulsed electric field, pulsed light, ultrasound and ultraviolet light) in relation to their effects on the quality and safety of nuts. All the treatments studied have shown promise with regard to the inhibition of the main microorganisms affecting nuts (e.g., Aspergillus, Salmonella, and E. coli). Furthermore, by optimizing the treatment, it is possible to maintain the organoleptic and functional properties of these products.

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.

High hydrostatic pressure treatment reduces the potential antigenicity of β-conglycinin by changing the protein structure during in vitro digestion

BACKGROUND

High hydrostatic pressure (HHP) treatment has been used to alleviate the allergenicity of soybeans, but there are little data about the potential antigenicity of β-conglycinin after HHP treatment.

RESULTS

We examined the effects of HHP treatment on the antigenicity and structure of β-conglycinin. When the pressure was 300 and 400 MPa, HHP treatment reduced the immunoglobulin (Ig)G binding capacity of β-conglycinin, while its IgE binding capacity did not change significantly. After in vitro digestion, both the IgE and IgG binding of β-conglycinin was obviously inhibited after HHP treatment at 400 MPa and 60 °C, although its binding capacity with linear epitope antibodies increased. Moreover, HHP treatment changed the secondary structure of β-conglycinin, the content of α-helix and random coils increased, while the β-sheet and β-turn decreased. After HHP treatment, the conformational structure was unfolded so that a large number of hydrophobic regions were exposed.

CONCLUSION

HHP treatment alleviated the potential antigenicity of β-conglycinin by modifying its structure, which facilitated in vitro digestion and destroyed epitopes. This research provides a new insight into the mechanism of HHP treatment that affects the sensitization of soy protein allergens. © 2022 Society of Chemical Industry.

Effect of high hydrostatic pressure on the edible quality, health and safety attributes of plant-based foods represented by cereals and legumes: a review

Consumers today are increasingly willing to reduce their meat consumption and adopt plant-based alternatives in their diet. As a main source of plant-based foods, cereals and legumes (CLs) together could make up for all the essential nutrients that humans consume daily. However, the consumption of CLs and their derivatives is facing many challenges, such as the poor palatability of coarse grains and vegetarian meat, the presence of anti-nutritional factors, and allergenic proteins in CLs, and the vulnerability of plant-based foods to microbial contamination. Recently, high hydrostatic pressure (HHP) technology has been used to tailor the techno-functionality of plant proteins and induce cold gelatinization of starch in CLs to improve the edible quality of plant-based products. The nutritional value (e.g., the bioavailability of vitamins and minerals, reduction of anti-nutritional factors of legume proteins) and bio-functional properties (e.g., production of bioactive peptides, increasing the content of γ-aminobutyric acid) of CLs were significantly improved as affected by HHP. Moreover, the food safety of plant-based products could be significantly improved as well. HHP lowered the risk of microbial contamination through the inactivation of numerous microorganisms, spores, and enzymes in CLs and alleviated the allergy symptoms from consumption of plant-based foods.

Protein profile of commercial soybean milks analyzed by label-free quantitative proteomics

The consumption of soy milk is increasing worldwide for its nutritional value and health benefits, however, its protein composition after commercialization is not well known. Technological and thermal treatments to which soy milk is subjected could affect the protein composition of the commercial products. This study compared the protein profile of 15 different commercial soy milks using a label-free quantitative proteomics approach. Proteins related to nutrient reservoir activity, endopeptidase inhibitor activity, lipid binding, and seed maturation contribute the most in terms of percentage mass. Their associated Gene Ontology terms are also enriched. Samples clustered into three groups based on their protein composition, with glycinins and beta-conglycinins being the most influential for determining the clustering. Amino acid composition estimated from the proteomics data also reflects the clustering of samples. Twenty allergenic proteins varying in abundance were identified, with Gly m 5 and Gly m 6 being the predominantly abundant allergens.

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data.

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.

Identification and comparison of proteomic and peptide profiles of mung bean seeds and sprouts

The objectives of this study were to analyze and compare the proteomic and peptide profiles of mung bean (Vigna radiata) seeds and sprouts. Label-free proteomics and peptidomics technologies allowed the identification and relative quantification of proteins and peptides. There were 1918 and 1955 proteins identified in mung bean seeds and sprouts, respectively. The most common biological process of proteins in these two samples was the metabolic process, followed by cellular process and single-organism process. Their dominant molecular functions were catalytic activity, binding, and structural molecule activity, and the majority of them were the cell, cell part, and organelle proteins. These proteins were primarily involved in metabolic pathways, biosynthesis of secondary metabolites, and ribosome. PCA and HCA results indicated the proteomic profile varied significantly during mung bean germination. A total of 260 differential proteins between mung bean seeds and sprouts were selected based on their relative abundance, which were associated with the specific metabolism during seed germination. There were 2364 peptides identified and 76 potential bioactive peptides screened based on the in silico analysis. Both the types and concentration of the peptides in mung bean sprouts were higher than those in seeds, and the content of bioactive peptides in mung bean sprouts was deduced to be higher.

Sprouted oat as a potential gluten-free ingredient with enhanced nutritional and bioactive properties

This study is aimed to produce and characterize a novel gluten-free ingredient from oat through sprouting at 18 °C for 96 h. The nutritional and bioactive properties as well as key enzymatic activities were studied in sprouted oat powder and compared with those of oat grain powder (control). Sprouted oat powder was an excellent source of protein (10.7%), β-glucan (2.1%), thiamine (687.1 μg/100 g), riboflavin (218.4 μg/100 g), and minerals (P, K, Mg and Ca), and presented better amino acid and fatty acid compositions and levels of γ-aminobutyric acid (54.9 mg/100 g), free phenolics (507.4 mg GA/100 g) and antioxidant capacity (1744.3 mg TE/100 g) than control. Enhanced protease and α-amylase and reduced lipase activities were observed in sprouted oat powder, which are promising features to improve its nutritional, sensorial and health-promoting properties. These results support the use of sprouted oat powder as a promising gluten-free functional ingredient.

Location of destroyed antigenic sites of Gly m Bd 60 K after three processing technologies

Gly m Bd 60 K, which is the α subunit of β-conglycinin, is a major soybean (Glycine max) allergen. We used high hydrostatic pressure (HHP), thermal techniques, and glycation to treat β-conglycinin, which can effectively reduce the antigenicity of β-conglycinin. β-conglycinin was used to immunize New Zealand rabbits, and the antiserum had a titer > 1: 1 × 105 and an IC50 of 2.254 μg/mL. β-conglycinin was subjected to HHP, thermal techniques, and glycation and mixed with rabbit antiserum against β-conglycinin to obtain the site-specific antiserum. The overlapping gene fragments of Gly m Bd 60 K were amplified by polymerase chain reaction (PCR), then cloned into a T7 phage vector and packaged in vitro, the recombinant T7 phages were constructed. Indirect ELISA (iELISA) was used to locate the destroyed antigenic sites and, after three rounds of segment expression and identification, the C2-1 and C2-2 fragments were identified as destroyed antigenic sites of Gly m Bd 60 K. Allergenicity analysis showed that the C2-1 and C2-2 fragments reacted with allergic patients' serum, which indicated that the destroyed sites were allergic sites.

Identification of antigenic sites destructed by high hydrostatic pressure (HHP) of the β subunit of β-conglycinin

β-conglycinin is one of the most allergenic proteins, and its constituent subunits α', α, and β are all potential allergens to humans. In the present study, we concentrated on the destructed antigenic sites of β subunit of β-conglycinin after high hydrostatic pressure (HHP) treatment. In this paper, the overlapping gene fragments of the β subunit of β-conglycinin were amplified by polymerase chain reaction (PCR) and cloned into T7 phage vectors. After being packaged in vitro, the recombinant T7 phage was constructed, and the overlapping fragments of the β subunit were displayed on the phage surface. The recombinant phages that expressed the overlapping fragments of the β subunit were used to react with specific antiserum by indirect ELISA to identify the HHP destructed antigenic sites. After three rounds of expression and identification, we used synthetic peptide technology to identify that the obtained fragment was a conformational epitope. We further confirmed that HHP treatment changed the conformational structure of β-conglycinin, which reduced the antigenicity of the protein.

Effect of microbial transglutaminase cross-linking on the quality characteristics and potential allergenicity of tofu

Microbial transglutaminase (MTGase) has been developed as a new tofu coagulant in recent years due to its good hydrophilicity, high catalytic activity, and strong thermal stability. This study aimed to investigate the effect of MTGase on the physicochemical properties and immunoreactivity of tofu relative to conventional coagulants [brine and glucono-δ-lactone (GDL)]. Structural changes of the MTGase cross-linked soymilk protein were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD) spectroscopy, ultraviolet (UV) absorption spectroscopy, and fluorescence spectroscopy. The IgE-binding capacity of MTGase cross-linked proteins was tested by enzyme-linked immunosorbent assay (ELISA). The physicochemical properties, quality characteristics, and surface microstructures of five different types of tofu were determined by the Kjeldahl nitrogen method, texture analysis, and scanning electron microscopy (SEM). The digestibility of tofu was evaluated in vitro by simulated gastrointestinal (GIS) digestion. A cell sensitization experiment was performed in vitro to evaluate the capability of tofu digestion products to induce the release of bioactive mediators from human basophil leukemia (KU812) cells. Results indicated that MTGase significantly changed the advanced structure of the soymilk protein. Compared with tofu without MTGase, the composite coagulant tofu containing MTGase exhibited better quality. MTGase improved the water-holding capacity (WHC) of the internal mesh structure and increased the yield of tofu. The digestion products of the composite coagulant tofu, especially the GDL plus MTGase tofu, induced KU812 cells to release fewer bioactive mediators compared with those of MTGase-free tofu. MTGase can not only improve the quality of conventional coagulant tofu but also reduce the potential allergenicity of tofu to a certain extent.

Inactivation Methods of Trypsin Inhibitor in Legumes: A Review

Seed legumes have played a major role as a crop worldwide, being cultivated on about 12% to 15% of Earth's arable land; nevertheless, their use is limited by, among other things, the presence of several antinutritional factors (ANFs - naturally occurring metabolites that the plant produces to protect itself from pest attacks.) Trypsin inhibitors (TIs) are one of the most relevant ANFs because they reduce digestion and absorption of dietary proteins. Several methods have been developed in order to inactivate TIs, and of these, thermal treatments are the most commonly used. They cause loss of nutrients, affect functional properties, and require high amounts of energy. Given the above, new processes have emerged to improve the nutritional quality of legumes while trying to solve the problems caused by the use of thermal treatments. This review examines and discusses the methods developed by researchers to inactivate TI present in legumes and their effects over nutritional and functional properties.

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.

Structure-based modelling of hemocyanin allergenicity in squid and its response to high hydrostatic pressure

The secondary, tertiary, and quaternary structures of squid hemocyanin (Hc) were characterised, and the relationship between Hc structure and allergenicity responses to high hydrostatic pressure (HHP) was modelled. The Hc allergenicity varied with its protein structure. Electrophoresis analysis revealed that HHP treatment significantly decreased the band intensity of Hc when increasing pressure from 200 and 400 MPa to 600 MPa. The protein structure analysis of squid Hc showed that while HHP treatment decreased the α-helix content, free sulfhydryl content, and R_g, it increased the random coil content, surface hydrophobicity index (Ho), Guinier aggregation number (〈N_agg〉_G) and average aggregation number (〈N_agg〉_Q). The α-helix and random coil contents of the 600 MPa treated samples were 23.67% and 37.54%, respectively, compared to 32.37% and 32.02% in the control, respectively. HHP treatment decreased the IgE and IgG-binding capacities, indicating a significant decrease in the allergenicity (P< 0.05) of squid Hc. This study provided meaningful information of applying HHP to reduce allergenicity, and explained the responses of Hc protein structure to HHP for lowering the allergenicity of squid.

Reactivity change of IgE to buckwheat protein treated with high-pressure and enzymatic hydrolysis

BACKGROUND

Buckwheat is a popular food material in eastern Asian countries that can cause allergenic response. This study was conducted to evaluate the effects of hydrolysis with papain and high-pressure (HP) treatment of buckwheat protein (BWP) on reactivity of immunoglobulin E (IgE) and its secondary structure.

RESULTS

Reactivity of IgE was examined by enzyme-linked immunosorbent assay (ELISA) with serum samples from 16 patients allergic to buckwheat. Reactivity of IgE to hydrolysate of BWP with papain showed a maximum decrease of 79.8%. After HP treatment at 600 MPa for 1 min, reactivity of IgE to BWP decreased by up to 55.1%. When extracted, BWP was hydrolyzed with papain overnight following HP treatment at 600 MPa which the reactivity of IgE decreased significantly by up to 87.1%. Significant changes in secondary structure of BWP were observed by circular dichroism (CD) analysis after hydrolysis with papain following HP treatment.

CONCLUSION

Reduction of reactivity of IgE showed a correlation with changes in secondary structure of BWP, which may cause changes in conformational epitopes. This suggests the possibility of decreasing the reactivity of IgE to BWP using combined physical and enzymatic treatments.

AFM and NMR imaging of squid tropomyosin Tod p1 subjected to high hydrostatic pressure: evidence for relationships among topography, characteristic domain and allergenicity

The surface topography, characteristic domain and allergenicity of squid tropomyosin Tod p1 (TMTp1) treated under single- and two-cycle high hydrostatic pressure (HHP) were analyzed.