The characterization of soybean oil body integral oleosin isoforms and the effects of alkaline pH on them

Effect of extraction pH on the emulsion stability and surface protein structure of soybean oil body

In this study, the pH was varied (6.0-11.0) during the extraction of soybean oil body (SOB), and the stabilities of the corresponding emulsions as well as the structural properties of SOB surface proteins were investigated. The extraction pH was found to affect both the SOB emulsion stability and surface protein structure. Micromorphological analysis showed that the degree of SOB dispersion was higher under alkaline conditions compared to other treatment conditions (acidic or neutral). Structural changes in the SOB surface proteins, as evaluated using changes in the α-helix and β-sheet contents and fluorescence intensity, were more pronounced when extraction was performed at pH 11.0. Structural changes in SOB surface proteins also affected the amino acid fractions, surface hydrophobicity, and free sulfhydryl content. Overall, an extraction pH of 11.0 resulted in optimal SOB emulsion stability and had the greatest effect on the structural properties of the SOB surface proteins.

Comparative analysis of physicochemical properties and functionalities of artificial oil bodies stabilized by different seed oil body proteins

In this study, ‌perilla seed oil body protein (PO), hempseed oil body protein (HO), and cucumber seed oil body protein (CO) were utilized to prepare artificial oil bodies (AOBs), and the impact of protein type on their physicochemical properties was investigated.‌ ‌Compared to HO and CO, PO exhibited a lower zeta potential value of -48.27 mV, a higher surface hydrophobicity of 21,122.67, and a smaller particle size of 105.71 nm. Its emulsifying activity index (EAI) and emulsion stability index (ESI) were 83.06 m2/g and 167.9 %, respectively. ‌Furthermore, AOBs stabilized by PO demonstrated smaller particle size and a higher amount of interfacial adsorbed protein compared to those prepared by HO and CO.‌ ‌Additionally, the encapsulation results indicated that PO-AOBs exhibited a higher encapsulation efficiency of 98.34 %. The retention rates of the loaded curcumin were 56.94 % after exposure to 90 °C and 94.06 % after UV light exposure for 7 h. ‌Moreover, both digestion and antioxidant experiments indicated that PO-AOBs facilitated better release of curcumin in the intestine, leading to enhanced antioxidant properties and increased bioavailability.‌ These findings offer ‌new insights into the development of novel AOBs, which hold promise for diverse applications in food delivery systems.

Fat substitute in salad dressing: The role of soybean oil body self-aggregates in enhancing texture and rheological property

Salad dressing have become a popular condiment in many countries. However, their high fat content may contribute to obesity and related health issues. In this study, mild and extensive purification were used to extract soybean oil body (SOB) with different protein compositions, and further modulated the interfacial charge interactions, thereby producing SOB self-aggregates for fat substitute in salad dressing. Mild purification of SOB increased extrinsic protein content, while extensive purification reduced extrinsic protein content. The mild purification system showed the largest particle size and segregated network structure close to the isoelectric point. However, the extensively purified system exhibited a charge reversal from negative to positive, forming a compact network. Both self-aggregates exhibited shear thinning and elastic properties. Increasing SOB self-aggregate concentration enhanced brightness, electrostatic repulsion and steric hindrance in salad dressing. SOB self-aggregates prepared with extensive purification at pH 5.0, formed a dense network structure that facilitated droplet arrangement, thereby imparting optimal viscoelasticity, enhanced interactions, and thixotropic recovery to salad dressing. This work presents a method based on different protein composition and charge modulation for incorporating oil body as ingredients in spreadable condiments without thickener as label-free products.

Genome-wide identification, transcript profiling and functional analyses of PCP gene family in Wucai (Brassica campestris)

Pollen coat proteins (PCPs) are cysteine-rich small-molecule proteins, which exhibit high levels of polymorphism and are expressed in gametocytes. Previous investigations have revealed that PCP genes are involved in pollen wall synthesis, pollen-stigma recognition, and pollen development and germination. However, gene expression and function of PCP family in pollen development is not well understood in Wucai (Brassica campestris L.). In this study, genome-wide identification and expression analysis of the BcPCP gene family members were conducted, including their physical and chemical properties, chromosome localization, phylogenetic relationships, gene structure, and tertiary structure. A total of 20 BcPCP genes were identified and classified into three subfamilies showing high homology to Arabidopsis thaliana. Expression pattern analysis indicated that the BcPCP gene family exhibits higher expression levels in reproductive organs, suggesting their potential involvement in the reproductive development. Notably, BraA02g002400.3 C, potentially associated with male sterility, was identified through multiple transcriptomic and proteomic datasets. Subsequently, sequence analysis revealed its homology with the Arabidopsis GRP20 gene, and thus it was named BcGRP20. Functional analysis of this gene showed that overexpression of BcGRP20 gene in the Arabidopsis grp20 mutant could restore anther fertility. Overall, our findings indicate that BcGRP20 plays a critical role in pollen development and may be the causative gene for male sterility in Wucai. This study provides candidate genes for further functional identification of BcPCP genes in Wucai, which are crucial for anther development.

Unveiling the applications of membrane proteins from oil bodies: leading the way in artificial oil body technology and other biotechnological advancements

Oil bodies (OBs) function as organelles that store lipids in plant seeds. An oil body (OB) is encased by a membrane composed of proteins (e.g., oleosins, caleosins, and steroleosins) and a phospholipid monolayer. The distinctive protein-phospholipid membrane architecture of OBs imparts exceptional stability even in extreme environments, thereby sparking increasing interest in their structure and properties. However, a comprehensive understanding of the structure-activity relationships determining the stability and properties of oil bodies requires a more profound exploration of the associated membrane proteins, an aspect that remains relatively unexplored. In this review, we aim to summarize and discuss the structural attributes, biological functions, and properties of OB membrane proteins. From a commercial perspective, an in-depth understanding of the structural and functional properties of OBs is important for the expansion of their applications by producing artificial oil bodies (AOB). Besides exploring their structural intricacies, we describe various methods that are used for purifying and isolating OB membrane proteins. These insights may provide a foundational framework for the practical utilization of OB membrane proteins in diverse applications within the realm of AOB technology, including biological and probiotic delivery, protein purification, enzyme immobilization, astringency detection, and antibody production.

Pectin polysaccharide contribution to oleosome extraction after wet milling of rapeseed

Oleosomes are lipid composites providing energy storage in oilseeds. They possess a unique structure, comprised of a triglyceride core stabilized by a phospholipid-protein membrane, and they have shown potential to be used as ingredients in several food applications. Intact oleosomes are extracted by an aqueous process which includes soaking, milling, and gravitational separation. However, the details of the complexes formed between oleosomes, proteins and pectin polysaccharides during this extraction are not known. It was hypothesized that pectins play an important role during the oleosome separation, and different proteins will be complexed on the surface of the oleosomes, depending on the pH of extraction. Rapeseed extracts were treated with and without pectinase (Pectinex Ultra SP-L) and extracted at pH 5.7 or 8.5, as this will affect electrostatic complexation. Acidic conditions led to co-extraction of storage proteins, structured as dense oleosome emulsions, stabilized by a network of proteins and polysaccharides. Pectinase intensified this effect, highlighting pectic polysaccharides' role in bridging interactions among proteins and oleosomes under acidic conditions. The presence of this dense interstitial layer around the oleosomes protected them from coalescence during extraction. Conversely, under alkaline conditions, the extraction process yielded more purified oleosomes characterized by a larger particle size, most likely due to coalescence. Nevertheless, pectinase addition at pH 8.5 mitigated coalescence tendencies. These results contribute to a better understanding of the details of the colloidal complexes formed during extraction and can be used to modulate the composition of the extracted fractions, with significant consequences not only for yields and purity but also for the functional properties of the ingredients produced.

Enhancing Rheological and Textural Properties of Gelatin-Based Composite Gels through Incorporation of Sesame Seed Oleosome-Protein Fillers

In this study, the protein and oleosomes of sesame seeds were extracted individually and used to prepare a gel composed of gelatin, protein, and oleosomes. Mixtures of gelatin and sesame seeds protein were prepared, and oleosomes with different percentages (0, 10, 20 and 30% of their weight) were used. Different amounts of oleosomes in the composite gel samples were examined for their morphological, rheological, and textural properties. The results of the viscoelastic properties of different composite gel samples indicated that a higher percentage of oleosomes would increase the storage modulus (G'), loss modulus (G″), and complex viscosity (η*). The storage modulus of all gel samples was greater than the loss modulus, suggesting a solid behavior. So, in the sample with 30% oleosome, the storage modulus and the loss modulus reached 143,440 Pascals and 44,530 Pascals. The hardness and breaking force in samples containing 30% oleosome reached 1.29 ± 0.02 and 0.17 ± 0.02, respectively. In general, it can be said that composite gels based on gelatin-sesame seed protein modified with oleosome can be used as a part of food components in various dairy products, gelatin desserts, lean meat products and the production of useful products.

Effect of Heat Treatment on the Digestive Characteristics of Different Soybean Oil Body Emulsions

Soybean oil body (SOB) emulsions were prepared using OBs extracted at pH 11.0 and pH 7.0. The pH 11.0-SOB comprised oleosins, whereas pH 7.0-SOB comprised extrinsic proteins and oleosins. All SOB emulsions were heated at 60-100 °C for 15 min. Heating may lead to the release of extrinsic proteins from the surface of pH 7.0-SOB due to heat-induced denaturation. The total proportion of α-helix and β-sheets gradually decreased from 77 (unheated) to 36.2% (100 °C). During stomach digestion, the extrinsic protein hydrolysis of heated pH 7.0-SOB emulsions was fast between 60 and 80 °C, and it then slowed between 90 and 100 °C; heating inhibited the oleosin hydrolysis of pH 7.0- and 11.0-SOBs. Heat treatment promoted aggregation and coalescence, and it resulted in increased particle sizes for all emulsions. Larger aggregates were found in heated pH 7.0-SOB emulsions, and larger oil droplets were found in heated pH 11.0-SOB emulsions. After intestinal digestion, the droplets of all SOB emulsions gradually dispersed, and particle sizes decreased. Different heating temperatures had lesser effects on particle sizes and microstructures. Lipolysis was affected by the extraction pH and heating. For pH 11.0-SOB emulsions, the FFA release tendency was greatly affected by the heating temperature, and heating to 80 °C resulted in the highest FFA release (74%). However, all pH 7.0-SOB emulsions had similar total FFA releases. In addition, the droplet charges of heated pH 7.0-SOB emulsions were lower than those of unheated pH 7.0-SOB emulsions in both the intestine and stomach phases; however, the charge changes in different pH 11.0-SOB emulsions showed the opposite tendency. This study will offer guidance regarding the application of SOB emulsions in food.

Lipid Droplets from Plants and Microalgae: Characteristics, Extractions, and Applications

Plant and algal LDs are gaining popularity as a promising non-chemical technology for the production of lipids and oils. In general, these organelles are composed of a neutral lipid core surrounded by a phospholipid monolayer and various surface-associated proteins. Many studies have shown that LDs are involved in numerous biological processes such as lipid trafficking and signaling, membrane remodeling, and intercellular organelle communications. To fully exploit the potential of LDs for scientific research and commercial applications, it is important to develop suitable extraction processes that preserve their properties and functions. However, research on LD extraction strategies is limited. This review first describes recent progress in understanding the characteristics of LDs, and then systematically introduces LD extraction strategies. Finally, the potential functions and applications of LDs in various fields are discussed. Overall, this review provides valuable insights into the properties and functions of LDs, as well as potential approaches for their extraction and utilization. It is hoped that these findings will inspire further research and innovation in the field of LD-based technology.

Impact of processing on the oxidative stability of oil bodies

Plant lipids are stored as emulsified lipid droplets also called lipid bodies, spherosomes, oleosomes or oil bodies. Oil bodies are found in many seeds such as cereals, legumes, or in microorganisms such as microalgae, bacteria or yeast. Oil Bodies are unique subcellular organelles with sizes ranging from 0.2 to 2.5 μm and are made of a triacylglycerols hydrophobic core that is surrounded by a unique monolayer membrane made of phospholipids and anchored proteins. Due to their unique properties, in particular their resistance to coalescence and aggregation, oil bodies have an interest in food formulations as they can constitute natural emulsified systems that does not need the addition of external emulsifier. This manuscript focuses on how extraction processes and other factors impact the oxidative stability of isolated oil bodies. The potential role of oil bodies in the oxidative stability of intact foods is also discussed. In particular, we discuss how constitutive components of oil bodies membranes are associated in a strong network that may have an antioxidant effect either by physical phenomenon or by chemical reactivities. Moreover, the importance of the selected process to extract oil bodies is discussed in terms of oxidative stability of the recovered oil bodies.

Effects of ultrasound-assisted salt (NaCl) extraction method on the structural and functional properties of Oleosin

²We propose a new ultrasound-assisted salt (NaCl) Oleosin extraction method, where the addition of NaCl induces the dissociation of Oleosin subunits and promotes the unfolding of the protein spatial structure. The yield of Oleosin post extraction and purification and solubility of Oleosin obtained using the proposed method were higher than those of Oleosin extracted using traditional methods, by 17.6% and 122.9%, respectively; reduction in particle size (to 52 nm) was also noted. Hydrogen bond dissociation, increase in surface hydrophobicity, and disulfide bond formation occurred simultaneously. However, the overall structure of Oleosin was not negatively affected. The physical properties of Oleosin, such as water and oil absorption, emulsification, and antioxidant activity, were improved, and the rate of Oleosin digestion decreased during the in vitro simulated digestion process. The proposed method provides a theoretical basis for producing proteins. This method can be utilized for effective extraction of Oleosin to achieve sustained release of the produced proteins.

Oleosin Cor a 15 is a novel allergen for Italian hazelnut allergic children

BACKGROUND

Hazelnut allergy, which is characterized by symptoms that range from mild to severe, is one of the most common allergies in children throughout Europe, and an accurate diagnosis of this allergy is therefore essential. However, lipophilic allergens, such as oleosins, are generally underrepresented in diagnostic tests. We therefore sought to characterize the IgE reactivity of raw and roasted hazelnut oleosins, using the sera of hazelnut-allergic pediatric patients.

METHODS

Raw and roasted hazelnut oil body-associated proteins were analyzed by means of 1D and 2D electrophoresis and MS. Oleosin IgE reactivity was assessed by immunoblotting with the sera of 27 children who have confirmed hazelnut allergies and from 10 tolerant subjects. A molecular characterization of the oleosins was performed by interrogating the C. avellana cv. Jefferson and cv. TGL genomes, and through expression and purification of the recombinant new allergen.

RESULTS

A proteomic and genomic investigation allowed two new oleosins to be identified, in addition to Cor a 12 and Cor a 13, in hazelnut oil bodies. One of the new oleosins was registered as a new allergen, according to the WHO/IUIS Allergen Nomenclature Subcommittee criteria, and termed Cor a 15. Cor a 15 was the most frequently immunorecognized oleosin in our cohort. Oleosins resulted to be the only immunorecognized allergens in a subgroup of allergic patients who showed low ImmunoCAP assay IgE values and positive OFC and PbP. Hazelnut roasting resulted in an increase in oleosin immunoreactivity.

CONCLUSION

A novel hazelnut oleosin, named Cor a 15, has been discovered. Cor a 15 could play a role in eliciting an allergic reaction in a subgroup of pediatric patients that exclusively immunorecognize oleosins. The high prevalence of hazelnut oleosin sensitization here reported further confirms the need to include oleosins in routine diagnostic procedures.

Effects of pH on the Composition and Physical Stability of Peanut Oil Bodies from Aqueous Enzymatic Extraction

Peanut oil body (POB), which is rich in unsaturated fatty acids and bioactive substances, is widely used in cosmetics, food, and medicine. Compared with synthetic emulsifiers, peanut oil bodies have health advantages as natural emulsions. The physicochemical properties of oil bodies affect their food processing applications. To improve peanut oil body yield, cell-wall-breaking enzymes were screened for aqueous enzymatic extraction. The optimum conditions were as follows: enzymatic hydrolysis time, 2 h; material-to-liquid ratio, 1 : 5 ( $m/v$ ); enzyme concentration, 2% ( $v/m$ ); and temperature, 50°C. Oil body stability was closely related to pH. With increasing pH, the average particle size and zeta-potential of the oil bodies increased, indicating aggregation, as confirmed by microstructure analysis. At pH 11, exogenous proteins at the oil body interface were eluted, leaving endogenous proteins, which led to a decreased interfacial protein content and oil body aggregation. Therefore, oil body stability decreased under alkaline pH conditions, but no demulsification occurred.

Comparison of Two Different Natural Oil Body Emulsions: in vitro Gastrointestinal Digestion

The surface compositions and structure of oil bodies (OBs) are dependent on the oil crop, and these factors affect in vitro gastrointestinal digestion behaviors. Herein, a comparative study was conducted to examine the in vitro gastrointestinal digestion characteristics of two natural emulsions prepared with soybean seeds and rapeseed OBs during gastrointestinal digestion process. The average particle size of soybean OBs and rapeseed OBs emulsions was 0.46 and 5.02 µm, respectively. The droplet size of soybean seed and rapeseed OBs emulsions was large with relatively low zeta-potentials at 30 min digestion time in simulated gastric fluid condition. The droplet size of two natural OBs emulsions decreased with increasing digestion time in simulated gastric fluid condition. The average droplet size of both emulsions gradually decreased with increasing digestion time in simulated intestinal fluid conditions. The zeta-potential of the two emulsions increased with increasing digestion time in simulated intestinal fluid conditions. The extent of free fatty acids of soybean OBs emulsions was significantly higher than rapeseed after 20 min digestion time in simulated intestinal fluid conditions. The obtained results suggested that plant OBs could be useful as natural emulsifiers in the development of functional food and achieve controlled release of bioactive compounds from emulsions during gastrointestinal digestion.

Effect of water bath-assisted water extraction on physical and chemical properties of soybean oil body emulsion

Soybean oil body (SOB), rich in polyunsaturated fatty acids and biologically active substances, is used as a natural emulsifier in food processing. In addition, SOB is healthier than synthetic emulsifiers. However, the physical and chemical properties of the SOB emulsion directly affect its application in food processing. In order to study the effect of water bath extraction (WBAE) on SOBs, the effects of WBAE method on the composition of SOBs, the zeta potential, average particle size, oxidation stability, and viscosity characteristics of SOB emulsions were researched. It was found that both protein and moisture contents of SOB decreased with increasing WBAE temperature; however, lipid content increased. These results were attributed to the exogenous proteins gradually denatured and dissociated with extraction temperature from 60°C to 100°C. Increasing the extraction temperature, the average particle size of the SOB emulsions increased, the oxidative stability was improved, the Zeta potential and viscosity decreased, and the fluidity of emulsions was improved. The SOB extracted at 100°C has broad application prospects in food, and this research is meaningful for supplying fundamental information for selecting proper extraction temperature of SOBs.

Combination of Alcalase 2.4 L and CaCl2 for aqueous extraction of peanut oil

The combined application of CaCl₂ and Alcalase 2.4 L to the aqueous extraction process of peanuts was evaluated as a method to destabilize the oil body (OB) emulsion and improve the oil yield. After adding 5 mM CaCl₂ , the oil yield was reached to 92.0% which was similar with that obtained using Alcalase 2.4 L alone, and the required enzyme loading was decreased by approximately 60 times. In addition, the demulsification mechanism during aqueous extraction process was also investigated. Particle size and zeta-potential measurements indicated that the stability of the peanut OB emulsion dramatically decreased when CaCl₂ was added. Under these conditions, the demulsification of Alcalase 2.4 L performed was more efficiently. SDS-PAGE results showed that adding CaCl₂ changed the subunit structure of the peanut OB interface proteins and promoted the cross-linking among the arachin Ara h3 isoforms, resulting in unstable emulsions.

Identification of a caleosin associated with hazelnut (Corylus avellana L.) oil bodies

Caleosins are involved in several cellular and biological processes that are closely associated with the synthesis, degradation and stability of oil bodies (OB). Because of the importance and the multiple roles of these OB-associated proteins, in silico identification of sequences corresponding to putative caleosins in the hazelnut genome has been performed, and the association with seed OB was verified using a proteomic approach. Five full-length sequences (CavCLO-H1, CavCLO-H2, CavCLO-H3, CavCLO-L1, CavCLO-L2), belonging to the two groups of caleosins (H and L), have been identified in the hazelnut genome. The number of identified caleosins is in agreement with that previously observed in other plant species, confirming that caleosins comprise small gene families in plants. A proteomic approach allowed us to verify only the presence of CavCLO-H1 in hazelnut OB, suggesting that several members inside this family could have different roles during plant growth and development. In silico analysis also suggests that CavCLO-H1 may act as a peroxygenase.

Comparison of Various Soybean Allergen Levels in Genetically and Non-Genetically Modified Soybeans

Several analyses of allergen levels have been reported as part of the safety assessment of genetically modified (GM) soybean; however, few comprehensive analyses have included new allergens. Thus, in this study the levels of eight major soybean allergens, including Gly m 7 (a newly reported soybean allergen), were semi-quantitatively detected in six GM soybeans and six non-GM soybeans using antigen-immobilized ELISA and immunoblotting. We also analyzed the IgE-reactivity to these soybeans through immunoblotting, using sera from three soybean-allergic patients. The results showed that there were no significant differences in the levels of the major soybean allergens in the GM and non-GM soybeans. Moreover, there were no significant differences in the serum IgE-reactive protein profiles of the patients, as analyzed using immunoblotting. These results indicate that, in general, CP4-EPSPS-transfected GM soybeans are not more allergenic than non-GM soybeans.

Improving the Stability of Oil Body Emulsions from Diverse Plant Seeds Using Sodium Alginate

In this study, peanut, sesame, and rapeseed oil bodies (OBs) were extracted by the aqueous medium method. The surface protein composition, microstructure, average particle size d 4 ,   3 , ζ-potential of the extracted OBs in aqueous emulsion were characterized. The stability of the OB emulsions was investigated. It was found that different OB emulsions contained different types and contents of endogenous and exogenous proteins. Aggregation at low pHs (<6) and creaming at high pHs (7 and 8) both occurred for all of three OB emulsions. Sodium alginate (ALG) was used to solve the instability of OB emulsions under different conditions-low concentration of ALG improved the stability of OB emulsions below and near the isoelectric point of the OBs, through electrostatic interaction. While a high concentration of ALG improved the OB emulsion stability through the viscosity effect at pH 7. The OB emulsions stabilized by ALG were salt-tolerant and freeze-thaw resistant.

Peanut Oil Body Composition and Stability

This study was aimed to assess the effect of membrane structure on the stability of peanut oil bodies extracted by enzyme-assisted extraction. The influence of pH, NaCl concentration, and temperature on the physicochemical properties of peanut oil bodies was characterized using ζ-potential and particle size. The results indicated that the peanut oil bodies had strong stability (ζ-potential, >20 mV) at pH values away from the isoelectric point (pH 4.8), at a low salt concentration (NaCl concentration, <10 mM), and in a certain temperature range (35 to 55 °C). The stable structure of the oil body was closely related to its structure. Phospholipids, along with membrane proteins, were major components of the oil body membrane. Therefore, the phospholipid composition and content were measured and the types of membrane proteins of the oil bodies were identified. The results showed that phosphatidylcholine and phosphatidylserine were major components of the oil body phospholipids. Two-dimensional electrophoresis showed that the oil bodies contained both intrinsic proteins and extrinsic proteins, which might play an important role in the stability of oil bodies during enzyme-assisted extraction processing.

Effect of Physiochemical Factors and Peanut Varieties on the Charge Stability of Oil Bodies Extracted by Aqueous Method

In order to explore the scientific basis for the application of oil bodies (OBs) from different peanut varieties in food, the effect of NaCl (0-100 mM), thermal processing (25-45°C, 1 h) and pH (3.0, 7.4, and 9.0) on their zeta potentials was analyzed in this study. The zeta potentials of OB suspensions (in 10 mM phosphate buffer) prepared from five peanut varieties in different salt concentrations (0-100 mM) were positive at pH 3.0, while they remained negative at pH 7.4 and 9.0. The absolute values of zeta potentials were over 20 mV at a lower salt concentration (< 10 mM NaCl) at pH 3.0 and 7.4. Particularly, the values of zeta potentials of Yuhua27 and Yuhua9830 were as high as 40 mV in the absence of NaCl at pH 7.4. The OBs exhibited diverse change trends between the five peanut varieties in the temperatures from 25 to 45°C (0 mM NaCl, pH 7.4). The OBs from Yuhua9830 exhibited the best thermal adaptability at the different temperatures tested than the other four peanut varieties. These outcomes suggested that OBs extracted from different varieties possess diverse properties and may provide a new insight into choosing a suitable peanut variety for the food industry.

Lipophilic Allergens, Different Modes of Allergen-Lipid Interaction and Their Impact on Asthma and Allergy

Molecular allergology research has provided valuable information on the structure and function of single allergenic molecules. There are several allergens in food and inhalant allergen sources that are able to interact with lipid ligands via different structural features: hydrophobic pockets, hydrophobic cavities, or specialized domains. For only a few of these allergens information on their associated ligands is already available. Several of the allergens are clinically relevant, so that it is highly probable that the individual structural features with which they interact with lipids have a direct effect on their allergenic potential, and thus on allergy development. There is some evidence for a protective effect of lipids delaying the enzymatic digestion of the peanut (Arachis hypogaea) allergen Ara h 8 (hydrophobic pocket), probably allowing this molecule to get to the intestinal immune system intact (sensitization). Oleosins from different food allergen sources are part of lipid storage organelles and potential marker allergens for the severity of the allergic reaction. House dust mite (HDM), is more often associated with allergic asthma than other sources of inhalant allergens. In particular, lipid-associated allergens from Dermatophagoides pteronyssinus which are Der p 2, Der p 5, Der p 7, Der p 13, Der p 14, and Der p 21 have been reported to be associated with severe allergic reactions and respiratory symptoms such as asthma. The exact mechanism of interaction of these allergens with lipids still has to be elucidated. Apart from single allergens glycolipids have been shown to directly induce allergic inflammation. Several-in parts conflicting-data exist on the lipid (and allergen) and toll-like receptor interactions. For only few single allergens mechanistic studies were performed on their interaction with the air-liquid interface of the lungs, in particular with the surfactant components SP-A and SP-D. The increasing knowledge on protein-lipid-interaction for lipophilic and hydrophobic food and inhalant allergens on the basis of their particular structure, of their capacity to be integral part of membranes (like the oleosins), and their ability to interact with membranes, surfactant components, and transport lipids (like the lipid transfer proteins) are essential to eventually clarify allergy and asthma development.

Allergy to Peanut, Soybean, and Other Legumes: Recent Advances in Allergen Characterization, Stability to Processing and IgE Cross-Reactivity

Peanut and soybean are members of the Leguminosae family. They are two of the eight foods that account for the most significant food allergies in the United States and Europe. Allergic reactions to other legume species can be of importance in other regions of the world. The major allergens from peanut and soybean have been extensively analyzed and members of new protein families identified as potential marker allergens for symptom severity. Important recent advances concerning their molecular properties or clinical relevance have been made. Therefore, there is increasing interest in the characterization of allergens from other legume species such as lupine, lentil, chickpea, green bean, or pea. As legumes are mainly consumed after thermal processing, knowledge about the effect of such processing on the allergenicity of legumes has increased during the last years. In the present review, recent advances in the identification of allergens from peanut, soybean, lupine, and other legume species are summarized and discussed. An overview of the most recently described effects of thermal processing on the allergenic properties of legumes is provided and the potential IgE cross-reactivity among members of the Leguminosae family is discussed.

Heat-induced inactivation mechanism of soybean Bowman-Birk inhibitors

Due to the complications of the soymilk system, the heat-induced Bowman-Birk inhibitor (BBI) inactivation mechanism is not well known. In this study, two BBI samples with low and high purities were prepared from soymilk. It was confirmed that three groups (A, C, and D) of BBI, which are contained in soybean seeds, were transferred into soymilk during processing. On heating, it was found that 1) the two subdomains of BBI were not equally heat stable, 2) the conformation of BBI gradually changed, 3) some amino acid residues (namely, cystine, serine and lysine) in BBI were degraded, 4) BBI did not tend to form intermolecular cross-links with another BBI, but did slightly with non-BBI proteins. Based on some previous studies, the conformational change of BBI was attributed to β-elimination reactions on the amino acid residues of BBI and the subsequent intramolecular reactions induced by the products yielded by the β-elimination reactions.

Relevance of Lipophilic Allergens in Food Allergy Diagnosis

PURPOSE OF REVIEW

The purpose of this review is to provide available data on a new class of allergens, the oleosins, and their diagnostic value. There is evidence that allergen extracts used for in vivo as well as in vitro diagnostic tests do not contain oleosins because these proteins are lipophilic and nearly insoluble in saline or aqueous solutions. So far, only oleosins of peanut, sesame and hazelnut have been registered as allergens. Reports on IgE-binding tests performed with oleosins of different species with sera from allergic patients show that IgE specific for oleosins are associated with severe allergic reactions which is why they should be part of the diagnostic tests in the future.

RECENT FINDINGS

Recent findings showed that oleosins purified from in shell-roasted peanuts revealed a higher IgE-binding capacity when compared to raw ones. Naturally purified as well as recombinantly produced peanut oleosins can be used in basophil activation test. The synopsis of all reports on different thermal processing of several oleosin sources and the respective data obtained with patients sera investigated via immunoblot and basophil activation test points to the recommendation that-if naturally purified oleosins are used, they should mostly be obtained from roasted food allergen sources. For immunoblot and basophil activation test, both, naturally purified oleosins as well as recombinant modified oleosins are valuable diagnostic tools.

Peanut oleosins associated with severe peanut allergy-importance of lipophilic allergens for comprehensive allergy diagnostics

BACKGROUND

Peanut allergy is one of the most common and most severe food allergies in Western countries and its accurate diagnosis to prevent potential life-threatening allergic reactions is crucial. However, aqueous extracts used for routine diagnostic measurements are devoid of lipophilic allergens such as oleosins. We have recently succeeded in the isolation and purification of these unique proteins, and the present study evaluates their allergenic potential and clinical relevance.

OBJECTIVE

We sought to assess allergenicity and sensitization prevalence of oleosins obtained from both raw and in-shell roasted peanuts. In addition, we tested the utilization of natural and recombinant oleosins for allergy diagnostic purposes.

METHODS

Oleosin sensitization, prevalence, and impact of thermal processing were analyzed by immunoblot with sera from 52 peanut-allergic individuals displaying different clinical phenotypes. The application of natural and recombinant oleosins for allergy diagnostics was investigated by basophil activation test (BAT). IgE-binding epitopes were identified by oligopeptide microarray.

RESULTS

Sensitization to oleosins was observed exclusively in peanut-allergic subjects suffering from severe systemic reactions. IgE-binding capacity of oleosins derived from in-shell roasted peanuts was increased as shown by immunoblot analysis and BAT. Both natural and recombinant molecules can be used to identify oleosin-sensitized patients by BAT. A linear epitope of Ara h 15 was determined that displays high similarity to other seed-derived oleosins.

CONCLUSIONS

Oleosins are clinically relevant peanut allergens and most likely associated with severe allergic symptoms. In-shell roasting increases their allergenicity, which is consistent with the observation that most allergic reactions are in connection with roasted peanuts.