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In this study, we found the inhibitory effect of d-Tryptophan (d-Trp) on the bacterial growth and spoilage potential of P. fluorescens and S. baltica. The effectiveness of d-Trp in bacterial growth inhibition was highly dependent on environmental NaCl concentrations. The growth/no growth models were developed to clarify the relationship between salt and d-Trp concentrations for optimal growth-inhibitory effect. It showed that higher levels of NaCl (3.5%) with d-Trp (15 mM) are required for growth inhibition. The d-Trp treatment combined with NaCl also retarded the psychrotrophic growth and reduced the respiratory active bacteria at low temperature, indicating that the inhibitory effect of d-Trp might be associated with the tolerance to osmotic and cold stress. Furthermore, the treatment d-Trp combined NaCl (artificial seawater) on salmon fillets was investigated. During refrigerated storage, the d-Trp treated salmon fillet either inoculated with S. baltica or P. fluorescen maintained remained a relatively low level of total volatile basic nitrogen (TVBN) (below 30 mg N/100 g during 8-days storage) and delayed increase of low total viable bacteria counts (TVC) with a longer lag phase of 2 days.

Currently, there is a need to explore the effects of different types of protein-anthocyanin complexations, as well as the possible changes in the nutrition and allergenicity of the formed complexes. Here, we systematically investigated the covalent and non-covalent interactions between cyanidin-3

This study aims to reveal the mechanism of the interaction between folic acid (FA) and egg ovalbumin (OVA) through the method of multi-spectroscopic, molecular docking, and molecular dynamics simulation in order to probe OVA as the possibility of a carrier of unstable vitamins. The results of the fluorescence spectra indicated a static quenching in the OVA-FA with a strong affinity of 6.998 × 10

Backgrounds As one of the most important cereals, wheat (Triticum aestivum) can cause severe allergic reactions, such as baker's asthma, allergic rhinitis, and atopic dermatitis. A growing number of people are developing allergies to Chinese wheat; however, only a few wheat cultivars have been screened on allergenicity in China. Objective The aim of the present study was to assess the allergenicity of different Chinese wheat cultivars and characterize wheat allergen profiles of patients with allergic rhinitis. Methods We determined protein (soluble protein, gliadin, and glutenin) composition in Chinese wheat by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the immunoglobulin E (IgE) binding capacity by enzyme-linked immunosorbent assay (ELISA) and Western blot using 10 positive sera from wheat allergy patients. We identified 5 gel bands with significant IgE binding capacity using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results Soluble protein, albumin, and globulin, showed the highest allergenicity, followed by gliadin, while glutenin only had slight allergenicity. In soluble protein, 5 protein bands with molecular weights of 27, 28, 53, 58, and 62 kDa showed very significant allergenicity. Meanwhile, the relative abundances of 28 kDa-protein and 58 kDa-protein were significantly positively correlated with the IgE-binding capacity of Chinese wheat cultivars, which were identified as rRNA N-glycosidase and β-amylase, respectively, among other proteins in those highly complex gel bands. Conclusion and clinical relevance 28 kDa-protein (rRNA N-glycosidase) and 58 kDa-protein (β-amylase) were speculated to be the main allergens of Chinese wheat causing baker's asthma and allergic rhinitis. These results provide new insights into the prevention and treatment of wheat allergy and the development of hypoallergenic wheat products, whose clinical significance is worth further evaluation.

Graphical abstract, Highlights • The role of pre-ultrasound on β-LG–phenolic binding at various pH was investigated. • Pre-ultrasound at 35% amplitude strengthened the binding affinity of EGCG/CA to β-LG. • Pre-ultrasound promoted changes in the protein spatial structure by phenolic binding. • Dimer/monomer form of β-LG distinctly affects the complex property under ultrasound. • Pre-ultrasound with EGCG binding improved foaming and emulsifying properties of β-LG., There is a need to understand the ultrasound-induced changes in the interactions between proteins and phenolic compounds at different pH. This study systematically explored the role of high-intensity ultrasound pre-treatment on the binding mechanisms of β-lactoglobulin (β-LG) to two common phenolic compounds, i.e., (−)-epigallocatechin-3-gallate (EGCG) and chlorogenic acid (CA) at neutral and acidic pH (pH 7.2 and 2.4). Tryptophan fluorescence revealed that compared to proteins sonicated at 20% and 50% amplitudes, 35%-amplitude ultrasound pre-treatment (ULG-35) strengthened the binding affinities of EGCG/CA to β-LG without altering the main interaction force. After phenolic addition, ULG-35 displayed a similar but a greater extent of protein secondary and tertiary structural changes than the native protein, ascribed to the ultrasound-driven hydrophobic stacking among interacted molecules. The dominant form of β-LG (dimer/monomer) played a crucial role in the conformational and interfacial properties of complexes, which can be explained by the distinct binding sites at different pH as unveiled by molecular docking. Combining pre-ultrasound with EGCG interaction notably increased the foaming and emulsifying properties of β-LG, providing a feasible way for the modification of bovine whey proteins. These results shed light on the understanding of protein–phenolic non-covalent binding under ultrasound and help to develop complex systems with desired functionality and delivery.

Celiac disease (CD) is a prevalent disorder with autoimmune features. Dietary exposure of wheat gluten (including gliadins and glutenins) to the small intestine activates the gluten-reactive CD4+ T cells and controls the disease development. While the human leukocyte antigen (HLA) is the single most important genetic factor of this polygenic disorder, HLA-DQ2 recognition of gluten is the major biological step among patients with CD. Gluten epitopes are often rich in Pro and share similar primary sequences. Here, we simulated the solution structures changes of a variety of gluten epitopes under different pH and temperatures, to mimic the fermentation and baking/cooking processes. Based on the crystal structure of HLA-DQ2, binding of differently processed gluten epitopes to DQ2 was studied in silico. This study revealed that heating and pH change during the fermentation process impact the solution structure of gluten epitope. However, binding of differently treated gluten epitope peptide (GEP) to HLA-DQ2 mainly depended on its primary amino acid sequence, especially acidic amino acid residues that play a pivotal role in their recognition by HLA-DQ2.

Despite being the fastest growing sector, the modern aquaculture industry faces serious challenges such as the lack of protein source in feed, the susceptibility to pathogens, and deterioration in quality during culture and storage. Bacterial biomass is considered as a proper protein source for feed, and the beneficial bacterial species protect aquatic animals from infection or reduce spoilage of products. In this review, we summarized the application of beneficial bacteria to aquatic products, focusing mainly on the nutritional, anti-pathogenic, anti-spoilage and immunoregulatory functions of these bacteria. We then discussed the relationship between beneficial bacteria, intestinal microbiota and host immunity, and the recent progress and drawbacks of the technology.

Put was the main biogenic amine produced by Shewanella baltica. PL and PP were the main QS autoinducers of S. baltica. PL and PP displayed significant positive correlation with Put. DKPs and Put production and odc gene expression were inhibited by anthocyanins. Anthocyanins were proposed as new QSIs and seafood preservative candidates.

Tropomyosin (TM), the predominant shellfish allergen, has induced severe food allergy worldwide, but efficient prevention and cure measures are limited nowadays. In the present study, we introduced an approach to eliminate Penaeus chinensis TM by Maillard reaction with reducing sugars including ribose, galacto-oligosaccharide (GOS) and chitosan-oligosaccharide (COS), which reduced the allergenicity by up to 60%. We also evaluated the conformational changes of TM during reaction by far-UV circular dichroism, and found the reaction-induced alternation from α-helix to β-sheet. We further determined the effect of Maillard reaction on TM allergenic epitopes to investigate the detailed mechanisms, and revealed the structure preference of different sugars. Correlation analysis with experimental data revealed that α-helix mediated the allergenicity elimination by Maillard reaction. There results provided theoretical foundations for the improvement and application of Maillard reaction in allergenic food processing.

The production of biogenic amines (BAs) set considerable obstacles in seafood preservation. However, the characteristic BAs and their roles in the spoilage profiles in large yellow croaker were still poorly understood. The BAs contents, free amino acids (FAAs) contents, aerobic bacterial count, sensory evaluation and several characteristic physicochemical indexes were monitored during storage at 4 °C. It's forcefully uncovered that the putrescine and cadaverine were the main BAs and the sum value of them could be used as a novel quality indicator instead of BAI. The reasonable limitation for unaccepted corruption was suggested be around 60 mg/kg. The regression model (r > 0.8, P < 0.05) at 4 °C indicated a significant correlation between the main BAs and total volatile basic nitrogen (TVB-N), protein hydrolysis index (P.I.%) as well as pH value, offering a new interpretation form for the physiochemical properties of BAs in aquatic products. Additionally, the evolution of FAAs show the predominant role of lysine, proline, histidine, glycine, and alanine during the whole storage and it can be concluded that BAs biosynthesis in large yellow croaker were moderately related with their precursor substance. This work provides a preliminary insight into the origin of BAs in large yellow croaker. PRACTICAL APPLICATION: It was proposed that the sum value of putrescine and cadaverine which were the main BAs can be used as a novel quality indicator instead of BAI in large yellow croaker. And the regression models of BAs and other physiochemical indexes provided a new perspective for comprehending the spoilage profiles involving BAs biosynthesis. The study may potentially contribute to improving the evaluation of seafood freshness and provide new target site for seafood preservation.

Food allergy is a severe food safety problem worldwide. Probiotics are effective in alleviating food allergy whereas antibiotics may exacerbate allergenic responses, but the knowledge on the interplay between them during food allergy is limited. In the present study, we investigate the activity of probiotic strain Lactobacillus casei (Lc) and antibiotic cocktail (Abx) on in a food allergy mouse model. The results showed that Lc relieved allergenic symptom and changed allergen-specific antibodies isotypes. Moreover, Lc upregulated chemokines in the spleen, and promoted regulatory CD103+ DC and IgA-producing B cell proliferation. In contrast, the application of Abx eliminated all these beneficial effects of Lc. Microbiota analysis revealed that the commensal genus Butyricicoccus was a critical mediator in the process. These results revealed the mechanisms of Lc and Abx interaction on food allergy and provided Butyricicoccus as a potential therapeutic target for food allergy.

Food allergy is one of the most important food safety problems that has attracted increasing attention. The food allergy experimental models provide not only the accurate allergen detection and evaluation methods but also the powerful approaches for mechanism investigations. In this paper, we reviewed the common food allergy cell models including mast cell, basophil granulocyte and basophil, as well as the animal models of BALB/c mouse, C3H/HeJ mouse, and BN rat. We also introduced zebrafish, a promising model organism for investigating immunity though lacking direct applications in food allergy to date, and focused on traumatic inflammation, bacterial infection and viral infection models. In addition, we also summarized the clinical diagnostic research methods for food allergy. The elucidation of these topics will help researchers to understand the characteristics and mechanisms of various models and thus select the proper models for particular study, so as to support further investigations of food allergy. Keywords: Food allergy, Cell model, Animal model, Zebrafish, Clinical study

Ovomucoid (OVM), known as the major allergen in egg white, has gained increasing concerns in industrialized countries. Here, we found the deglycosylation and Maillard reaction with galactooligosaccharide (GOS) and fructooligosaccharide (FOS) can induce conformational transformation of OVM from other structures (β-turn, strang, and random coils) to α-helix. We also introduced an approach to reduce the allergenicity of Gallus domesticus OVM by Maillard reaction with GOS and FOS. However, the OVM glycated by mannosan (MOS) and deglycosylated OVM exhibited higher allergenicity than native OVM. Therefore, GOS and FOS, especially GOS, could be applied in the reduction of the potential allergenicity of OVM through glycation. Furthermore, these findings may provide new insights into the development of hypoallergenic egg products. PRACTICAL APPLICATION: In this study, the allergenicity and conformation of OVM treated with deglycosylation and glycation (GOS, FOS, and MOS) were investigated. The results would provide a better understanding of the effects of deglycosylation and Maillard reaction with different reducing sugars on the molecular characteristics of OVM and further provide new insights into the development of hypoallergenic egg products.

To explore effect of the structural properties of porphyra haitanensis polysaccharide on its biological activity, degraded porphyra polysaccharides were separated and purified by Cellulose DEAE-52 and Sephadex G-100 chromatography, obtaining three purified components (P1, P2 and P3). All the three components were sulfate polysaccharides containing the repeating units of → 3) β-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →, and → 3) β-D-galactose (1 → 4) α-L-galactose-6-S (1 →, and → 3) 6-O-methyl-β-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →. The molecular weight of the three fractions was measured to be 300.3, 130.4 and 115.1 kDa, respectively. Their antioxidant activity was investigated by the determination of the free radical scavenging effect and ferric reducing power. It was found that P1, P2 and P3 possessed marked antioxidant activity. It was also found that they appreciably enhanced the proliferation, phagocytic ability and nitric oxide secretion in RAW264.7 cells. Lower molecular weight and higher sulfate content were beneficial to bioactivities of P. haitanensis polysaccharides. Overall, P2 and P3 possess superior immuno-modulatory activity to that of P1 and PHP. Thus, the current work will provide the basis for the better utilization of P. haitanensis to develop the related functional foods.

Biogenic amines (BAs) are not only well-known indicators for food freshness but can cause serious harm to the body after excessive consumption, which makes the determination of its content in food of great significance. In this work, a simple and convenient method for colorimetric detection of BAs was developed based on the sensitivity of the polymerization of dopamine to the presence of BAs on the surface of gold nanoparticles (AuNPs). Taking histamine as a representative, the system exhibited a distinct color change from wine red to black among the amine concentration of 1–100 μg/mL with the detection limit of 2.8 μg/mL. The detection system also exhibited sensitivity to other common kinds of BAs, such as putrescine, cadaverine, spermine, spermidine, tyramine, and tryptamine. Moreover, the proposed method showed encouraging performance in visual detection of the freshness of real samples, which provided a new approach for food quality and freshness evaluation.

The degraded polysaccharides from Porphyra yezoensis (DPPY) prepared using the H2 O2 -Vc method under optimized conditions were isolated and purified by DEAE Cellulose-52, and Sephadex G-100, providing four pure components, namely, DPPY-0, DPPY-0.1, DPPY-0.3, and DPPY-0.5. Their relative molecular weights were measured to be 10.8, 10.7, 18.7, and 35.5 kDa, respectively. GC-MS analysis revealed that all the four fractions were mainly composed of galactose, together with a small portion of glucose, mannose, xylose, and rhamnose. Structural analysis revealed that the purified polysaccharides mainly possess a backbone of (1 → 3)-β-D-galactose (1 → 4)-3,6-anhydro-α-L-galactopyranose (G-A) units and (1 → 3)-β-D-galactose (1 → 4)-α-L-galactose-6-sulfate (G-L6S) units. They were found to promote the proliferation of RAW264.7 macrophages and enhance phagocytosis of the RAW264.7 cells. Antioxidant assays indicated that DPPY-0.5 possessed the most potent reducing power and free radical scavenging ability among the four purified polysaccharides. High sulfate content and proper molecular weight of these fractions are favorable to their immunomodulatory and antioxidant activities. PRACTICAL APPLICATIONS: Porphyra yezoensis, common economic red algae widely distributed in East Asian countries, contains a high content of polysaccharides with a variety of biological activities. However, P. yezoensis polysaccharide (PPY) has not been well utilized due to the relatively low biological activities and lack of understanding of its structure-activity relationship. Thus, it is necessary to improve the bioactivities and elucidate the structure-activity relationship of this polysaccharide for its practical use. In the present work, four purified fractions (DPPY-0, DPPY-0.1, DPPY-0.3, and DPPY-0.5) were isolated from the degraded P. yezoensis polysaccharide, and were investigated for their antioxidant and immunoregulatory activities. The results of the present work will lay a foundation for the application of the degraded P. yezoensis polysaccharide in the food industry as a functional food ingredient.

In this work, the preventive effect of depolymerized sulfated polysaccharides from Eucheuma serra (DESP) on bacterial diarrhea by regulating intestinal flora was investigated in vivo. Based on the enterotoxigenic Escherichia coli (ETEC)-infected mouse diarrhea model, DESP at doses ranging from 50 mg/kg to 200 mg/kg alleviated weight loss and decreased the diarrhea rate and diarrhea index. Serological tests showed that the levels of inflammation-related factors were effectively suppressed. Furthermore, the repaired intestinal mucosa was verified by morphology and pathological tissue section observations. Compared with the model group, the richness and diversity of the intestinal flora in the DESP group increased according to the 16S rRNA high-throughput sequencing of the gut microbiota. Specifically, Firmicutes and Actinobacteria increased, and Proteobacteria decreased after DESP administration. At the family level, DESP effectively improved the abundance of Lactobacillaceae, Bifidobacteriaceae, and Lachnospiraceae, while significantly inhibiting the growth of Enterobacteriaceae. Therefore, the antimicrobial diarrhea function of DESP may be related to the regulation of intestinal microbiota.

Unveiling specific interactions between nanoparticles (NPs) and proteins could benefit a better control of NPs' performance in recognition-based detection, imaging and drug delivery. Herein, we investigated the specific recognition between an aptamer modified gold nanoparticle (Apt-AuNP) and its target protein arginine kinase (AK) through a coffee-ring effect (CRE)-based approach. The evaporated droplets of the Apt-AuNP with AK featured a ring-disk-ring transition with elevated AK concentration and a disk pattern was found when the Apt was saturated by AK. Moreover, the AK concentration versus ring thickness curve below the saturation point was proved to fit in an exponential function, indicating the strong association between the Apt-AuNP and AK. In contrast, the ring thickness above the saturation point fitted in a Gompertz growth model that was similar with the Apt-AuNPs incubated with the nonspecific protein (bovine serum albumin, BSA), suggesting that AK was nonspecifically adsorbed onto the AuNPs. The impact of the specific NP-protein interaction on the translation of CRE into macroscopic patterns was further utilized to identify target food allergen AK by the Apt-AuNPs over nontarget allergens (tropomyosin, ovalbumin and β-lactoglobulin). This work provided new insight into the general NP-protein association process and demonstrated the feasibility of employing CRE as an effective tool to profile the specific interactions between NPs and proteins.

Pseudomonas fluorescens is a specific spoilage bacteria in seafood, which has the ability to maintain growth and reproduction at low temperatures. There are some functional proteins in Pseudomonas fluorescens to defense the harm of cold to its life activities. Hence, disrupting this defense mechanism may be a good way to control food spoilage. In this study, we screened the food ingredients database to search for potential cold defense mechanism inhibitors of P. fluorescens PF08 by using virtual screening. From the screening results, we found a compound with inhibitory activity — l -phenylalanine. Moreover, the effects of l -phenylalanine on the cold defense mechanism were determined. l -phenylalanine is difficult to inhibit bacterial growth at room temperature. However, it significantly inhibits the growth ability of Pseudomonas fluorescens PF08 and the production of biofilm at 4 °C. In addition, we also found that l -phenylalanine can compress RpoS and Algk, which undoubtedly interferes with the function of proteins.

Tropomyosin (TM), a major allergen in shellfish, has raised increasing concern in industrialized countries and resulted in an urgent need for accurate, simple, and sensitive methods for tracing its presence in food products. Herein, we proposed a sandwich biosensor that employed the rationally imprinted magnetic particles and aptamer modified carbon dots for the detection of TM in seafood products. The multi-point initiated polydopamine was employed as molecular imprinting polymer on magnetic particles, which was subjected to antifouling surface modification to achieve efficient separation of TM. By taking the aptamer modified carbon dots as signal probes, a sandwich assay was achieved with the limit of detection (LOD) being 30.76 ng mL−1 (S/N = 3). The proposed method not only possessed excellent specificity towards TM but exhibited great accuracy. The sandwich biosensor was further used to quantitatively analyze TM in five shrimp and five shrimp processed products, which proved that the proposed biosensor could detect TM in commercial samples and had a great application prospect.

Wheat (Triticum aestivum) contains various allergenic proteins and induces diverse allergic reactions. Although many allergens are found to be glycoproteins, research on glycosylated allergens in wheat is rare. In this study, the main glycoprotein in wheat soluble protein was purified by sequential multi-column chromatography including affinity chromatography, gel filtration chromatography, and ion-exchange chromatography. The purified proteins were identified as globulin-1 S allele by liquid chromatography-tandem mass spectrometry and characterized by circular dichroism spectra. The strong IgE-binding capacity of the purified fractions was further demonstrated, suggesting globulin-1 S allele to be a novel allergen in wheat. Further de-N-glycosylated treatment by N-Glycosidase F showed that N-glycosylation enhanced the IgE-binding of globulin-1 S allele. These results identified globulin-1 S allele as a novel allergen in wheat, demonstrated the role of glycosylation in IgE-binding, and provided new insights into the prevention and treatment of wheat allergy.

Dietary proteins and phenolic compounds are commonly co-existing components that readily interact with each other to yield complexes in a wide range of food systems. The formed complexes play a critical role in the physiochemical characteristics of both reacting molecules, thereby impacting nutritional and quality profiles of related products. In this review, we provided the most updated knowledge on dietary protein-phenolic interactions related with food science and human nutrition, including their mechanisms of complexation, analytical technologies, and alterations in the functionality and nutraceutical properties of both reacting partners. Their potential applications in the industries regarding stability during food processing and storage, impacts on product quality, and fabrication of novel delivery systems for liable bioactives were also discussed. The interactions between dietary proteins and phenolics, either via non-covalent or covalent processes, are ubiquitous in food systems and are closely associated with chemical structures of both compounds and the surrounding conditions, mainly temperature, pH, and the presence of phenolic oxidases. Albeit in different ways, such intermolecular associations induced changes in protein conformational structures, which subsequently impacted their techno-functional properties, digestibility, and allergenic potentials; in turn, the bioaccessibility/bioavailability and health-protecting features of interacted phenolics were modified to various extents, as noticed by in vitro and in vivo evidence. Largely depending on the interaction molecules and preparation steps, those influences can be either favorable or unfavorable in different systems and therefore can be tailored to develop food products and nutraceuticals with maximized functionality and quality attributes.

Currently, there has been a surge of interest in revealing the interactions between plasma and food matrices. In this study, we investigated the impacts of atmospheric cold plasma (ACP) treatment on the structural, physicochemical and allergenic characteristics of soybean protein isolate (SPI). SPI dispersions were subjected to ACP treatments at different frequencies (80 to 100 Hz) and durations (1 to 10 min) to investigate the effects of exposing conditions. Results showed that ACP induced reactive oxygen species-mediated oxidation of soy proteins, resulting in modifications in the secondary and ternary structures of SPI. As a consequence, functional properties of SPI, such as emulsifying (56 to 168%, compared with control) and foaming properties (60 to 194%) were influenced by varying degrees. In addition, under certain circumstance (120 Hz, 5 min), the IgE-binding level of SPI was decreased by up to 75%, when compared to the control. Moderate treatment yielded products with improved functionality and reduced allergenicity, while extensive exposure induced a loss of vendibility due to protein aggregation. PRACTICAL APPLICATION: In this study, we demonstrated for the first time, that plasma species reacted with soybean proteins, resulting in spatial structural changes which are closely related with protein functionality and allergenicity. ACP interacts with macromolecules in aqueous systems and thus can be an alternative and promising nonthermal approach in modifying soybean proteins, whereas the exact role of different processing parameters needs to be well-elaborated.

Shewanella baltica, one of the dominant spoilers of seafoods, can synthesize putrescine from ornithine under acidic conditions, which could result in food spoilage and health problems. We identified three regulatory enzymes (SpeC, SpeF, and PotE) in the ornithine decarboxylation (ODC) pathway of S. baltica by searching the NCBI database and exploring their functional roles through gene knock-out technology. The ornithine decarboxylase SpeC is an auxiliary adjustor of the ODC system, whereas the ornithine-putrescine transporter SpeE and ornithine decarboxylase SpeF participate in the production of extracellular putrescine. Exogenous addition of ornithine and putrescine promotes the extracellular secretion of putrescine by upregulating the expression of speF and potE. The putrescine biosynthesis and alkalization of cytoplasm is enhanced at weak acidic pH compared with neutral pH, especially at pH 6.0. The maximum upregulation of ODC genes and the optimum decarboxylation activity of SpeF are achieved in a weak acidic environment (pH 6.0), suggesting that the ODC pathway plays an important role in putrescine production and the cytoplasmic acid counteraction of S. baltica. This study contributes to a wider understanding of spoilage mechanisms in food systems and provides theoretical support for developing novel seafood preservation methods. HIGHLIGHTS

Cow's milk protein allergy, which occurs in approximately 5-10% of the population of infants and children, has become an important public food safety problem. As a major allergen in cow's milk, the most abundant protein casein (CN) is considered to be potent in inducing food allergy. In recent years, ultrasound treatment has played a significant role in the field of colloidal particulate system. In this study, we found that ultrasound treatment dramatically decreased the diameter of a CN particle to less than 100 nm in the presence of Tween 80, producing colloidal casein (c-CN) with high transparency. The electrophoretic and transmission electron microscopy analysis showed that the advanced protein structure of CN changed significantly. In addition, the enzyme-linked immunosorbent assay with allergic sera showed that the immunoglobulin-E-binding capacity of c-CN was significantly decreased. In the meantime, the LAD2 mast cell line degranulation assay demonstrated that ultrasound treatment made CN hypoallergenic. The colloidal and hypoallergenic properties of c-CN were stably maintained for more than 30 days. Likewise, the allergenicity of fresh whole milk also decreased after ultrasound treatment. This work provided an effective way to reduce the allergenicity of milk allergen, which could be beneficial to the production of hypoallergenic cow's milk.

Arginine kinase (AK) is one of the most important allergens in shrimp products. Herein, a novel immunoassay for quantitation of AK was developed using the antibody modified gold nanoparticle (AuNP) and quantum dot (QD). When the first antibody modified AuNP (AuNP-Ab1) was bridged by AK with the secondary antibody modified QD (QD-Ab2), fluorescence resonance energy transfer (FRET) would occur between the AuNP and QD, which led to a decrease in fluorescent signals. The decrease in fluorescence intensity was found to correlate linearly with the log of AK concentration in the range of 1.0 × 10-6-1.0 × 10-3 mg/mL (R2 = 0.9909) and the detection limit was 0.11 ng/mL. The immunoassay was further proved to have encouraging specificity, precision and accuracy. Compared with existing methods, this study provided a promising approach to develop a highly sensitive and selective detection method for AK in shrimp related food samples.

Porphyra haitanensis polysaccharide (CPH) was degraded by pectinase to improve its biological activities. Box-Behnken response surface design was used to optimize the hydrolysis conditions. The molecular weight of CPH and the degraded P. haitanensis polysaccharide (DCPH) were measured to be 524 and 217 kDa, respectively. GC-MS spectrometry results showed that CPH and DCPH were mainly composed of galactose. In vitro antioxidant assays indicated that DCPH possessed improved radical scavenging activity and ferric iron reducing power when compared to those of CPH. In H2 O2 -treated RAW264.7 cells, DCPH was also found to be more effective in reducing the generation of malondialdehyde and reactive oxygen species than CPH. The immunomodulatory assays demonstrated that DCPH possessed superior activities in enhancing the proliferation, phagocytosis, and NO secretion in a RAW264.7 macrophage cell model to those of CPH. PRACTICAL APPLICATIONS: Polysaccharide is the most abundant bioactive component of an edible red algae Porphyra haitanensis. However, the use of CPH is limited due to its relatively low biological activities. Thus, in order to fully utilize P. haitanensis, it is necessary to enhance the biological activities of CPH for its practical use. An efficient and practical method to enhance the bioactivities of P. haitanensis polysaccharide has been developed in the present work. The DCPH prepared in this work could have potential applications in food and medicinal areas.

Shewanella baltica is the specific spoilage microorganism of Pseudosciaena crocea during low-temperature storage. Exploring the correlation between cold adaptability and spoilage potential may provide a new perspective for prolonging shelf life of aquatic products. In the present study, we investigated the synthesis pathway of unsaturated fatty acid (UFA) responsible for regulating cold adaptability in Shewanella baltica and its effect on spoilage potential. FabR and FadR, as key regulators of membrane unsaturated fatty acids synthesis pathway, were identified in S. baltica. FabR was significantly down-regulated at 4 °C compared to at 30 °C, yet FadR displayed the opposite results. By overexpressing fabR and fadR genes at 4 °C, we found that FabR and FadR had negative and positive effects on UFA content and membrane fluidity as well as spoilage potential, respectively. These data indicated that FabR and FadR functioned collectively to increase the membrane fluidity for better cold adaptability at low temperature, resulting in the maintenance of spoilage potential of S. baltica.

An authenticity-based method was developed to detect economically motivated adulteration (EMA) in milk. To achieve this goal, 46 peptides released from trypsin digested milk proteins were identified and marker peptides were further selected based on their digestibility and stability characteristics to allow further quantifications of the milk proteins in the original samples using an isotope-dilution ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-TQMS). Furthermore, to detect EMA in milk samples, 22 authentic milk powder samples were analyzed using the isotope-dilution UPLC-TQMS, and an authenticity threshold value --70.26 g/100 g as the content of all five major milk proteins to total protein—was established to evaluate milk samples with high adulteration risks. Finally, the threshold value was validated using soy protein adulterated milk samples. Results showed that the reported authenticity-based method was sensitive enough to detect the tampering of milk samples with as little as 10 % soy protein added. It is clear that this newly developed authenticity-based detection method is a powerful tool to detect unknown adulteration risks in milk samples.

A novel nanocomposite film was fabricated by carboxymethyl chitosan (CMCS) and nano MgO for potential food packaging applications. The impregnation of MgO nanoparticles into CMCS was evidenced by the X-ray diffraction and FTIR spectroscopy. SEM micrographs revealed a dense layer of MgO formation in the CMCS matrix, which is a major contributor to the improvement of crystallinity. Compared with pure CMCS, CMCS/MgO composites confer improved thermal stability, better UV shielding performance, as well as water-insolubility, improving the feasibility of using CMCS-based biopolymer films as food packagings, especially in the case of water-rich food. These physical properties were further enhanced with the increase in MgO content. Furthermore, MgO nanoparticles can simultaneously provide CMCS with increased elasticity and ductility at a rather low filler content (1.0 % by weight). For biological properties, CMCS/MgO composites exhibited excellent antimicrobial activity against Listeria monocytogenes and Shewanella baltica.

Large yellow croaker (Pseudosciaena crocea) is a popular and nutritious but also highly perishable fish species, with Shewanella baltica being the primary spoilage bacteria during low-temperature storage. Clarifying the factors promoting spoilage will facilitate efforts to predict and control the shelf life of foods. This study focused on spoilage-related genes in two Shewanella baltica strains with different spoilage potentials. Using whole genome sequencing and alignment, three distinguishing genes (torT, cysM and trxB) were identified. Further protein sequence comparison and protein structure modeling revealed possible motifs responsible for the spoilage activity. Moreover, diketopiperazine (DKP) quorum sensing (QS) signaling molecules regulated biofilm formation and spoilage gene expression, indicating a relationship between the QS system, biofilm formation and spoilage potential. Our results suggest that DKPs and spoilage genes are potential targets for developing novel food antiseptics, as well as new markers for fish product spoilage.

Large yellow croaker (Pseudosciaena crocea) is a cultivated fish of great economic importance and abundant nutritional value. However, due to its high protein and water contents, it is susceptible to decomposition, leading to considerable economic loss and adverse effects on consumer health. Here, we assessed the function of the bacterial strain Bacillus coagulans L1208 (Bcoa) in preserving large yellow croaker during storage at 4°C and found that Bcoa elongates the shelf-life significantly. Further investigations showed that Bcoa prolongs the storage time mainly by suppressing the growth of spoilage bacteria. Moreover, a novel bacteriocin, designated as Coagulin L1208 and produced by Bcoa, was purified and identified by N-terminal sequencing. Finally, the activity of Coagulin L1208 for suppressing spoilage bacteria during the preservation of large yellow croaker was assessed. Our results reveal the mechanism by which Bcoa aids the preservation of large yellow croaker and identify Coagulin L1208 as a potential novel antiseptic.

Major royal jelly protein 1 (MRJP1) is the most abundant protein in royal jelly (RJ), and the level of MRJP1 has been suggested as a promising parameter for standardization and evaluation of RJ authenticity in quality. Here, a quantitative method was developed for the quantification of MRJP1 in RJ based on a signature peptide and a stable isotope-labeled internal standard peptide FFDYDFGSDER*(R*, 13C6, 15N4) by ultraperformance liquid chromatography–tandem mass spectrometry. Recoveries of the established method ranged from 85.33 to 95.80%, and both the intra- and interday precision were RSD < 4.97%. Quantification results showed that content of MRJP1 in fresh RJ was 41.96–55.01 mg/g. Abnormal levels of MRJP1 were found in three commercial RJs and implied that these samples were of low quality and might be adulterated. Results of the present work suggested that the developed method could be successfully applied to quantify MRJP1 in RJ and also could evaluate the quality of RJ.

Protein glycation and formation of advanced glycation end-products (AGEs) impose threats to the human health. This study firstly investigated the inhibition of Chinese bayberry (Myrica rubra) phenolics on AGEs formation through mechanistic analysis. Four common Chinese bayberry cultivars were selected to prepare phenolic-rich extracts (CBEs) and characterized for phenolic composition, and their anti-AGE properties were evaluated in multiple in vitro systems. Total sixteen phenolics were quantified in CBEs by UPLC-ESI-MS/MS. CBEs reduced total and specific fluorescent AGEs formation in various simulating models, and protected the protein from structural modification, oxidation, and cross-linking. Mechanistic analysis unveiled that scavenging of free radicals, inactivation of transition metals, interaction with protein to form complexes, and trapping of reactive α-dicarbonyls to form adducts underlain the mechanisms of the anti-glycative actions of CBEs. Chinese bayberry fruits, especially the cultivars Biqi and Wuzi, may be a promising dietary strategy to mitigate AGEs load in the human body.

Alcalase hydrolysis of soybean proteins was shown effective in degrading epitopes, but with a significant loss of tastes and functional properties. In this study, the combined use of controlled Alcalase hydrolysis and transglutaminase (TGase)-cross-linking was used to produce hypoallergenic soybean protein hydrolysates (SPHs) with improved flavor and techno-functional properties. Through establishing the kinetic model of heterogeneous enzymatic processes, SPHs with different degrees of hydrolysis (2.5–10.0%) were obtained and polymerized by TGase to yield products with various peptide components. Results showed that post-hydrolysis cross-linking rearranged the (poly)peptides in SPHs via glutaminyl modifications. Following TGase-treatments, due to the masking of bitter-active peptides and free amino acids, the bitterness of SPHs was significantly reduced with a slight improvement in the overall flavor. Furthermore, TGase–cross-linking rescued multiple techno-functionalities of SPHs, particularly their emulsifying and foaming properties. Using sera from soybean-allergic individuals, it was evidenced that TGase-addition did not generate neoallergens and the residual allergenicity of SPHs was not distinctly affected. The final products maintained 44–71% reduction in the IgE-binding levels in comparison to the unhydrolyzed protein. Combining limited Alcalase hydrolysis with TGase–cross-linking provides a feasible way to produce hypoallergenic soybean ingredients with desired flavor and functional attributes.

Marine red algae are rich sources of sulfated polysaccharides as bioactive ingredients and hydrocolloid molecules. In this study, sulfated polysaccharides (YGAP, EGAP, and NGAP) were extracted from Gelidium amansiis that were harvested from three different sea areas of China. Characterization of these polysaccharides shows that they contain 3.7–4.0% sulfate and are mainly composed of galactose, glucose, fucose, arabinose, and mannose. The FT-IR and 13C NMR analysis indicate that the sulfated polysaccharides are agar-type galactans containing 3,6 anhydro-α- l -galactopyranose and β- d -galactopyranose residues. By using various in vitro models, all sulfated polysaccharides, particularly EGAP, exhibit the ability to scavenge O2•– and OH· radicals and reducing power. Additionally, in a glucose-glycated BSA system, the polysaccharides show an inhibitory effect on protein glycation and formation of specific advanced glycation end-product. Their anti-glycative property is attributed to their anti-oxidant activity and trapping capacity of methylglyoxal. Given that these polysaccharides possess agar-like structures, they were used to prepare bioactive films and expectedly, transparent and homogeneous films were obtained. The films display high water barrier properties with retained antioxidant and anti-glycation activities as above. These results expand the current knowledge of G. amansiis polysaccharides as nutraceuticals and hydrocolloids, which would benefit their applications in the food industry.

Cyclic diguanylate (c-di-GMP) is a second messenger involved in the regulation of various physiological processes in bacteria. However, its function in spoilage bacteria has not yet been addressed. Here, we studied the function of a tandem GGDEF-EAL domain protein, Sbal_3235, in the spoilage bacterium Shewanella baltica OS155. The deletion of sbal_3235 significantly reduced the c-di-GMP level, biofilm formation, and exopolysaccharide, trimethylamine (TMA), and putrescine production; sbal_3235 deletion also downregulated the expression of the torS and speF genes and affected membrane fatty acid composition. Site-directed mutagenesis in conserved GGDEF and EAL motifs abolished diguanylate cyclase (DGC) and phosphodiesterase (PDE) activity, respectively. These data indicate that Sbal_3235 is an essential contributor to the c-di-GMP pool with bifunctional DGC and PDE activity, which is involved in the biofilm formation and spoilage activity of S. baltica OS155. Our findings expand the biochemical role of c-di-GMP and uncover its link to spoilage activities, providing novel targets for food quality and safety controlling.

Food allergy is a serious food safety problem worldwide, and the investigation of food allergens is the foundation of preventing and treating them, but relevant knowledge is far from sufficient. With the advent of the "big data era", it has been possible to investigate food allergens by high-throughput methods, proposing the concept of allergomics. Allergomics is the discipline studying the repertoire of allergens, which has relatively higher throughput and is faster and more sensitive than conventional methods. This review introduces the basis of allergomics and summarizes its major strategies and applications. Particularly, strategies based on immunoblotting, phage display, allergen microarray, and bioinformatics are reviewed in detail, and the advantages and limitations of each strategy are discussed. Finally, further development of allergomics is predicted. This provides basic theories and recent advances in food allergomics research, which could be insightful for both food allergy research and practical applications.

Tropomyosin (TM) is the major allergen in shellfish, which causes severe food allergy worldwide and shows wide cross-reactivity in different species. Transglutaminase (TG) and tyrosinase (Tyr) are protein modification enzymes that catalyze substrate cross-linking and change protein structures and properties. The aim of this work was to investigate the effect of TG and Tyr on TM. After TG/Tyr treatment, the cross-linking and protein structural change were observed by SDS-PAGE, scanning electron microscopy and circular dichroism. Furthermore, ELISA and mast cell degranulation assay with allergic sera demonstrated the allergenicity reduction after treatment. An in vivo TM-sensitization mouse model showed that both TG and Tyr treatments reduced the IgE-induction capacity of TM but maintained the IgG-induction ability, making the treated TM a potential hypoallergen. Moreover, TG-but-not-Tyr-treated TM promoted regulatory T cell proliferation and thus may facilitate the establishment of oral tolerance. This work provided an effective method to reduce TM allergenicity and produce hypoallergens, which has broad application prospects in low allergenic food production and allergen-specific immunotherapy.

Background: Shrimp tropomyosin (TM) is a major food allergen that may cause serious allergic responses, lactic acid-producing bacteria (LAPB) are believed to alleviate food allergy, but the mechanisms have not been fully clarified. The aim of this work is to investigate the mechanisms of LAPB in ameliorating food allergy-induced intestinal mucosal disorders and to investigate whether or not these disorders occur by the regulation of gut microbiota and metabolism. Methods: A TM allergy BALB/c mouse model was established, and two LAPB strains, Bifidobacterium longum (Bi) and Bacillus coagulans (Bc), were used for oral treatment in sensitized mice. The allergic mucosal disorders were assessed by histological analysis and ELISAs. Additionally, microbiota and metabolic modifications were determined by 16S rRNA gene amplicon sequencing and GC-TOF-MS, respectively. Results: YSPB administration suppressed TM-induced intestinal mucosal disorders, restored allergenic Th2 cell over-polarization and dysbiosis, and regulated gut arginine and proline metabolism pathways. Statistical analysis suggested the metabolites aspartate and arginine, as well as several commensal flora groups, to be the critical mediators in the process. Conclusions: These data demonstrated the correlation between allergic mucosal disorder, T cell subtype differentiation, gut microbiota composition and intestinal metabolism especially the arginine and proline metabolism pathways. We also revealed the significant effects of LAPB in ameliorating food allergy and maintaining the mucosal ecosystem. This study confirmed the efficiency of LAPB in relieving food allergy, provided Bi and Bc as the potential treatment approaches, and suggested amino acid metabolism pathways might be the novel targets for potential clinical applications. Keywords: Animal models, Food allergy, Gut microbiota, Metabolism, Probiotics

In the past decade, food allergies have occurred frequently, and the number of allergic people has been increasing, making it a serious problem that jeopardized public health. A large number of researchers are dedicated to the exploration of food allergy mechanisms and how to prevent and treat food allergies. Allergenicity evaluation of food proteins is the basis of all food allergy-related researches. At present, there are many methods and strategies for evaluating the allergenicity of food proteins, such as bioinformatics analysis, serological analysis, cell experiment, and animal experiment, and each has its own advantages and disadvantages. In addition, there are currently no globally accepted standards for assessing the allergenicity of food proteins. Different methods often lead to differences in conclusions, making the data on food allergies highly variable. The search and construction of an effective standard for allergenic assessment of food allergens will help to reduce the incidence and slow the trend of food allergies.

Food allergy is an adverse systemic immune response against food. With the continuous progress of social progress and globalization, the incidence of allergic diseases has been escalating. About 30–40% of people in the world suffer from various allergic diseases, and morbidity and mortality show rising trend year by year. Unfortunately, there are no effective methods to prevent and eradicate food allergy nowadays. So the only safe and effective way available nowadays is to avoid eating or contacting with allergens. Therefore, eliminating food allergens by food processing methods is an effective way. Although most allergens and antigenic determinants can tolerate various forms of food processing methods to a certain extent, many researches have shown that particular food processing can still affect the allergenicity. In the field of food processing, physical, chemical, enzymatic, and fermentation methods can modify the activity of allergens. Protein is one of the main components of food, and it is also an important nutrient as well as the predominant allergen category in people’s diet. Food processing methods can cause the change of spatial structure and physicochemical properties of protein macromolecules and therefore destroy the allergenic epitopes of protein. This chapter will introduce the common and advanced application of physical, chemical, and biological approaches in the elimination of allergens in food.

With the improvement of people’s living standards, the labeling management of allergens in food is increasingly valued by people of all countries. However, compared with the United States, the European Union, and several other countries and organizations, most third world countries still have a large gap in the management level of allergen labels in food. This chapter summarizes the management of food allergens labeling, the revision process of labeling instructions, and the management of cross-contamination by major countries and organizations around the world. In addition, we compare the status of food allergens labeling management in the EU and China as a typical representative of third world countries and summarize the shortcomings in the Chinese management of food allergens, mainly including imperfect regulations and standards for food allergen labeling, lack of risk assessment of food allergens, no cross-contamination regulations, and low consumer awareness on food allergens.

Food allergy represents an important issue in the field of food safety in industrialized countries because of the severity of allergenic reactions for affected persons even with small amounts of food. Recently, the food industries and legislative and regulatory agencies in different countries have formulated new regulations about displaying food allergen on food labels. Therefore, consumer protection and food labeling require reliable detection and quantification methods of allergens in food products. Several analytical approaches, with the ability of quantifying and detecting traces of allergenic ingredients, which target either the allergenic proteins or allergen markers (peptide fragment or gene segment) have been developed. The most popular methods for allergen detection can be mainly divided into two large groups: the protein-based approaches and the DNA-based approaches. Protein-based methods include enzyme-linked immunosorbent assays (ELISA), MS methods, and biosensors. On the basis of the amplification of specific DNA fragments, DNA-based methods can trace the potential presence of culprit allergen, which include polymerase chain reaction (PCR) and real-time PCR. In this chapter, we present the advances about specific and highly sensitive analytical methods in the field of food allergens detection, which can avoid the influence by the presence of matrix components.

In recent years, with the improvement of food production and industrialization as well as the development of transgenic technology and the popularization of genetically modified food, the incidence of food allergic diseases is on the rise and has become a common chronic disease that endangers people’s physical and mental health, especially those of children’s. The World Health Organization (WHO) has listed food allergy as the sixth problem affecting people’s health, and the research on food allergen has become one of the public issues of global concern. This chapter will discuss multiple allergens in the “big eight” categories of food allergens. Biochemical characteristics associated with food allergens like the presence of multiple, linear IgE-binding epitopes seem to predominate among food allergens, more so than common structural features. Here, the recent studies on the identification of structure and potential epitopes of food allergens are also presented. Due to the high sequence homology and structural similarity of food allergens in different species, especially the major allergens, cross-reactivity is common; therefore a comprehensive introduction to the cross-reactivity among different origins of allergens is also reviewed.