Investigation of the mechanism underlying the influence of mild glycation on the digestibility and IgG/IgE-binding abilities of β-lactoglobulin and its digests through LC orbitrap MS/MS

Effects of saccharide type and extended heating on the Maillard reaction and physicochemical properties of high-solid gelatin gels

This research delves into the Maillard reaction (MR) in high-solid gelatin-saccharide mixtures consisting of 8% and 72% of allulose, fructose, or fructo-oligosaccharides, which were subjected to varied duration (0-60min) of thermal processing prior to gelation. Physicochemical properties of the gels, including color, chemical composition, protein crosslinking, mechanical strength, in-vitro digestibility and antioxidant activities, were characterized. At pH ∼5.5 and intermediate water activities (0.6-0.7), fast browning was observed through sugar degradation and sugar-amine interactions, which were intensified by prolonged heating. The MR reactivity of saccharides followed: AL > FRU > FOS. Characteristic products (MRPs, e.g., α-dicarbonyls, 5-hydroxymethylfurfural, and advanced glycation end products) were identified, with the spectra of MRPs varying significantly between monosaccharides and oligosaccharides. The MR-induced protein glycation and crosslinking exhibited certain negative impacts on the gel strength and in-vitro protein digestibility. Furthermore, all gelatin-saccharide mixtures exhibited augmented antioxidant properties, with the gelatin-AL mixtures displaying the highest free radical scavenging rates.

Characterization and functional properties of Maillard reaction products of β-lactoglobulin and polydextrose

The Maillard reaction products (MRPs) between polydextrose (PDX), a popular polysaccharide in formula powder, and β-lactoglobulin (β-LG), a major whey protein, were studied in aggregation degree, structure, hydrophobic, antigenic and antioxidant activity changes of β-LG. Incubation of PDX and β-LG (60 ℃, 79% relative humidity) for up to 72 h yielded MRPs with increases in furosine, UV absorbance, fluorescence intensity and loss of free amino groups. High molecular weight β-LG-PDX MRPs were observed by SDS-PAGE. Circular dichroism spectroscopy revealed negligible change in β-LG secondary structure. Changes in the tertiary structure of β-LG were detected by tryptophan fluorescence spectroscopy consistent with an increase in surface hydrophobicity of heated β-LG-PDX. Antigenicity reduction of β-LG in β-LG-PDX reached its peak when heated for 24 h. After heating for 72 h, DPPH radical-scavenging activity of β-LG-PDX increased by 7.4-fold, and the ferric reducing antioxidant power reached 61.1 µmol ascorbic acid/g protein.

Isolation and allergenicity evaluation of glycated α-lactalbumin digestive products and identification of allergenic peptides

This study aimed to isolate and evaluate the allergenicity of glycated α-lactalbumin (ALA) digestive products and identify its allergenic peptides. The digestive products of native-, alone glycated- and ultrasound-assisted glycated ALA (ALA-D, ALA-gal-D, 100ALA-gal-D) were isolated into three fractions (F1, F2 and F3). High-resolution mass spectrometry showed that the digestion-resistant peptides of F2 and F3 mainly distributed in amino acid sequence (AA) 25-31, AA32-53, AA40-53, AA54-60, AA80-90, AA94-104. The allergenicity of the three fractions of glycated ALA was lower than that in ALA-D, indicating glycation of ALA could indeed reduce its allergenicity after digestion. Furthermore, most fractions isolated from high glycation-degree ALA had the lowest allergenicity. The IgG/IgE binding abilities of synthesized peptides indicated that AA94-104 firstly identified by us embodied the strongest allergenicity and might be the potential allergenic peptide. This will provide a theory for preparing hypoallergenic products based on the identified allergenic peptides.

Maillard Reaction Induced Changes in Allergenicity of Food

Food allergy is increasing in prevalence, posing aheavier social and financial burden. At present, there is still no widely accepted treatment for it. Methods to reduce or eliminate the allergenicity of trigger foods are urgently needed. Technological processing contributes to producing some hypoallergenic foods. Among the processing methods, the Maillard reaction (MR) is popular because neither special chemical materials nor sophisticated equipment is needed. MR may affect the allergenicity of proteins by disrupting the conformational epitope, disclosing the hidden epitope, masking the linear epitope, and/or forming a new epitope. Changes in the allergenicity of foods after processing are affected by various factors, such as the characteristics of the allergen, the processing parameters, and the processing matrix, and they are therefore variable and difficult to predict. This paper reviews the effects of MR on the allergenicity of each allergen group from common allergenic foods.

Insight into the mechanism of d-allose in reducing the allergenicity and digestibility of ultrasound-pretreated α-lactalbumin by high-resolution mass spectrometry

The mechanism of d-allose in reducing the allergenicity and digestibility of ultrasound-pretreated α-lactalbumin (α-LA) was studied. The intensity reduction and peak red shift occurred in fluorescence spectra of glycated samples. Enzyme-linked immunosorbent assay and basophil degranulation analysis showed that d-allose significantly reduced the allergenicity of α-LA, and ultrasound-pretreated α-LA showed the lowest allergenicity after glycation. Compared with α-LA, the degree of hydrolysis decreased in glycated samples. Size-exclusion high-performance liquid chromatography showed that the glycated α-LA was resistant to digestive enzymes. The glycated sites and average degree of substitution per peptide molecule were determined using LC Orbitrap MS/MS. These results suggested that the masking of linear allergenic epitopes by glycation could reduce the allergenicity. Therefore, the combination of ultrasound pretreatment and glycation is a potential method to reduce protein allergenicity in food processing and provides a useful approach for the application of rare sugars in food processing.

Investigation on the Anaphylaxis and Anti-Digestive Stable Peptides Identification of Ultrasound-Treated α-Lactalbumin during In-Vitro Gastroduodenal Digestion

Our previous studies indicated that ultrasound treatment can increase the anaphylaxis of protein. However, investigation on the anaphylaxis changes of ultrasound-treated α-lactalbumin (ALA) during digestion is lacking. The anaphylaxis of ultrasound-treated ALA and its digesta was investigated. The anti-digestive stable peptides were identified by high-resolution mass spectrometry. Ultrasound induced the tertiary structure of ALA to unfold and increased its anaphylaxis. During digestion, the anaphylaxis of both gastric and gastroduodenal digesta was further increased. There are two reasons for this phenomenon. On the one hand, linear epitopes played an important role in affecting anaphylaxis compared with the conformational epitope, and some linear epitopes were still retained on the anti-digestive stable peptides produced after gastroduodenal digestion, resulting in increased anaphylaxis after digestion. On the other hand, the presence of intact ALA molecules after digestion still remained strong anaphylaxis. Compared with the digesta of untreated ALA, the digesta of ultrasound-treated ALA possessed higher anaphylaxis. The results indicated that ultrasound increased the anaphylaxis of ALA during digestion.

Mechanism on the Allergenicity Changes of α-Lactalbumin Treated by Sonication-Assisted Glycation during In Vitro Gastroduodenal Digestion

Physical-assisted chemical modification is effective to reduce the allergenicity of α-lactalbumin (ALA). However, there are few in-depth studies on the allergenicity changes of physical-assisted chemical-modified ALA during digestion. The effect of gastroduodenal digestion on the allergenicity changes of ALA treated by sonication-assisted glycation was assessed. Digestion of both ALA and its glycated forms generated peptide fractions, and intact undigested glycated ALA in the hydrolysates still covalently bound to d-galactose. High-resolution mass spectrometry revealed that a higher glycation degree was discovered in sonication-preprocessed ALA compared to native ALA. Enzyme-linked immunosorbent assay and basophil degranulation showed that sonication-assisted glycation could significantly reduce ALA allergenicity. The allergenicity of both gastric and gastroduodenal hydrolysates was further increased, and the hydrolysates of sonication-assisted glycated ALA showed the lowest allergenicity. The reason could be the shielding effect of the linear epitope found to be caused by a higher glycation degree; although linear epitopes were exposed, d-galactose covalently bound to intact undigested glycated ALA in the hydrolysates retained its masking role. These results indicated that sonication-assisted glycation could be a promising method to prepare immunotherapeutic agents for allergen immunotherapy to achieve the purpose of allergy desensitization.