Role of the bolus degree of structure on the protein digestibility during in vitro digestion of a pea protein-fortified sponge cake chewed by elderly

This study investigated the digestibility of proteins in a pea protein-fortified sponge cake, as well as the impact of the degree of structure of the bolus produced by elderly subjects on the digestibility of proteins by combining ex vivo and in vitro approaches via the standardized protocol INFOGEST. The sponge cakes were consumed by a group of 20 elderly subjects with contrasting physiology, their boli were recovered just before swallowing, and their apparent viscosity was measured to delineate the bolus degree of structure. According to this criterion, two pools were formed with boli from subjects selected at the extremes: low viscosity and high viscosity, with apparent viscosity values (at 120 s⁻¹) of 124 ± 18 and 208 ± 19 Pa s, respectively. The sponge cakes and the two pools underwent in vitro digestion. Protein hydrolysis kinetics was followed by measuring the released primary amino groups (NH₂) and by sodium-dodecyl-sulfate polyacrylamide gel electrophoresis at different time points. For all samples, the representative bands of pea proteins disappear gradually during digestion, accompanied by the appearance of bands indicating the presence of proteins with M_W < 15 kDa. In addition, the NH₂ concentrations increase over time and do not differ between sponge cake and pea protein isolate. Moreover, the degree of structure of the food bolus has no significant effect on the concentration of NH₂ released. These results showed that pea proteins in a fortified sponge cake are bioaccessible under standardized conditions and that the degree of structure of the bolus did not influence protein digestibility for these foods.     

Combined microwave and enzymatic treatments for ��-lactoglobulin and bovine whey proteins and their effect on the IgE immunoreactivity

Effect of combined microwave (MW) and enzymatic hydrolysis on the human immunoglobulin E (IgE)-binding properties of ??-lactoglobulin (??-lg) and other whey proteins (WP) was investigated. Separated ??-lg and full whey protein isolate (WPI) were hydrolyzed with trypsin, chymotrypsin, mixture of trypsin/chymotrypsin, and pepsin at three microwave power levels: 50?W during 1 and 5?min, 100 and 200?W during 1 and 3?min. The immunoreactivity of the obtained hydrolysates resulting from combined microwave protease treatment was assessed using sera of young patients allergic to bovine whey proteins. The application of microwave treatment at 200?W enhances the hydrolysis of ??-lg by pepsin in 3?min and decreases significantly its immunoreactivity. The extensive hydrolysis of the microwave-treated ??-lg and WPI with trypsin, chymotrypsin, and the mixture of trypsin with chymotrypsin did not have an impact on the IgE binding of the products obtained in all the studied conditions.     

Proteolytic action of Lactobacillus delbrueckii subsp. bulgaricus CRL 656 reduces antigenic response to bovine β-lactoglobulin

The whey protein β-lactoglobulin (BLG) is highly allergenic. Lactic acid bacteria can degrade milk proteins. The capacity of Lactobacillus delbrueckii subsp. bulgaricus CRL 656 to hydrolyse the major BLG epitopes (V41–K60; Y102–R124; L149–I162) and decrease their recognition by IgE of allergic patients was evaluated. The intensity of BLG degradation was analysed by Tricine SDS–PAGE and RP-HPLC. Peptides released were identified by LC–MS/MS and the hydrolysates were tested for their capacity to inhibit IgE binding by ELISA test. L. delbrueckii subsp. bulgaricus CRL 656 degraded BLG (35%, 8 h). The sequence analysis of the released peptides indicated that this strain degraded three main BLG epitopes. BLG-positive sera (3–5 year old children) were used for testing IgE binding inhibition of BLG hydrolysates from the Lactobacillus strain. The hydrolysates were less immuno-reactive (32%) than the heated BLG. L. delbrueckii subsp. bulgaricus CRL 656 could be used for developing hypoallergenic dairy products.     

Characterization of new strain Lactobacillus paracasei I-N-10 with proteolytic activity: Potential role in decrease in β-casein immuno-reactivity

The proteolytic activity of thirty-three LAB isolates from Mongolian tarag was tested on skimmed milk. The strain displaying the highest proteolytic activity was purified and presented by 16S rDNA sequencing 99.9?% homology with Lactobacillus paracasei 1-4-2A. It was named L. paracasei I-N-10. Proteases of L. paracasei I-N-10 hydrolyze predominately ??-casein and in some level ??_S2-casein; hydrolysis of ??_S1-casein was not observed. Proteolytic activity was optimal at 42?°C and neutral pH. Proteases of L. paracasei I-N-10 were inhibited by serine- and metalloproteases inhibitors. PCR amplification revealed the presence of prtP gene, which was identical to prtP gene of L. paracasei genus. Mass spectrometry analysis of ??-casein hydrolysate allowed to characterize 7 peptides resulting from proteolysis by L. paracasei I-N-10. The isolated strain was able to cleave ??-casein in different sites including 2 of the major linear epitopes implicated in its allergenicity. Being sensitive to main antibiotics classes, L. paracasei I-N-10 could be considered as safe and used as starter culture with a potential role in decreasing ??-casein immuno-reactivity.