High-pressure homogenization of raw and pasteurized milk modifies the yield, composition, and texture of queso fresco cheese

Immunoglobulin G4 in eosinophilic esophagitis: Immune complex formation and correlation with disease activity

BACKGROUND

Recent studies have shown deposition of immunoglobulin G4 (IgG4) and food proteins in the esophageal mucosa of eosinophilic esophagitis (EoE) patients. Our aims were to assess whether co-localization of IgG4 and major cow's milk proteins (CMPs) was associated with EoE disease activity and to investigate the proteins enriched in proximity to IgG4 deposits.

METHODS

This study included adult subjects with EoE (n = 13) and non-EoE controls (n = 5). Esophageal biopsies were immunofluorescence stained for IgG4 and CMPs. Co-localization in paired samples from active disease and remission was assessed and compared to controls. The proteome surrounding IgG4 deposits was evaluated by the novel technique, AutoSTOMP. IgG4-food protein interactions were confirmed with co-immunoprecipitation and mass spectrometry.

RESULTS

IgG4-CMP co-localization was higher in the active EoE group compared to paired remission samples (Bos d 4, p = .02; Bos d 5, p = .002; Bos d 8, p = .002). Co-localization was also significantly higher in the active EoE group compared to non-EoE controls (Bos d 4, p = .0013; Bos d 5, p = .0007; Bos d 8, p = .0013). AutoSTOMP identified eosinophil-derived proteins (PRG 2 and 3, EPX, RNASE3) and calpain-14 in IgG4-enriched areas. Co-immunoprecipitation and mass spectrometry confirmed IgG4 binding to multiple food allergens.

CONCLUSION

These findings further contribute to the understanding of the interaction of IgG4 with food antigens as it relates to EoE disease activity. These data strongly suggest the immune complex formation of IgG4 and major cow's milk proteins. These immune complexes may have a potential role in the pathophysiology of EoE by contributing to eosinophil activation and disease progression.

Microstructure of a Model Fresh Cheese and Bioaccessibility of Vitamin D₃ Using In Vitro Digestion

In this study, the effect of a composition (protein to fat (P/F) ratio) and a processing condition (homogenization pressure for emulsification of cheese milk) on the texture, microstructure, and bioaccessibility of vitamin D₃ of a model acid coagulated fresh cheese was evaluated. It was hypothesized that increasing P/F ratios (0.9, 1.3, 1.7, and 2) and homogenization pressures (17, 50, 75, and 150 MPa) will decrease the particle size of the cheese milk emulsion. The decreased emulsion particle size will result in a more rigid and elastic cheese matrix with smaller pore sizes, with an increased interfacial surface area of fat particles, which will then improve the bioaccessibility of vitamin D₃. The P/F ratio exhibited a positive impact on the texture in a large deformation analysis. On the other hand, the effect of the P/F ratio and homogenization pressure was not significant on rheological properties of the cheese using a small deformation by means of a frequency sweep test, nor the porosity determined by environmental scanning electron microscopy (ESEM). These results suggested that the modification of the microstructure of acid coagulated fresh cheeses required other variables than P/F ratio and homogenization pressure probably due to a compression step after curd formation. Interestingly, the bioaccessibility of vitamin D₃ measured by in vitro digestion was reduced as P/F ratio and homogenization pressure increased, which may indicate a reinforced protein⁻protein interaction that affected protein hydrolysis.

The major cow milk allergen Bos d 5 manipulates T-helper cells depending on its load with siderophore-bound iron

The mechanisms of allergic sensitization to milk are still elusive. The major allergen Bos d 5 belongs to the lipocalin-family and thus is able to transport numerous ligands. In this study we investigated its ability to bind to iron-siderophore complexes and tested the immune-modulatory properties of Bos d 5 in either forms. Structural and in silico docking analysis of Bos d 5 revealed that Bos d 5 is able to bind to iron via catechol-based flavonoids (quercetin, myricetin, luteolin) that act as siderophores as confirmed by spectral-analysis and iron staining. Calculated dissociation constants of docking analyses were below 1 µM by virtual addition of iron. When incubated with human peripheral blood mononuclear cells (PBMCs), only the apo-form of Bos d 5 led to an increase of CD4+positive cells and significantly elevated IL13 and IFNγ-levels. In contrast, holo-Bos d 5 decreased numbers of CD4 expressing cells and induced apoptosis. Taken together, our data give evidence that Bos d 5 is capable of binding iron via siderophores. Moreover, our data support for the first time the notion that the form of application (apo- or holo-form) is decisive for the subsequent immune response. The apo-form promotes Th2 cells and inflammation, whereas the holo-form appears to be immunosuppressive.

High-pressure processing inactivates Listeria innocua yet compromises Queso Fresco crumbling properties

The objective of this study was to determine the effectiveness of high-pressure processing to inactivate Listeria innocua (a Listeria monocytogenes surrogate) in Queso Fresco, and to study the effects of the high-pressure treatment on cheese-crumbling properties. Queso Fresco was made with pasteurized, homogenized milk, lactic acid bacterial starter culture, chymosin, and flake salt. Cheeses were pressed (0.1 MPa) for 1h before crumbling and inoculation with a cocktail of 3 strains of L. innocua, and then pressed for 12 h (0.1 MPa). High-pressure processing treatments of sliced cheese rounds included pressure from 400 to 600 MPa for 1 to 25 min. Cheese sample temperatures, initially approximately 21°C, increased during pressurization and decreased gradually during the holding time. The highest temperature increase was to 23.6°C at 600 MPa. Greater than 5-log reductions occurred at set-point pressures of 500, 550, or 600 MPa when held for at least 15, 3, or 1 min, respectively. However, because inactivation was neither complete nor permanent and crumbling properties were not maintained under the conditions tested in this study, high-pressure processing is not recommended for Queso Fresco applications.