The pattern of peptides released from dairy and egg proteins is highly dependent on the simulated digestion scenario

Evaluating the gastrointestinal (GI) fate of proteins is part of the assessment to determine whether proteins are safe to consume. In vitro digestion tests are often used for screening purposes in the evaluation of potential allergenicity. However, the current pepsin resistant test used by the European Food Safety Authority, only corresponds to fasted gastric conditions representative of a late phase adult stomach. In addition, these tests are performed on isolated proteins and the effect of the food matrix and processing are not systematically considered. The aim of this research is to compare three different static in vitro GI scenarios that are physiologically relevant. Namely, an infant, early phase (fed state) adult and late phase (fasted state) adult model. These protocols are applied to well-characterised isolated dairy (β-lactoglobulin and β-casein) and egg (lysozyme and ovalbumin) proteins and the impact of food matrix/processing on their proteolysis is also investigated. A combination of SDS-PAGE, LC-MS/MS and spectrometric assay was used for the evaluation of the proteolysis. Results highlight differences across the three GI scenarios whether on isolated proteins or within food matrices. The infant model led to incomplete digestion, leaving intact egg proteins, either isolated or in the food matrix, and intact β-lactoglobulin in the milk. In addition, peptides greater than 9 amino acids were found throughout the intestinal phase for all proteins studied, regardless of the scenario. This reinforces the difficulty of linking protein digestibility to potential allergenicity because many other factors are involved that need further investigation

A Temporal -omic Study of Propionibacterium freudenreichii CIRM-BIA1T Adaptation Strategies in Conditions Mimicking Cheese Ripening in the Cold

Propionibacterium freudenreichii is used as a ripening culture in Swiss cheese manufacture. It grows when cheeses are ripened in a warm room (about 24°C). Cheeses with an acceptable eye formation level are transferred to a cold room (about 4°C), inducing a marked slowdown of propionic fermentation, but P. freudenreichii remains active in the cold. To investigate the P. freudenreichii strategies of adaptation and survival in the cold, we performed the first global gene expression profile for this species. The time-course transcriptomic response of P. freudenreichii CIRM-BIA1T strain was analyzed at five times of incubation, during growth at 30°C then for 9 days at 4°C, under conditions preventing nutrient starvation. Gene expression was also confirmed by RT-qPCR for 28 genes. In addition, proteomic experiments were carried out and the main metabolites were quantified. Microarray analysis revealed that 565 genes (25% of the protein-coding sequences of P. freudenreichii genome) were differentially expressed during transition from 30°C to 4°C (P<0.05 and |fold change|>1). At 4°C, a general slowing down was observed for genes implicated in the cell machinery. On the contrary, P. freudenreichii CIRM-BIA1T strain over-expressed genes involved in lactate, alanine and serine conversion to pyruvate, in gluconeogenesis, and in glycogen synthesis. Interestingly, the expression of different genes involved in the formation of important cheese flavor compounds, remained unchanged at 4°C. This could explain the contribution of P. freudenreichii to cheese ripening even in the cold. In conclusion, P. freudenreichii remains metabolically active at 4°C and induces pathways to maintain its long-term survival

Ovalbumin aggregation due to heating in solution increases its in vitro digestibility, compared to the native and dry-heated protein

Ovalbumin aggregation due to heating in solution increases its in vitro digestibility, compared to the native and dry-heated protei

Ovalbumin aggregation due to heating in solution increases its in vitro digestibility, compared to the native and dry-heated protein

Ovalbumin aggregation due to heating in solution increases its in vitro digestibility, compared to the native and dry-heated protei

Ovalbumin aggregation due to heating in solution increases its in vitro digestibility, compared to the native and dry-heated protein

Ovalbumin aggregation due to heating in solution increases its in vitro digestibility, compared to the native and dry-heated protei

Structural markers of the evolution of whey protein isolate powder during aging and effects on foaming properties

The market for dairy powders, including high addedvalue products (e.g., infant formulas, protein isolates)has increased continuously over the past decade. However, the processing and storage of whey proteinisolate (WPI) powders can result in changes in their structural and functional properties. It is therefore ofgreat importance to understand the mechanisms and to identify the structural markers involved in the agingof WPI powders to control their end use properties. This study was performed to determine the effects ofdifferent storage conditions on protein lactosylations, protein denaturation in WPI, and in parallel on theirfoaming and interfacial properties. Six storage conditions involving different temperatures (θ) and wateractivities (aw) were studied for periods of up to 12 mo.The results showed that for θ ≤ 20°C, foaming propertiesof powders did not significantly differ from nonaged whey protein isolates (reference), regardless of the aw.On the other hand, powders presented significant levels of denaturation/aggregation and protein modificationinvolving first protein lactosylation and then degradation of Maillard reaction products, resulting in a higherbrowning index compared with the reference, starting from the early stage of storage at 60°C. These changesresulted in a higher foam density and a slightly better foam stability (whisking) at 6 mo. At 40°C, powdersshowed transitional evolution. The findings of this study will make it possible to define maximum storage durationsand to recommend optimal storage conditions in accordance with WPI powder end-use properties