Improving the in vitro digestibility of rapeseed albumins resistant to gastrointestinal proteolysis while preserving the functional properties using enzymatic hydrolysis.

Study of in vitro digestibility of high-quality isolate of rapeseed albumins (RA) was carried out in this work, using Size-Exclusion Chromatography. A poor in vitro digestibility of the RA isolate was highlighted (15%). The aim of this study was therefore to improve the RA in vitro digestibility by enzymatic hydrolysis while preserving its attractive functional properties. Alcalase, Flavourzyme and Prolyve were used to obtain 12 hydrolysates with various degrees of hydrolysis (DH) and compositions. All hydrolysates showed improved digestibility and those with the highest DH showed the best improvements. Techno-functional properties of these hydrolysates were also characterized. The poor emulsion capacity of initial RA was improved and results showed that extent proteolysis can be a good way to improve both digestibility and functional properties. Moreover, optimal conditions for RA proteolysis were identified to produce with Flavourzyme a partial hydrolysate (still containing 50% intact RA) that is both digestible and functional.

In Vivo Digestion of Egg Products Enriched with DHA: Effect of the Food Matrix on DHA Bioavailability.

The aim of the present study was to determine to what extent the food matrix could affect the release of docosahexaenoic acid (DHA) during digestion and its incorporation into systemic circulation. In this aim, three DHA-enriched egg products having the same composition but different structure were developed: omelet, hard-boiled egg, and mousse. Then, nine pigs fitted with T-shape cannulas at duodenal level and a jugular venous catheter were fed with the DHA-enriched egg products, and duodenal effluents and plasma were collected throughout the postprandial period. Results highlighted an undeniable effect of the food matrix on digestion parameters and DHA bioavailability. The transit of DHA and protein through the duodenum was faster after the ingestion of the mousse than after the ingestion of the omelet and hard-boiled egg. While most of the DHA and protein ingested under the form of mousse had already passed through the duodenum 4.5 h after its ingestion, significantly higher quantities were still present in the case of the omelet and hard-boiled egg. In terms of bioavailability, the omelet was the most efficient vector for delivering DHA into systemic circulation. It supplied 56% and 120% more DHA than the hard-boiled egg and the mousse, respectively.

The food matrix affects the anthocyanin profile of fortified egg and dairy matrices during processing and in vitro digestion.

The aim of the present study was to understand to what extent the inclusion of anthocyanins into dairy and egg matrices could affect their stability after processing and their release and solubility during digestion. For this purpose, individual and total anthocyanin content of four different enriched matrices, namely custard dessert, milkshake, pancake and omelettete, was determined after their manufacturing and during in vitro digestion. Results showed that anthocyanin recovery after processing largely varied among matrices, mainly due to the treatments applied and the interactions developed with other food components. In terms of digestion, the present study showed that the inclusion of anthocyanins into food matrices could be an effective way to protect them against intestinal degradation, and also the incorporation of anthocyanins into matrices with different compositions and structures could represent an interesting and effective method to control the delivery of anthocyanins within the different compartments of the digestive tract.

Stability and bioaccessibility of anthocyanins in bakery products enriched with anthocyanins.

Anthocyanins, water soluble polyphenols, have been associated with several beneficial health effects. The aim of this study was to determine how the baking process and food matrix affect anthocyanin stability and bioaccessibility in bakery products in order to develop functional foods. Three well known regularly consumed bakery products (buns, breadsticks and biscuits) were enriched with anthocyanin (AC) isolated from grape skin alone or in combination with docosahexaenoic acid (AC + DHA) to reveal knowledge on AC as active ingredients in real food systems rather than pure compounds. Anthocyanin amounts added to the formulations of buns, breadsticks and biscuits were 34 mg per 100 g, 40 mg per 100 g and 37 mg per 100 g, respectively. The effect of processing, storage and the food matrix on AC stability and bioaccessibility was investigated. In addition, the sensory properties of bakery products were evaluated. Breadsticks enriched with AC and AC + DHA received the lowest scores in the pre-screening sensory test. Therefore breadsticks were excluded from further analysis. AC retentions, which were monitored by determination of malvidin 3-O-glucoside, in the bun and biscuit after baking were 95.9% (13.6 mg per 100 g) and 98.6% (15.2 mg per 100 g), respectively. Biscuits and buns enriched only with AC showed significantly higher anthocyanin bioaccessibilities (57.26% and 57.30%, respectively) than the same ones enriched with AC + DHA. AC stability in enriched products stored for 21 days was significantly lower than in products stored for 7 days (p < 0.05). However, this loss can be accepted as negligible since more than 70% of AC was retained in all the products.

Human IgE binding and in vitro digestion of S-OVA.

S-OVA, a more thermostable form of ovalbumin (OVA), was formed from native OVA or egg white in vitro, by heating at high pH, and by storage at low temperatures. S-OVA showed a much lower reactivity against IgE than OVA, although this difference in IgE binding was minimized after simulated gastro intestinal digestion, despite S-OVA was more resistant to proteolysis, particularly to pepsin, than its native form. It is, therefore, likely that the transformation of OVA to S-OVA does not affect its ability to sensitise or trigger allergic reactions at the duodenal level. These results are discussed in the light of the described conformational changes reported to occur in the transition between OVA and S-OVA.

Identification of an IgE reactive peptide in hen egg riboflavin binding protein subjected to simulated gastrointestinal digestion.

Riboflavin binding protein (RfBP) is a minor protein in hen egg; its potential involvement in egg allergy has seldom been studied. The aim of this work was to investigate the IgE binding capacity of RfBP before and after simulated gastrointestinal digestion. It was shown that digestion of RfBP mainly occurred during the gastric phase. The protein fragments resulting from the subsequent duodenal phase remained linked through disulfide bonds. Both the intact protein and its digests were subjected to inhibition ELISA with sera obtained from patients allergic to egg. The results revealed significant IgE binding to intact RfBP, whereas the digests showed reduced but substantial IgE binding levels, with serum-to-serum variability. The RfBP digests were then subjected to immunoblot with allergic patients' sera, and the IgE-reactive peptides were further analyzed by MALDI-TOF/TOF mass spectrometry for sequence determination. The RfBP sequence 41-84 was identified as a novel IgE binding peptide in patients allergic to egg.