Whey Protein Isolate-Xylose Maillard-Based Conjugates with Tailored Microencapsulation Capacity of Flavonoids from Yellow Onions Skins

The objective of this study is to encapsulate flavonoids from yellow onion skins in whey protein isolates (WPI) and xylose (X), by Maillard-based conjugates, as an approach to improve the ability to entrap flavonoids and to develop powders with enhanced antioxidant activity. WPI (0.6%, w/v) was conjugated to X (0.3%, w/v) through the Maillard reaction at 90 °C for 120 min, in the presence of a flavonoid-enriched extract. Two variants of powders were obtained by freeze-drying. The glycation of WPI allowed a better encapsulation efficiency, up to 90.53 ± 0.29%, corresponding to a grafting degree of 30.38 ± 1.55%. The molecular modelling approach was used to assess the impact of X interactions with α-lactalbumin and β-lactoglobulin on the ability of these proteins to bind the main flavonoids from the yellow onion skins. The results showed that X might compete with quercetin glucosides to bind with α-lactalbumin. No interference was found in the case of β-lactoglobulin. The microstructural appearance of the powders revealed finer spherosomes in powder with WPI–X conjugates via the Maillard reaction. The powders were added to nachos, followed by a phytochemical characterization, in order to test their potential added value. An increase in antioxidant activity was observed, with no significant changes during storage.

Multifunctional Ingredient from Aqueous Flavonoidic Extract of Yellow Onion Skins with Cytocompatibility and Cell Proliferation Properties

Significant quantities of onion are cultivated annually, such that industrial processing leads to an appreciable amount of by-products, estimated at around 500,000 tons. Onion skins are considered an important source of naturally occurring antioxidant compounds, particularly flavonoid compounds. Our study follows the development of a sustainable solution in order to manage the by-products of yellow onion skins by designing ingredients with multifunctional activities. A green solvent aqueous extraction of flavonoids was applied to obtain a safe, flavonoid-enriched extract, yielding a total flavonoid content of 50.21 ± 0.09 mg quercetin equivalent (QE)/g dry weight (DW), and an antioxidant activity of 250.81 ± 6.76 mM Trolox/g DW. Complex biopolymeric matrices consisting of whey protein isolates, whey protein hydrolysates, maltodextrin, and pectin were further dissolved in the flavonoid-enriched aqueous extract, followed by freeze-drying. Two powders were obtained, both showing satisfactory phytochemical content and good stability during storage. The application of confocal microscopy revealed that the microscopic structure of the powders have a distribution of the bioactive compounds within the biopolymeric matrices. The in vitro digestion suggested remarkable stability in the gastric tract and a flavonoid-controlled release in the intestinal phase. A significant compatibility range of up to 1 mg/mL for both powders was found, whereas concentrations between 10 and 250 µg/mL stimulated cell proliferation after 24 h of cultivation. The powders showed satisfactory thermal and pH stability, which favors their addition to different food matrices.

Transcriptome-based identification of the beneficial role of blackcurrant, strawberry and yellow onion to attenuate the cytopathic effects of Clostridium difficile toxins

BACKGROUND: Clostridium difficile Infection (CDI) can lead to diarrhea and fulminant colitis. C. difficile infects the host using toxins. Recent studies report prevalence of CDI in the small intestine. Berries are known to contain antioxidants and phenolic compounds that might mitigate bacterial infection. OBJECTIVE: We explored the impact of C. difficile toxins on the small intestine using an in vitro approach and used systems biology techniques together with data integration to identify food compounds that can reduce their cytopathic impact. METHODS: Differentiated Caco-2 cells were exposed to C. difficile toxins and the transcriptomic changes were studied. To identify foods with potential beneficial counteracting effects, the transcriptomic profiles were integrated with transcriptomics data from Caco-2 cells exposed to various food compounds and analyzed using multivariate analysis. RESULTS: Beneficial food candidates, selected by multivariate analysis, such as blackcurrant, strawberry and yellow onion were further examined for their potential to counteract the effect of the toxin-induced disruption of cell integrity and toxin translocation. Our results confirmed effects of food compounds, on the cytopathic effects of toxins in the small intestine. CONCLUSION: Blackcurrant, strawberry and yellow onion can counteract C. difficile toxins induced effects.

THE USE OF ONION PEEL EXTRACT TO INHIBIT THE THERMAL OXIDATION OF POLYETHYLENE

The paper studies experimentally the antioxidant activity of onion peel acetone extracts of three varieties (Albion F1, Kaba, Red Baron) in the inhibition process of polyethylene thermal oxidation. The onion varieties differ in the color of their surface scales (colorless (white onion), yellow-orange (yellow onion), red (red onion)) and in the antioxidant properties of their extracts: red onion> yellow onion >> white onion. The results correspond to the mass of the extracted substances. A different sequence of onion varieties has been obtained in terms of the inhibitory effectiveness of their extracts: yellow onion> red onion >> white onion. The comparison of the extracted onion peel extracts with the industrial antioxidant Irganox 1010 in terms of inhibitory efficiency has been carried out. The paper presents and analyzes the IR spectra of the extracts. An increase in the extraction time from 24 hours to 56 days leads to an increase in the antioxidant properties of the extracts of all three varieties, but an increase in the inhibition efficiency is noted only for Albion F1 onion peel extract. In Red Baron and Kaba varieties, the main part of biologically active substances with antioxidant action is extracted from the peel into acetone during the first days of extraction.

Co-Microencapsulation of Flavonoids from Yellow Onion Skins and Lactic Acid Bacteria Lead to Multifunctional Ingredient for Nutraceutical and Pharmaceutics Applications

In this study, flavonoids extracted from yellow onion skins and Lactobacillus casei were encapsulated in a combination of whey protein isolate, inulin and maltodextrin with an encapsulation efficiency of 84.82 ± 0.72% for flavonoids and 72.49 ± 0.11% for lactic acid bacteria. The obtained powder showed a flavonoid content of 89.49 ± 4.12 mg quercetin equivalents/g dry weight (DW) and an antioxidant activity of 39.27 ± 0.45 mM Trolox/g DW. The powder presented a significant antidiabetic and anti-inflammatory potential, with an inhibitory effect on α-amylase, lipase and lipoxygenase of 76.40 ± 2.30%, 82.58 ± 3.36% and 49.01 ± 0.62%, respectively. The results obtained for in vitro digestion showed that the coating materials have a protective effect on the flavonoids release. Cytotoxicity results indicated that the powder was cytocompatible up to a concentration of 500 μg/mL. The functional potential of the powder was tested by adding in a selected food matrix, highlighting a good stability of the phytochemicals, whereas an increase with 1 log cell forming unit (CFU)/g DW was observed after 21 days of storage. The obtained results are promising in the valorization of natural antioxidants in combination with lactic acid bacteria in order to develop multifunctional ingredients with value-added for food and pharmaceutics applications.

Tailoring the Health-Promoting Potential of Protein Hydrolysate Derived from Fish Wastes and Flavonoids from Yellow Onion Skins: From Binding Mechanisms to Microencapsulated Functional Ingredients

This study focuses on combining different bioprocessing tools in order to develop an in-depth engineering approach for enhancing the biological properties of two valuable food by-products, namely fish waste and yellow onion skins, in a single new bioactive formulation. Bone tissue from phytophagous carp (Hypophthalmichthys molitrix) was used to obtain bioactive peptides through papain-assisted hydrolysis. The peptides with molecular weight lower than 3 kDa were characterized through MALDI-ToF/ToF mass spectrometry and bioinformatics tools. As a prerequisite for microencapsulation, the ability of these peptides to bind the flavonoids extracted from yellow onion skins was further tested through fluorescence quenching measurements. The results obtained demonstrate a considerable binding potency with a binding value of 106 and also the presence of one single or one class of binding site during the interaction process of flavonoids with peptides, in which the main forces involved are hydrogen bonds and van der Waals interactions. In the freeze-drying microencapsulation process, an efficiency for total flavonoids of 88.68 ± 2.37% was obtained, considering the total flavonoids and total polyphenols from the powder of 75.72 ± 2.58 quercetin equivalents/g dry weight (DW) and 97.32 ± 2.80 gallic acid equivalents/g DW, respectively. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test on the L929 cell line cultivated in the presence of different concentrations of microencapsulated samples (0.05–1.5 mg/mL) proved no sign of cytotoxicity, the cell viability being over 80% for all the samples.