Co-Microencapsulated Black Rice Anthocyanins and Lactic Acid Bacteria: Evidence on Powders Profile and In Vitro Digestion.

Two multi-functional powders, in terms of anthocyanins from black rice (Oryza sativa L.) and lactic acid bacteria (Lactobacillus paracasei, L. casei 431®) were obtained through co-microencapsulation into a biopolymer matrix composed of milk proteins and inulin. Two extracts were obtained using black rice flour as a raw material and hot water and ethanol as solvents. Both powders (called P1 for aqueous extract and P2 for ethanolic extract) proved to be rich sources of valuable bioactives, with microencapsulation efficiency up to 80%, both for anthocyanins and lactic acid bacteria. A higher content of anthocyanins was found in P1, of 102.91 ± 1.83 mg cyanindin-3-O-glucoside (C3G)/g dry weight (DW) when compared with only 27.60 ± 17.36 mg C3G/g DW in P2. The morphological analysis revealed the presence of large, thin, and fragile structures, with different sizes. A different pattern of gastric digestion was observed, with a highly protective effect of the matrix in P1 and a maximum decrease in anthocyanins of approximatively 44% in P2. In intestinal juice, the anthocyanins decreased significantly in P2, reaching a maximum of 97% at the end of digestion; whereas in P1, more than 45% from the initial anthocyanins content remained in the microparticles. Overall, the short-term storage stability test revealed a release of bioactive from P2 and a decrease in P1. The viable cells of lactic acid bacteria after 21 days of storage reached 7 log colony forming units (CFU)/g DW.

Bovine ß-lactoglobulin peptides as novel carriers for flavonoids extracted with supercritical fluids from yellow onion skins.

Our study describes in detail the binding mechanism between the main flavonoids that were extracted from onion skins by supercritical CO2 and peptides from whey proteins, from the perspective of obtaining multifunctional ingredients, with health-promoting benefits. The supercritical CO2 extract had 202.31 ± 11.56 mg quercetin equivalents/g DW as the major flavonoid and antioxidant activity of 404.93±1.39 mM Trolox/g DW. The experiments on thermolysin-derived peptides fluorescence quenching by flavonoids extract allowed estimating the binding parameters, in terms of binding constants, and the number of binding sites. The thermodynamic analysis indicated that the main forces involved in complex formation were hydrogen bonds and van der Waals interactions. Molecular docking tests indicated that peptide fluorescence quenching upon gradual addition of onion skin extract might be due to flavonoids binding by Val15 -Ser21 . All 7 to 14 amino acids long peptides appeared to have affinity toward quercetin-3,4'-O-diglucoside and quercetin-4'-O-monoglucoside. The study is important as a potential solution for reuse of valuable resources, underutilized, such as whey peptides and yellow onion skins flavonoids for efficient microencapsulation, as a holistic approach to deliver healthy and nutritious food. PRACTICAL APPLICATION: A growing interest was noticed in the last years in investigating the interactions between proteins and different biologically active compounds, such as to provide knowledge for efficient development of new food, pharmaceutical, and cosmetic products. Recent studies suggest that flavonoid-protein complexes may be designed to improve the functional performance of the flavonoids. The results obtained in this study bring certain benefits in terms of exploiting the bioactive potential of both flavonoids and bioactive peptides, for developing of formulas with improved functional properties.

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.