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In this study, polyphenol oxidase (PPO) was extracted from Prunus domestica and partially purified by ammonium sulfate precipitation, hydrophobic interaction chromatography, and ion exchange chromatography. The final purification step revealed a 32.81-fold purification, and the molecular mass was estimated to be 65 kDa by SDS-PAGE. The purified PPO showed enzymatic activity mainly toward five substrates, namely catechol, catechin, 4-methyl catechol, chlorogenic acid, and L-3,4-dihydroxyphenylalanine, whereas it showed no activity toward caffeic acid, ferulic acid, p -coumaric acid, p -cresol, and l -tyrosine. The optimum pH and temperature values were 6.0 and 25 °C, respectively. The enzyme showed high stability in the pH range of 5.0–7.0 and in the temperature range of 25–65 °C. The most effective inhibitors of this enzyme were found to be ascorbic acid and l -cysteine. The thermal inactivation followed a first-order kinetic model, with activation energy of E a 150.46 ± 1.29 kJ/mol. PPO extracted from plum showed stability at high pressure, with enzyme activation at 500 MPa. [ABSTRACT FROM AUTHOR]

Highlights: [•] Spectroscopy results indicate two distinct tyrosinases species at high temperatures. [•] Tyrosinases tend to aggregate after 10min at 75°C. [•] Temperature increase causes alteration of the substrate binding site of tyrosinase. [•] The changes in tyrosinase structure over 60°C might lead to enzyme inactivation. [ABSTRACT FROM AUTHOR]

Sea buckthorn carotenoids extracted using CO 2 supercritical fluids method were encapsulated within whey proteins isolate by transglutaminase (TG) mediated crosslinking reaction, coacervation and freeze drying. The encapsulation efficiency was 36.23 ± 1.58%, with β-carotene the major carotenoid present in the powder. The confocal analysis revealed that TG-ase mediated cross-linking reaction enhanced the complexes stability to such a manner that a double microencapsulation was performed. The powder showed an antioxidant activity of 2.16 ± 0.14 mMol Trolox/g DW and an antifungal activity against Penicillium expansum MIUG M11. Four variants of domestic ice creams were obtained, with a total carotenoids content variation of 1.63 ± 0.03 mg/g D.W. in sample with 2% powder and 6.38 ± 0.04 mg/g D.W. in samples with 4% extract, having satisfactory antioxidant activity. The storage stability test showed a decrease in both total carotenoids content and antioxidant activity in all samples during 21 days at −18 °C. A protective effect of microencapsulation was evidenced. [ABSTRACT FROM AUTHOR]

A comprehensive study regarding the microencapsulation of bioactives from elderberry extract ( Sambuci nigra ) by whey proteins was performed. Quenching experiments allowing the estimations of binding parameters for anthocyanins and flavonoids from elderberry extract by whey proteins isolate were first performed. The binding parameters values highlighted a preferential binding of the flavonoids, whereas a dynamic quenching process involving multiple binding sites was suggested. The HPLC analysis allowed identification of major anthocyanins and flavonoids in the extract, as delphinidin-3-glucoside and catechin hydrate. Molecular docking tests carried out to identify the particularities of the interaction between these bioactives from elderberry by β-lactoglobulin indicated affinity varying with the type of complex and different binding sites for each ligand. The results indicated that the complex with anthocyanins is thermodynamically stable, while the complex with the main flavonoid appears rather unstable. Further, elderberry bioactives were encapsulated within whey proteins isolate and pectin, with an encapsulating efficiency of ∼98%. The confocal laser scanning microscopy revealed the presence of various spherical or polygonal formations with sizes ranging from 40 to 150 μm. The powder showed a significant amount of polyphenols (5.59 ± 0.02 mg GA/g DW), flavonoids (1.19 ± 0.02 mg CE/g DW) and anthocyanins (307.82 ± 1.57 mg C3G/g DW), whereas the antioxidant activity was 3695.67 ± 0.67 μM Trolox/g DW. The remarkable antioxidant activity of the powder highlights the potential use of the microcapsules as natural antioxidants in food and derivatives. The thermal stability experiments evidenced a significant protective effect on anthocyanins degradation, whereas an increase in flavonoid content was found. [ABSTRACT FROM AUTHOR]

The use of highly functional carotenoids from different sources in food industry is limited mostly because of their poor water-solubility and low thermal stability. To overcome these drawbacks, the sea buckhorn ( Hippophae rhamnoides L) carotenoids extract was encapsulated with whey proteins isolate and gum acacia by coacervation and freeze drying. Results from encapsulation efficiency, total carotenoids, confocal laser microscopy and FTIR indicated that the carotenoids molecules were successfully encapsulated within whey proteins isolate cages. The powder had a total carotenoids content of 2.82 ± 0.17 mg/g D.W. The confocal microscopy revealed the encapsulation of carotenoid compounds, with the formation of spheroids of 2–30 μm, whereas some of them merge together and generate coacervates that exceed 25 μm in diameter. Both the extract and the microencapsulated powder showed a significant antioxidant activity. The spectrum of the complex showed bands specific to the carotenoids, esters and dicarboxylic acids, but also bands specific for whey proteins. Also, formation of more hydrogen bonds within the coarcervates was suggested. The powder was tested further in muffins formulation. The products were characterized in terms of physico-chemical, microbiological, phytochemicals, antioxidant activity, texture, color parameters, sensory analysis and storage stability. The muffins had a total carotenoids content of 2.42 ± 1.29 mg/100 g D.W. and a corresponding antioxidant activity of 293.90 ± 2.07 μM Trolox/g D.W. A significant decrease in carotenoids content (up to 55%) and antioxidant activity was observed in the first 21 days of storage. A slight decrease in luminosity was observed, whereas no significant differences were found in a* and b* values. [ABSTRACT FROM AUTHOR]

Sour cherries ( Prunus cerasus L) anthocyanins were encapsulated with bovine β-lactoglobulin by freeze drying. Three experimental states of protein were in depth characterized: un-treated protein, heat-treated protein and cross-linked protein-anthocyanins complex. The encapsulation efficiency was significantly higher for the cross-linked complex. The docking procedure indicated that β-lactoglobulin has three different ligand binding sites, namely an internal cavity defined by the β-barrel, a hydrophobic pocket located on the protein surface in a groove between the α-helix and the β-barrel, and a patch close to Trp 19 -Arg 124 residues. FT-IR analysis showed higher contribution of β-sheet structures in anthocyanins binding with respect to the α-helix, in particular in the case of cross-linked samples. The distribution of anthocyanin inside the protein molecules was highlighted by confocal laser scanning microscopy. Preliminary processing through thermal treatment and cross-linking allowed obtaining twofold larger protein aggregates as encapsulating matrices compared to untreated samples. The highest antioxidant activity was observed for the pre-heat treated samples. The in vitro digestibility results suggested that β-lactoglobulin protects anthocyanins from the gastric digestion, their release being facilitated in the intestine. [ABSTRACT FROM AUTHOR]

Sea buckhorn ( Hippophae rhamnoides L) carotenoids extracted by using CO 2 supercritical fluids (SC-CO 2 ) method were encapsulated with whey proteins isolate by coacervation and freeze drying. The SC-CO 2 yielded a 121.10 g oil/kg dried berries and 4517.54 mg carotenoids/kg dried berries. Two experimental stages were tested as follow: proteins-carotenoids and cross-linked proteins-carotenoids complex. The encapsulating efficiency was higher for the cross-linked complex. The HPLC analysis allowed the identification of carotenoid composition of sea buckthorn extract and powders, highlighting the fact that the variant obtained by crosslinking allowed entrapping a significantly higher amounts of esters and a lower amount of β-carotene. The laser confocal scanning microscopy revealed the distribution of bioactive compounds inside the coacervates, which exceed 30 μm in diameter, whereas larger spherosomes (50–80 μm size) were observed in cross-linked proteins-carotenoids complex. The scanning electron microscopy suggested the presence of the particles evenly distributed, with spherical dents corresponding to the homogeneous presence of sea buckthorn extract. No significant difference was observed in antioxidant activity, whereas the cross-linked sample showed significant higher antifungal activity for the Penicillium expansum MIUG M11. [ABSTRACT FROM AUTHOR]