Fabrication and characterization of nanoemulsions for encapsulation and delivery of vitexin: antioxidant activity, storage stability and in vitro digestibility.

BACKGROUND: Nanoemulsions were prepared as an encapsulation and delivery system for vitexin, a poorly water-soluble antioxidant. This study evaluated how the type and concentration of the dispersed oil phase and vitexin loading impacted droplet characteristics and nanoemulsion stability. The influences of storage temperature on antioxidant activity and in vitro gastrointestinal digestion on nanoemulsion stability were also investigated. RESULTS: Nanoemulsions prepared at different dispersed oil concentrations showed diverse characteristics and stability. Highest stability against droplet aggregation and phase separation with small oil droplets (< 150 nm) was observed for nanoemulsions prepared using 300 g kg-1 medium-chain triglyceride oil. These nanoemulsions are able to entrap and deliver vitexin with high encapsulation efficiency (88-90%) with no significant effect on emulsion stability. Vitexin-loaded nanoemulsions were stable during storage when refrigerated (4 °C) and at room temperature (25 °C) for up to 45 days with no effect on their antioxidant activity. Significantly delayed lipolysis rate and decreased extent of lipid digestion were observed in vitexin-loaded nanoemulsions. CONCLUSIONS: Stable vitexin-loaded nanoemulsions were successfully produced by high-pressure homogenization using a mixture of Tween 80 and lecithin as emulsifiers. Vitexin-loaded nanoemulsions stabilized with a mixture of these two emulsifiers were effective in retaining antioxidant activity during storage and protecting vitexin from changes during gastrointestinal digestion. Our results suggested that nanoemulsions were effective vitexin delivery systems for food applications. © 2022 Society of Chemical Industry.

Optimization of accelerated aqueous ethanol extraction to obtain a polyphenol-rich crude extract from rambutan (Nephelium lappaceum L.) peel as natural antioxidant.

An accelerated solvent extraction method was used to recover polyphenol-rich crude extract from rambutan (Nephelium lappaceum L.) peel, a waste product from the canning industry. The influence of extraction parameters including temperature, extraction time and ethanol concentration on extraction yield, total phenolic content, total anthocyanin content, and ABTS antioxidant activity was investigated. A Box-Behnken design and response surface methodology were used to optimize the extraction process. Optimal conditions were obtained at temperature, extraction time, and ethanol concentration of 60 °C, 34 min, and 54 vol%, respectively. These optimum conditions gave 333.01 ± 5.84 mg gallic acid/g, 318.28 ± 5.56 mg cyanidin-3-O-glucoside/g, and 3.05 ± 0.04 mmol Trolox/mg for total phenolic content, total anthocyanins content, and ABTS activity, respectively with extraction yield of 28.68 ± 1.48 wt%. Important active compounds found in the extract were geraniin, ellagic acid, shikimic acid and corilagin. Crude extract concentrations of 50-500 mg/kg retarded linoleic acid oxidation but efficacy was lower than synthetic antioxidants at 200 mg/kg. The current findings indicated that accelerated aqueous ethanol extraction was an effective method for the recovery of a crude extract rich in polyphenols from rambutan peel with the potential to be used as a natural antioxidant.

Effects of extrusion temperature and puffing technique on physical and functional properties of purpled third-generation snack after heat treatment.

This work aimed to investigate the effects of extrusion temperature (100 105 and 110 °C) and puffing technique (microwaving (210, 420 and 560 W.) and deep frying (170 and 190 °C)) on physical and functional properties of third-generation snack containing purple sweet potato and butterfly pea flower. Snack qualities in terms of physical properties (expansion ratio, bulk density, color and texture) and functional properties (total anthocyanin content, total phenolic content and antioxidant capacity) were subsequently determined. The results showed that extrusion temperature did not significantly affect the color of snack pellets. However, it significantly affected the functional properties of the snack pellets. Snack pellet produced from extruder at 110 °C contained significantly higher functional properties when compared to those extruded at 100 and 105 °C (p < 0.05). In addition, the study of the puffing method indicated that an increase of microwave power level and frying temperature resulted in a decrease of hardness. On the other hand, the increase of microwave power level and frying temperature caused an increase of antioxidant capacity in the puffed snacks. Moreover, microwave puffing could help preserve the color and antioxidant capacity better than deep frying. Especially, microwaved snack had total anthocyanin content twice more than that puffed by frying. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-021-05234-x.

Emulsion stabilization mechanism of combination of esterified maltodextrin and Tween 80 in oil-in-water emulsions.

Esterified maltodextrins (EMs) were prepared using enzyme-catalyzed reaction of maltodextrin (DE of 16 and 9) and palmitic acid. The emulsion stabilization mechanism was investigated of a combination of Tween 80 and EM in oil-in-water emulsion to determine interfacial tension, ζ-potential, non-adsorbed Tween 80 in centrifuged-serum of emulsion, and fluoresced microstructure. The interfacial tension and non-adsorbed Tween 80 content of combination of Tween 80 and EM-stabilized oil-in-water emulsions were closed to those of sole Tween 80-stabilized emulsion. The ζ-potential of sole Tween 80-stabilzed emulsion had a small positive charge but ζ-potential changed to small negative charge as EM was added into Tween 80-stabilzed emulsion. Fluorescence microstructure confirmed that EM was adsorbed on oil droplet surface, stabilized by Tween 80. The mechanism of emulsion stabilization may conclude that Tween 80 was mainly adsorbed at oil surface and EM may interact with Tween 80 to form a double stabilization layer without competitive replacement.