The influence of resveratrol encapsulated into liposomes (prepared with a commercial lipid mixture of phospholipids, phospolipon 90NG, using the thin film and proliposome methods) on the structural ...properties of the liposome membrane was investigated by electron paramagnetic resonance (EPR) spectroscopy, fluorescence spectroscopy, and differential scanning calorimetry. Two fluorophores and two spin probes were used to monitor the characteristics of membranes made from a commercial mixture of phosphatidylcholine. Resveratrol was positioned rather in the inner part of the liposome membranes causing reduction in membrane fluidity. Moreover, resveratrol induced a concentration‐dependent decrease in the gel‐to‐liquid crystalline phase transition temperature (from 41.3 to 38.3°C, for a saturated 1,2‐dipalmitoyl‐sn‐glycero‐3‐phospatidylcholine bilayer). The antioxidant activity of resveratrol was confirmed by its 95% inhibition of lipid peroxidation, compared to liposomes without resveratrol exposed to the same conditions. Similarly, EPR spectroscopy spin trapping showed an 87% reduction in the spectra intensity of the hydroxyethyl radical, which indicates the efficiency of resveratrol for inhibition of OH radical production. Practical applications: Resveratrol is in the limelight all over the world as a health‐beneficial compound widely investigated as natural antioxidant suitable for prevention of human cardiovascular diseases and inhibition of low‐density lipoproteins oxidation. Public interest in prevention of diseases through enriched staple foods grows each day. Nonetheless, addition of antioxidants to aqueous‐based food can be limited due to their troublesome characteristics. Liposomes are nanocarriers that may be used to overcome the disadvantages and they can be used for food applications. Liposomes could be prepared using only natural components and therefore the new formulations could be quickly implemented. Still, the application of liposomes in food systems is not widespread due to time consuming manufacturing processes and high costs. The presented results provide marks and suggestions to food manufacturers and scientists on how to make broader use of resveratrol‐loaded liposomes which add value and improve the quality of existing food products. The influence of resveratrol encapsulated into liposomes (prepared using the thin film and proliposome methods) on the structural properties of the liposome membrane was investigated by electron paramagnetic resonance spectroscopy, fluorescence spectroscopy, and differential scanning calorimetry. The antioxidant activity of resveratrol was confirmed by its inhibition of lipid peroxidation and by spin trapping.
The aim of this study was to optimize the parameters of the extraction of total flavonoids from stinging nettle leaf. Comparison of the effects of different solvents on total flavonoid content showed ...that, regardless of extraction time, aqueous-methanolic extracts had higher total flavonoid content than aqueous-ethanolic extracts. So, full factorial design and response surface methodology (RSM) were employed to estimate the effects of methanol content (50, 75, and 100 %) and extraction time (30, 60, and 90 minutes) on total flavonoid content and antioxidant capacities of the extracts. RSM analysis showed that methanol content in the solvent influenced significantly total flavonoid content and FRAP (Ferric Reducing Antioxidant Power Assay) antioxidant capacity, while extraction time had no significant effect on either of the responses. Extraction parameters for maximal total flavonoid content were estimated to be 69 % aqueous-methanol and 67 min, and 65 % aqueous-methanol and 83 min for maximal FRAP antioxidant capacity. DPPH (2,2-diphenyl-1-picrylhydrazyl) antioxidant capacity was not significantly affected by extraction time or methanol percentage in the solvent.
Nanofibers made of natural proteins have caught the increasing attention of food scientists because of their edibility, renewability, and possibility for various applications. The objective of this ...study was to prepare nanofibers based on pumpkin leaf protein concentrate (LPC) as a by-product from some crops and gelatin as carriers for vitamin B12 using the electrospinning technique. The starting mixtures were analyzed in terms of viscosity, density, surface tension, and electrical conductivity. Scanning electron micrographs of the obtained nanofibers showed a slight increase in fiber average diameter with the addition of LPC and vitamin B12 (~81 nm to 109 nm). Fourier transform infrared spectroscopy verified the physical blending of gelatin and LPC without phase separation. Thermal analysis showed the fibers had good thermal stability up to 220 °C, highlighting their potential for food applications, regardless of the thermal processing. Additionally, the newly developed fibers have good storage stability, as detected by low water activity values ranging from 0.336 to 0.376. Finally, the release study illustrates the promising sustained release of vitamin B12 from gelatin-LPC nanofibers, mainly governed by the Fickian diffusion mechanism. The obtained results implied the potential of these nanofibers in the development of functional food products with improved nutritional profiles.
Enzymatic hydrolysis of food proteins is convenient method to improve their functional properties and physiological activity. Herein, the successful covalent attachment of alcalase on alginate micron ...and submicron beads using the carbodiimide based chemistry reaction and the subsequent application of the beads for egg white and soy proteins hydrolysis were studied. In addition to the electrostatic extrusion technique (EE) previously used by others, the potential utilization of a novel ultrasonic spray atomization technique without drying (UA) and with drying (UAD) for alginate submicron beads production has been attempted. The immobilization parameters were optimized on microbeads obtained by EE technique (803 ± 23 µm) with respect to enzyme loading and alcalase activity. UA and UAD techniques resulted in much smaller particles (607 ± 103 nm and 394 ± 51 nm in diameter, respectively), enabling even higher enzyme loading of 671.6 ± 4 mg g−1 on the carrier and the highest immobilized alcalase activity of 2716.1 IU g−1 in the standard reaction. The UAD biocatalyst exhibited also better performances in the real food system based on egg white or soy proteins. It has been shown that the immobilized alcalase can be reused in seven successive soy protein hydrolysis cycles with a little decrease in the activity.
PDF
