Enzymatically preparation of starch nanoparticles using freeze drying technique - Gelatinization, optimization and characterization

Starch nanoparticles (SNPs) in colloidal forms were prepared using enzymatically pretreatment and four different gelatinization methods based on autoclave, microwave, ultrasonication and normal heating with stirring. Furthermore, SNPs in powder form were prepared using freeze drying technique. Results indicated that the formed SNPs using starch solution (1 % W/V) and ultrasonication technique had lowest mean particle size (151 nm) and PDI (0.173), and highest zeta potential (-8.8 mV) values. Optimization procedure using response surface methodology, based on central composite design, indicated that using 1.5 mL of α-amylase and sonication time of 15 min, SNPs with lowest particle size (49.3 nm) and highest zeta potential (-10.8 mV) were produced. Using prepared colloidal solution under optimal conditions, SNPs powder were produced by freeze dryer, adjusted at pressure and temperature of 100 Pa and - 70 °C, for 24 h. Results indicated that formed SNPs powder with squared-shape, had particle size, zeta potential, specific surface area, decomposition temperature of 197 nm, -13.9 mV, 1.9 m²g^-1 and 162 °C, respectively. While, for native starch these values were 5018 nm, -6.01 mV, 0.68 m²g^-1 and 170.2 °C, respectively. Results revealed that emulsification ability of SNPs powder was three times higher than that of the native starch.

Astaxanthin–garlic oil nanoemulsions preparation using spontaneous microemulsification technique: optimization and their physico–chemical properties

Garlic oil in water nanoemulsion was resulted through subcritical water method (temperature of 120 °C and pressure of 1.5 bar, for 2 h), using aponin, as emulsifier. Based on the prepared garlic oil nanoemulsion, astaxanthin–garlic oil nanoemulsions were prepared using spontaneous microemulsification technique. Response surface methodology was employed to evaluate the effects of independent variables namely, amount of garlic oil nanoemulsion (1–9 mL) and amount of provided astaxanthin powder (1–9 g) on particle size and polydispersity index (PDI) of the resulted nanoemulsions. Results of optimization indicated that well dispersed and spherical nanodroplets were formed in the nanoemulsions with minimum particle size (76 nm) and polydispersity index (PDI, 0.358) and maximum zeta potential value (−8.01 mV), using garlic oil nanoemulsion amount of 8.27 mL and 4.15 g of astaxanthin powder. Strong antioxidant activity (>100%) of the prepared astaxanthin–garlic oil nanoemulsion, using obtained optimum amounts of the components, could be related to the highest antioxidant activity of the colloidal astaxanthin (>100%) as compared to that of the garlic oil nanoemulsion (16.4%). However, higher bactericidal activity of the resulted nanoemulsion against Escherichia coli and Staphylococcus aureus, were related to the main sulfur bioactive components of the garlic oil in which their main functional groups were detected by Fourier transform-infrared spectroscopy.

Intensification and optimization of the process for thyme oil in water nanoemulsions preparation using subcritical water and xanthan gum

Intensified process based on subcritical water conditions (120 °C and 1.5 atm, for 2 h) was utilized to prepare thyme oil in water (O/W) nanoemulsions. In this technique, water and xanthan gum, as green solvent and natural microbial emulsifier, were utilized. Results of gas chromatography revealed that Thymol and Carvacrol were two main bioactive compounds of the extracted thyme oil. Effects of amounts of xanthan gum (0.05–0.25 g) and thyme essential oil (0.2–0.8 mL) on size of oil nanodroplets and polydispersity index (PDI) of the resulted nanoemulsions were evaluated using response surface methodology. Results demonstrated that the produced thyme O/W nanoemulsion by 0.242 mL thyme oil and 0.140 g xanthan gum had smallest average nanodroplet size (150 nm) and PDI (0.088). Furthermore, monodispersed and spherical in shape thyme oil nanodroplets were provided in the nanoemulsion using these optimal conditions with zeta potential value of −10.1 mV and antioxidant activity of 17.4%. Results also indicated that this prepared nanoemulsion had high fungicidal and bactericidal activities toward Penicillium digitatum and Escherichia coli, respectively.

Green synthesis of cobalt oxide nanoparticles using Citrus medica leaves extract: characterization and photo-catalytic activity

The study deals with the green and eco-friendly synthesis and characterization of cobalt oxide nanoparticles using leaf extract of Citrus medica plant. The crystalline nature and functional groups analysis of cobalt oxide Nps was confirmed by X-ray diffraction and diffused reflectance infra-red spectroscopy respectively. The band gap of the Nps was calculated using Tauc plot. Scanning microscope analysis was carried out to get an insight to the structural morphology of the catalyst. The catalyst was found to be very active for the degradation of methyl orange dye using a very small amount of catalyst (0.006 g) using ultra violet radiation source. Approximately, 90% of the dye (Initial Conc. 10 mg L−1) was degraded in 60 min at natural pH (6.5). The dye degradation increased with increase in pH of the solution, due to the enhanced production of OH radicals, at higher pH values. Different experimental parameters like catalyst amount, agitation speed, initial pH of the solution, initial concentration of dye and recycling of the catalyst were varied to test the performance of the catalyst.

Effects of rotation speed and time, as solvent removal parameters, on the physico-chemical properties of prepared α-tocopherol nanoemulsions using solvent-displacement technique

A bottom-up approach based on solvent-displacement technique was used to prepare α-tocopherol nanoemulsions. Effects of two main evaporation parameters namely, rotation speed (1 × 10-9 × 10 rpm) and rotation time (5-15 min) of utilized vacuum rotary evaporator, on the mean particle size, polydispersity index (PDI) and α-tocopherol degradation of the formed nanodroplets were evaluated using response surface methodology. Obtained results suggested three polynomial regression models for predicting the studied response variables' affected by selected evaporation parameters. Relatively high coefficients of determination for suggested models (> 0.7839) confirmed the suitability of the generated models. Multiple-optimization procedure revealed that the optimum amounts of evaporation speed and time were 30 rpm and 10 min, respectively, which in that, prepared spherical α-tocopherol nanoemulsions had mean particle size, PDI and concentration values of 48.9 nm, 0.232 and 358.7 mg/L, respectively.

Green approach in food nanotechnology based on subcritical water: effects of thyme oil and saponin on characteristics of the prepared oil in water nanoemulsions

Thyme oil in water nanomulsion was prepared under subcritical water conditions using water and saponin, as solvent and emulsifier, respectively. Gas chromatography revealed that there were 44 bioactive components in the extracted thyme essential oil which, thymol and carvacrol were two mains of them. Experiments were designed based on central composite design and effects of amounts of saponin and thyme essential oil were evaluated on particle size, polydispersity index (PDI) and zeta potential of the prepared nanoemulsions using response surface methodology. Obtained results revealed that more desirable thyme oil nanoemulsions with minimum particle size (184.51 nm) and PDI (0.514), and maximum zeta potential (- 22.51 mV) were prepared using 0.94 g of saponin and 0.28 mL of thyme essential oil. Furthermore, results indicated that prepared nanoemulsion using obtained optimum production conditions had relatively high antioxidant activity (24%) and high antibacterial and antifungal activities against Staphylococcus aureus and Penicillium digitatum.

Preparation of Ginger Oil in Water Nanoemulsion Using Phase Inversion Composition Technique: Effects of Stirring and Water Addition Rates on their Physico-Chemical Properties and Stability

Ginger oil in water (O/W) nanoemulsions, were produced using phase inversion composition method and Tween 80, as emulsifier. Effects of processing parameters namely, stirring rate (100 to1000 rpm) and water addition rate (1–10 mL/min) were evaluated on the physico-chemical, morphological, antioxidant and antimicrobial properties of the prepared O/W nanoemulsions using response surface methodology (RSM). Results indicated that well dispersed and spherical ginger nanodroplets were formed in the nanoemulsions with minimum particle size (8.80 nm) and polydispersity index (PDI, 0.285) and maximum zeta potential value (−9.15 mV), using stirring rate and water addition rate of 736 rpm and 8.18 mL/min, respectively. Insignificant differences between predicted and experimental values of the response variables, indicated suitability of fitted models using RSM. Mean particle size of the prepared nanoemulsion using optimum conditions were changed from 8.81 ± 1 to 9.80 ± 1 nm, during 4 weeks of storage, which revealed high stability of the resulted ginger O/W nanoemulsion. High antioxidant activity (55.4%), bactericidal (against Streptococcus mutans) and fungicidal (against Aspergillus niger) activities of the prepared nanoemulsion could be related to the presence of gingerols and shogaols, a group of phenolic alkanones, in the ginger oil, which those were detected by gas chromatography method.