Adsorption-desorption of phenolic compounds from olive mill wastewater using a novel low-cost biosorbent.

Several materials have been investigated for the adsorption of olive mill wastewater phenolic compounds. However, researchers have focused on the development of novel, low-cost, with high adsorption capacity adsorbents, originated from the food industry as by-products. The aim of this work was the investigation of the effectiveness of a juice industry by-product, pomegranate seed, for the adsorption of olive mill wastewater phenols. Furthermore, chemical activation and thermal activation of the adsorbent took place in order to improve total phenols uptake and afterwards, desorption process in hydrochloric acid was studied. After the determination of equilibrium time, the effects of temperature (20-60 °C), solution's pH (4.0-8.0), initial sorbate concentration (50-500 mg/L), sorbent mass concentration (0.01-0.05 g/mL OMW), and sorbent particle size (0.149-1.180 mm) on adsorption yield were studied performing batch experiments. The maximum phenols uptake observed was 92.8% after 10 min, at 30 °C and a pH of 5.0, with an initial sorbate concentration of 162.5 mg/L, a sorbent mass concentration of 0.02 g/mL, and a sorbent particle size of 0.922 mm. Langmuir, Freundlich, and Temkin isotherms were developed for the equilibrium description, while pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were applied to investigate adsorption kinetics. The experimental data were best fitted to the Langmuir model, whereas the kinetic data followed the pseudo-first-order kinetic model. The results of the study were promising indicating that pomegranate seed could be used as a novel and low-cost biosorbent. Graphical abstract.

Stability of pomegranate peel polyphenols encapsulated in orange juice industry by-product and their incorporation in cookies.

Orange juice by-products are proposed as a "green" wall material for the encapsulation of pomegranate peel extract. Stability of crude and encapsulated peel extract was studied under accelerated storage conditions, in terms of phenolic content, antiradical activity, and color. The obtained extracts were used as biofunctional components in cookies, at a phenolics concentration of 5000 ppm. Their effects on phenolics content, antioxidant activity, color, and sensory attributes during baking and storage were examined. It was observed that a large amount of phenolic compounds was degraded during baking even if they were coated. However, encapsulation had a significant effect (p < 0.05) on the retention and the activities of phenolic compounds as compared to non encapsulated. Moreover, the results showed that the extracts could be incorporated in cookies without negatively affecting sensory quality.

A natural approach in food preservation: Propolis extract as sorbate alternative in non-carbonated beverage.

Propolis extract was investigated as potential substitute for sorbate in orangeade. Extract was prepared by using aqueous solution of hydroxypropyl-beta-cyclodextrins. Propolis extract was incorporated in non-carbonated orange soft drinks and its antioxidant activity, microbiological stability and color changes were estimated and compared to those of orangeade containing potassium sorbate. l-Ascorbic acid (AsA) degradation at concentrations 0.13 and 1.3% w/w was investigated in the presence of propolis during storage using High Performance Liquid Chromatography-Ion Exclusion Column (HPLC-IEC). The results indicate that the rate of degradation decreased with an increase in ascorbic acid concentration, while addition of propolis affected the degradation rate of samples containing a high AsA concentration. The antifungal effect of propolis extract, potassium sorbate and their combination was assayed. Results showed the inhibition of Aspergillus spp. and B. bruxellensis inhibited in low combined concentrations antimicrobials, while Aspergillus spp. and T. macrosporus were inhibited at 450 mg/g propolis extract.

Development and characterization of a new encapsulating agent from orange juice by-products.

The replacement of maltodextrins as carriers for the spray drying of sticky and sugar based bioactives is an important development for the food industry. In this work, orange juice industry by-product was used to obtain a high dietary fiber powder to be used as carrier material. This powder was characterized with respect to its physical and chemical properties related to the process of encapsulation by spray drying. Adsorption isotherms of orange waste powder were determined at 30, 45, and 60°C. The data were fitted to several models including two-parameter (BET, Halsey, Smith, and Oswin), three-parameter (GAB), and four-parameter (Peleg) relationships. The GAB model best fitted the experimental data. The isosteric heat of sorption was determined from the equilibrium sorption data using the Clausius-Clapeyron equation. Isosteric heats of sorption were found to decrease exponentially with increasing moisture content. The enthalpy-entropy compensation theory was applied to the sorption isotherms and indicated an enthalpy controlled sorption process. Glass transition temperatures (Tg) of orange waste powder conditioned at various water activities were determined and a strong plasticizing effect of water on Tg was found. These data were satisfactory correlated by the Gordon and Taylor model. The critical water activity and moisture content for the orange waste powder were 0.82 and 0.18g water/g solids, respectively, at a storage temperature of 25°C.

Green ultrasound-assisted extraction of carotenoids from pomegranate wastes using vegetable oils.

The objective of this work was to develop a new process for pomegranate peels application in food industries based on ultrasound-assisted extraction of carotenoids using different vegetable oils as solvents. In this way, an oil enriched with antioxidants is produced. Sunflower oil and soy oil were used as alternative solvents and the effects of various parameters on extraction yield were studied. Extraction temperature, solid/oil ratio, amplitude level, and extraction time were the factors investigated with respect to extraction yield. Comparative studies between ultrasound-assisted and conventional solvent extraction were carried out in terms of processing procedure and total carotenoids content. The efficient extraction period for achieving maximum yield of pomegranate peel carotenoids was about 30min. The optimum operating conditions were found to be: extraction temperature, 51.5°C; peels/solvent ratio, 0.10; amplitude level, 58.8%; solvent, sunflower oil. A second-order kinetic model was successfully developed for describing the mechanism of ultrasound extraction under different processing parameters.

The effect of influent temperature variations in a sedimentation tank for potable water treatment--a computational fluid dynamics study.

A computational fluid dynamics (CFD) model is used to assess the effect of influent temperature variation on solids settling in a sedimentation tank for potable water treatment. The model is based on the CFD code Fluent and exploits several specific aspects of the potable water application to derive a computational tool much more efficient than the corresponding tools employed to simulate primary and secondary wastewater settling tanks. The linearity of the particle conservation equations allows separate calculations for each particle size class, leading to the uncoupling of the CFD problem from a particular inlet particle size distribution. The usually unknown and difficult to be measured particle density is determined by matching the theoretical to the easily measured experimental total settling efficiency. The present model is adjusted against data from a real sedimentation tank and then it is used to assess the significance of influent temperature variation. It is found that a temperature difference of only 1 degrees C between influent and tank content is enough to induce a density current. When the influent temperature rises, the tank exhibits a rising buoyant plume that changes the direction of the main circular current. This process keeps the particles in suspension and leads to a higher effluent suspended solids concentration, thus, worse settling. As the warmer water keeps coming in, the temperature differential decreases, the current starts going back to its original position, and, thus, the suspended solids concentration decreases.