Adsorption of hesperidin from aqueous solutions on styrene-divinylbenzene (SDVB) and acrylic resins was investigated at different pH values (1.5-5.5) and temperatures (10-40 degrees C). Adsorption was not affected by pH variation, whereas it increased on increasing temperature for the SDVB resins and remained substantially unchanged for the acrylic ones. The different behavior of the two types of resins was ascribed to the different wetting, because of their hydrophobic or partially hydrophilic properties, respectively. The equilibrium data at 20 degrees C were determined on 13 commercial resins displaying a wide range of surface areas (S(A), 330-1200 m(2)/g) and pore radii (P(R), 20-260 A). Data were well fitted to the Freundlich isotherm, and its parameters were used to compare the adsorption capacity of different resins. The most effective resin is a SDVB copolymer with the largest S(A) (1200 m(2)/g) and an intermediate P(R) (90 A). The Freundlich constants (K(F)) were rationalized in terms of a two parameter equation, including S(A) and P(R) as independent variables. The adsorption constant increased on increasing both S(A) and P(R) for the resins having P(R)

This paper describes a new procedure for obtaining hesperidin from the waste orange peel of the citrus industry. It is based on the adsorption of dilute extracts of hesperidin on a styrene-divinylbenzene (SDVB) resin and the desorption in much more reduced volumes by means of alkaline eluents. Hesperidin immediately precipitates with good yield and high purity after acidification of the concentrated solutions, thus overcoming disadvantages due to the high dilution. Different experiments were carried out to examine operating conditions in each phase of the process. Hesperidin was extracted from peel with an aqueous saturated Ca(OH)(2) solution, allowing precipitation of calcium pectates from colloidal pectins that can interfere in the subsequent phases of adsorption and separation of hesperidin. The clear extracts were neutralized to optimize adsorption on resin. The most effective eluent was 0.5 N NaOH solution containing 10% ethanol. Recycling of the crystallization liquor improved the yield and purity of the product and reduced the acid amount required for neutralizing fresh alkaline extracts. Resin must be washed after each adsorption-desorption cycle and regenerated after five cycles. Results can constitute a useful starting point for an industrial application. A flow scheme of the process is also reported.

Adsorption of cyanidin-3-glucoside in aqueous batch solutions was studied at pH 3.5 and 20 degrees C using 13 commercial resins with different hydrophobicity, surface areas (SA, 330-1200 m2/g), and pore radii (PR, 20-260 A). The solute affinity toward different resins was described in terms of Langmuir and Freundlich parameters; experimental data were well-fitted to the two isotherms, which were both utilized to compare resins adsorption capacity. The styrene-divinylbenzene EXA-118 resin (SA, 1200 m2/g; PR, 90 A) showed the maximum effectiveness among the tested resins; a good efficacy for removing cyanidin 3-glucoside was shown also by EXA-90 (SA, 630 m2/g; PR, 105 A). Some experiments on a styrene-divinylbenzene resin and an acrylic one demonstrated that adsorption was not influenced by pH variations of the solution within the range of 1.0-4.5. For the 10 resins having PR < or = 105 A, correlation analysis evidenced the linear increasing dependence of Freundlich constant KF on physical characteristics of surface area and pore radius. The adsorption of cyanidin 3-glucoside at 20 degrees C was compared with that of hesperidin performed in batch runs on the same resins. Moreover, the best resin (EXA-118) was tested with a sample of pigmented orange juice to assess its performance in terms of selectivity, adsorption, and desorption capabilities on a real matrix.

A pulp wash (PW) coming from a plant for citrus processing of pigmented oranges was utilized as a starting material to recover anthocyanins, using the procedure of concentration on resin. Six commercial food-grade resins were tested to find the more suitable ones for adsorbing anthocyanins, and 96% ethanol was used as eluent for desorbing them. An automated experimental apparatus was developed to perform the adsorption-desorption procedure on column. The kinetics results in a batch system and experiments on column showed that the more efficient resins are those made of styrene-divinylbenzene having a pore radius ranging from 70 to 150 A and a surface area from 600 to 800 m(2)/g, namely, Sepabeads SP 70 and Relite EXA 90. The richest fractions collected from these resins contained about 95% of the anthocyanins in a volume of about 2% of the loaded PW. The HPLC profile of the desorbed anthocyanins is the same as that in PW. These fractions contain other phenol compounds, such as hesperidin and derivatives of hydroxycinnamic acids, in remarkable amounts. Ethanol can be easily removed from the solution and recycled, thus affording a much more concentrated product which can find application as a food colorant or antioxidant ingredient for a nutritional integrator.

This paper describes a procedure for recovering hesperidin from the waste water of orange juice processing, namely, yellow water, by concentration of diluted extracts on styrene-divinylbenzene resin. Turbid raw material flowing out from centrifuges of essential oil separation contains considerable amount of hesperidin ( approximately 1 g/L) mainly associated with solid particles. Yellow water was treated with calcium hydroxide until pH 12 to solubilize hesperidin, filtered, neutralized at pH 6, and loaded on resin up to saturation. Desorption with 10% ethanol aqueous solutions at different NaOH concentrations (0.23-0.92 M) assured high concentration of hesperidin in selected fractions (10-78 g/L), from which it precipitated in high yield and purity immediately after acidification at pH 5. Best results were obtained using 0.46 M NaOH as eluent: 71.5% of the adsorbed hesperidin was desorbed in 300 mL, with an overall 64% yield of isolated product at 95.4% purity (HPLC). These experiments can constitute a useful starting point for an industrial application.