Ana Serrano-Martínez

Use of cyclodextrins to recover catechin and epicatechin from red grape pomace

The capacity of cyclodextrins (CDs) to extract phenolic compounds from grape pomace was evaluated and compared with that of ethanol/water or aqueous extraction. The extraction method (stirring and ultrasound), temperature and time were also studied. Total phenolic compounds (TPC) and antioxidant activity were measured, and HPLC analysis was used to identify the phenolic compounds. The extracts obtained using the ethanol/water mixture presented the highest TPC content and antioxidant activity, followed by those obtained using CD solutions. The addition of CDs to the extractant agent had a selective effect on the extraction of catechin and epicatechin. The yield of catechin and epicatechin by using aqueous solutions of CDs was similar to that obtained using organic solvents as ethanol.

Effect of ripening on protein content and enzymatic activity of Crimson Seedless table grape

The evolution of °Brix, protein content, polyphenoloxidase activity and peroxidase activity during the ripening of Crimson Seedless table grape was studied in three consecutive years (2006, 2007 and 2008). The total protein content was determined according to Bradfords dye binding method, and polyphenoloxidase (PPO) and peroxidase (POD) were extracted using Triton X-114 and characterised using spectrophotometric methods. The year had a statistically significant effect on all the studied parameters and there was an interannual correlation in the evolution of protein, PPO, POD and °Brix. All the studied parameters were statistically correlated, except POD activity with protein content. Weather conditions during the ripening period had a greater effect on protein content than PPO and POD activity.

Kinetic characterisation and thermal inactivation study of red alga (Mastocarpus stellatus) peroxidase

Peroxidase (POD) was extracted from red alga (Mastocarpus stellatus) using Triton X-114 and characterised by UV-spectrophotometry. Optimum activity using 2,2´-azinobis(3-ethylbenzothiazolinesulphonic acid) (ABTS) as the H-donor was obtained at pH 5.0. In the presence of the anionic detergent, sodium dodecyl sulphate (SDS), however, POD was inactivated at all the pH values studied and totally inactivated at 1mM SDS. When the enzyme was kinetically characterised, the KM and Vm values for ABTS were found to be 13mM and 40μM/min, respectively. In addition, when the H2O2 concentration was increased, at a fixed concentration of ABTS, the activity was inhibited at the highest H2O2 concentrations. In a study of the effect of several reducing agents, l-cysteine was found to be the most active. A thermal inactivation study showed a first-order inactivation kinetic, and the Arrhenius plot yielded a straight line with a slope equivalent to an activation energy of 121.6kJ/mol. Significant inactivation occurred at temperatures of>35°C, with>90% of the relative activity being lost after only 5min of incubation at 48.4°C.

Optimization of a method for preparing solid complexes of essential clove oil with β‐cyclodextrins

BACKGROUND Clove oil (CO) is an aromatic oily liquid used in the food, cosmetics and pharmaceutical industries for its functional properties. However, its disadvantages of pungent taste, volatility, light sensitivity and poor water solubility can be solved by applying microencapsulation or complexation techniques. RESULTS Essential CO was successfully solubilized in aqueous solution by forming inclusion complexes with β-cyclodextrins (β-CDs). Moreover, phase solubility studies demonstrated that essential CO also forms insoluble complexes with β-CDs. Based on these results, essential CO-β-CD solid complexes were prepared by the novel approach of microwave irradiation (MWI), followed by three different drying methods: vacuum oven drying (VO), freeze-drying (FD) or spray-drying (SD). FD was the best option for drying the CO-β-CD solid complexes, followed by VO and SD. CONCLUSION MWI can be used efficiently to prepare essential CO-β-CD complexes with good yield on an industrial scale.

Fluorimetric determination of sulphathiazole in honey by means the formation of CDs inclusion complexes

The inclusion complex of sulphathiazole in β-cyclodextrin has been investigated. A 1:2 stoichiometry of the complex was established and formation constants K2 (42.83 ± 3.27 M(-1)) and K1 (4.98 ± 0.36 M(-1)) were calculated by using the changes produced on the native fluorescence of the drug, when included on the hydrophobic cyclodextrin cavity. An enhancement in the fluorescence emission of sulphathiazole and protection of the drug against photochemical reactions has been attained upon inclusion. In solutions of β-CD dual emission (458 nm) was noticed in STZ. Formation of the inclusion complex of STZ should result in dual emission, which is due to a twisted intramolecular charge transfer band (TICT). A fluorimetric method for the determination of sulphathiazole has been proposed and applied in honey without sample treatment. The optimized fluorimetric method showed detection and quantitation limits of 9.74 ng/g and 32.48 ng/g, respectively. Selectivity is high, showing no cross-reactivity to other chemically related antibiotics. The results obtained for blind honey samples (mean recovery 97%), were in good agreement with those obtained by liquid chromatography separation and mass spectrometry detection (LC-MS) (mean recovery 102%), showing that the proposed method might be used for the determination of sulphathiazole residues without expensive equipment.

EFFECT OF CYCLODEXTRIN AND EXTRACTION METHOD ON PHENOLIC COMPOUNDS EXTRATION FROM RED WINE POMACE

Extraction of phenolic compounds has been always conditioned to the use of organic solvents. An alternative to reduce the use of organic solvents in phenolic compounds extraction can be the cyclodextrins (CD). This work aims to determine the effect of cyclodextrins and extraction method on the extraction of phenolic compounds and antioxidant capacity of extracts. Phenolic extractions were made from Monastrel red variety pomace. Extractions were made by ultrasound and microwave at 50oC during 10’ with aqueous solutions of a-, b-, g-, HP-a-, HP-b-, HP-g-CD 50 mM, water and ethanol/water (1:1 v/v). Total phenolic compounds, procyanidins, flavanols, favonols and antioxidant capacity were measured. The final extraction of total phenolic compounds and antioxidant capacity obtained by using cyclodextrins were higher than those obtained by using water, but lower than those obtained by using ethanol/water. Microwave extraction extracted 75% more of total phenolics than ultrasound. Moreover, CDs had a selective effect on phenolics extraction. Extraction of flavanols and flavonols with CDs were similar to those obtained by using etanol/water. Type of CDs had also a great effect on favonols extraction. In conclusion, CDs could be used as an alternative to organic solvents for the extraction of specific phenolic compounds from pomace.

YIELD AND FRUIT QUALITY RESPONSE OF SWEET PEPPER GENOTYPES GROWN UNDER SOILLESS CULTIVATION

Total yield, physical, and phytochemical characterization of three yellow and five red-colored sweet pepper genotypes were analyzed under fully controlled environmental and irrigation conditions under soilless culture. Results showed both greater fruit firmness and pericarp thickness in the red-colored genotypes than in the yellow ones. However, no significant differences between these two colors were found for total yield, shape index and dry matter percentage. Additionally, peroxidase activity, total protein and total phenolic compounds were not modified according with the color of the genotype. With respect to the genotypes studied, ‘Cierva’, ‘A67’, ‘Traviatta’, ‘Cabezo’ and ‘Limona’ showed the highest yields in the “extra” fruit category whilst ‘Disco’ and ‘Zar’ showed the lowest. Additionally, ‘Cierva’ and ‘Cabezo’ showed higher protein concentration and peroxidase activity than any other genotype.