Betaxanthin-Rich Extract from Cactus Pear Fruits as Yellow Water-Soluble Colorant with Potential Application in Foods

Cactus pear (Opuntia ficus-indica) fruit juice is a source of betaxanthin pigments which can be used as a natural yellow food colorant. The HPLC chromatographic pigment pattern corresponding to the betaxanthin-rich extract revealed the presence of four betaxanthins, of which indicaxanthin (proline-betaxanthin) accounts for around 85%. A betaxanthin-rich water-soluble food colorant from cactus pears fruits was produced by spray-drying microencapsulation using maltodextrin as a wall material. The resulting powder was characterized by scanning electron microscopy, and its apparent color was analyzed by spectrometry. The stability of the microcapsules was examined at +20, +4 and??20 °C in the dark during six months of storage. The degradation of betaxanthins was delayed by microencapsulation and their colorant stability increased at lower temperatures. The potential application of the colorant microcapsules was successfully assessed in two food model systems: a yogurt and a soft-drink. Both foods presented an attractive pale yellow color. Pigment retention and color parameters were investigated during storage under controlled conditions. Slight changes in the pigment retention, in both model systems, pointed to excellent preservation in the dark, even after 28 days at 4 °C. However, the presence of light contributed to betaxanthin deterioration. Spray-drying microencapsulation succeeds in reducing volumen of the pigment extract and can be easy in storage and delivery of the powders. It is proved to be a suitable process that can be recommended for stabilizing betaxanthins from cactus pears to be used as water-soluble natural colorants in foods.     

Relationships between Levels of Lead,Cadmium, Zinc,and Copper in Soil and Settleable Particulate Matter in Cartagena (Spain)

In this article we report the relationships between heavy metals(Pb, Cd, Zn, Cu) in soil and settleable particulate matter usingdata from 6 yr at six different sampling points withinCartagena, a Spanish Mediterranean city. The use of enrichmentfactors and factor analysis allowed us to predict the majorsources of these metals. Soils were classified as one of threetypes: soils from polluted zone L, soils from polluted zone Z,and non-polluted soils. Settleable particulate matter was alsoclassified in the following three groups: Industrial zone, Urbanzone, and Intermediate zone. Enrichment factors showed that soilsfrom polluted zone L are enriched in Pb and Cd when compared with soils from polluted zone Z, and soils from polluted zone Zare enriched in Zn and Cu when compared with soils from pollutedzone L. In this context, soils from polluted zones L and Z areidentified as specific sources of metals in the settleableparticulate matter samples. We also suggest the importance ofanthopogenic contribution of metals to soil-enrichment fromancient times up to the present. This process was most severeduring the XIX century, when our city suffered an importantindustrial development. The concentration of these heavy metalsare also affected by regional meteorological conditions, whichinclude scarce rainfalls and a significant wind dispersion ofsoil aerosols.     

Thermal Stability of Selected Natural Red Extracts Used as Food Colorants

The color degradation of aqueous solutions of six natural red pigment extracts (elderberry, red cabbage, hibiscus, red beet, Opuntia fruits and red cochineal) used commercially as food colorants was investigated at temperatures between 50 and 90 °C. Color degradation was studied in respect to both spectral properties and visual color. The remaining absorbance at 535 nm as a function of the incubation time and temperature was used to quantify the degradation process. Red cochineal was the most thermoresistant extract with a remaining absorbance of 95 % after 6 h at 90 °C. Anthocyanin extracts (elderberry, red cabbage, hibiscus) showed remaining absorbance percentages of 63.8, 46.1 and 26.7, respectively. Betacyanin extracts (red beet, Opuntia fruits) were the most thermosensitive maintaining only 12.5 and 1.7 %, respectively, of the initial absorbance at 535 nm. Applying a first-order kinetic model to the degradation processes, reaction rate constants (k) and half-life periods (t _1/2 ) were calculated. The temperature dependence of the degradation rate constant obeyed the Arrhenius relationship, with activation energies (E _a ) ranging between 3.02 and 53.37 kJ?mol^?1. The higher activation energy values indicated greater temperature sensitivity. Changes in visual color attributes corroborated the high thermal stability of the red cochineal extract.