The extraction of anthocyanins present in the skin of the dragon fruit was performed using trifluoroacetic acid (TFA) plus a mixture of methanol, acetic acid and water; the anthocyanins were then purified with a LC-18 cartridge, using methanol acidified with TFA as eluent, reaching concentrations of 44.3865 ± 1.3125 mg/100g of sample. The extracts were put through stability tests under different storage conditions, modifying the pH of the extracts (pH of 1, 4 and 6), the temperature (4˚C, 25˚C and 68˚C) and the absence and presence of light for a time period of 4 days; the tests indicated that anthocyanins remain more stable at a temperature of 4˚C with a pH of 4 in the absence of light, retaining up to 80% of the pigment. Three anthocyanins were partially identified in the extracts by high performance liquid chromatography (HPLC); they were: cyanidin 3-O-glucoside, cyanidin 3,5 O-glucoside and pelargonidin 3,5 O-glucoside.

En este trabajo se evaluaron algunos cambios físicos y químicos que ocurren durante el crecimiento y maduración del fruto de pitahaya (Hylocereus undatus), para definir el estado de madurez al corte que dé mejor calidad organoléptica y mayor aceptación por el consumidor. El desarrollo de los frutos fue en campo, a 26.1 °C y 73.9 mm de temperatura y precipitación media durante el periodo de evaluación. A partir de la apertura de la flor se evaluaron cambios en los diámetros polar y ecuatorial, peso fresco de fruto entero, pulpa y cáscara, y cuando apareció la primera coloración rojiza en la superficie se evaluó color de cáscara, firmeza de la pulpa, contenido de sólidos solubles totales (°Brix), contenido de azúcares reductores, acidez titulable, contenido de ácido ascórbico y percepción sensorial. La maduración ocurrió entre los 25 y 31 d después de la apertura floral, con transición del color de la cáscara de un verde claro con partes de color rojo incipiente a un rojo-púrpura, proceso en el cual hubo reducción de la firmeza. Los contenidos de azúcares reductores y °Brix aumentaron de 2.4 a 6.6 % y de 4.6 a 12.6 %, respectivamente; el contenido de ácido málico disminuyó de 1.4 a 0.4 %, lo que favoreció el aumento de la relación °Brix/acidez; el contenido de ácido ascórbico disminuyó de 14.7 a 9.6 mg/100 g. A los 31 d los frutos medían 8.9 cm en diámetro polar, 8.2 cm en diámetro ecuatorial y 469.2 g en peso. El sabor varió de agridulce a dulce entre los 27 y los 31 d, y la mayor aceptación de los frutos se registró entre los 29 y 31 d.

The browning of fruits can be considered as an enzymatic oxidation which is believed to be one of the main causes of quality loss during post-harvest handling. The enzymes responsible for this are the oxidoreductases; the polyphenol oxidase (PPO) (monophenol, o-diphenol, oxygen oxidoreductase; EC 1.14.18.1) belongs to this group. This enzyme, which is found in the sapodilla plum (Achras sapota), was purified using a phenylsepharose and a SephacrylS-200 columns. The molecular weight of the purified enzyme was estimated to be about 66 kDa by gel filtration and 29 kDa by SDS-PAGE. A single protein band was found using the latter system (SDS-PAGE), which shows that the PPO of the pulp of the sapodilla plum may be composed of two protein subunits with similar molecular weight. The optimum pH was 7.0 and the optimum temperature 60˚C. The most effective inhibitors tested were ascorbic acid, sodium metabisulfite and acetic acid.

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Starch is widely used in industry. However, it must be modified to improve its properties and broaden its applications. The objective of this study was to investigate the effects of reaction time and pH on the main properties of oxidized Ramon starch (OS). Samples of native Ramon starch (NS) were oxidized with sodium hypochlorite (3.0 g active chlorine/100 g starch) at reaction times and pHs varying from 30 to 120 min and 8 to 11, respectively, according to a central composite rotatable design. The results were analyzed using a response surface methodology (RSM). Reaction time and pH had a significant effect on the carboxyl group content and color of the Ramon starch gel. The appearance of NS granule was similar to OS. Oxidation was more intense in starch treated at a pH of 11.6 and a reaction time of 75 min. The optimal conditions to obtain a whiter starch gel (L* = 41.5) were a reaction time of 86.4 min and a pH of 10.6. The OS showed lower values of total phenolic compounds compared to NS. The oxidation of NS with sodium hypochlorite can be used to obtain a whiter starch with different properties and broaden its potential applications in industry