Showing papers by "Francisco A. Tomás-Barberán published in 1999"

Effect of postharvest storage and processing on the antioxidant constituents (flavonoids and vitamin C) of fresh-cut spinach.

Abstract: The effect of modified atmosphere packaging (MAP) and cooking on the flavonoids and vitamin C content (ascorbic + dehydroascorbic acid; AA + DHAA) of fresh-cut spinach was evaluated. The total flavonoid content (approximately 1000 mg kg(-)(1) f.w.) remained quite constant during storage in both air and MAP atmospheres, while vitamin C (750 mg kg(-)(1)f.w.) was better preserved in MAP-stored spinach. AA was transformed to DHAA during storage, and its concentration was higher in MAP-stored tissues. The free-radical scavenging activity of the isolated flavonoids was tested, and only those flavonoids with either a dihydroxyl grouping or acylated with ferulic acid showed significant activity. A decrease in the total antioxidant activity was observed during storage, particularly important in MAP-stored spinach. The higher content of DHAA and lower content of both AA and antioxidant flavonoids in the MAP-stored samples could explain this antioxidant activity decrease. Boiling extracted 50% of total flavonoids and 60% vitamin C in the cooking water. However, flavonoid glucuronides were extracted more in the cooking water than the other glycosides. The vitamin C content of the cooked tissue was higher in those samples stored in MAP.

Color Stability of Strawberry Jam as Affected by Cultivar and Storage Temperature

Abstract: The stability of three strawberry cultivars was evaluated for changes in jam color quality during processing and storage at 20 degrees, 30 degrees and 37 degrees C for 200 days. Anthocyanin content was determined by HPLC. The effect of cultivar, processing and storage on jam pigments, instrumental color (L*, a*, b*) and consumer preference were also determined. 'Oso grande' jam had the lowest anthocyanin concentration (110 mg/g f.w), higher monomeric pigment degradation during processing and storage, highest pH, least desirable color score from the sensory panel and shortest shelf-life. Similarities were found between jams prepared with 'Chandler' and 'Tudla' cultivars, as well as initial differences in total anthocyanin concentrations (195 and 130 mg/g f.w.).

Evolution of juice anthocyanins during ripening of new selected pomegranate (Punica granatum) clones

Abstract: For five new clones of pomegranate, culti- vated under homogeneous conditions, changes in juice anthocyanin contents during ripening were studied. Six anthocyanin pigments were found to be responsible for the red color of pomegranate juice. These were quanti- tatively and qualitatively analyzed by high-performance liquid chromatography and identified as delphinidin 3- glucoside and 3,5-diglucoside, cyanidin 3-glucoside and 3,5-diglucoside and pelargonidin 3-glucoside and 3,5-di- glucoside. Generally, there was an increase in juice pig- mentation during fruit ripening. In the early fruit-ripen- ing stages, delphinidin 3,5-diglucoside was the main pigment, followed by cyanidin 3,5-diglucoside, while in the later stages, the monoglucoside derivatives cyanidin 3-glucoside and delphinidin 3-glucoside increased con- siderably. The pelargonidin derivatives were always present in small amounts. Previous studies have shown that six anthocyanins are found in the juice of pomegranates, namely del- phinidin 3-glucoside and 3,5-diglucoside, cyanidin 3- glucoside and 3,5-diglucoside, and pelargonidin 3-glu- coside and 3,5-diglucoside (1). The peel contains only the pelargonidin and cyanidin derivatives, and no del- phinidin is detected (5). Anthocyanin content and evolution during the de- velopment and postharvest storage of pomegranates have been studied previously (1). During the first steps of development the 3,5-diglucosides are the main pig- ments present in the juice, with delphinidin glycosides being the main pigment type, while during the optimum harvesting time, the 3-glucosides are the main pigments and the cyanidin derivatives are the predominant com- pounds. The aim of the present work was to evaluate and quantify the anthocyanin content of five different pom- egranate clones with distinctive quality characteristics (acidity, color stability, etc.), and to follow the changes in juice pigmentation, both qualitatively and quantita- tively, during the development of the fruit. The effect of fruit location in the tree was also studied.

Influence of processing and storage condítions in strawberry jam color

Abstract: Se ha estudiado la influencia que ejerce el tiempo y temperatura de procesamiento y el almacenamiento en confituras de fresa, asi como el efecto que ejerce la luz durante su almacenamiento. El tiempo de ebullicion fue determinante para la obtencion de un producto de calidad, ya que con tiempos superiores a 15 minutos se obtenian confituras poco atractivas. Tambien se observo que la exposicion de las confituras a la luz, durante su almmacenamiento no ejercia una influencia clara en la degradacion de los antocianos ni en el color. En todos los casos no se observo la existencia de relacion proporcional entre la degradacion de antocianos y la alteracion del color. Al mantener la fruta en congelacion durante largos periodos de tiempo (p.e., un ano) se produjeron perdidas de antocianos superiores al 77% sin embargo fueron menores del 20% si se mantenian a -20oC durante 6 meses.

Influence of processing and storage conditions in strawberry jam color / Influencia de las condiciones de tratamiento y de almacenamiento en el color de confituras de fresa:

Abstract: The influence of time and temperature of processing on the color of strawberry jams, and the time and presence of light during their storage is evaluated. Results showed that processing time is the determinant for obtaining color quality products, as boiling for over 15 min has a deleterious effect. The effect of daylight during storage caused insignificant color and anthocyanin losses, when com pared with storage under dark conditions. However, there was no direct relationship between antho cyanin loss during processing and storage and the color observed under any of the assayed condi tions. The freezing of fruit for long periods (one year) for future jam preparation provoked 77% of anthocyanin losses. Nevertheless, fruit could be stored at -20°C for six months, since less than 20% loss of anthocyanins was noted.