Carbon dioxide-induced changes in color and anthocyanin synthesis of stored strawberry fruit

Anthocyanin concentrations increased in both external and internal tissues of 'Selva' strawberries (Fragaria xananassa Duch.) stored in air at 5°C for 10 days, but the increase was lower in fruit stored in air enriched with 10 or 20 kPa CO2. Flesh red color was less intense in CO2 storage than in air storage. Activities of phenylalanine ammonia lyase (PAL) and UDP glucose: flavonoid glucosyltransferase (GT) decreased during storage, with decreases being greater in both external and internal tissues of strawberry fruit stored in air + 20 kPa CO2 than in those kept in air. Activities of both PAL and GT in external tissues of strawberries stored in air + 10 kPa CO2 were similar to those in fruit stored in air, while enzyme activities in internal tissues more closely resembled those from fruit stored in air + 20 kPa CO2. Phenolic compounds increased during storage but were not affected by the storage atmosphere. The pH increased and titratable acidity decreased during storage; these effects were enhanced in internal tissues by the CO2 treatments, and may in turn have influenced anthocyanin expression.Articl

Colour response of 'Cripps' Pink' apples to postharvest irradiation is influenced by maturity and temperature

Preliminary experiments indicated that postharvest irradiation enhanced anthocyanin synthesis in 'Cripps' Pink' apples. Consequently this system was used to understand the effects of maturity and temperature on anthocyanin synthesis. Fruits harvested 5, 4, 3, 2 and 1 weeks prior to predicted commercial harvest did not develop a red blush in response to postharvest irradiation (72h with high-pressure sodium lights at 20°C). Fruits harvested at maturity rapidly developed a red blush in response to irradiation. Mature 'Cripps' Pink' apples harvested from two growing regions were subjected to 120h of irradiation at 6 or 20°C following 0, 2 or 5 days at -0.5°C. Fruits harvested from the cooler area (Ceres) and irradiated immediately showed greater red colouration at 6°C than at 20°C. The difference between the temperatures was no longer significant after fruits have been stored for 5 days at -0.5°C prior to irradiation. Fruits harvested from the warmer area (Grabouw) were consistently redder when irradiated at 6°C than 20°C. In a separate experiment, fruits were stored for 20 days at -0.5°C prior to irradiation at either 6°C or 20/6°C (day/night). The alternating temperature resulted in better colour of fruits from both areas. In a final experiment, well-coloured 'Cripps' Pink' apples were irradiated at 37°C to simulate periods of high temperature that occur in summer. The hue angle of the fruits increased from 29.3 to 48.3° after 144h of light indicating a loss of red colour. The anthocyanin concentration decreased over 50% during the same period. Fruits kept at 37°C in the dark did not lose red colour. © 2001 Elsevier Science B.V.Articl

Postharvest irradiation enhances anthocyanin synthesis in apples but not in pears

'Cripps' Pink' apples (Malus xdomestica Borkh.) subjected to 72 hours of postharvest irradiation developed a better red blush with high pressure sodium (HPS) (hue angle 56.5°) than with UV-B plus incandescent (UVB+I) lamps (hue angle 70.7°). Only HPS lamps were used in subsequent experiments. The increase in red color (hue angle decrease of 14.9°) in 'Braeburn' apples held at -0.5°C for 8 weeks prior to treatment was smaller than in fruit stored for 4 weeks (hue angle decrease of 23°). No increase in color or anthocyanin concentration was observed in 'Forelle' pears (Pyrus communis L.) that were similarly treated. 'Forelle' pears were harvested with or without attached stem and leaves to determine whether precursor availability restricted postharvest color development. Fruit were irradiated with HPS at 20/20°C and 20/6°C (day/night) for 168 hours. The absence of leaves hastened the decrease in hue angle, but this was due to yellowing and not to development of red blush. Since 'Forelle' pears showed no response to light after harvest, two fully red cultivars, Bon Rouge and Red Anjou, were irradiated with HPS lamps for 72 hours. Hue angle was not affected by irradiation. Thus, anthocyanin synthesis was stimulated by postharvest irradiation with HPS lights in apples, but not in pears.Articl

Regulation of Pear Color Development in Relation to Activity of Flavonoid Enzymes

Changes in activity of phenylalanine ammonia-lyase (PAL) and UDPGalactose: flavonoid-3-o-glycosyltransferase (UFGT) during the development of pear (Pyrus communis L.) fruit and in response to cold fronts were assessed and related to changes in red color. Red and blushed pear cultivars attained maximum redness and highest anthocyanin concentrations in immature fruit. Red color generally faded toward harvest UFGT activity increased over fruit development and was apparently not limiting to color development However, the fading of red color and the decreasing level of phenolic compounds toward harvest might relate to decreasing PAL activity. Skin color and enzyme activity in the red pear 'Bon Rouge' displayed little responsiveness to low temperatures. In contrast, low temperatures increased red color and activity of both PAL and UFGT in the blushed pear 'Rosemarie'. Consistent with the general pigmentation pattern described above, the effect of temperature on enzyme activity was much greater early during fruit development than in the week before harvest.Articl

Carbohydrates and postharvest leaf blackening of proteas

Glucose, fructose, sucrose, and starch concentrations were determined in leaves and inflorescences of protea cutflower cultivars soon after harvest and at the onset of leaf blackening while standing in water. At the onset of leaf blackening sugars and starch were lower in both inflorescences and leaves. Proportionately, sugars and starch decreased more in leaves than in inflorescences. Flower-bearing shoots of 'Sylvia' were pulsed individually with 5% glucose solution until each shoot had taken up 10 mL solution. Water served for control treatment. Flowers were then stored for 21 days at 1°C. After pulsing and after cold storage groups of flowering shoots were separated into inflorescence, leaf and stem components and glucose and starch content determined. Glucose content, determined upon completion of pulsing treatments, was significantly greater in all shoot components of shoots pulsed glucose compared with nonpulsed control shoots. Glucose content of leaves was significantly greater after storage for shoots pulsed than control shoots. Starch content of leaves determined upon completion of pulsing treatments was significantly greater in shoots pulsed with glucose than that of controls. There was a significant decrease in starch content for all tissue types during 21 days of storage. Pulsing flower stems of seven protea cultivars before 3 weeks cold storage significantly reduced the incidence of leaf blackening when assessed both on day 1, and again on day 7 after 3 weeks of cold storage. Supplementing holding solutions with 1% or 2% glucose reduced leaf blackening of proteas pulsed with glucose and cold stored for 3 weeks.Articl

High-density orchards improve the quality of 'Songold' plums from lower, more shaded canopy positions

Gel breakdown is a major postharvest problem in 'Songold' plums (Prunus salicina Lindl.) that is exacerbated in fruit harvested from lower canopy positions in large trees. Modern high-density orchards with small trees aggressively address this problem through improved light distribution. Fruit quality was observed over two years from different canopy positions in modern plum orchards trained to high-density V- and spindle systems to determine if the incidence of gel breakdown reported in the lower canopy of large, widely spaced plum trees is reduced. There was no significant difference in incidence of gel breakdown in the top or base of the canopy in any of the experiments. Fruit shaded with 80% shade netting, showed an increased tendency of gel breakdown compared to the exposed control. Effective light management in an orchard can improve plum fruit quality.Articl

Anthocyanin Degradation in Detached Pome Fruit with Reference to Preharvest Red Color Loss and Pigmentation Patterns of Blushed and Fully Red Pears

Exposed fruit of 'Rosemarie' blushed pear (Pyrus communis L.) displayed daily fluctuations in color in response to temperature while color was more stable in other blushed and fully red cultivars. 'Rosemarie' pears increased in redness with the passing of cold fronts, but rapidly lost red color during intermittent warmer periods. Studies on anthocyanin degradation in detached apples and pears indicated that preharvest red color loss was due to net anthocyanin degradation at high temperatures. In support, anthocyanin degradation in attached 'Rosemarie' pears corresponded with a warm period during fruit development. Susceptibility to color loss was dependent on the ability of fruit to accumulate anthocyanin. This is due to an exponential relationship between anthocyanin concentration and hue at high pigment levels and a linear relationship at lower pigment levels. Blushed and red pear cultivars that accumulate more anthocyanin with lesser dependence on climatic conditions were less susceptible to fluctuation in color.Articl