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Eric A. Curry

Within red cultivars, highly colored apples are often preferred. In addition to being esthetically more appealing. better color often indicates riper, better tasting fruit. Anthocyanin synthesis in apples is influenced by many external factors including light, temperature, nutrition, pruning, thinning, growth regulators, and bagging. Bagging is the practice of enclosing young fruitlets in several layers of paper to promote color development after the bag is removed in the fall before harvest. In experiments related to the temperature optimum of color development in various cultivars, bagging was used to produce fruit void of anthocyanins. Double layer paper bags (black-lined outer bag, red inner bag) were placed on `Akafu-1 Fuji', `Oregon-Spur Delicious', and the early coloring `Scarlet Spur Delicious' on June 21, 1993. Bags were not removed until fruit was taken to the lab on September 22 for both `Delicious' and `Fuji'. Whereas bagged `Fuji' apples were without red pigment, bagged `Delicious' sports showed considerable red pigment development, completely covering the apple in the case of the blush-type `Scarlet Spur' and showing streaks without pigment in the snipe-type `Oregon-Spur'.

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Jungmin Lee, Chad E. Finn and Ronald E. Wrolstad

The total anthocyanin and total phenolic content of wild (samples from 4 populations) and cultivated (samples from 32 populations) Pacific Northwestern American Vaccinium species (V. membranaceum, V. ovalifolium, and V. deliciosum) were evaluated. The total monomeric anthocyanin content of all huckleberry samples analyzed ranged from 101 to 400 mg/100 g (expressed as cyanidin-3-glucoside), and the total phenolics varied from 367 to 1286 mg/100 g (expressed as gallic acid). Cluster analysis separated the samples into four different groups based on their anthocyanin and total phenolic content. Two groups had greater anthocyanin pigment and total phenolics; one consisted entirely of cultivated V. ovalifolium (LIG10, VAC485, VAC487, LIG33, LIG9, LIG2, and VAC349) and the other consisted of just cultivated V. membranaceum (LIG25). Significant variations in total anthocyanins, total phenolics, and the ratio of the total anthocyanins and total phenolics were observed among the different V. membranaceum, V. ovalifolium, and V. deliciosum populations cultivated in the Willamette Valley, Ore. The profile of the individual anthocyanins of the wild V. membranaceum, wild V. ovalifolium, and V. corymbosum `Rubel' were conducted by high-performance liquid chromatography. The chromatograms of V. membranaceum, V. ovalifolium, and `Rubel' were distinctly different in the amounts of delphinidin, cyanidin, and malvidin glycosides.

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Deirdre M. Holcroft, Maria I. Gil and Adel A. Kader

`Wonderful' Pomegranates (Punica granatum L.) were placed in jars ventilated continuously with air or air enriched with 10 or 20 kPa CO2 at 10 °C for 6 weeks. Samples were taken initially and after 1, 2, 4, and 6 weeks, and postharvest quality attributes were measured. The arils of the pomegranates stored in air were deeper red than the initial controls and than those stored in CO2-enriched atmospheres. This increased color was associated with increased anthocyanin concentration. Arils from fruit stored in air enriched with 10 kPa CO2 had a lower anthocyanin concentration than air-stored fruit, and atmospheres enriched with 20 kPa CO2 had even lower levels, possibly from suppressed anthocyanin biosynthesis. Anthocyanin concentration correlated well with the activity of phenylalanine ammonia lyase but not with glucosyltransferase activity. Moderate CO2 atmospheres (10 kPa) prolong the storage life and maintain quality of pomegranates, including adequate red color intensity of the arils.

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D.M. Holcroft, M.I. Gil and A.A. Kader

Carbon dioxide-enriched atmospheres are used to reduce decay incidence and severity and extend the postharvest life of strawberries. However, depending on the cultivar, carbon dioxide concentrations of ≥20% can be detrimental to color (change from red to purple) and flavor (development of off-flavors). Our objective was to determine the effect of elevated carbon dioxide levels on the stability of the anthocyanins and other phenolic compounds to examine their role in color changes of strawberries. Freshly harvested strawberries were placed in jars ventilated continuously with air or air enriched with 10%, 20% or 40% carbon dioxide at 5°C for 10 days. Anthocyanins and other phenolics were extracted at 0, 5, and 10 days from homogenized samples. The samples were purified using Sep-pac C18 cartridges. The purified methanolic extract was injected directly into HPLC coupled to a photodiode array detector. Cyanidin-3-glucoside, pelargonidin-3-glucoside, and pelargonidin-3-rutinoside were identified as the major anthocyanins. After 5 and 10 days in storage there was a reduction in the total amount of anthocyanins. This degradation was lower in air than in carbon dioxide-treated strawberries, but the anthocyanin profile remained the same. Flavonols (e.g., quercetin and kaempferol derivatives) and phenolic acids (e.g., ellagic acid) decreased during storage, and this decrease was exacerbated by elevated carbon dioxide atmospheres. Carbon dioxide-induced changes in the quantities of the previously listed anthocyanins and phenolic compounds may be the cause of color changes from red to purple in strawberries.

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Deirdre M. Holcroft, Maria I. Gil and Adel A. Kader

The influence of CO2 on color and anthocyanin concentration in the arils of `Wonderful' pomegranate (Punica granatum L.) was investigated. Pomegranates were placed in jars ventilated continuously with air or air enriched with 10% or 20% CO2 at 10°C for 6 weeks. Samples were taken initially, and after 1, 2, 4, and 6 weeks and anthocyanin concentration was measured by HPLC. The arils of the pomegranates stored in air were deeper red than those stored in CO2-enriched atmospheres. This increase in red color resulted from an increase in anthocyanin concentration. Arils from fruit stored in air+10% CO2 had a lower anthocyanin concentration than air-stored fruit, and atmospheres enriched with 20% CO2 suppressed anthocyanin biosynthesis. Anthocyanin concentration was well-correlated to the activity of phenylalanine ammonia lyase (PAL), but not to glucosyltransferase (GT) activity. Moderate CO2 atmospheres (10%) prolong the storage life and maintain the quality of pomegranates, including an adequate red color of the arils.

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Wilhelmina Kalt, Christopher Lawand, Daniel A.J. Ryan, Jane E. McDonald, Horst Donner and Charles F. Forney

The antioxidant properties of blueberries have been examined only in ripe fruit, although fruit of different maturities are used in processed food products. In this study, highbush blueberry cultivars Bergitta, Bluegold, and Nelson highbush blueberry fruit at different stages of ripeness were examined to characterize differences in oxygen radical absorbing capacity (ORAC) and the phenolic components responsible for ORAC. Underripe fruit at different stages of maturity were also stored at 20 °C for up to 8 days to assess changes in ORAC and phenolic content. Anthocyanin content was substantially higher in fruit of more advanced stages of ripeness. In contrast, the phenolic content and ORAC were lower in the riper fruit. Anthocyanins continued to form during storage, although rate of pigment formation declined after about 4 days. Less anthocyanin pigment was formed in the less ripe fruit. After 8 days of storage, the anthocyanin content of fruit harvested 5% to 50% or 50% to 95% blue exceeded that of ripe fruit. Up to 60% of the total phenolic content could be accounted for by anthocyanins. ORAC was positively correlated with total phenolic content (R 2 = 0.78), but not with anthocyanin content.

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Aparna Gazula*, Matthew D. Kleinhenz, Joseph C. Scheerens, Peter P. Ling and John G. Streeter

Anthocyanins (Antho) are the source of red color in plants and the intensity of redness is an important quality parameter in red leaf lettuce. Despite the importance of Antho in leaf lettuce, little information is available regarding the effects of major production-related factors, such as planting date, on their levels. To address this issue, field studies were conducted in 2002 and 2003 in which Antho levels were measured in nine lettuce varieties planted in early and late summer (ES and LS, respectively) using a RCB design. Leaf tissue was sampled 30 d after transplanting. Data for three strongly related Lolla Rossa-type varieties (`Lotto', `Valeria', `Impuls') are reported here. The planting date × variety interaction was significant; however, Antho concentrations were higher following planting in LS than ES, regardless of variety. Planting date effects were more pronounced in 2002, when differences in average daily temperature between ES and LS plantings tended to be larger. Regardless of planting date and year, Antho levels followed the pattern `Impuls' (three genes) > `Valeria' (two genes) > `Lotto' (one gene). Correlations between human visual and two types of instrumented assessments of color are being tested in samples from the same study.

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Su-Jeong Kim*, Chun-Woo Nam, Dong-Lim Yoo, Seung-Yeol Ryu and Ki-Sun Kim

Iris hollandica `Blue Magic' was treated with deionazed water as a control, 3% sucrose (Suc), 3% sucrose plus 0.4 mm silver thiosulphate (Suc+STS), 3% sucrose plus 200 mg·L-1 8-hydroxyquinoline sulphate (Suc+HQS) and 3% sucrose plus 100 mg·L-1 benzyl amino-purine (Suc+BA) for 4hrs and then transferred to tap water. The vase life treated with Suc+BA was extended 4 days longer than that of control. The treatment Suc+STS or Suc+HQS did not improve vase life. The amounts of water uptake and transpiration by all treatments decreased after harvest, but those values were higher in cut iris treated with Suc+BA than in those with control. Cut flowers treated with by Suc+BA markedly improved water balance, comparing with control which was quickly changed to minus value. Anthocyanin content in petals of cut flower treated with Suc+BA was 3.5 fold higher than that of control. The treatment by Suc+BA delayed discoloration in petals and senescence of cut Iris. Peroxidase (POD) activities of all treatments were reached maximum at 4th day after treatment and decreased thereafter. POD activity was highest when the cut iris was treated with Suc+BA. These results show that the use of Suc+BA is most effective treatment for improving the vase life and quality of cut Iris flowers.

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Aparna Gazula, Matthew D. Kleinhenz, John G. Streeter and A. Raymond Miller

Pigment concentrations in leaf tissue affect the visual and nutritional value-based indices of lettuce crop quality. To better discern the independent and interactive effects of temperature and cultivar on anthocyanin and chlorophyll b concentrations, three closely related Lolla Rosso lettuce cultivars (`Lotto', `Valeria', and `Impuls'), varying primarily in the number of genes controlling anthocyanin concentrations, were subjected to different air temperatures in controlled environments. Fifteen-day-old seedlings previously grown at 20 °C day/night (D/N) were transplanted into growth chambers maintained at 20 °C (D/N), 30/20 °C D/N and 30 °C D/N air temperatures. Twenty days later, leaf tissue was sampled for measures of pigment concentrations, calculated based on spectrophotometric absorbance readings taken at 530 nm (anthocyanin) and 660 nm (chlorophyll b) respectively. Although significant, the temperature × cultivar interaction resulted from differences in the magnitude (not direction) of the change in pigment concentrations among cultivars with changes in temperature. Regardless of cultivar, anthocyanin and chlorophyll b concentrations were highest, moderate and lowest after growth at 20 °C D/N, 30/20 °C D/N and 30 °C D/N respectively. Likewise, irrespective of temperature, anthocyanin and chlorophyll b concentrations followed the pattern `Impuls' (three genes) > `Valeria' (two genes) > `Lotto' (one gene). These data provide additional strong evidence that lettuce leaf pigment concentrations and growing temperatures are negatively related. The data also suggest that low temperatures during the dark phase may mitigate high temperature-driven reductions in lettuce leaf pigment levels.

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Carolyn E. Lister, Jane E. Lancaster and John R.L. Walker

Phenylalanine ammonia-lyase (PAL) activity was measured in a range of New Zealand-grown apple (Malus domestica Borkh.) cultivars at three stages of fruit development. Anthocyanin and total flavonoid levels were also measured (by HPLC) in the same fruit. There was wide variation in the level of PAL activity, anthocyanin and total flavonoid levels in different apple cultivars and at different stages of development. There was no apparent correlation between average PAL activity over the three developmental stages and final anthocyanin concentration (r = 0.34, P > 0.1), but there was significant correlation between average PAL activity over the three developmental stages and the final concentration of total flavonoids (r = 0.75, P < 0.02). An inhibitor, PAL-IS, was also assayed in the same fruit but no correlation was found between PAL-IS and final anthocyanin levels (r = -0.30, P > 0.1) or total flavonoid levels (r = 0.15, P > 0.1). These results suggest that PAL activity has an influence on total flavonoid levels in the fruit but that PAL-IS does not. Anthocyanin levels are likely controlled at a point in the flavonoid pathway other than PAL or PAL-IS.