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Brian A. Kahn and William G. McGlynn

samples. Duplicates then were averaged to give a final reading for each of the three replications. Readings were taken as CIE L* a* b* values using the D65 Standard Illuminant ( Commission Internationale de l'Éclairage, 1978 ). Hue angle for samples was

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Michele Renee Warmund

of each nut was selected for color measurement. Kernel color (L*, chroma, and hue angle) was recorded using a handheld spectrophotometer (CM-2600d; Konica Minolta Corp., Ramsey, NJ) with a 6-mm-diameter aperture and specular light was included. Two

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Kara Senger Lewallen and Richard P. Marini

The influence of photosynthetic photon flux (PPF) on peach [Prunus persica (L.) Batsch] fruit quality and the relationship between ground color and flesh firmness was studied by performing three experiments. Fruit with varying ground colors were sampled from different canopy positions with varying PPF. Fruit skin color was measured with a tristimulus colorimeter and values for L* (lightness), chroma (brightness), and hue angle (numerical values for color) were calculated for each fruit. Fruit from the canopy exterior generally were larger, had more surface area colored red, had higher soluble solids concentrations, and were darker, duller, and redder than fruit harvested from interior positions. In all three experiments, the relationship between hue angle and fruit firmness was affected by PPF, but the nature of the relationship (linear vs. curvilinear) and the influence of position was not consistent. When fruit were covered with aluminum foil or a section of the fruit surface was covered with duct tape to prevent light-induced red coloration of the skin, the relationship between hue angle and fruit firmness was similar for different canopy positions. Therefore, the relationship between ground color and fruit firmness is influenced by the light environment in which a fruit develops, and not by canopy position. Ground color does not seem to be a good indicator of fruit firmness because fruit with the same hue angle had greatly differing firmnesses.

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Evelyn Marais, Gerard Jacobs, and Deirdre M. Holcroft

`Cripps' Pink' apples (Malus ×domestica 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.

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Peter J. Landschoot and Charles F. Mancino

This study was conducted to determine: 1) if the Minolta CR-310 Chroma Meter can detect color differences among bentgrass (Agrostis stolonifera L., A. capillaris L.) cultivars maintained as a turf; 2) how the CR-310 parameters of hue angle, lightness, and chroma compare with visual color assessments; and 3) if the CR-310 can provide consistent color measurements among evaluators. Differences were detected among cultivars with respect to hue angle, lightness, and chroma. Hue angle and chroma were significantly correlated with visual color assessments when data were averaged across all evaluators. Lightness was not strongly associated with visual color assessment. Differences were found among evaluators for visual color assessment, lightness, and chroma, but not for hue angle measurements. Thus, hue angle appears to be the most consistent CR-310 parameter for measuring color of bentgrass turf. These results indicate that the CR-310 can be used to evaluate the color of bentgrass cultivars maintained as a turf and provides consistent hue angle measurements among evaluators, regardless of experience in rating turf color. The CR-310 is probably best used for measuring relative color differences and may be useful if cultivars of similar color are desired in blended turfs.

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Jonathan Dixon and Errol W. Hewett

Loss of green color (yellowing) in apples (Malus ×domestica Borkh.) is due to chlorophyll breakdown, an enzyme-mediated reaction conforming to first-order kinetics. Nondestructive measurements of yellowing, using a tristimulus chromameter, were related to chlorophyll content for `Cox's Orange Pippin' and `Granny Smith' apples stored at temperatures of 0 to 35 °C. Yellowing determined by rate constant (k) of total chlorophyll and changes in hue angle, as a function of temperature, increased slowly from 0 to 5 °C, increased exponentially from 5 to 20 °C, reached a maximum from 20 to 24 °C, then declined at higher temperatures. Values of k and the rate of change of hue angle were characterized by a modified Arrhenius equation. `Cox's Orange Pippin' apples harvested early had lower k and lower rates of hue angle change than late-harvested fruit. Values of k and hue angle change of `Granny Smith' apples differed between years but not between harvests. The method used to characterize the relationship between yellowing and temperature may describe changes in other important quality attributes of apple fruit during storage and shelf life and help evaluate the efficacy of cool-chain handling and storage systems.

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Morris Ingle and Edwin C. Townsend

Firmness, total soluble solids (TSS), starch concentration (starch index, SINDEX), and surface color (L*, a*, and b*) were measured for 18 `Delicious' apple strains (Malus ×domestica Borkh.) produced in a replicated, randomized planting at the West Virginia Univ. Experiment Farm, Kearneysville. There was a significant difference between 1991 and 1993 for firmness, L* on the blush or outer side (BL*), Bb*, BChroma, a* (nonblush side), hue angle, and Chroma. There were significant differences between strains in firmness and chromaticities and their derivatives, but not TSS or SINDEX. All measurements changed linearly with days after full bloom (DAFB). There were large chromaticity differences between the two sides of the fruit 130 DAFB, but the nonblush side changed more than the blush side, resulting in little difference at 158 DAFB. BL*(Ba*/Bb*) and L*(a*/b*) produced better separation of strains and sides than did Chroma, although the products were significantly correlated with hue angle and Chroma. The nonblush side of `Delicious' fruits should be monitored to obtain the highest percentage of fruit in the highest grades.

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D. Michael Glenn and G.J. Puterka

fruit were weighed and counted in each plot. In 2002, fruit were harvested after optimum maturity and only hue angle was measured. In 2003 and 2004, fruit were harvested at optimum maturity for storage based on firmness, starch index, and soluble solids

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M.S. Tian, C.G. Downs, R.E. Lill, and G.A. King

Ethylene production from florets of `Shogun' harvested broccoli (Brassica oleracea L.var. italica) held at 20C in darkness increased as the sepal tissues yellowed. The pattern of respiration rate and ethylene production from branchlets or entire heads was similar, although the magnitude of ethylene and carbon dioxide production appeared to be diluted by the other fleshy stem tissues. The reproductive structures, stamens and pistil, may have a role in determining the rate of sepal degreening, since removing them from florets reduced the yellowing rate. The pistil and stamens also had 7-fold higher levels of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity and more than double the ethylene production of other tissues within the floret. Stamen ACC oxidase activity was high on the first day after harvest, before yellowing became obvious. Changes in ACC oxidase activity of the pistil and stamens mirrored changes in ACC content in these tissues. The climacteric status of harvested broccoli was confirmed by exposure to 0.5% propylene. Propylene stimulated respiration and ethylene production and accelerated yellowing (measured as chlorophyll and hue-angle decline). Broccoli tissues did not respond to propylene immediately after harvest. In tissues aged in air before treatment, the time for response to propylene was shorter, a result suggesting a change in tissue sensitivity. Ethylene exposure induced a dose-dependent decline in hue angle, with 1 ppm ethylene giving the maximum response.

Open access

Rachel A. Itle, Eileen A. Kabelka, and James W. Olmstead

years. The presence of transgressive segregants for color space values L*, chroma, and hue within families were analyzed using a Tukey test at a 5% significance level for the F 2 , BC 1P1 , and BC 1P2 populations. Additionally, all hue angle values were