|Abstract or Summary
- A fruit color descriptive study was conducted on 'Max' and 'Sensation'
Red Bartlett, 'Columbia' and 'Gebhard' Red Anjou, 'Rogue Red', 'Rosired',
'Red Clapp' and 'Cascade' red pear varieties. A parallel comparative study was
done to test differences between related red strains. 'Max' was compared with
'Sensation' in three different growing regions: Medford, Hood River high
elevation and Hood River low elevation, while 'Columbia' was compared with
'Gebhard' in two locations: Medford and Hood River. The effect of modifying
temperature by evaporative cooling and of light quality on color of 'Sensation'
Red Bartlett pears were also evaluated. Anthocyanins of red pear skin were
characterized and quantified and their concentrations were related to fruit
In all the studies fruit color was measured with a portable tristimulus
colorimeter using the Commission Internationale de I'Eclairage color space (L*,
a* and b*) coordinates at four times during fruit maturation. Visual percentage
of blush was also evaluated. Evaporative cooling was done with overtree
sprinkler irrigation. Skin anthocyanins were extracted with acetone, isolated with
polyvinylpyrrolidone (PVPP) and recovered in 1% methanolic Hcl. The extract
was analyzed using high-performance liquid chromatography (HPLC) and thin-layer
chromatography (TLC). Monomeric anthocyanin content was determined in
an aqueous extract using a pH differential method. To study the effect of light
quality on color development, gelatin filters of different spectral transmittance
were attached over the exposed side of 'Sensation' pear fruits one month before
harvest. Chromaticity was recorded before the filters were placed and at harvest
after their removal. Following color measurements, anthocyanins were extracted
from individual skin disks.
In the descriptive study, every strain presented different color
development. Hue, chroma and L* increased with maturity in fruits of all
varieties except for 'Rogue Red' and 'Rosired'. 'Rosired' had the biggest change
in hue during maturity and 'Cascade' had the smallest. 'Columbia' and
'Gebhard' showed the smallest change in chroma and 'Rogue Red' had the
highest gain in L* value. There were high differences in color between exposed
and shaded fruit surfaces and at each stage of maturity for every variety. In
the variety comparison study various interactions were found among the main
factors: growing location, variety, surface of the fruit and stages of maturity.
Gain in chroma, hue and L* with maturity was higher in 'Max' than in
'Sensation', higher in Medford than in the other growing regions, and higher on
the shaded sides of fruit than on the exposed ones. Increase in chroma, hue and
L* value with maturity was higher in Hood River for 'Columbia' than for
'Gebhard', while the opposite was observed in Medford. Shaded fruit surfaces
had higher chromaticity values.
Evaporative cooling promoted red skin color. However, the increase in
coloration may have been due in part to advanced maturity stimulated by the
HPLC and TLC analyses confirmed the presence of a major and a minor
pigment which coeluted with cyanidin 3-galactoside and peonidin 3-galactoside.
The average content of anthocyanins in red pear skins was 6.83 mg/100 g of fruit
In the light quality study all filters yielded less hue than the control.
Wavelengths above 600 nm had the largest effect in chroma. Aluminum wrapped
fruit had the highest luminosity. Wavelengths form 400 to 500 nm gave darker,
less chromatic and redder pear fruit. All treatments especially longer
wavelengths yielded higher anthocyanin content than the control.