red varieties shall be covered with a good shade of solid red characteristic of 
variety for the extra fancy grade; 40 percent for U. S. Fancy; and 25 percent 
for U. S. No. 1. The requirements for the striped partially red varieties are; 
25 to 66 percent for extra fancy, 10 to 33 percent for U. S. Fancy, and from 
tinge to 25 percent for U. S. No. l. 
Lott (43) in his discussion of fruit maturation and ripening pointed out 
the very good use to which reflectance spectrophotometry could be put to 
characterize the color of yellow varieties of apples and showed how the Munsell 
color system offered a means of expression of the resultant color data from 
spectrophotometry. 
In Lott's work (42) reflectance curves were drawn for Transparent and 
Duchess varieties showing differences with advancing maturity great enough to 
indicate the possibility of establishing maturity standards on the basis of 
ground color. 
Many workers (20, 10, 27, 51, 52, 84, 78, 80, 66, 42) have shown the 
value of ground color as an Ge as of maturity. — Stoll (78) developed a chart 
for the Jonathan variety varying from light green to yellow, similar to the 
USDA ground color chart (50) but including one additional color. 
Smock (73) showed that amount of surface or red color on McIntosh apples 
was a poor index of maturity, but that ground color was one of the best indices, 
While there was some range from year to year, he thought that a ground color 
chart developed by F. W. Southwick for McIntosh improved this index. 
Porritt and Fisher (66) evaluated ground color of Golden Delicious by 
comparison of samples with Ridgeway color plates, 
Dayton (14) studying the distribution of red color in the skin of apples 
used the Nickerson Color Fan (57) to make visual comparisons with the color in 
individual cells of the epidermal and hypodermal layers of many varieties of 
apples. He found an apparent range in color from Munsell renotation 10 RP 
3/10, deep purplish red, to 2.5 R 9/3, pale pink, including all varieties under 
study. 
Aubert (1) reported a good relation between fruit quality and time of 
picking utilizing color plates of the International Color Code to assign some 
objectivity to visual comparison data. 
Lott (46) describes the development of his color standards for Golden 
Delicious apples which became a part of Illinois State grades for maturity in 
July 1959. These standards were developed from analysis of spectral reflec- 
tance curves of a large number of fruit evaluated over several years at various 
stages of maturation. Lott (47) reports that because of allowable variability 
in color and associated quality constituents, the apple grades widely used for 
packing Golden Delicious are unreliable as indices of degree of quality. He 
suggests that the use of color standards, such as the Illinois maturity 
standards, would provide standardization within practical limits and the 
elimination of low quality apples from packs thus making each grade designation 
an index of the degree of quality within the package, : 
Color measurement of apples has been made objective by the application 
of reflectance colorimeters and more recently by the light transmittance tech- 
nique of measurement of the intact fruit. 
Miller (54) in a rather comprehensive study of the relation of plastid 
pigments to color in Transparent and Golden Delicious varieties described a 
method whereby percent reflectance measurement of apple skin at 676 nm could 
be converted into weight of chlorophyll per unit area by means of standard 
curve prepared for the particular variety. He suggested that the standard 
curves might be the basis for maturity standards. In his work heavy 
8 
