Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 55-3
Title: Measurement of the color of citrus products
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Permanent Link: http://ufdc.ufl.edu/UF00072364/00001
 Material Information
Title: Measurement of the color of citrus products
Series Title: Citrus Station mimeo report
Physical Description: 3, 6 leaves : ; 28 cm.
Language: English
Creator: Huggart, R. L
Wenzel, F. W
Citrus Experiment Station (Lake Alfred, Fla.)
Florida Citrus Commission
Publisher: Florida Citrus Experiment Station :
Florida Citrus Commission
Place of Publication: Lake Alfred FL
Publication Date: 1954
 Subjects
Subject: Citrus juices -- Quality -- Florida   ( lcsh )
Fruit -- Color -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: R.L. Huggart and F.W. Wenzel.
General Note: Caption title.
General Note: "Oct. 12, 1954."
 Record Information
Bibliographic ID: UF00072364
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74326112

Full Text



Citrus Station Mimeo Report 55-3
Oct. 12, 1954


Measurement of the Color of Citrus Products
R. L. Huggart and F. W. Wenzel

Color is an important characteristic of citrus juices and concentrates.
Fruit variety and maturity, processing methods and other factors affect the color
of citrus products. Accurate and practical methods for measurement of the color
of juices and concentrates are desirable so that processors may pack throughout a
season products of uniform color and so that future standards may be established
by regulatory agencies based on data accurately obtained and carefully evaluated.

Since the Hunter Color Difference Meter had been used successfully to measure
color differences in tomato juices, strawberries and other fruit and vegetable
products, this investigation was undertaken to determine if this instrument would
be satisfactory for measuring the color of citrus juices and concentrates and
color differences in these products caused by such factors as fruit variety, pulp
content and storage.

The Hunter Color Difference Meter is a photoelectric tristimulus instrument.
The instrument was standardized using a NBS (National Bureau of Standards) enamel
plaque, test number G13383, with values of Rd = 60.7; a = -2.0; b = 22.7. A No.
8010-100 Hellige glass turbidimeter tube with fused on bottom plate was used as a
sample holder. This tube was approximately 56 mm. inside diameter and 142 nn,. in
height. Approximately 250 ml. of thoroughly mixed product was placed in this
sample holder and readings were made immediately so that separation and settling
of insoluble solids could be kept to a minimum. A large area of illumination, a
large aperture and the Rd scale were used.

Results reported in Tables 1 6 are color difference measurements for dif-
ferent citrus products, using the Hunter Color Difference Meter. Samples listed
in Table 1 were frozen orange concentrates obtained from three commercial plants
during the 1952-53 season. Measurements were made on both the concentrates and
the reconstituted juices. Considering the samples from Plant A, it is evident
that significant differences and trends were found in both the Rd and a values.
The most important trend was the increase in redness in the concentrates as the
season progressed, this being indicated by a gradual increase in the value of a.
The amount of the yellow component in the color did not vary greatly as is shown
by the small changes in the b value. In the samples from Plants B and C the more
significant differences in color were in the red component. In all of these
samples during the first part of the season, when early varieties of fruit were
being processed, the visual color of the reconstituted concentrates was yellow-
green, which changed as the season progressed to a yellow-orange or orange. These
same trends in color, as indicated by data in Table 2, were found in samples of
single-strength canned orange juices that were collected monthly during the 1953-
54 season from some commercial canning plants.

A total of 221 commercial samples were analyzed from 23 concentrate plants in
Florida. From 16 of these manufacturers, which represented the majority of the

Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
529h -10/12/54-RLH








frozen concentrated orange juice production in Florida, 9 to 14 samples were ob-
tained for testing from each processor during the months of December 1953 through
June 1954. This accounted for 177 samples or 80% of the commercial samples re-
ceived. Collection of 2 to 9 samples from each of the other 7 plants accounted
for the remaining 20%. The concentrates and corresponding reconstituted juices
were measured for color and color differences. The frequency with which a given
reading occurred for concentrates is presented in Table 3. Meter readings for
reconstituted juices are presented in Table 4. A characteristic mid-season con-
centrate, inferred from the frequency, would have an Rd value of 21.5, an a value
of 3.5 and a b value of 30.5. A second peak frequency, which would correspond to
a late season concentrate, is found at an Rd value of 18.5, an a value of 7.5 and
a b value of 30.5. A corresponding reconstituted juice would have an Rd value of
17.5, an a value of -5.5 for mid-season fruit or an a value of -3.5 for late sea-
son fruit, and a b value of 27.5.

Color differences between fresh citrus juices extracted from different va-
rieties of fruit are demonstrated by data presented in Table 5. Juice from the
Hamlin orange, an early variety, contained the smallest amount of redness, and was
predominantly yellow-green. Juice from Dancy tangerine, which had a dark orange
color, had a value for a of -1.8 indicating the largest amount of redness in any
of the juices examined. The grapefruit juices contained loss yellow component
than the orange juices as signified by the lower b values. The principal differ-
ence between the color of Hamlin orange juice and the grapefruit juices was in
the quantity of the yellow component.

The data included in Table 6 show that the amount of pulp, which consists
chiefly of particles of juice sacs, rag and albedo, does affect the color of con-
centrated citrus juices.

Color differences in blends of several reconstituted citrus concentrates are
shown in Table 7. The blending of Valencia orange concentrate with concentrated
juices made from early varieties of oranges, such as the Hamlin, results in a
product having a more intense orange color than that of a concentrate made entire-
ly from Hamlin oranges. Measurements with the Hunter Color Difference Meter
definitely show the increase in the yellow and red color components that result
when blends of orange and grapefruit juices are made. When Hamlin orange juice
is blended with Duncan grapefruit juice the resulting blend shows only an increase
in yellowness, whereas when Valencia orange juice is mixed with the grapefruit
juice an increase results in both redness and yellowness.

Data in Table 8 definitely indicate that there was little change in the color
of canned single-strength Pineapple or Valencia orange juices during storage of
these products for one year at various temperatures. Slight color changes in
canned grapefruit sections occurred after storage at 700F. for one year and a
marked darkening of this product was indicated in samples stored for one year at
800F. and 900F.

Color differences in fresh and processed citrus juices and concentrates
Occur because-of such factors as fruit variety, pulp content and storage. Al-
though these color differences can be objectively measured with the Hunter Color

Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
529i -10/12/54-RLH






-3-


Difference Meter, neither this instrument nor any other instrument now available
is satisfactory for determining objectively the actual visual color of a citrus
juice as seen by an observer.

The Hunter Color Difference Meter can be used to investigate changes that
take place in processed citrus products during processing and storage. It is
also useful for measuring color variations in commercial products to provide data
which may be used as the basis for establishing future quality standards.











































Florida Citrus Experiment Station and
Florida Citrus Commission, Lake Alfred, Fla.
529j -10/12/54-RLH








TABLE 1
Color measurements by the Hunter Color Difference Meter of frozen
orange concentrates obtained from Florida plants during the
1952-53 season


Concentrates
RA a b


Reconstituted Juices


Plant A


Date
packed


1-28-53
2- 6-53
3-13-53
3-24-53
4- 3-53
4-29-53
5- 8-53


1-27-53
2-11-53
3-12-53
3-21-53
4-30-53
7-13-53


1-26-53
2-12-53
3- 7-53
3-13-53
3-28-53
4-29-53


3.1
3.1
4.2
5.1
6.3
6.7
5.8


29.6
30.1
30.2
30.3
29.3
28.7
28.5


18.3
19.1
17.8
17.0
17.2
16.6
16.7


Plant B


3.2
3.0
4.2
6.7
5.6
6.9


29.7
30.3
29.5
29.4
30.2
30.2


18.8
20.3
19.6
18.1
19.0
18.3


21.3
20.1
18.4
18.9
17.6
15.9
15.8


18.8
19.7
17.5
17.2
19.0
18.6


21.0
20.7
21.3
19.8
19.1
19.5


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 529-10/12/54-RLH


Plant C
2.2 31.2 20.6
2.7 30.6 19.8
4.0 31.5 21.0
5.9 31.2 20.3
5.9 30.8 19.5
7.4 31.2 20.1


-6.7
-6.6
-5.9
-5.4
-4.2
-3.9
-4.4


-5.8
-6.5
-5.7
-3.7
-5.1
-3.6


-7.2
-7.1
-5.8
-4.2
-4.3
-2.9


25.8
26.6
27.4
26.8
27.1
27.2
26.4


26.4
26.9
28.1
27.6
27.1
27.2


27.3
26.7
27.9
28.9
28.6
29.0


-










TABLE 2
Color measurements by the Hunter
Meter of canned orange juices


Color Difference
obtained from


Florida plants

Month Rd a b
obtained
October 1953 22.6 -7.9 25.2
November 22.7 -7.1 26.3
December 24.2 -6.2 27.4
January 1954 21.5 -5.0 27.7
February 21.7 -4.5 29.3
March 24.5 -3.6 30.0
April 22.2 -2.4 29.2
May 20.5 -1.9 28./+


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 529a-10/12/54-RLH












TABLE 3
Hunter Color Difference Meter Values
Frequency Table
Concentrated orange juices obtained from Florida Plants
during the 1953-54 season


Rd
27.0-27.9
26.0-26.9
25.0-25.9
24.0-24.9
23.0-23.9
22.0-22.9
21.0-21.9
20.0-20.9
19.0-19.9
18.0-18.9
17.0-17.9
16.0-16.9
15.0-15.9
14.0-14.9


0.90
1.82
3.18
3.64
5.91
8.18
15.46
12.72
13.63
15.00
12.73
5.00
0.92
0.91


a
1.1-2.0
2.1-3.0
3.1-4.0
4.1-5.0
5.1-6.0
6.1-7.0
7.1-8.0
8.1-9.0
9.1-10.0


3.64
10.46
20.46
17.27
9.54
10.91
16.82
8.18
2.72


b
34.0-34.9
33.0-33.9
32.0-32.9
31.0-31.9
30.0-30.9
29.0-29.9
28.0-28.9
27.0-27.9
26.0-26.9
25.0-25.9


1.36
5.00
8.19
23.64
30.00
22.27
7.27
1.81

0.46
0.46


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 529b-10/12/54-PLH












TABLE 4
Hunter Color Difference Meter Values
Frequency Table
Reconstituted orange juices obtained from Florida plants
during the 1953-54 season


Rd
24.0-24.9
23.0-23.9
22.0-22.9
21.0-21.9
20.0-20.9
19.0-19.9
18.0-18.9
17.0-17.9
16.0-16.9
15.0-15.9
14.0-14.9


0.91
2.27
4.54
10.00
12.73
15.91
19.09
21.82
9.55
2.73
0.45


-a
7.0-7.9
6.0-6.9
5.0-5.9
4.0-4.9
3.0-3.9
2.0-2.9
1.0-1.9


%
1.36
20.00
27.73
12.72
17.27
16.81
4.11


b
29.0-29.9
28.0-28.9
27.0-27.9
26.0-26.9
25.0-25.9
24.0-24.9
23.0-23.9


%
3.64
12.73
44.54
30.00
8.18
0.45
0.46


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 529c-10/12/54-RLH













TABLE 5
Color measurements by the Hunter Color Difference Meter
different varieties of citrus fruits


Variety


Hamlin
Pineapple
Valencia
Temple


orange
If


Duncan grapefruit
Marsh ,
Ruby Red "

Dancy tangerine


14.3
15.7
15.0
12.5

12.6
10.3
10.8

17.1


-8.0
-6.5
-5.3
-5.4

-7.4
-7.0
-1.8

-1.8


19.2
24.3
26.1
22.4

6.2
6.4
8.6

26.8


of juices from


Visual Color
Yellow green
Light orange
Orange
Orange


Light
Light
Pink


green-yellow
green-yellow


Dark orange


TABLE 6
Color measurements by the Hunter Color Difference Meter of experimental
citrus concentrates containing different amounts of pulp

Variety Reconstituted Juices Concentrates
Pulp-% volume Rd a b
Pineapple orange 5 11.8 0.1 24.4
6 12.2 0.8 24.9
8 12.8 1.2 25.2
8 13.1 1.3 25.5
Duncan grapefruit 3 3.2.4 -6.7 13.3
5 13.3 -6.6 14.0
t 6 14.2 -6.6 14.5
9 15.5 -5.9 15.5
Dancy tangerine 3 14.1 7.2 26.6
3 14.6 8.1 27.0
4 14.7 8.7 27.2
5 15.2 9.3 27.5


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 529d-10/12/54-RLH


__














TABLE 7
Color measurements by the Hunter Color Difference Meter of blends of
reconstituted citrus concentrates
,


Hamlin* Valencia


Rd
13.5
13.4
13.5
13.4
13.4
13.3
13.3
13.3
13.5
13.2
13.8


a
-7.8
-7.4
-6.9
-6.3
-6.0
-5.1
-4.6
-4.3
-3.9
-3.2
-2.6


b
21.8
22.1
22.6
22.9
23.3
22.6
22.9
23.7
24.0
23.7
24.5


Duncan* Hamlin


Rd
11.6
11.3
11.7
11.6
11.3
11.4
11.9
11.7
11.7
12.6
11.7


a
-7.5
-8.1
-8.3
-8.3
-8.5
-7.9
-8.1
-7.7
-7.4
-7.3
-7.2


b
4.1
8.9
12.2
14.4
16.2
17.0
18.6
19.1
19.3
20.9
20.8


Duncan* Valencia


Rd
11.6
11.4
11.5
11.6
12.1
1.2.4
13.0
13.0
13.2
13.5
14.4


a
-7.5
-7.8
-7.4
-6.8
-6.3
-5.8
-5.1
-4.5
-3.9
-3.5
-3.1


b
4.1
12.6
16.4
18.2
20.2
21.6
22.5
23.3
24.1
24.3
24.6


TABLE 8
Color measurements by the Hunter Color Difference Meter of processed
citrus products after storage at different temperatures

Storage
12 mo. Pineapple Orange Juice Valencia Orange Juice Grapefruit Sections
OF. Rd a b Rd a b Rd a b
32 23.1 -4.9 28.4 21.2 -3.8 27.5 24.5 -7.4 15.3
60 23.5 -5.1 28.5 21.4 -3.6 28.1 25.0 -7.2 15.8
70 23.5 -4,9 28.3 21.3 -3.6 28.3 25.1 -6.3 17.0
80 22.9 -4.8 29.0 21.2 -3.6 28.3 22.9 -4.8 17.0
90 -- 19.5 -2.7 27.5 17.3 -1.2 18.2


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 529f-10/12/54-RLH


Blend
% volume
100*
90
80
70
60
50
40
30
20
10
0




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