AGRICULTURAL EXTENSION SERVICE
TESTING ORANGES FOR PROCESSING
What Every Grower Should Know
Boxes or Juice-Pounds Solids for Cannery Fruit?
M. J. SOULE, JR.
Associate Professor, Fruit Crops Department, University of Florida
College of Agriculture
FRED P. LAWRENCE
Citriculturist, Florida Agricultural Extension Service
Each season canneries in Florida process about three fourths
of the orange crop into frozen concentrate, chilled juice, single-
strength juice and other products. Fruit for single-strength
juice and similar uses is commonly purchased by weight. Oranges
of the highest possible internal quality are desired for frozen
concentrate since, in addition to having better flavors and aroma,
yields rise rapidly as the quantity of juice and pounds of total
Fig. 1.-Equipment and materials for maturity tests.
soluble solids per box increase. Most plants buy their fruit for
concentrate on this basis. It is also a profitable arrangement for
the grower because higher fruit quality is rewarded by a com-
mensurate return. Today, the grower who sends oranges to the
concentrate plant is no longer producing merely boxes but rather
juice and pounds of solids per acre.
The steps through which oranges pass as they are received
at the cannery and put into bins are of interest to everyone con-
cerned. Each load of fruit is weighed and then evaluated by
Federal-State inspectors of the Citrus and Vegetable Inspection
Division, Florida Department of Agriculture, in cooperation with
the United States Department of Agriculture. Inspection of a
representative sample ensures that only sound, wholesome
oranges which meet legal maturity standards are processed.
At the same time, the information provided by the tests is uti-
lized by the cannery to determine whether the fruit is suitable
for concentrate purposes, how the load should be blended with
other oranges as they are processed in order to maintain a uni-
form product, and finally, the basis upon which payment to the
seller will be made.
Minimum legal requirements for maturity of oranges used
for processing are set forth in the Florida Citrus Code of 1949,
as amended, and in the regulations, rules and orders of the
Florida Citrus Commission.
Maturity of citrus fruit in Florida is based on five factors:
color break caused solely by nature (excludes sunburn, insect
damage, etc.), juice content, total soluble solids, acid and ratio
of total soluble solids to acid. The standard box of oranges con-
tains 1/5 bushels and weighs 90 pounds. The crop year extends
from August 1 to July 31. In the case of oranges used in proc-
essed forms, the season is divided into two periods. From Au-
gust 1 through November 30, when comparatively few plants are
in operation, the requirements are the same as for natural-color
fruit shipped in fresh form. During the remainder of the year,
December 1 through July 31, there are no requirements for
color break, juice content or minimum acid. The complete sched-
ule is shown on page 3 in condensed form.
The cannery is required to equip and maintain a room in a
convenient location for inspectors. Testing facilities include
running water, a sink and drainboard, electric lights, and at
least one 110 to 115 volt power outlet. The bench-type fruit
reamer and other equipment used for official maturity tests are
shown in Figure 1. Because of the number and size of samples,
most processing plants provide a mechanical juice extractor and
finishing equipment of the same type used in their commercial
operations. Scales suitable for weighing samples of fruit and
juice are also provided. All of the equipment is handled care-
fully and washed regularly. Frequent checks are made to en-
sure uniformity and accuracy of results in the test procedures.
FACTOR Aug. 1- Nov. 1- Nov. 16- Dec. 1-
Oct. 31 Nov. 15 Nov. 30* July 31
Color break.......... 50%** 50%** 25% none
Juice......... ......... 4.5 gal.t 4.5 gal. 4.5 gal. none
Solids................ 9.0% 8.7% 8.5% 8.0%
Acid...................... 0.4% 0.4% 0.4% none
Ratio...................... 8.00-1 8.00-1 8.00-1 8.00-1
Required ratio...................................See below ......-.... ......
Period extends through July 31 for fruit shipped in fresh form.
** Parson Brown 25%.
t Per box.
Minimum Required Ratio
Solids Not Less Than Minimum Ratio
12.0% or above 8.00
For each increase of 0.1% in total soluble solids, there is a decrease of
0.05 in minimum required ratio.
Each load of oranges is weighed upon arrival at the process-
ing plant, and the net weight of fruit is obtained. Weight is then
converted into number of boxes by dividing by 90.
A representative sample of the entire load of fruit is taken
as the truck is unloaded. This is done by means of a mechanical
sampler which removes an orange at intervals. The fruits are
then weighed. The official sample for maturity test purposes
consists of at least one fruit per 10 boxes or not less than 10
oranges. In practice, a larger sample of about one-half box, or
40 to 45 pounds, is taken from the average-sized load. The reason
for this is that the cannery wishes to have the more nearly
exact information on internal quality, particularly juice content,
solids, and acid which a smaller sample will not provide.
Prior to December 1 each season, oranges must meet speci-
fied color-break requirements. Color of skin, along with other
factors, is indicative of the progress of ripening in citrus fruit.
A dark green color is associated with immaturity; therefore
oranges must show some orange or yellow coloration caused solely
by nature before they are legally mature. The test is made by
comparing individual fruit in a sample with a standard color disk.
Oranges delivered to a cannery between August 1 and De-
cember 1 must contain a minimum of 4.5 gallons of juice per
box. There is no requirement during the remainder of the year.
1. 185 -13.5
- 1. 093-
1. O01- 11. 5
5 o\ e
Fig. 2.-Nomograph for determining pounds of solids per box and pri
^ ~ ~
Price Per Pound
.(Adapted from Florida Citrus Mutual "Triangle", Vol. 6, No. 16.)
Juice is extracted from the fruit in the previously weighed sam-
ple. A mechanical extractor is used to squeeze out the juice
which is then freed of excess pulp and seeds by passing it through
a finisher. The quantity of juice per box may be expressed as
either pounds or gallons. The former is preferred, since it is a
more exact figure. Figuring gallons of juice per box is subject to
some inaccuracy because the weight per gallon varies according
to the percentage of total soluble solids present. Pounds of
juice and gallons of juice per box are calculated as follows:
weight of juice
(1) Pounds of juice per 90-pound box = X 90.
weight of sample
For example, if the fruit sample weighs 40 pounds and the juice ex-
tracted from it weighs 20 pounds, a 90-pound box contains X 90 = 45
pounds of juice. 40
weight of juice
(2) Gallons of juice per 90-pound box = ---- X
weight of sample
weight of juice per gal.
For example, if the fruit sample weights 40 pounds and the juice ex-
tracted from it weighs 20 pounds and a gallon of juice (containing 12.0%
solids) weighs 8.72 pounds, a 90-pound box contains X 5.16
gallons of juice. 40 8.72
The yield of juice from oranges is affected by a large number
of factors, among them variety, rootstock, soil type, cultural
practices, temperature and rainfall. Most oranges at prime ma-
turity contain from 45 to 52 pounds or 5 to 6 gallons of juice
TOTAL SOLUBLE SOLIDS OR BRIX
Orange juice contains a large number of soluble constituents,
the chief ones being sugars. Other important compounds are
citric acid, vitamin C, vitamin A and essential oils. About 85
percent of the total soluble solids are sugars and they are meas-
ured as such by means of a Brix hydrometer. This instrument,
which really indicates specific gravity, is calibrated to read di-
rectly in degrees Brix or percent of sucrose, at a temperature of
17.5 C. The term "solids" is subject to some confusion, as
orange juice always contains a certain amount of rag, pulp, bits
of seeds and other substances which are insoluble. These are
"insoluble solids". The term "Brix", or "degrees Brix", is fre-
quently used instead of total soluble solids.
Legal requirements for total soluble solids show a step-wise
decrease from 9.0 percent early in the season to 8.0 percent on
and after December 1. Oranges used for concentrate generally
measure 11 to 12 percent and above. The test for total soluble
solids is made by inserting a Brix hydrometer and a thermometer
into a tall cylinder filled with juice. After a few minutes to
permit the hydrometer to come to rest, it and the thermometer
are read. The appropriate temperature correction is added to
or subtracted from the hydrometer reading to give the proper
value at 17.5 C.
Fig. 3.-Making a citrus maturity test.
Pounds of total soluble solids per box are obtained by calcula-
tion. The percentage total soluble solids (degrees Brix) is multi-
plied by the pounds of juice per box. For example, if a box con-
tains 45 pounds of juice and 12 percent total soluble solids, there
are 45 X 0.12 5.40 pounds total soluble solids. If the quantity
of juice is given in gallons per box, pounds of total soluble solids
are obtained by multiplying gallons of juice by pounds of solids
per gallon (at the given percentage of total soluble solids). For
example, if a box contains 5.16 gallons and 1.047 pounds of total
soluble solids per gallon (at 12 percent), there are 5.16 X 1.047
5.40 pounds total soluble solids per box.
Orange juice contains chiefly citric acid, with smaller amounts
of malic, tartaric and succinic acids also present. A known
volume of juice is pipetted into a flask, a few drops of indicator
solution (phenolphthalein) are added, and the mixture is titrated
with a standard solution of sodium hydroxide to a pink endpoint
(Figure 3). The percentage of acid present in the juice is then
calculated from the amount of alkali consumed.
RATIO OF TOTAL SOLUBLE SOLIDS TO ACID
Ratio is the proportion of total soluble solids to acid. It is
determined by dividing percent total soluble solids by percent
acid. For example, if the juice contains 12 percent total soluble
solids and 1 percent acid, the ratio is 12 to 1. Desirable ratios
for oranges used by concentrate plants are from 12 to 1 to 18 to 1.
CERTIFICATE OF INSPECTION
After the tests for maturity and internal quality are com-
pleted in a satisfactory manner, the inspector will issue an in-
spection certificate for the load of fruit which was sampled.
The certificate shows the pounds (or gallons) of juice per box,
total soluble solids (degrees Brix), percent acid, and ratio. A
copy is furnished to the cannery and one may be given to the
grower if he makes suitable arrangements.
PRICE PER BOX
The price per box delivered to the processing plant is obtained
by multiplying pounds total soluble solids per box by the price
per pound. For example, if a box contains 5.40 pounds of total
soluble solids and the price is 40 cents a pound, the delivered-in
price is 5.40 X $.40 = $2.16.
The nomograph, Figure 2, can be used to obtain price per box
directly. A ruler is laid on the left side of the nomograph to
connect the proper values for total soluble solids and either
pounds (red) or gallons (black) of juice per box. The point on
the pounds-solids-per-box line is marked. The ruler is then
moved over to the right side to connect the point on the pounds-
solids line with the proper price per pound solids. The price per
box may then be marked.
Note.-An example of how the nomograph may be used is
shown by the dashed line in red.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida,
Florida State University and United States Department of Agriculture, Cooperating
M. O. Watkins, Director