Group Title: Citrus Station mimeo series - Florida Citrus Commission ; 63-2
Title: Relation of specific gravity of whole fruit to the internal quality of oranges
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Permanent Link: http://ufdc.ufl.edu/UF00072409/00001
 Material Information
Title: Relation of specific gravity of whole fruit to the internal quality of oranges
Series Title: Citrus Station mimeo series
Physical Description: 3 leaves : ill. ; 28 cm.
Language: English
Creator: Ting, S. V., 1918-
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: 1962
 Subjects
Subject: Oranges -- Quality -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: S.V. Ting.
General Note: Caption title.
General Note: "October 2, 1962."
Funding: Citrus Station mimeo report ;
 Record Information
Bibliographic ID: UF00072409
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 75259187

Full Text






Citrus Station Mimeo Series 63-2
October 2, 1962


Relation of Specific Gravity of Whole Fruit to the Internal Quality of Oranges

S. V. Ting
Florida Citrus Commission
Lake Alfred, Florida


The use of specific gravity measurement as a criterion for separating frozen
oranges from sound fruit has been successfully employed because frozen oranges
are often drier and thus lower in specific gravity. Fruit with thick peels are
also much lower in specific gravity. In both the frozen fruit and those with
thick peel, the juice content is lower. Although the juice content of a fruit is
the main factor affecting its specific gravity, the soluble solid content of the
juice is also important.

This report shows the relationship of specific gravity and juice character-
istics related to the internal quality of various sizes of both Pineapple and
Valencia oranges. Both correlation and regression of specific gravity to the
pounds-solids factor were studied for fruit of various sizes. Attempts were made
to determine the pounds-solids per 90-lb. box of oranges by the measurement of
their specific gravity.

Material and Methods

Sampling. Both Pineapple and Valencia oranges were picked and sized in
the packing house and samples of 20 to 30 fruit of each size were selected, with
the exception of the two smaller sizes of Valencias, only 17 fruit of size 250
and 10 fruit of size 288 were obtained from h boxes of this variety. The Pine-
apple oranges were harvested in March and the Valencias in April.

Method used in measuring the specific gravity of fruit. A simple technique
for the measurement of specific gravity of individual fruit was developed. A
beaker large enough so that an orange could be submerged in water is filled half-
full of water and tared on a direct reading balance, i.e. Mettler balance. A
fruit is carefully placedcin the water. The increase in weight is that of the
fruit. Since most oranges float, the fruit is pushed below the surface of the
water with a loop of stainless steel rod. The second reading then indicated on
the balance represents the weight of water of equivalent volume to that of the
fruit. The ratio of the first to the second readings is the specific gravity
provided a slight correction is made for the volume of the rod submerged in water.
If the orange is heavier than water, the second reading is obtained by holding
the fruit on the loop while still submerged in the water. This method was found
to be faster and more accurate than the conventional water displacement technique.

Determination of juice content and other juice characteristics. One of the
important factors for determining the pounds-solids of a sample is the juice


Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
10/2/62 SVT











content. For our study, two types of juice extractors have been used to deter-
mine the juice content. In the first series of this study on Pineapple oranges
a hand press-type juice extractor was used. In the second series with Valencia
oranges, a slow turning, electric motor-driven juice reamer was acquired for
that purpose. It was noted that the juice obtained on the reamer contained con-
siderably more pulp than that from the press-type juice extractor. In both cases
the fruit was cut transversely into two halves, and the juice exhaustively ex-
tracted until consecutive weighing of the residue showed relatively insignificant
changes in weight. The difference in weight between that of the fruit and the
residue after extraction was the weight of the juice. Juice content was calcu-
lated as per cent by weight.

The total soluble solids in the juice were determined refractometrically and
the acid titrated. The pounds-solids per 90-lb. box were calculated

Experimental Results and Discussion

The percentage composition of the component parts of various sizes of both
Pineapple and Valencia oranges is shown in Table 1. Since the juice for the two
varieties were extracted on different types of extractors, a critical comparison
of the juice content of the two varieties cannot be made. However, the differ-
ence in juice content of the two varieties were much greater than could be
accounted for by the difference due to the types of extractors. The percentage
of the peel was not affected by the different extractors used. Pineapple oranges
had a considerably higher percentage of peel than Valencias. The rag and seeds
of Pineapple oranges was found to be almost twice that of Valencias. Since the
juice from Valencia oranges contained much pulp, slightly higher percentages by
weight were expected. The effect of fruit size on the percentage of various
components of the two varieties indicated that there was a tendency for the small
fruit to have slightly less peel and more juice.

The average specific gravities and juice characteristics of fruit of various
sizes of the two varieties are shown in Table 2. The specific gravity for
corresponding sizes was much higher for Valencia oranges than that for Pineapples.
Within each variety, the larger fruit had much lower specific gravity than the
smaller fruit, which were higher in soluble solids, titratable acidity, and juice
content by weight. The calculated values for pounds-solids per 90-lb. box was
also much higher for small fruit.

A linear relationship was found between specific gravity and pounds-solids
in both varieties (Figures 1 and 2). The range for specific gravity of Valencia
oranges was between 0.92 and 1.01 while that for Pineapple oranges was much
wider varying from 0.8h to 0.99. The average pounds-solids per 90-lb. box was
5.62 for the Pineapple oranges and 7.55 for Valencias.

Since the size of fruit greatly affect its specific gravity and since the
sizes of fruit in any given load is normally distributed, it is important to find
out whether the correlation and regression coefficients in any given size group


Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
10/2/62 SVT







8.0



7.0



6.0


*0


. .


.86 .88


.90 .92 .94
Specific Gravity


.96


.98 1.00


Fig. 1. A
90 pound


9.0



8.0



7.0



6.0


scatter diagram showing the relationship between pounds-solid per
box and the specific gravity of pineapple orange. March, 1962


* .


*~ C .


. 27.38 X-8.8

Y- 27.38X-18.85


.92 .93 .94 .95 .96 .97 .98 .99 1.00 1.01

Specific Gravity

Fig. 2. A scatter diagram showing the relationship between pounds-solid per
90 pound box and the specific gravity of valencia orange. April, 1962


C
I ..
C
.
*C

* 0


5.0


4.0


3.0
.8


4


YU 21.38X- 14.55


I I ) I I I I


I-- *.
:*







Table 1. The percentage composition of the component
parts of Pineapple and Valencia oranges of
different sizes. March, 1962.
Peel Rag and Seeds Juice1
% by weight
Pineapple oranges
126 27.6 26.7 45.6
150 27.5 25.1 47.3
176 25.9 24.6 49.3
216 26.8 23.4 49.7
250 25.2 23.9 50.7
288 2 .6 2. 50.9
324 23.2 25.0 51.7
Valencia oranges
126 21.7 13.9 64.4
150 21.1 14.0 65.0
176 20.6 13.5 65.8
200 20.7 13.3 65.9
216 19.7 13.4 66.8
250 19.2 15.1 65.8
288 19.2 16.9 63.8


1 Juice was


not finished.


Table 2. Average specific gravities and juice characteristics related to the
internal quality of Pineapple and Valencia oranges of different sizes.
Number Juice Total soluble Total acid Pounds-solids
Size of Specific content solids1 as citric Brix/acid per 90-lb.
fruit gravity % by wt. Brix % by wt. ratio box
Pineapple oranges
126 20 .919 45.6 11.46 0.69 16.6 4.70
150 20 .932 47.3 12.05 0.73 16.5 5.13
176 20 .939 49.3 12.24 0.73 16.8 5.44
216 20 .939 49.7 12.97 0.86 15.1 5.79
250 19 .952 50.7 13.51 0.85 15.9 6.14
288 20 .959 50.9 13.25 0.84 15.8 6.04
324 18 .965 51.5 13.18 0.83 15.9 6.10
Valencia oranges
126 30 .946 6h4. 11.86 0.86 13.9 6.87
150 30 .958 65.0. 12.44 0.98 12.9 7.28
176 30 .964 65.8 12.91 0.98 13.4 7.64
200 30 .967 65.9 13.03 1.03 13.0 7.72
216 30 .975 66.8 13.10 1.05 12:8 7.87
250 17 .975 65.8 13.66 1.17 12.0 8.09
288 10 .980 63.8 13.64 1.34 10.4 7.84
1 Not corrected for total acid.


Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
10/2/62 SVT











are significant. In Table 3 are shown these coefficients between specific gravity
and pounds-solids per 90-lb. box for Valencia oranges of different sizes. With
30 fruits or 28 degrees of freedom, all correlation and regression coefficients
were significant. These highly significant regression coefficients indicate that
it should be possible to predict the total pounds-solids of a sample after its
specific gravity has been determined.





Table 3. Correlation and regression coefficients for specific
gravity and pounds-solids per 90-lb. box of Valencia
oranges of different sizes.

No. of Correlation Regression
Size fruit coefficient coefficient
126 30 .9034HO 26.81H-
150 30 .62 6- 18.9*i
176 30 56 7* 1.0; -
200 30 .654* 16.0 -
216 30 .847 25,6
250 17 .64n. s. 16.9*
288 10 .61'n.s.' 6.5n.s.

Totals 177 .808C* 27.4 ,-

Significant
'' Highly significant
n.s. Not significant
















Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
10/2/62 SVT




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