Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; CES 65-7
Title: Method for measuring the water-soluble volatile constituents of citrus juices and products
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 Material Information
Title: Method for measuring the water-soluble volatile constituents of citrus juices and products
Series Title: Citrus Station mimeo report
Physical Description: 6 leaves : ill. ; 28 cm.
Language: English
Creator: Dougherty, Marshall H
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: 1964
Subject: Citrus juices -- Analysis -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references (leaves 5-6).
Statement of Responsibility: Marshall H. Dougherty
General Note: Caption title.
General Note: "October 6, 1964."
 Record Information
Bibliographic ID: UF00072428
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 75969801

Full Text

Citrus Station Mimeo Report CES 65-7
October 6, 1964

Method for Measuring the Water-Soluble Volatile Constituents of Citrus
Juices and Products

Marshall H. Dougherty
Florida Citrus Commission
Lake Alfred, Florida

Flavor enhancement of citrus concentrates has, over the years, been of
considerable interest to the citrus industry. Since the advent of concentrated
citrus juices, single-strength juices, used as cutback, and coldpressed citrus
oils have been materials used for flavor enhancement of concentrates after their
removal from the evaporator. As time has passed, the concentrate industry has
become very competitive and more economical ways to prepare better quality pro-
ducts have become of prime importance. Processing equipment and procedures have
been improved resulting in more economical production but the flavor of the pro-
duct has suffered. Flavor enhancement now seems to be foremost in the minds of
management as a means of quality improvement and also as a possible way to further
reduce production costs.

A flavor enhancement material being used presently is orange essence. This
material is recovered either from the fresh juice or the condensate from the
evaporation of the juice. The definition of essence (1) is "a substance obtained
from a plant, drug, or the like by distillation or other process, and containing
its properties in concentrated form". This would indicate that the essence com-
ponents are the more volatile components in the original material.

Concentration of citrus juices is effected by vacuum evaporation and the
loss of volatile flavor constituents is inevitable. These volatile substances
can be recovered and added back to concentrates as a flavor enhancement material.
Although no correlation data are available, it is believed that there is a re-
lationship between the water-soluble volatile constituents and the flavor of
citrus juices and other citrus products. If the amount of water-soluble vola-
tile constituents (volatile content) of fresh citrus juices and their essences
could be determined, it would prove helpful in calculating the amount of essence
or other materials to be used for flavor enhancement.

Jensen (2) reported on a method for determining the volatile content of
apple juice and Charley (3) reviewed a number of publications dealing with
methods, other than chromatographic, of analyzing for volatile materials from
fruit juices. All methods are based on distillation followed by dichromate
oxidation of the volatile substances in the distillate. In all cases a rather
complicated procedure was used to obtain, first, an "oxidation number" and then

Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
400-10/6/64 MHD

an "aroma number", either of which were indicative of the volatile content of
the juices. The procedure described in this paper is a suitable, quick method
which gives a value for water-soluble volatile components in citrus juices,
essences, and other products. It is a relatively simple procedure requiring
apparatus and instruments similar to thosewhich all quality control laboratories
in citrus processing plants should have.

The method consists of taking a suitable sample of fresh or reconstituted
juice or essence, diluting it, if necessary, to 300 ml with distilled water, and
distilling it at atmospheric pressure. The distillate is passed through an oil
separatory trap (5) (Clevenger) and 50 ml of oil-free distillate collected. The
chemical oxygen demand (COD) of the 50 ml of distillate is then determined
colorimetrically (4) and a value is calculated for the amount of water-soluble
volatile components in the product. The units for this value are parts per
million chemical oxygen demand per ml of material (ppm COD/ml). When analyzing
any concentrated juice, the analysis is made on the reconstituted juice and the
value reported as that of the reconstituted product. The method includes the
following steps:

1. A 300 ml sample or a sample diluted to 300 ml with distilled
water is placed in a distillation apparatus, which contains the oil trap
immediately-after the condenser, a few boiling chips are added and 50 ml
of oil-free distillate collected in a graduated cylinder.

2. The distillate is transferred to a 50 ml, round bottom, boil-
ing flask containing a few glass beads, and 25 ml of 0.25 IT C.P. potassium
dichromate solution are added from a pipette.

3. While constantly mixing, 75 ml of reagent grade concentrated
sulfuric acid are slowly added to the mixture from a dispensing burette.

4. The boiling flask is fitted with a water-cooled condenser
and the mixture brought to a boil and refluxed for 10 minutes.

5. After cooling the solution in a running water bath, the
percent light transmittance through the solution is determined using
an AC Model Fisher Electrophotometer, a 650 mu filter and a 10 mm
diameter cuvette.

6. The oxygen demand of the mixture is found by referring to
a standard curve. The oxygen demand is then divided by the ml of
sample used (Step 1) and the value for the water-soluble volatile
content of the sample is obtained.

The placement of the oil trap in the distillation apparatus is shown in
Figure 1. It is necessary to remove the oil from the distillate for two
reasons. First, because it is impossible to quantitatively recover it during
both the distillation and subsequent transfer of the distillate to the oxi-
dation vessel. The oil has a very high COD content and small differences in
the amount of oil oxidized cause large variations in values obtained. Secondly,

Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
400-10/6/64 MHD


-_--50 ml. GRADUATED


there are relatively small amounts of oil in orange essence and consequently
very little is included when essence alone is used as a flavor enhancer. Oil
is another flavor enhancement material that will more than likely be added to
the product in the form of coldpressed oil or juice oil.

The sample dilutions (Step 1) can be made a standard procedure, except
when analyzing essences. If freshly extracted or single-strength juice is
being analyzed, 75 ml of juice diluted to 300 ml with distilled water is
used. Reconstituted juices from concentrates containing flavor enhancers
other than essence require a full 300 ml sample. When analyzing essences, from
1.0 to 25 ml of the essence is diluted to 500 ml depending on the volatile con-
tent of the essence. This dilution must be determined by trial and error but
once the source and standardization of the essence is established, the dilution
should be constant.

The standard curve used to determine the chemical oxygen demand (Step 6) is
shown in Figure 2. However, if this curve is to be used, it should be reproduced
on a piece of graph paper so that more accuracy can be obtained. The coordinates
of the curve are as follows:

ppm COD % Transmission ppm COD % Transmission
100 96.5 700 70.7
200 91.4 800 67.0
300 86.7 900 65.2
400 82.5 1000 61.5
500 78.3 1100 59.9
600 74.5

It must be pointed out that this curve can be used only with the Model AC
Fisher Electrophotometer using a 650 mu filter and a 10 mm cuvette. If any
other instrument is used, coordinates for a new curve must be determined for
that instrument. Regardless of what instrument is used, a blank sample of 50
ml of distilled water must be run through the oxidation portion of the analysis
(Steps 2-4) once each day that this procedure is employed and used to set the
instrument on 100 percent transmission.

The water-soluble volatile content of fresh juices, concentrated juices,
orange essences, and juice emulsions have been measured using this method.
The concentrated juices analyzed included those enhanced with fresh cutback
juice.and coldpressed oil, juice emulsion, juice oil, and essence. Samples
of evaporator pump-out at 55 and 590 Brix were also analyzed. Values obtained
for some orange products, which were produced in the pilot plant, are shown in
Table 1. The two values given for each product are the minimum and maximum
values obtained for products of that type analyzed.

Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
400-10/6/64 MHD



0 ^80



0 100 200 300 400 500 600 700 800 900 1000 1100

Table 1. Water-Soluble Volatile Content of Some Orange Products
Enhancing Volatile content
Product material value (ppm COD/ml)
Fresh juice (Pineapple) 5.5- 7.1
Fresh juice (Valencia) 5.9- 10.5
Concentrate (pump-out) 0.27- 0.38
Juice emulsion*' 12.3- 14.9
Essence 10.0-755.0
Concentrate Fresh juice + C.P. oil 0.75- 1.00
Concentrate Juice oil 0.27- 0.30
Concentrate Juice emulsion*' 0.37- 0.53
Concentrate Essence 4.0 6.0

* Obtained from A. P. Distelkamp, Centrico, Inc., and 0. R. McDuff, Adams
Packing Association. Juice emulsion produced by centrifuging orange juice
and contains constituents from both juice and peel oil.

The values obtained by this method of analysis have been used to calculate
the amount of essence to add to a concentrated juice to give a reconstituted
juice of a desired water-soluble volatile content. The calculation is made using
the following two formulas:

Formula 1. (V P) x F
Where: V = Desired volatile content value of reconsti-
tuted juice.
P = Volatile content value of pump-out concentrate.
E = Volatile content value of essence.
F = Fold of concentrated product.
G = Gallons of essence in one gallon of concen-
trated juice.

Formula 2. S x 100
W (G x 8.35)
Where: S = Weight of solids in concentrated juice
W = Weight of concentrated juice (lb/gal).
G = Value obtained from formula 1.
B = Required Brix of the evaporator pump-out.

The first formula is used to calculate the volume of essence needed in the
final concentrated product. The pump-out Brix, therefore, must be higher than
in the final product so that the essence addition will bring the Brix of the
final product to the desired level. The second formula is used to calculate the
required pump-out Brix. The values used in this formula can be found in a
standard sugar table.
In using formula 1, the volatile content value for the pump-out concentrate
(P) must be determined by analyzing a few such concentrates in the desired Brix

Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
400-10/6/64 MHD


range. Thereafter, a fairly accurate assumption should be possible. When
adding essence to a concentrate to raise the volatile content to the range of
that of fresh juice, the pump-out contributes about 10o of the volatile con-
tent. Therefore, an error of only approximately 1% in the volatile content of
the reconstituted product will result from a 10% error in the assumed value for

An example of the use of these two formulas is given in the following

A four-fold (420 Brix) concentrated orange juice is to be flavor
enhanced with essence so that the reconstituted juice will have a
water-soluble volatile content value of 4.0. The essence to be used
has a value of 250. How much essence will be required and what will be
the required pump-out Brix?

Using Formula 1.:
V = 4.0, P = 0.5 (assumed), F = 4 and E = 250

(V P) x F (4 0.5) x 4 0.056 gal. of essence
E 250 250

Now Using Formula 2.:
G = 0.056 and from the sugar table S = 4.157 and W = 9.895

S x 100 4.157 x 100 415.7 415.7
w (G x 8.35) 9.895 (0.056 x 8.55) 9.895 0.468 9.427

= 44.1 Brix

In other words, the addition of 0.056 gal. of essence having a value of 250
to 0.944 gal. of 44.1 Brix concentrated orange juice will result in 1.0 gal, of
420 Brix concentrate which, when reconstituted, will give a juice having a water-
soluble volatile content value of 4.0.

After calculating the amount of essence to use, it is important to make
the addition of essence quite accurately. A small amount of an essence having
a high volatile content goes a long way and deviations from the calculated
volume needed can cause a sizeable error in the desired volatile content of
the final product.

Literature Cited

1. The American College Dictionary. Random House, New York, N. Y. (1953).

2. Jensen, M. Determination of aroma in fruit juices and fruit juice con-
centrates with a quick method. Proc. Scientific Technical Commission,
International Federation of Fruit Juice Producers, 3, 63-67 (1961).

Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
400 10/6/64 MHD

3. Charley, V. L. S. Volatile constituents of fruit juices. Proc.
Scientific Technical Commission, International Federation of Fruit
Juice Producers, 4, 365-373 (1962).

4. McNary, R. R., M. H. Dougherty, and R. W. Wolford.
the chemical oxygen demand of citrus waste waters.
Industrial Wastes, 29 (8) 894-900 (1957).

Determination of
Sewage and

5. United States Department of Agriculture, Agricultural Marketing Service,
Washington, D. C. United States standards for grades of frozen concen-
trated orange juice. December 1, 1955.

Florida Citrus Commission and
Florida Citrus Experiment Station,
Lake Alfred, Florida.
400 10/6/64 MHD

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