Preliminary report on the processing and handling of citrus oil emulsions

Material Information

Preliminary report on the processing and handling of citrus oil emulsions
Series Title:
Citrus Station mimeo report
Kesterson, J. W
Hendrickson, Rudolph
Citrus Experiment Station (Lake Alfred, Fla.)
Florida Citrus Commission
Place of Publication:
Lake Alfred FL
Citrus Experiment Station :
Florida Citrus Commission
Publication Date:
Physical Description:
2 leaves : ; 28 cm.


Subjects / Keywords:
Citrus oils -- Processing -- Florida ( lcsh )
Citrus oils -- Handling -- Florida ( lcsh )
Emulsions ( jstor )
Essential oils ( jstor )
Screening tests ( jstor )
government publication (state, provincial, terriorial, dependent) ( marcgt )
non-fiction ( marcgt )


General Note:
Caption title.
General Note:
Statement of Responsibility:
J.W. Kesterson and R. Hendrickson.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
76804306 ( OCLC )


This item has the following downloads:

Full Text

Citrus Experiment Station CES 68-8E
and Florida Citrus Commission,
Lake Alfred, Florida 450-10/12/67-JWK


J. W. Kesterson and R. Hendrickson
University of Florida Citrus Experiment Station
Lake Alfred, Florida

The increasing quantity of citrus processed each year has resulted in over-
loaded peel oil recovery plants. Centrifuges purchased for over-capacity are
soon found to be insufficient for the proper recovery of citrus oils. After
the Industry wisely choose to avoid the use of wetting agents to break emulsions,
the capacity of most centrifuges were exceeded daily. This practice has resulted
in emulsions so thick, buttery and gel-like in consistency that it is impossible
to process and handle them effectively without the excessive use of water. The
addition of water at this point is double-edged. While it permits the emulsions
to remain fluid for proper processing, it simultaneously increases the quantity
of waste effluent. This dilution results in greater over-all losses even though
the percent oil in the effluent has been maintained at a minimum.

Years of experience suggested that most of the difficulty was due to the
large quantity of insoluble solids present in the oil emulsions. After some
study it was found that these insoluble solids for the most part were extremely
fine pieces of citrus pulp, rag and juice sacs. The fine state of these
particles coupled with acidic conditions releases the pectin which caused the
emulsions to become very thick and in some instances gel. The general concept
of oil extraction needs to be revised. Actually the oil cells are ruptured
by pressure and the oil washed away rather than pressed from the peel. Many
cases exist where the screw-type finishers in common use by Industry are set
very tight and actually grind up the peel. Experiments utilizing shaker screens
as finishers were consequently made to ascertain if this condition could be
avoided and eliminated. Two such experiments were completed at a commercial
processing plant this past season. Each test was made over a two day operating
period and results are shown in Table 1.

Data in Table 1 show that when the shaker-screen was used it was possible
to reduce the water usage by one-half at this particular plant. The emulsions
produced by the shaker-screen were extremely low in insoluble solids and were
very thin, fluid and did not require the addition of water for processing. The
reverse was true for the screw-type finisher. Any normal type finisher used
improperly will give the same type result but there is less chance to use the
shaker-screens improperly. The aldehyde content of oils produced by the shaker-
screen was some 7 to 9% higher than that in oils produced by the screw-type
finisher. Insoluble solids can conceivably act as ion-exchange resins and
selectively adsorb the aldehydes from the oil or possibly increase the pectin
content of the emulsion which in some way prevents the recovery of the higher
molecular weight compounds and lowers the aldehyde content. In either case the
result is the same and previous work has shown that the aldehyde content is low
in oils produced from emulsions that contain a high insoluble solids content.

While actual yield data are not available, the processor who cooperated in
these tests stated that the yields might have been increased by some 5 to 10%,

but in any event no reduction in yield occurred. In these tests the shaker-
screens had a tendency to foul on the first part of the screen but a fine water
spray eliminated this trouble.

The information which we have presented is on the basis of only two trials
and would be more conclusive had we been able to make replicated tests but this
was not possible. We consider these two tests to be significant even though we
realize that conditions are not the same in every processing plant. Those pro-
cessors who are having difficulty in handling oil emulsion should certainly
evaluate this process change. The main advantages found in using a shaker screen
for finishing oil emulsions are:

1. Reduced insoluble solids in the emulsions.

2. Less water needed to process the emulsions.

3. Improved aldehyde content (7 to 9%).

Aldehyde content is important considering many purchases are contingent upon
this factor.

From the standpoint of waste pollution oil plants are responsible for many
problems. The above processing change could possibly help in reducing the
quantity of effluent from these plants, as well as, the quantity of insoluble
solids. In addition strict quality control should be maintained at all times
to determine if the oil plant is operating properly. The effluent from the
oil plant can be further processed utilizing a stripper (de-oiler) to recover
the major portion (70-80%) of the oil not removed by the centrifuges as a
distilled oil, giving another valuable by-product. This is especially so when
lemons and limes are processed. Removing citrus oils from citrus wastes also
helps to alleviate a troublesome waste pollution problem.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 450-10/12/67-JWK

Table 1. Physicochemical Properties of Coldpressed Orange Oils
Finishers as Compared to Shaker Screens.

Produced by Screw-Type

Test No. 1 2
Type finisher Shaker screen Screw-type Shaker screen Screw-type
Mesh size 60 mesh 0.020 in. 60 mesh 0.020 in.
Water use gal/hr. 900 1800 900 1800
%-insoluble solids in
oil emulsion 0.45 5.35 0.50 6.25
Sp. gray. 250C/250C 0.8434 0.8435 0.8431 0.8429
Ref. Ind." 20 1.4733 1.4733 1.4730 1.4731
Ref. Ind 7f 2D 10% dist. 1.4720 1.4719 1.4719 1.4719
Difference 0.0013 0.0014 0.0011 0.0012
Opt. Rot.O 25 +96.62 +96.62 +97.11 +96.93
Opt. Rot. ( 25 10% dist. +98.22 +98.22 +97.98 +97.98
Difference + 1.60 + 1.60 + 0.87 + 1.05
Aldehyde content % 1.54 1.44 1.68 1.54
Evap. Res. % 2.72 2.69 2.16 2.23