Tangerine Coatings

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Tangerine Coatings

• Robert Hagenmaier

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Washing gt Waxing

• In Florida, the washing procedure is designed for
  the dirtiest fruit. It is so highly abrasive
  that not only dirt, but also natural waxes, are
  removed. Therefore, non- coated fruit tends to
  lose weight rapidly during storage.
• In short, the washing procedure makes it
  necessary to apply coatings.

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How Florida washing affects tangerines.
Not washed Washed with polyproplylene brush
Internal O2 () 17 15
Internal CO2 () 2 4
Weight loss at 20?C, 60 R.H. 0.6/day 1.0/day
Main storage problem Mold Shrinkage
No difference in weight loss when washed with
sponge
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What coating to use?

• All coatings have their individual advantages and
  disadvantages.
• For citrus fruit sold in the U.S. and Japan,
  shellac and resin coatings are often used for
  maximize shine, even if these cause deterioration
  in fruit flavor.

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Murcott stored 1 week at 21?C
Wax coating (PE-Cand) High-gloss Rosin-Shellac
Internal O2 () 9.9 1.3
Internal CO2 () 5.6 34
Flavor (0 to 15) 11.0 5.7
Ethanol (ppm) 581 3366
Ethyl Acetate (ppm) 1.1 6.0
Isopentanol (ppm) 0.3 1.1
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Industry coatings, Murcott, 7 days, 21?C
Carnauba wax, O2 perm. 4400 ml mil M-2
day-1atm-1
Rosin, O2 perm 650 ml mil M-2day-1atm-1
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Proportion of Murcott tangerines that had ethanol
contentlt1500 ppm, after 7 days storage at 21?C

• 23 Coated with shellac-rosin.
• 90 carnauba wax-shellac.
• 100 polyethylene wax

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Different coatings on Tangerines
Coating Internal CO2 (kPa) Internal O2 (kPa)
No coating 3.5 15.3
Polyethylene wax 5.7 7.0
58 PE, 42 candelilla wax 6.0 10.4
93 Carnauba wax, 7 rosin 8.7 6.3
Shellac/resin 20.4 3.5
Better
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Conclusions

• For tangerines stored at 20?C, coatings made
  with waxes are much more quality-friendly than
  those made with shellac and/or wood resin.
• There is some difference between various waxes.
  Polyethylene wax has the highest O2/CO2
  permeability and usually gives slightly lower
  ethanol content than other waxes.

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To wax or not to wax, that is the question.

• Almost always
• Apple
• Orange
• Grapefruit
• Tangerine

• Rarely
• Mango
• Tomato
• Grape
• Melon
• Pineapple
• Prune

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How tangerine coatings are evaluated.

• Appearance
• visual gloss
• adhesion (little coating rubs off).
• Flavor after storage compared to fruit with other
  coating treatments.
• Chemical Indicators, if stored at 20C.
• Internal O2 should be gt 2 kPa
• Internal CO2 should be lt 15 kPa
• Ethanol lt 1500 ppm, 7 days _at_20C.

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Citrus Coatings

• MICROEMULSIONS
• Main Components
• water, wax, fatty acids, and ammonia or
  morpholine.
• Properties low-medium gloss, high-medium gas
  exchange, good-fair moisture barriers.

• SOLUTIONS
• Main components water, shellac or resin, ammonia
  or morpholine.
• Properties high gloss, low gas exchange,
  poor-fair moisture barriers.

----------------- Mixtures mostly of wax with
some added shellac or wood rosin.
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A typical Florida tangerine
Surface area 190 cm2

• Weight 230 grams

Average amount of coating applied in Florida
citrus packinghouses Wet weight 335
mg Dry weight 67 mg
The surface density of the dried coating is
therefore 67 mg/190 cm2 0.35 mg/cm2
about 3.5 ?m thick.
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Wax microemulsions,nano-technology in the
service of fruit preservation.

• With the exception of root crops (which are
  dipped in melted paraffin), almost all wax
  coatings for fruit are applied as microemulsions.
• Therefore, it is of some importance to know
  something about wax microemulsions.

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A hypothetical cross-sectional view of a 3.5
?m-thick coating made up of wax globules of
differing sizes.
Dried regular emulsion
Dried microemusion
6 ?m diameter
0.5 ?m
3.5 ?m
3.5 ?m
These globules have diameter of 0.2 ?m (200
nanometers).
Globules in cows milk have 10, 50 and 90
percentile diameters of 0.5, 3.5 and 6 ?m,
respectively.
For different microemulsions made in our
laboratory, mean wax globule diameters were 60 to
600 nanometers.
Dried microemulsion
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Emulsions vs Microemulsions
Emulsions Microemulsions
Appearance White Translucent
Gravity separation Cream formation Stable
Preparation High-energy Low energy
Coating microemulsions are of the anionic type,
meaning that the globules are surrounded by
negatively charged fatty-acid molecules.
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Minor ingredients in microemulsions

• Fatty Acids. These usually amount to 10-25 of
  the weight of the wax, at least half being
  food-grade oleic acid. The rest myristic,
  lauric or palmitic acid.
• Base. Needed to raise pH and ionize the fatty
  acids. Some NaOH or KOH is useful, but a
  volatile base is needed, and for this the only
  legal options are ammonia (NH3) or morpholine
  (C4H9NO).

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Wax Ingredients

• Polyethylene wax. Synthetic wax. Approved by FDA
  and EU, but not Japan. Cheap. Highest gas
  exchange of all waxes. Fair moisture barrier.
  Good gloss. Widely used in commercial fruit
  coatings. Brittle. MP100-140?C
• Carnauba wax. Natural wax from Brazil. Approved
  by FDA, EU, Japan. Expensive. Good gas
  exchange. Good moisture barrier. Good gloss.
  Widely used in commercial fruit coatings. Hard
  brittle. MP85?C

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Waxes . . .

• Candelilla wax. Approved by FDA, EU, Japan.
  Natural wax from Mexico. Excellent moisture
  barrier. Medium gas barrier. Soft. Low gloss.
  MP68?C
• Beeswax. Approved by FDA, EU, Japan. Natural
  wax. Low gloss. Needs mixing with other waxes
  to make microemulsion. MP65?C

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Waxes . . .

• Paraffin wax. Made by dewaxing of airline fuel.
  Cheap. Approved by FDA and Japan, but not EU.
  Excellent moisture barrier. Medium gas barrier.
  Needs mixing with other waxes to make
  microemulsion. MP65?C.
• Others.
• Rice bran wax. Difficult to emulsify. Approved
  by FDA, EU, Japan.
• Petroleum wax. Made from dewaxing of lubricants.
  Approval same as paraffin wax.

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A Coating Cookbook

• I have made about 800 different wax
  microemulsions in the laboratory. Here now are
  the recipes for a few of these that seem suitable
  for tangerines.

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Typical Microemulsion Formula

• Wax 100
  g
• Fatty acid 20
  g
• Ammonia solution (30 NH3) 20g
• Water
  480g
• Antifoam (polydimethylsiloxane) 5 mg
• -------------------
• Usually about 20 of the NH3 is lost during
  emulsification. About 12 g morpholine can often
  be used instead of the ammonia.

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Preparation of Microemulsions

• Wax microemulsions are not prepared simply by
  mixing the ingredients in a container. Instead,
  special techniques must be used.

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Carnauba wax with morpholine. This is similar in
ingredients and technique (water-to-wax method)
to the first emulsion ever made (in 1958).
Suggestion make it your first, also.

• Melt 100 g Carnauba wax (3 or 4), 20 g food-grade
  oleic acid, 14 g morpholine, and antifoam.
  Slowly add 350 g hot water, while mixing.

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Equipment for Water-to-wax Method

• Two glass beakers and two heaters.
• Mixer. Normally use a mixer with propeller blade,
  but once I made a good emulsion with a hand-held
  plastic spatula

Step 1. Melt the wax, fatty acids and base
Step 2 slowly add the hot water.
Hot water
Heater
Heater
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Procedure for Water-to-wax Method

• Put the mixture of wax, fatty acids and base in
  an open container. Some initial water (less than
  half the amount of wax) may also be added before
  melting the wax.
• Melt the above mixture by heating to about 15?C
  above the melting point of wax.
• Slowly add hot water to the molten wax, with
  mixing. Maintain high temperature during this
  addition so that the wax does not solidify. When
  all water is added, rapidly cool the mixture to
  50?C.

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Polyethylene with morpholine, made with
wax-to-water method.

• Melt 50 g AC629, 50g AC680,13g food-grade oleic
  acid, 5 g myristic acid. Add 17g morpholine and
  pour into 350 mL hot water with antifoam.
  (Wax-to-water technique)
• Notes
• The boiling point of morpholine is 128?C
• The softening point of these PE waxes 101-110 ?C
• Food grade oleic acid is a mixture of fatty
  acids, containing about 75 oleic (C181) and 15
  linoleic (C182).

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Equipment and Procedure for Wax-to-water method
The molten wax is slowly poured into hot water
being stirred with propeller blade.
Mixer
Molten mixture of polyethylene wax, fatty acids
and morpholine, T about 120?C
Water at 95?C antifoam
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Polyethylene-ammonia made by pressure method.

• ? To a pressure cell add
• 100 g AC629
• 14 g food-grade oleic
• 6 g myristic acid
• 15 g 30 ammonia
• 100 g water, with antifoam
• ? Heat to 120?C with stirring, and then add 350
  mL hot water.

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Equipment for the Pressure Method
Mixer
High-pressure water pump
Heated, high-pressure cell with mixer
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Procedure for Pressure Method

• Add all ingredients except about 75 of water,
  which is added after the initially added
  ingredients have been heated to 20?C gt wax
  softening point.
• The pressure method, although difficult and
  expensive, is used because
• it often makes the best-quality microemulsions.
• It sometimes is the only feasible method, for
  example, when using ammonia with a wax that melts
  at temperatures above about 90?C.

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Summary 3 methods for making microemulsions.

• Water-to-wax
• Wax-to-water
• Pressure method
• Which method to use depends on the chemistry of
  the emulsion and what equipment is available.

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Method depends on chemistry ammonia or
morpholine?

• Ammonia Inexpensive. Approved by FDA and EU.
  Ammonia-based microemulsions are more difficult
  to make because of high NH3 volatility. Final
  NH3 should be enough for pH gt 9.2.
• Morpholine Used in most U.S. coatings, probably
  because of ease of use. Approved by FDA but not
  by EU or Japan. Unfortunately, it is a substrate
  for N-nitrosomorpholine, a carcinogen. Add
  enough morpholine to achieve final pH gt8.8.

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Modified water-to-wax method (water-to-(wax
water)

• Carnauba wax with NH3. The container used is a
  240mL aluminum beer can. Add 40g carnauba wax
  (grade 3 or 4), 3.2 g food-grade oleic acid, 2.0
  g lauric acid,1.2 g myristic acid,15 mL water and
  antifoam. Melt and slowly add 28 mL 8 NH3,
  followed by 160 mL hot water.

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Two water-to-wax recipes for candelilla wax.

• With ammonia In aluminum can, melt a mixture
  of 50 g candelilla wax, 6.5 g food-grade oleic
  acid, 2.5 g myristic acid and antifoam. Add 25 g
  10 ammonia and 200 mL hot water.
• With morpholine Melt these 100 g candelilla
  wax, 10 g food-grade oleic acid, 13 g morpholine
  and antifoam. Add 430 g hot water.
• --------
• Note the quality of the candelilla wax may
  require adjustment of these recipes.

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Two ways to make microemulsions with wax mixtures

1. Mix two wax microemulsions separately made, for
   example, a candelilla- and a polyethylene wax
   microemulsion.
2. Melt the same two waxes together and then make a
   microemulsion by any of the three techniques.

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A wax mixture for tangerines.

• Polyethylene-Candelilla. To a pressure cell add
  116 g AC316, 84g candelilla wax, 36 g food-grade
  oleic acid, 10 g myristic acid, 36 g 30 NH3, 100
  mL water and antifoam. Heat to 150?C and add 800
  mL water.

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High-gloss coatings made from shellac or wood
rosin (not suitable for tangerines)

• These typically contain about 17 shellac and/or
  wood rosin, plus morpholine and other minor
  ingredients. ( or possibly NH3)
• Shellac is approved by EU and Japan, and
  unofficially approved by FDA.
• Wood rosin is approved only by FDA, only for
  citrus fruit.

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Wax-shellac mixtures

• Mix wax microemulsion with a shellac solution
  (previously prepared) with similar pH. For
  tangerines, the wax content should be 5-20 times
  that of the shellac.
• The shellac solution can be made by adding solid
  shellac to a hot (80-90?C), rapidly stirred
  mixture of water and ammonia (or water and
  morpholine).

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Happy cooking!!

• Instead of using only commercially available
  coatings for research work, I recommend that the
  scientist make some of her own coatings, whose
  composition is known and can be reported.
• The composition of purchased coatings is unknown,
  because manufacturers do not reveal that
  information.