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Tangerine Coatings

Tangerine Coatings. Robert Hagenmaier. Washing > 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.

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Tangerine Coatings

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  1. Tangerine Coatings Robert Hagenmaier

  2. Washing > 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.

  3. How Florida washing affects tangerines. * No difference in weight loss when washed with sponge

  4. 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.

  5. Murcott stored 1 week at 21◦C

  6. 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

  7. Proportion of Murcott tangerines that had ethanol content<1500 ppm, after 7 days storage at 21◦C • 23% Coated with shellac-rosin. • 90% ““ carnauba wax-shellac. • 100% ““ polyethylene wax

  8. Different coatings on Tangerines Better

  9. 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.

  10. Almost always Apple Orange Grapefruit Tangerine Rarely Mango Tomato Grape Melon Pineapple Prune To wax or not to wax, that is the question.

  11. How tangerine coatings are evaluated. • Appearance • visual gloss • adhesion (little coating rubs off). • Flavor after storagecompared to fruit with other coating treatments. • Chemical Indicators, if stored at 20°C. Internal O2 should be > 2 kPa Internal CO2 should be < 15 kPa Ethanol < 1500 ppm, 7 days @20°C.

  12. SOLUTIONS Main components: water, shellac or resin, ammonia or morpholine. Properties: high gloss, low gas exchange, poor-fair moisture barriers. MICROEMULSIONS Main Components: water, wax, fatty acids, and ammonia or morpholine. Properties: low-medium gloss, high-medium gas exchange, good-fair moisture barriers. Citrus Coatings ----------------- Mixtures: mostly of wax with some added shellac or wood rosin.

  13. A typical Florida tangerine Weight: 230 grams Surface area: 190 cm2 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.

  14. 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.

  15. 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 cow’s 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

  16. Emulsions vs Microemulsions Coating microemulsions are of the ‘anionic’ type, meaning that the globules are surrounded by negatively charged fatty-acid molecules.

  17. 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).

  18. 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. MP=100-140◦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. MP=85◦C

  19. Waxes . . . • Candelilla wax. Approved by FDA, EU, Japan. Natural wax from Mexico. Excellent moisture barrier. Medium gas barrier. Soft. Low gloss. MP=68◦C • Beeswax. Approved by FDA, EU, Japan. Natural wax. Low gloss. Needs mixing with other waxes to make microemulsion. MP=65◦C

  20. 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. MP~65◦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.

  21. 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.

  22. 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.

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

  24. 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.

  25. 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. Hotwater Heater Heater

  26. 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.

  27. 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 (C18:1) and 15% linoleic (C18:2).

  28. 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

  29. 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.

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

  31. 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 > 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.

  32. 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.

  33. 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 > 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 >8.8.

  34. 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.

  35. 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.

  36. Two ways to make microemulsions with wax mixtures • Mix two wax microemulsions separately made, for example, a candelilla- and a polyethylene wax microemulsion. • Melt the same two waxes together and then make a microemulsion by any of the three techniques.

  37. 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.

  38. 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.

  39. 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).

  40. 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.

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