WAX MICROEMULSION FORMULATIONS USED AS …

1 Proc. Fla. State Hart. Soc. 111:251-255. 1998. WAX MICROEMULSION FORMULATIONS used AS fruit COATINGS Robert D. Hagenmaier Citrus and Subtropical Products Laboratory USDA, ARS, SAA Box 1909 Winter Haven, FL 33883-1909 e-mail: Additional index words. Edible coatings, 'Hamlin' oranges, 'Sunburst' tangerines. Abstract. Wax microemulsions were made with three emulsifi-cation techniques. FORMULATIONS are presented for making an-ionic microemulsions with carnauba wax, candelilla wax, oxidized polyethylene, beeswax, paraffin, montan wax and var ious hydrocarbon waxes, and also for making nonionic micro emulsions with squalene, hydrocarbon waxes and rice bran wax. Citrus fruit were coated with various mixtures of a wax emulsion and rosin. Those coatings with higher percentage wax had lower internal CO2 and higher O2.

2 In recent years we have evaluated the performance of var ious wax microemulsions as food and fruit coatings (Hagen maier and Baker, 1993, 1994a, 194b, 1996, 1997). In the course of those studies, more than 600 microemulsions were made in our laboratory, in attempts to develop better coat ings. In our published studies <10% of the microemulsions were used , as there was insufficient time to thoroughly evalu ate all of those made. Here now is a summary of all formula tions, not just the 10% included in our publications. Why were so many different FORMULATIONS made? First, in the course of work on coatings it became evident that the per formance of any particular wax as a coating depended consid erably on the quality of the emulsions and also the presence of minor ingredients in the formula.

3 Thus, a conclusion about the potential as edible coating of any given wax would seem to require the testing of a number of different formula tions. Secondly, in order to make progress in developing wax coatings, it was considered necessary to know the composi tion of any coatings used . In early work, the wax microemul sions evaluated in our laboratory were samples received from suppliers whose FORMULATIONS were proprietary information. We found that much trial and error was involved in arriving at suitable FORMULATIONS , which resulted in many trials. In gen eral, little information on wax MICROEMULSION FORMULATIONS was found in the literature (Bennett, 1975), especially formu lations whose ingredients were restricted to those approved for use in foods.

4 The purpose here is to make available the techniques and ingredients used in our laboratory to make wax microemul sions, in order to make it easier for others to make and test these, particularly for use as food and fruit coatings. South Atlantic Area, Agricultural Research Service, Department of Agriculture. Mention of a trademark or proprietary product is for identifica tion only and does not imply a guarantee or warranty of the product by the Department of Agriculture. The Department of Agriculture prohib its discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual ori entation, and marital or family status. Materials and Methods Polyethylene waxes E10 and E20 were from Eastman Chemical (Kingsport, TN); AC629, AC680, AC673 and AC316 were from Allied Signal Inc.

5 (Morristown, NJ); and PED121 was from Clariant Corp. (Charlotte, NC). FDA approval for polyethylene wax (oxidized polyethylene) is given in 21 CFR (FDA, 1995). The candelilla wax (21 CFR ) was bleached (No. 75 from Strahl & Pitsch Inc., W. Babylon, NY, type cbw2 from Berial, S. A., Mexico D. F., or No. 7808 from Botanical Wax, Arlington Heights, IL) or unbleached 'filtrada' from Berial, S. A. The beeswax (21 CFR ) was from Koster Keunen Inc. (Sayville, NY). The rice bran wax (21 CFR ) was from Strahl & Pitsch or Koster Ke unen Inc. Yellow No. 3 and No. 1 carnauba wax (21 CFR ) were from Strahl & Pitsch Inc. The petroleum wax (21 CFR and ) with 61 C , was Parvan 4450 from Exxon (Houston, TX). The paraffin wax (CFR ) type 126, also with 61 C , was from Koster Ke unen Inc.

6 Rosin modified maleic wood resin (21 CFR ) was type 807 Afrom Resinall Corp. (Stamford, CT). Hydrogenated wood rosin (21 CFR ) was Foral AX from Hercules Inc., (Wilmington, DE). The montan wax (21 CFR ) was type KPS from Clariant Corp. Hydrocarbon waxes Polywax 500 (21 CFR ) and Be Squarel95 (21 CFR ) were from Petrolite Corp. (Tulsa, OK). The oleic acid (21 CFR ) was Emersol 6321, from Henkel Corp. (Cincinnati, OH). The myristic acid was Hystrene 9014 from Witco Corp. (Memphis, TN) and Emery 655 from Hen kel Corp. Mineral oil (21 CFR ) was from Squibb 8c Sons (Princeton, NJ) and petrolatum jelly (21 CFR ) was from Albertson's (Boise, ID). The surfactants were sorbi-tan monostearate (21 CFR ), Capmul S from Abitec Corp. (Janesville, WI) or Durtan 60 from Durkee Industrial Foods (Cleveland, OH).

7 Glycerol mono/di-oleate (21 ,GRAS) was GMO-Kfrom Abitec Corp. Polysor-bate 60 (21 CFR ) was Capmul POE-S from Abitec Corp. or Tween 60 Kfrom ICI Surfactants (Wilmington, DE) Microemulsions were made by three methods. For the wa ter-to-wax method, the wax and other ingredients (less the water) were heated 10-20 C above the melting point of the wax, hot water (95-100 ) slowly added with stirring, and the mixture cooled to 50 C in a water bath, with stirring. For the wax-to-water method the same molten wax mixture was poured into the vortex of hot water being rapidly stirred in a beaker, and the mixture cooled in the same manner. For the pressure method, which is similar to the water-to-wax method, the unmelted wax, together with part of water (the initial wa ter) was placed in a 2-liter pressure cell (Parr Instrument Co.)

8 , Moline, IL), heated to approximately 10-30 C above the melt ing point of the wax, hot water forced into the cell with a pump (Haskel Inc., Burbank, CA) and the emulsion cooled to 50 C. For all three methods the total amount of water in corporated was that required to make an emulsion contain ing 60-80% water. The quality of the emulsions was evaluated by appearance and performance. Appearance was primarily evaluated by measurement of turbidity with the Ratio/XR turbidimeter Proc. Fla. StateHort. Soc. Ill: 1998. 251 (Hach Co., Loveland, CO). This measures turbidity over the range 0-2000 nephelometric turbidity units (NTU). In addi tion, the amount of cream that separated by gravity was ob served after storage at about 25 C for at least one week. For measurement of gloss, the emulsions were dried on polystyrene weigh boats ( g on an area of 25 cm2) or ap plied to apples or citrus ( ml per fruit ).

9 Gloss was evaluated by panel or by measurement of gloss units ( ) with a re flectance meter (micro-TRI-gloss, BYK Gardner Inc., Silver Spring, MD). Tendency of coatings to 'fracture' was deter mined subjectively after hitting and rubbing together two pieces of fruit , then wiping the contact surfaces with a black cloth, and rating the amount of coating found on the cloth ( = none; = minimal; = significant but acceptable; = heavy and unacceptable; and = virtually all coating removed). The coatings applied to citrus fruit consisted of mixtures of a wax MICROEMULSION made of various mixtures of a wax emulsion and a wood rosin solution. The wax MICROEMULSION contained carnauba No. 3, E20, Foral AX and morpholine and the balance water. The rosin solu tion contained Resinall 807A, oleic acid, morpholine and the balance water.

10 The five coatings used consisted of 0, 5, 15, 30 and 100% of the rosin solution and the balance wax MICROEMULSION . The coated fruit were stored 7 days at 21 C. Internal gases and air flux were measured (10 fruit per treatment). Air flux is the amount of air passing through the peel at an applied pressure of atmosphere (Hagenmaier and Baker, 1993). Samples of internal gases for internal O2 and CO2 analyses (ten fruit per treatment) were withdrawn by syringe from fruit submerged in water for the occasion. The CO2 concen trations were measured with a Hewlett Packard 5890 gas chro-matograph fitted with a GSQ column (30 m x mm from J&W, Folsom, CA) and a thermal conductivity detector. The O2 concentration of the same samples was measured with a Model 507 analyzer (Inpack, Wilmington, MA).