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Wax Microemulsion Formulations Used As Fruit Coatings

Wax Microemulsion Formulations Used As Fruit Coatings

Proc. Fla. State Hart. Soc. 111:251-255. 1998.

WAX MICROEMULSION FORMULATIONS USEDAS FRUIT COATINGS

Robert D. Hagenmaier Materials and Methods U.S. Citrus and Subtropical Products Laboratory USDA, ARS, SAA E10 and E20 were from Eastman P.O. Box 1909 Chemical (Kingsport, TN); AC629, AC680, AC673 and AC316 Winter Haven, FL 33883-1909 were from Allied Signal Inc. (Morristown, NJ); and PED121 e-mail: [email protected] was from Clariant Corp. (Charlotte, NC). FDA approval for polyethylene (oxidized polyethylene) is given in 21 CFR Additional index words. Edible coatings, 'Hamlin' oranges, 172.260 (FDA, 1995). The (21 CFR 184.1976) 'Sunburst' tangerines. was bleached (No. 75 from Strahl & Pitsch Inc., W. Babylon, NY, type cbw2 from Berial, S. A., D. F., or No. 7808 Abstract. Wax microemulsions were made with three emulsifi- from Botanical Wax, Arlington Heights, IL) or unbleached cation techniques. Formulations are presented for making an- 'filtrada' from Berial, S. A. The (21 CFR 184.1973) ionic microemulsions with , candelilla wax, was from Koster Keunen Inc. (Sayville, NY). The rice bran oxidized polyethylene, beeswax, paraffin, montan wax and var wax (21 CFR 172.890) was from Strahl & Pitsch or Koster Ke ious waxes, and also for making nonionic micro unen Inc. Yellow No. 3 and No. 1 carnauba wax (21 CFR with squalene, hydrocarbon waxes and rice bran 184.1978) were from Strahl & Pitsch Inc. The wax wax. Citrus fruit were coated with various mixtures of a wax (21 CFR 172.88 and 178.3710) with 61°C m.p., was Parvan and . Those coatings with higher percentage wax had lower internal CO2and higher O2. 4450 from Exxon (Houston, TX). The (CFR 178.3710) type 126, also with 61°C m.p., was from Koster Ke unen Inc. Rosin modified maleic (21 CFR In recent years we have evaluated the performance of var 172.210) was type 807Afrom Resinall Corp. (Stamford, CT). ious wax microemulsions as food and fruit coatings (Hagen Hydrogenated wood rosin (21 CFR 172.210) was Foral AX maier and Baker, 1993, 1994a, 194b, 1996, 1997). In the from Hercules Inc., (Wilmington, DE). The montan wax (21 course of those studies, more than 600 microemulsions were CFR 172.210) was type KPS from Clariant Corp. Hydrocarbon made in our laboratory, in attempts to develop better coat waxes Polywax 500 (21 CFR 172.888) and Be Squarel95 (21 ings. In our published studies <10% of the microemulsions CFR 172.886) were from Petrolite Corp. (Tulsa, OK). The were used, as there was insufficient time to thoroughly evalu oleic acid (21 CFR 172.860) was Emersol 6321, from Henkel ate all of those made. Here now is a summary of all formula Corp. (Cincinnati, OH). The myristic acid was Hystrene 9014 tions, not just the 10% included in our publications. from Witco Corp. (Memphis, TN) and Emery 655 from Hen Why were so many different formulations made? First, in kel Corp. Mineral (21 CFR 172.878z) was from Squibb 8c the course of work on coatings it became evident that the per Sons (Princeton, NJ) and petrolatum jelly (21 CFR 172.880) formance of any particular wax as a coating depended consid was from Albertson's (Boise, ID). The surfactants were sorbi- erably on the quality of the emulsions and also the presence tan monostearate (21 CFR 172.842), Capmul S from Abitec of minor ingredients in the formula. Thus, a conclusion Corp. (Janesville, WI) or Durtan 60 from Durkee Industrial about the potential as edible coating of any given wax would Foods (Cleveland, OH). mono/di-oleate (21 seem to require the testing of a number of different formula CFR182.4505,GRAS) was GMO-Kfrom Abitec Corp. Polysor- tions. Secondly, in order to make progress in developing wax bate 60 (21 CFR 172.836) was Capmul POE-S from Abitec coatings, it was considered necessary to know the composi Corp. or Tween 60Kfrom ICI Surfactants (Wilmington, DE) tion of any coatings used. In early work, the wax microemul Microemulsions were made by three methods. For the wa sions evaluated in our laboratory were samples received from ter-to-wax method, the wax and other ingredients (less the suppliers whose formulations were proprietary information. water) were heated 10-20°C above the of the We found that much trial and error was involved in arriving wax, hot water (95-100°) slowly added with stirring, and the at suitable formulations, which resulted in many trials. In gen mixture cooled to 50°C in a water bath, with stirring. For the eral, little information on wax microemulsion formulations was found in the literature (Bennett, 1975), especially formu wax-to-water method the same molten wax mixture was poured into the vortex of hot water being rapidly stirred in a lations whose ingredients were restricted to those approved beaker, and the mixture cooled in the same manner. For the for use in foods. pressure method, which is similar to the water-to-wax method, The purpose here is to make available the techniques and the unmelted wax,together with part of water (the initial wa ingredients used in our laboratory to make wax microemul ter) was placed in a 2-liter pressure cell (Parr Instrument Co., sions, in order to make it easier for others to make and test Moline, IL), heated to approximately 10-30°C above the melt these, particularly for use as food and fruit coatings. ing point of the wax, hot water forced into the cell with a pump (Haskel Inc., Burbank, CA) and the emulsion cooled South Atlantic Area, Agricultural Research Service, U.S. Department of to 50°C. For all three methods the total amount of water in Agriculture. Mention of a trademark or proprietary product is for identifica corporated was that required to make an emulsion contain tion only and does not imply a guarantee or warranty of the product by the ing 60-80% water. U.S. Department of Agriculture. The U.S. Department of Agriculture prohib The quality of the emulsions was evaluated by appearance its discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual ori and performance. Appearance was primarily evaluated by entation, and marital or family status. measurement of turbidity with the Ratio/XR turbidimeter

Proc. Fla. StateHort. Soc. Ill: 1998. 251 (Hach Co., Loveland, CO). This measures turbidity over the acceptable by the Code of Federal Regulations for use in food range 0-2000 nephelometric turbidity units (NTU). In addi and/or fruit coatings. The ingredients for all of these coat tion, the amount of cream that separated by gravity was ob ings consist only of water, wax, fatty acids and a base (morpho served after storage at about 25°C for at least one week. line or ammonia, sometimes supplemented with KOH). For measurement of gloss, the emulsions were dried on The ranges indicated for various ingredients in Table 1 polystyrene weigh boats (0.5 g on an area of 25 cm2) or ap mean only that good emulsions were made in our laboratory plied to apples or citrus (0.3 ml per fruit). Gloss was evaluated within that range. Sometimes our only attempts were within by panel or by measurement of gloss units (G.U.) with a re that range, and sometimes poor emulsions were made with in flectance meter (micro-TRI-gloss, BYK Gardner Inc., gredients outside that range. Table 1 shows only the successes Spring, MD). Tendency of coatings to 'fracture' was deter and not the many failures. mined subjectively after hitting and rubbing together two Carnauba wax emulsions. The type of carnauba wax used pieces of fruit, then wiping the contact surfaces with a black was Yellow No. 3 for most of our carnauba wax formulations. cloth, and rating the amount of coating found on the cloth Those made in the pressure cell generally had lower turbidity (1.0 = none; 2.0 = minimal; 3.0 = significant but acceptable; and cream than those made in beakers by water-to-wax or 4.0 = heavy and unacceptable; and 5.0 = virtually all coating wax-to-water methods, and the same was true for other waxes removed). as well. This is generally well known (Burns and Straus, 1965). The coatings applied to citrus fruit consisted of mixtures However, pressure vessels are expensive and not always avail of a wax microemulsion made of various mixtures of a wax able. The water-to-wax method was used extensively for mor- emulsion and a wood rosin solution. The wax microemulsion pholine-based carnauba wax emulsions, and these were contained 7.6% carnauba No. 3, 8.2% E20, 0.8% Foral AX generally very easy to make. As a demonstration, a good qual and 4.5% morpholine and the balance water. The rosin solu ity carnauba wax microemulsion (turbidity = 530 NTU) was tion contained 16.4% Resinall 807A, 4.6% oleic acid, 8.8% made with a stirring rod being the only mixing equipment morpholine and the balance water. The five coatings used (data not shown). Carnauba emulsions made by the wax-to- consisted of 0, 5, 15, 30 and 100% of the rosin solution and water method, by contrast, generally were quite turbid, ex the balance wax microemulsion. The coated fruit were stored cept when Foral AX was added before emulsification (5% was 7 days at 21°C. Internal gases and air were measured (10 sufficient, data not shown). However, addition of this ingredi fruit per treatment). Air flux is the amount of air passing ent seems to be approved only for waxes used as citrus coat through the peel at an applied pressure of 0.08 atmosphere ings (21 CFR 172.210). (Hagenmaier and Baker, 1993). Compared with morpholine, those emulsions made with Samples of internal gases for internal O2 and CO2 analyses aqueous ammonia as an ingredient are of more general ac (ten fruit per treatment) were withdrawn by syringe from ceptability with foods because this ingredient is GRAS (21 fruit submerged in water for the occasion. The CO2 concen CFR 184.1139). Morpholine, by contrast, is approved as an in trations were measured with a Hewlett Packard 5890 gas chro- gredient only for those formulations used as a fruit coating matograph fitted with a GSQ column (30 m x 0.53 mm i.d. (21 CFR 172.235). Ammonia could not be used for making from J&W, Folsom, CA) and a thermal conductivity detector. carnauba wax emulsions by the water-to-wax method because The O2 concentration of the same samples was measured with this boiled off too quickly, as the relatively high melting point a Model 507 analyzer (Inpack, Wilmington, MA). Standard of this wax (85°) requires that the emulsification temperature gas mixtures were used for calibration. be somewhat high. For ammonia-based emulsions made in Statistix 4.1 (Analytical Software, Tallahassee, FL) was the pressure cell, best results were obtained by heating the used for computation of statistical parameters. Error bars on mixture of wax, initial water, fatty acids and ammonia to the graphs show standard errors when these are not covered 120°C, followed by addition of enough hot water to attain by the symbols. about 25% total . A small amount of KOH was added when making some carnauba wax emulsions, because some

Results and Discussion observations, not statistically significant, suggested this im proved gloss of the coatings (data not shown). Experience has shown that a necessary condition for hav Combinations of carnauba and candelilla waxes. Mixtures of ing a good wax coating is that the wax be prepared as a micro candelilla wax and carnauba wax with >45% candelilla had emulsion, so that when the water evaporates the emulsion will sufficiently low melting point to make it possible to make have a smooth surface. This means that the wax emulsion has emulsions in an open beaker by the water-to-wax method wax globules of sufficiently small size (<0.2 |im diameter) that without having the ammonia flash off (Table 1). The tech it appears transparent to translucent, and not milky white nique was to add the ammonia (by syringe) under the surface, (Prince, 1977). For present purposes it was considered the to an agitated 95°C mixture of wax and 10% water (under a wax was successfully emulsified if the wax globule size was suf hood), then adding the remainder of the hot water. The pres ficiently small that turbidity <1500 NTU and the cream sure cell would be much preferred for ammonia-based emul formed by gravity separation made up <7% of the volume. sions, however. With morpholine rather than ammonia as the These criteria may have been too strict, as some microemul- base, microemulsions with various ratios of combinations of sions with turbidity >2000 NTU, especially those made with carnauba and candelilla waxes were made over a fairly wide high-melting polyethylene, had no cream formation and may range of conditions. have been suitable for use as coatings. Candelilla wax. Emulsion quality was quite dependent on Out of >600 attempts to prepare suitable anionic wax mi- the grade and lot no., more so than other waxes. Type S&P 75 croemulsions, >200 were made that met these criteria. was used for most work. With one batch, many morpholine- Table 1 summarizes the formulations of the anionic micro- based emulsions with turbidities as low as 315-500 NTU were emulsions. All of these emulsions were made with ingredients made with 8-10 g oleic acid/100 g wax, using the water-to-wax

252 Proc. Fla. StateHort. Soc. Ill: 1998. Table 1. Components of anionic wax microemulsions with turbidity <1500 NTU (g/100 g wax) and less than 10% cream layer "'•.

Fatty acids (g/100) gwax Morpholine, Emulsification NH3, KOH Lowest turb. Type wax Oleic Total technique (moles/100 gwax) pH (NTU)

C3W 14-20 14-20 WWX 0.10-0.20 mor. + <0.01 KOH 9.1-9.3 400 6-20 8-24* PC(70-110) 0.14-0.26 NH,, + 0.01 KOH 9.2-10.6 325 C1W 12-15 20? WWX 0.14-0.21 NH3 9.2-9.6 423 20 20 wwx 0.23 mor. 8.8 462 75% C3W, 25% RBW 25 25 wwx 0.17 mor. NV NV 50% C3W, 50% CnW 7-8 20? WWXorPC(50) 0.25 NHS 9.5-10.1 280 20-50% C3W, bal CnW 7-11 20 WXW or WWX 0.15 mor. 8.7-9.0 230 CnW 8-15 8-20" WWX 0.07-0.18 mor. 8.6-9.1 175 5-15 12-24X WWX or PC (48-100) 0.21-0.26 NH, 9.2-10.1 166 0-12 6-16X WWX 0.08 mor. + (U3NH, 8.7-9.2 339 60-80% AC316, balance CnW 18-20 23-25? PC (50-150) 0.3 NH,+ 0-0.14 mor. 9.6-10.1 482 50-80% AC673, balance CnW 14-25 19-25? PC (50-100) 0.32 NH3 9.8-10.0 58 50-90% AC673, AC680 or E20, 18-28 18-28 WXW 0.17-0.23 mor. 8.6-9.0 178 balance CnW AC629orE10 0-20 12-20 WXW 0.11-0.20 mor. 8.7-8.9 330 AC680 or E20 0-13 18-20? PC(50) 0.26 NH3 9.5-9.9 233 0-28 12-28? WXW 0.17-0.21 mor. 8.5-8.8 204 AC673 18-20 18-20 WXW or PC(160) 0.22 mor. 9.3 577 50% E20, 50% PtW 0-18 18 WXW 0.20 mor. 8.9-9.1 857 88% CnW, 12% PfnW 12 15? PC (50) 0.21 NH3 +0.03 mor. 9.3 540 50-67% BW, bal. CnW 0-11 22X WWXorPC(50) 0.25 NH3 9.4 351 50% BW, 50% C3W 11-12 22-24 WWX 0.18 mor. 8.7 1250 40-60% C3W, balance W20 18-31 18-31 WXW 0.17-0.22 mor. 8.5-8.9 200 nr ACfi7^ MW 12-15 12-15 WXW 0.18 mor. 8.8 480 82% AC680,18% PfnW 13 17? WXW 0.17 mor. 8.9 660

Abbreviations for table: C3W = Carnauba wax No. 3, C1W = Carnauba wax No. 1, CnW = Candelilla wax, BW = beeswax, RBW = , PfnW = paraf fin wax, PtW = petroleum wax or BeSquare, MW = montan wax, WWX = water-to-wax, WXW = wax-to-water, PC(50) = pressure cell with initial water of 50 g/ 100 g wax, Mor = morpholine, turb. = turbidity, NTU = nephelometric turbidity units. ^Balance myristic acid, i.e., the only two fatty acids are oleic and myristic. "Balance myristic or .

method. With a second batch, and also with types cbw2 or fil- had higher gloss when coated with carnauba or candelilla wax trada, a minimum of 10 g oleic acid was required to make emulsions that were rapidly cooled (data not shown). emulsions with turbidities of 700-1000. Emulsions with both Oxidized Polyethylene. The higher-density polyethylene wax batches are included in Table 1. es tended to make coatings with higher gloss than low-density Ammonia-based candelilla emulsions were made by two polyethylene (data not shown). Unfortunately, the higher- methods. Those made with the water-to-wax method typically density tend to be more difficult to emulsify, had turbidities of about 1000 NTU. Those made in the pres partly because of the higher softening points. Types AC629, sure cell had somewhat lower turbidities (typically about 300 E10, AC680 and E20 were rather easy to emulsify by the wax- NTU) when made with either of the two batches of S&P can to-water or pressure cell method (Table 1). Good emulsions delilla wax just mentioned. The least turbid (175 NTU) was were made with various combinations of oleic, stearic, palmit candelilla microemulsion containing 6 g oleic acid and 6 g ic, myristic and lauric acids, although those made with only palmitic acid per 100 gwax (Table 1). In general, good emul lauric acid tended to be somewhat turbid. The more dense sions were made in the pressure cell by heating the wax mix polyethylenes (types AC 673 and AC 316) were more difficult ture to 100-130°C before addition of the balance of the water to emulsify. Fruit coatings made from the higher-melting to achieve about 25% total solids. polyethylene types tended to fracture, especially AC316, For both carnauba and also the candelilla wax emulsions which the manufacturer considered too hard to recommend the lowest turbidity was achieved with different combinations as a fruit coating (data not shown). of fatty acids depending on whether ammonia or morpholine Polyethylene wax-candelilla wax mixtures. Addition of 55 g was used (Table 1). With morpholine and no ammonia, the candelilla wax per 100 g AC316 was sufficient to prevent frac least turbid emulsions were made with oleic acid without sup ture of the coating without marked decrease in gloss. With plementation with myristic or palmitic acid. With ammonia AC673, only 35 g candelilla/100 g polyethylene wax was suffi and no morpholine, some saturated was required; cient (data not shown). Addition of improved gloss the least turbid emulsions were made with about 16% fatty ac and flexibility of AC673-candelilla coatings but not AC316- id, consisting of about half oleic and half myristic or palmitic candelilla coatings. With AC316 (softening point 140°C) acid. Candelilla and carnauba wax coatings in general had good emulsions were made with the pressure cell at 146- higher gloss if the microemulsions were rapidly cooled. For 179°C, and with AC673 (softening point 115°C) at cell tem example, candelilla wax coatings on polystyrene had mean peratures of 143-162°C. Exceptionally low-turbidity AC673- gloss at 20° of 31 NTU when made from microemulsions that candelilla wax microemulsions (turbidity < 70 NTU) were had been cooled from 70 to 40°C in about 2 min, compared made at pressure cell temperature of 161-162°C (Table 1). to 6 NTU for those cooled in about 20 min (data not shown). These appeared completely clear, like solutions. At higher Red Delicious apples coated with carnauba or candelilla wax cell temperatures, some charred deposits were found on the

Proc. Fla. StateHort. Soc. Ill: 1998. 253 interior walls of the pressure cell and emulsion turbidity was applied as a 10% hexane solution was used to establish its ef higher. fectiveness for this use (McDonald et al., 1993). Use of an Polyethylene wax was also useful for forming co-emulsions aqueous emulsion would seem more acceptable than the hex with other difficult-to-emulsify waxes. Note, for example, the ane solution, providing it is effective. emulsions that contain petroleum wax and paraffin wax (Ta Anionic emulsions with rice bran wax had somewhat high ble 1). For the formulations whose wax component consisted turbidity when mixed with 3 parts by weight carnauba wax of 50% polyethylene wax and 50% petroleum wax, emulsions and emulsified with 22 g oleic acid 0.17 moles morpholine with virtually the same turbidity were made with either oleic per 100 g wax. acid or as the only fatty acid. Wax coating formulations are often mixtures of wax mi- Beeswax. Beeswax emulsions with low turbidity could only croemulsion and other ingredients added to improve gloss or be made by mixing the beeswax with other waxes (Table 1). spread. An example would be citrus coatings made from mix Beeswax emulsions were difficult to make by the water-to-wax tures of wood rosin and wax microemulsion. Oranges and method because the viscosity was very high before inversion. tangerines with such coatings tended to have higher internal Formulations with more than 50% beeswax had 20-30% CO2 as rosin percentage increased (Fig. 1). Flux was virtually cream and very high turbidity. Beeswax coatings tended to the same for all coated fruit, both oranges and tangerines, have low gloss. 0.4-0.7 ml/min, and the dependence of internal O2 or CO2 on Montan wax. Montan wax microemulsions (Table 1) tend flux was not significant (data not shown). Interior gases were, ed to have low gloss when dried as coatings (data not shown). however, significantly dependent, p < 0.001, on rosin content. It is important that any coating spread well on surfaces. Thus it seems that internal gas differences were determined The polyethylene, candelilla wax, paraffin and beeswax for more by the permeance of the coatings than differences in mulations tended to bead up on surfaces, whereas those con the tendency of different coatings to block diffusion through taining carnauba and montan wax had better spread. Spread pores. It is generally well known that coatings high in rosin es was generally better with higher solids content. Spread was ter tend to increase internal CO2 and lower internal O2 also generally improved with addition of a leveling agent, (Hagenmaier and Baker, 1994). such as shellac or protein (Hagenmaier and Baker, 1997). In addition to the formulations just discussed, hundreds Sunburst tangerines: uncoated fruit more were formed by mixing separate microemulsions. In all cases where anionic emulsions of low turbidity were mixed, had 9.1 % O2and 7.8% CO2 the resulting emulsions had turbidity intermediate between those being mixed, and no evidence of incompatibility was ev ident. However, formulations made by mixing separate emul sions might have different properties than those made by mixing waxes before emulsification. Wax may not rapidly dif fuse from one globule to another. Nonionic emulsions. (Table 2) Nonionic microemulsions were made with nonionic emulsifiers rather than fatty acids (X and base. Except for squalene, the ingredients used for the -o-r--< i i \ r r — i 9 nonionic emulsions are also accepted by FDA for foods. The nonionic emulsions tended to be somewhat more turbid than 20 40 60 80 100 the anionic emulsions, except for the squalene emulsion which had a turbidity of only 446 NTU (data not shown). In retro % rosin (balance wax) spect, it would seem that insufficient amounts of emulsifiers Figure la. Interior gas compositions with coatings made with different ra may have been used in many of these formulations. The values tios of wood rosin to wax. shown for hydrophile-lipophile balance (HLB) are weight-av erage values based on the following values for individual surfac tants: 14.9 for polysorbate 60, 4.7 for sorbitan monostearate 3 and 3.4 for glycerol monooleate (Petrowski, 1976). Hamlin oranges: uncoated fruit The squalene emulsion seems to have potential as a vehi cle for applying squalene to prevent chilling injury. Squalene had 18.6% O2 and 2.8% CO2

Table 2. Nonionic emulsions made by the water-to-wax method.

Wax or Lipid Emulsifiers (g/100 g wax) HLBZ

polysorbate 60: 47-67 g oleic monoglyceride: 12-24 g Squalene sorbitan monostearate: 0-7 g 11.2-11.9 polysorbate 60: 13 g ., « Parvan 4450 sorbitan monostearate: 7 g 20 40 60 80 100 , petrolatum polysorbate 60: 19 g 11.2 or rice bran wax: lOOg sorbitan monostearate: llg polysorbate 60: 26 g % rosin (balance wax) Polywax 500 12.3 sorbitan monostearate: 9 g Figure lb. Interior gas compositions with coatings made with different ra 'Hydrophile-lipophile balance. tios of wood rosin to wax.

254 Proc. Fla. State Hort. Soc. Ill: 1998. Compared to 'Hamlin oranges, the internal O2 of coated FDA, Code of Federal Regulations (CFA), Food and Drug Administration, Ti 'Sunburst' tangerines was much lower and the internal CO2 tle 21. 1995. Note: this is also the source for all other CFR regulations cited in the higher (Fig. 1), indicating that gas permeance was much text. Hagenmaier, R. D. and R. A. Baker. 1993. Reduction in gas exchange of cit higher for the oranges. As mentioned, the air flux was virtual rus fruit by wax coatings. J. Agr. Food Chem. 41 (2):283-287. ly the same for both types of fruit. Therefore, the reason for Hagenmaier, R. D. and R. A. Baker. 1994a. Wax microemulsions and emul the difference is the difference in the gas permeance, rather sions as citrus coatings. J. Agr. Food Chem. 42(4):899-902. than any difference in open pores through which gas diffused Hagenmaier, R. D. and R. A. Baker.. 1994. Internal gases, content and gloss of citrus fruit coated with polyethylene wax, camauba wax, shel (Hagenmaier and Baker, 1993). lac or resin at different application levels. Proc. Fla. State Hort. Soc. In summary, formulations were presented for making wax 107:261-265. microemulsions. Coatings made from a mixture of wax micro- Hagenmaier, R. D. and R. A. Baker. 1996. Edible coatings from candelilla wax emulsion and rosin had lower permeance to CO2 and O2 with microemulsions. J. Food Sci. 61(3):562-565. increasing amounts of wood rosin. Hagenmaier, R. D. and R. A. Baker. 1997. Edible coatings from morpholine- free wax microemulsions. J. Agric Food Chem. 45:349-352. McDonald, R. E., T. G. McCollum and H. E. Nordby. 1993. Temperature con Literature Cited ditioning and surface treatments of grapefruit affect expression of chill ing injury and gas diffusion. J. Amer. Soc. Hort. Sci. 118(4):490-496. Bennett, H. 1965. 'Industrial Waxes' Volumes 1 and 2, Chemical Pub. Co, Petrowski, G. E. 1977. Food-grade emulsifiers-part II. Food Technology, Inc. NY. 1975 27(7):36-40. 1976. Burns, F. G. and I. Y. Straus. 1965. Chemical Specialties Mfrs. Assoc, Proc. of Prince, L. M. Microemulsions, Theory and Practice. Academic Press, New Annual Meeting, 52:226-7. York, NY.

Proc. Fla. State Hort. Soc. 111:255-257. 1998.

PROGRESS ON BLOSSOM END CLEARING IN GRAPEFRUIT

Ed Echeverria, Jacqueline Burns, and William Miller Introduction and Review of Literature University of Florida, Citrus Research and Center 700 Experiment Station Road Previous studies have indicated that Blossom End Clear Lake Alfred, FL 33850 ing (BEC) in grapefruit is markedly influenced by tempera ture, fruit turgidity, and fruit impact forces (Echeverria and Burns, 1994). Studies conducted in a commercial packing Additional index words. Postharvest. house setting as well as under controlled conditions demon strated that elevated pulp temperature and reduced relative Abstract. Blossom-end clearing (BEC) in grapefruit is a disorder humidity increased the appearance of BEC. High fruit impact that typically appears as a water-soaked area on the blossom- forces during handling, such as those that may occur in areas end of fruit. Previously we have shown that BEC (1) can be completely eliminated by proper postharvest handling, (2) can of the packingline (e.g., the fruit dump site), increase the ap be reduced by overnight storage of harvested fruit at 75°F, 95% pearance of BEC in fruit lots packed later in the season when RH before handling through the packingline, and (3) can be re outside temperatures are high. In addition, it was observed duced by reducing fruit impact forces on the packingline. In that BEC appeared more frequently in fruit in which the cen this study we used controlled impact studies to demonstrate tral spongy core had disappeared. As fruit mature and age, that BEC could be induced more readily in field-harvested fruit, the disappearance of the spongy core occurs naturally and where pulp temperatures were high. Reducing pulp tempera creates a hollow central core that may weaken the segment tures by overnight storage at 70 F, 95% RH markedly reduced juncture. A significant fruit impact can rupture the segment the appearance of BEC. The incidence of BEC steadily in juncture and enclosed juice vesicles, permitting the released creased throughout the harvesting season from late January juice to travel through the open central core and to the peel to June, and we could not demonstrate a peak of BEC appear ance during bloom time. Withholding irrigation 24 hours before unobstructed. A wet or 'clear' area appears on the peel usual harvest did not affect the occurrence of BEC. Symptoms of ly located on, but not limited to, the blossom end of the fruit. BEC can appear in less than 5 minutes after fruit impact. The Under natural conditions, temperature and fruit turgidity severity of symptoms may be associated with the amount of al may play a larger role in BEC development as temperature bedo available to absorb juice released on fruit impact. and humidity increase and fruit age during the harvest sea son. The aim of this project was to investigate the interrela tionship between fruit age, temperature, fruit turgidity and the incidence of BEC. We harvested fruit throughout the sea son and induced BEC under various temperature regimes. We attempted to alter fruit turgidity by altering the irrigation Florida Agricultural Experiment Station Journal Series No. N-01677. This project was supported by a grant from the Florida Department of Citrus. strategy immediately before harvest. Commercial packers

Proc. Fla. State Hort. Soc. Ill: 1998. 255

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