Preharvest Lipophilic Coatings Reduce Lenticel Breakdown Disorder in 'Gala' Apples

(peel) arc often linked to climatic conditions during the growing season and are initiated when a partic- ular metabolic system(s) exhibits strcss- induced hysteresis. These include russet, staining, cracking, splitting, flecking, bitter pit, blotch, lenticel marking, radiation injury, delayed sunscald, superficial scald, and Soft scald (Mehcriuk et al., 1994; Pierson et al., 1971; Porritt et al., 1982). Together, these disorders may render unmarketable as niuch as 20% of total production. Considering that the value of apples in Washington state alone in 2006 was $1.4 billion (National Agricul- Preharvest Lipophilic Coatings Reduce tural Statistical Service, 2007), reduc- Lenticel Breakdown Disorder in 'Gala' Apples ing the loss due to physiological disorders is of significant economic importance. " 3 Eric A. Curry '14 , Carolina Torrcs , and Luis Ncubaucr Since 2000, lenticel breakdown disorder (LR) has been a high priority area for research investigations in the ADDITIONAL INDEX wons. Mt1us xdomestici, physiological disorder, storage, cuticle, microcracking, wax, lipids, 'Fuji', 'Granny Smith', 'Golden Delicious' and apple growing regions of the United States. LB symptoms are not SUMMARY. Lenticel breakdown disorder (LB), most prevalent on 'Gala' (Malus x visible at harvest nor are they usually domestiot) apples, especially in arid regions, has also been observed on other apparent on unprocessed fruit after common cultivars. Depending on the preharvest environment, fruit maturity, and storage. It is usually after typical frLlit length of storage, LB usually appears as one or more round, darkened pits, centered ymp- on a lenticel, ranging in diameter from 1 to 8 mm. Symptoms are not visible at processing and packing that s harvest nor are they usually apparent on unprocessed fruit after storage. However, toms are fully expressed (Fig. 1). following typical fruit processing and packing, symptoms are fully expressed after Particularly frustrating for the ware- 12 to 48 h. Because the 3 to 4 weeks preceding 'Gala' harvest are usually the hottest house is that it may take up to 48 It for and least humid, we theorized that desiccation stress was a main causative factor. 1,11 to appear after fruit have been Thus, several unique lipophulic formulations were developed that might reduce packed (E.A. Curry, personal obser- desiccation potential during this period of hot and weather and rapid fruit vation). If symptoms are detected enlargement. Emulsions of lipophilic formulations were applied to whole trees at before shipment, there are often sig- various dosages and timings. In 2005, using a single handgun application 1 day nificant repacking costs; if unde- before harvest, the best treatment reduced LB by about 20% in fruit stored 90 days tected, the negative impact on repeat at -1 °C. The following season, the best treatment from a single handgun application 7 days before harvest reduced LB by 35% after 90 days at -1 °C, whereas sales can be lasting. 3 weekly applications beginning 3 weeks before harvest reduced LB in similarly The distinctive features of LB stored fruit by as much as 70%. In 2007, the best single treatment applied 1 week are: 1) it is not visible at harvest, 2) before harvest using a commercial airblast sprayer reduced LB by almost 50% after symptoms on unprocessed fruit in 90 days at -I °C. storage are not visible, 3) symptoms are expressed mainly after typical pro- n apples, development of physio- during storage. Disorders related to cessing (dump tank, washing, waxing, logical disorders is a function of dysfunctions or aberrations in the and packing), 4) pitting is round and J many components, including cul- development of the epidermal tissue centered on the lenticel, 5) little if any tural management, growing environ - ment, fruit maturity, and conditions Units To convert U.S. to SI, To convert SI to U.S., Mention of a trademark, proprietary product or multiply by U.S. unit SI unit multiply by

vendor does not constitute a guarantee or warranty char kPa of the product b the U.S. Dept. of Agriculture and y 29.5735 II oz ni, 0,0338 does not imply its approval to the exclusion of other 0.3048 ft 01 3.2808 products or vendors that also may be suitable. 3.78i4 gal L 0.2642 'U.S. Department of Agriculture, Agricultural 9.3 540 gal/acre L-ha 0.1069 Research Service, Tree Fruit Research Laboratory, 2.54 inch(es) cm 0.3937 1104 N. Western Avenue, Wenatchee, WA 98801 25.4 inch(es) mm 0.0394

'PACE International LLC, 5661 Branch Road, inch cm2 0.1551) 6.4516 Wapato, WA 98951 mm2 0.0016 645). 1600 incls2 'Pace international I.LC, Av. Am. Vespucio N. 2680, 4.4482 hf N 0.2248

Ofleina N. 101, Conchali Santiago-Chile, Chile micron Am ppm 4Corresponding author. E-mail address: eric.curr@ ars.usda.gov . (°F-32) ± 1.8 'F IC 1.8 x°C) + 32

690 October-December 2008 18(4) WA ___

Fig. 1, Lenticel breakdown (LB) disorder on 'Gale Gala' (A), 'Golden Delicious' (B), 'Royal Gala' (C and D), and 'Imperial Gala' (E) apples. Insets in A and B show - .-. close-up of pitted lenticels. , corking of the cortex tissue is evident, Initial studies were focused on and 6) there is a cavity underlying the poststorage processing, and a number sunken pit. It is different from jon- of factors were identified that, if athan spot and lenticel spot in that modified, could significantl y reduce, s V^C^_ pitting is always present and usuall y but not eliminate, svniptom expres- -. . progressive with increased time in sion (Curry, 2003). Importantly, this A •' .. ,. storage. earlier work established that certain Although prevalent on 'Gala' orchards (or blocks within orchards) Fig. 2. Pitted lenticel (similar in size to apples, especiall y 'Royal Gala', LB showed no propensity for LB, that shown in Fig. 1E) from a 'Royal has also been observed on 'Fuji', and whereas others were highl y suscepti- Gala' apple viewed perpendicular to the to a lesser degree on 'Granny Smith', ble. Our efforts then focused on fruit surface (A). Dashed line indicates that fruit flesh was cut vertically 'Golden Delicious' (Fig. 1B), and preharvest environment. through the center of the pit with a 'Delicious'. Early symptoms on Previous studies showed that single-edged razor to show one-half of packed fruit from regular atmosphere water vapor permeance of apple the pit in water (B), and the other half (RA) storage are visible in angled cuticle in storage was linked to cuticle of the pit freeze-dried and examined light as slight indentations in the microcracking (Maguire etal., 1999). using scanning electron microscopy epidermis about 1 to 2 mm, usually This, together with our ensuing ob- (C). Micrograph in C is a digital mirror symmetrical and centered on a lenti- servation (E .A. Curry, unpublished image to correspond with the picture in ccl, without any darkening. With data) that fruit subject to conditions B. time, the depth of the dimple of high desiccation potential during increases and the pit often becomes the final weeks of fruit enlargement Our objective in this series of trials progressively darker. The darkening had a greater propensity to develop was to determine if preharvest topical appears to he largely a function of LB, led to the hypothesis that re- application(s) of hipophilic coatings how many layers of cells have desic- ducing water vapor permeance of would reduce the incidence and/or cated, thereby compressing the cell the cuticle preharvest by applying severity of LB in 'Gala' apples in RA walls, and the degree of phenolic a lipid-based, hydrophobic coating storage. browning therein. When a fully devel- would reduce LB development on oped pit is sliced in half, a cavity is fruit in storage. Hydrophilic and lip- Materials and methods present commencing several cell layers ophilic edible films and coatings have Trials were conducted over two beneath the liypodermis (Fig. 2). been shown to alter food moisture crop seasons in Washington State and In severe cases, pits max' overlap and content (1)ebeaufort et al., 1998; one in Chile, in commercial orchards appear coalesced. Generall y, there is Hagenmaier and Shaw, 1990; Kester that had had a history of LB for little corking in the cortex beneath and Fennema, 1989; Morillon et al., several years. In addition to an un- the pit (Fig. 2C). 2002; Quezada-Gallo et al., 2000). treated control, treatments included

October-December 2008 18(4) 691 [I TECHNOLOGY AND PRODUCT REPORTS the following three products man- subsequent trials was collected about (Svstat Software, San Jose, CA). Nor- uflhc tu rcd by Pace International 7 d after the last application, which mally distributed data were subjected (Seattle, WA): 1) 2.5% EpiShield I SI preceded commercial harvest b y 1 to to analysis of variance and means were a concentrated emulsifiable mixture 2 d. Seventy apples were collected separated using luke y's Studentized of plant extracts and vegetable esters; from each replication and were trans- range test ( uso). Data not normally 2) 1.5% PrimaFresh' 50-V, an emul- ported to the laboratory, of which 60 distributed [mean LB incidence (%), sifiable concentrate of blended veg- were placed on fiber tra ys in card- mean LB severity (pits/cm 2 )] were etable oils; and 3) 5% Natural board boxes and kept in RA storage at subjected to the Kruskal-Wallis test. Shine rM 9000, an emulsifiable con- -1 °C for poststorage evaluation. At Differences among treatment means centrate of carnauba wax. None of the 0, 90, and 180 d at —1 °C plus 24 h at were assessed at I'!!^- 0.05. orchards used in these experiments 23 °C, 10 fruit from each replication FRUIT SURFACE EXAMINATION had overtree irrigation or cooling, were evaluated for fruit quality. USING SCANNING ELECTRON nor was there an measurable precip- Internal ethylene concentration MICROSCOPY (SEM). In 2006-07, itation during or after treatment (IEC) was measured by inserting an additional fruit were also collected applications. 18-gauge needle equipped with a for the evaluation of treated cuticular 2005-06, CHELAN, WASHINGTON. rubber septum through the fruit calyx surfaces. Apples were picked by the A block of 8- year-old 'Imperial into the central cavity and withdraw- stem and calyx and were placed snug- Gala'/'Malling 106' ('M.106') trees ing 0.5 nil. of core gas. Ethylene was gly into foam trays with the longitu- on sandy loam was used from which measured using a gas chromatograph dinal side of the fruit perpendicular to comparable trees were preselected for (model 5880A; Hewlett Packard, the alley, outward. These were placed similar crop load and vigor. Treat- Avondale, PA) equipped with a 1 -m in RA storage until further exanlina- ments were arranged in a completely Poropak (Waters Corp., Milford, tion. At 0, 90, and 180 d after stor- randomized design with six replicates MA) Q column according to standard age, peel tissue from three similar fruit Of three trees. Formulations were mixed protocols for flame ionization detec- was excised for evaluation by SEM. on site in 100 1. of water and ap- tion. Ground color was measured Sample preparation was similar tothe plied to runoff 1 d before harvest (on with a ColorFiex (model 45/0; method by Curry (2005) with the 31 Aug.) using a variable-pressure Hunter Laboratories, Reston, VA) following modifications. Untouched hand-held nozzle operating at about using the Hunter L* , a* , b* system portions of cuticle 4 to 5 mm in 2 Lmin and the hue angle (h) calculated. diameter and 0.2 mm thick were 2006-0 7, MALAGA, WASHINGTON. Firmness was measured at two loca- shaved by hand about midway An orchard block of 7-year-old 'Gale tions per fruit, after removing the peel between the stem and the equator, Gala'/'M.106' trees on sandy loam to a depth of 2 mm, with a Texture just proximal to the widest part of was used from which comparable Analyzer (TA-XT2; Texture Technol- the fruit, using a 0.01 2-mm-thick trees were preselected for similar crop ogies, Scarsdale, NY) equipped with double-edge stainless steel razor pre- load and vigor. Treatments were an 11.1-mm probe. Starch conver- viouslv rinsed with acetone and air- arranged in a complete randomized sion was assessed using a scale of I dried to remove an y residual oil. design with six replicates of three to 6 with 6 = no starch remaining. Samples were taken from the side trees. Formulations were mixed on At 90 and 180 d in RA storage, facing the alley. The shaved cuticle site and applied as previously an additional 20 apples per replicate section was fixed to a 24-mm alunii- described 1 week before harvest (sin- were subjected to a small-scale pilot num stub using double-sided carbon gle treatment applied on 24 Aug.) or packing line to induce LB. First, cold tape by pressing the edges of the weekly beginning 3 weeks before fruit were submerged in a 33 °C water entire section onto the tape using harvest (three successive applications bath for 5 min. Immediately there- a pair of fine-tipped tweezers under applied on 17, 24, and 31 Aug.). after, fruit were placed on a small- a stereomicroscope. The stub was 2007, LINARES, CHILE. Formu- scale research packing line and con- placed in a small, glass vacuum desic- lated treatments were applied to a veyed through a soap wash, cool water cator containing packaged silica gel uniform block of 9-year-old 'Royal rinse, wax treatment, brush polisher, and kept at 10°C and 1.3 kPa fhr 24 Ii Gala'/seedling, to runoff, using a warm air dryer, and were then placed or until further treatment. Before commercial airhlast sprayer at a vol- on trays in cardboard boxes and SEM evaluation, mounted tissue was ume of 1900 L-ha 1 week before returned to —I °C for 48 h. Fruit were coated with platinum using a Desk II harvest (single application on 13 removed from the cold and left on cold sputter coater (Denton Vacuum, Feb.) or weekly starting 4 weeks open trays at 23 °C for 24 h bet-ore Morristown, NJ) fitted with a tilting before harvest (four treatments ap- evaluation. LB was assessed simpl y by omm - rotating head. With the sample plied on 23 and 30 Jan., and 6 and counting the number of discrete, len- 47 mm from the platinum target, a 13 Feb.). Treatments were arranged tied-centered pits within a 2-cm- coating thickness of 20 nm was in a complete randomized design diameter ring placed over the most achieved after 75 s at 40 milliamps with six replicates of three trees per severely affected area of the fruit. Data and 2.6 Pa. Coated samples were kept replicate. are presented as the percentage of in a vacuum desiccator and held SAMPLE COLLECTION AND fruit with 1.11 symptoms and/or the under low vacuum at 1.3 kPa and QUALITY EVALUATION. Fruit from the number of discrete pits per square 10 °C until they were microscopically first trial was collected the day after centimeter surface area per apple. examined using a scanning electron treatment, whereas fruit from the two STATISTICAL ANALYSIS. Statistics microscope (Vega-IT model 51361,M; wem-e performed using Systat 11 Tescan, Brno, Czech Republic) 692 HrdinoIogy October-Deccnibcr 2008 18(4) equipped with secondary and back- trial, maximum expression occurred lenticels (Table 2). Similar to the scattered electron detectors. Unless after 90 d in RA, and no increase was previous year's study, most of the otherwise noted, images were ob- measurable at 180 d (data not shown). LB (17%) was present after 90 d tained at 10 kV and 7.4 mPa. Fruit quality attributes were no differ- in storage. ent among treatments (data not Using a single application 1 week Results shown). These preliminary data sug- before harvest, only 5% Natural

2005-06, CHELAN, WASHINGTON. gested that prcharvest application of Shine""" 9000 resulted in fruit with Fruit from this site developed se- certain lipophilic formulations could less LB after 90 d in storage; vere LB after 90 and 180 d storage reduce the number of fruit expressing however, after 180 d, there was at -1 °C plus simulated packinghouse LB after storage plus processing. no dit}crence from the control. processing. Although incidence was 2006-07, MALAGA, WASHINGTON. Whereas a single application of l.5% comparable between treatments, Although incidence of LB oil PrimaFresh 50-V showed an inci- the percentage of fruit exhibiting at this location was lower than in dence of 10.8% after 90 d in storage, symptoms was lowest for the Epi- years prior, almost 20% of untreated which was not significantl y different ShieldTM treatment (Table 1). Nor- fruit in RA storage ftr 180 d from the control, LB incidence with mally, symptom expression increases were deemed unmarketable due to this treatment did not increase as did with time in storage; however, in this presence of one or more dark pitted the other treatments. Using three preharvest applications, all treated fruit after 90 d in storage showed Table 1. Effect of a single aqueous application of proprietary lipid formulations LB incidence !^70% of the untreated administered by a low-pressure hand gun to whole 'Imperial Gala'/'M.106' controls (Table 2). Although inci- apple trees 1 d before harvest (31 Aug. 2005) in Chelan, WA, on expression of dence increased after all lenticel breakdown (LB) after 90 d of storage at -1 "C (30.2 uF). 90 ci 'III reduction in LB Treatment Mean LB incidence (%) Mean LB severity (pits/cm2)Y ranged from 41% to 65% of untreated controls. There was no significant Control 83 a' 1.6 a difference in the percentage of fruit 2.5% EpiShield'" 65 h 1.4 ab with LB among fruit receiving appli- 1.5% PrimaFrcshv 50-V 81 a 1.3 h cations of an y of the formulations 5/0% Natural 76 at) 1.4 ab within a sampling date. Shine I M 9000 EFFECT OF TREATMENT ON FRUIT 'EpiShield' M, PrimaFresh v SO-V. and Natural Shine 9000 are products of Pacc International (Seattle, WA). QUALITY. Although there were no 1 pit/cm' = 64516 pits/inch'. 'Values within a column with the same letter are not significantl y different at PS 0.05 using the Kruskal-Wallis test differences among treatments on for nonparametric distribution. fruit quality at harvest, some

Table 2. Effect of treatment and number of applications of proprietary lipid formulations applied in 2006 to whole 'Gale Gala'/'M. 106' apple trees in Malaga, WA, on apple fruit quality and incidence of lenticel breakdown (LB) after 90 or 180 d of storage at -1 5C (30.2 °F). Treatments were applied using a low-pressure handgun. Multiple applications were applied weekly beginning 3 weeks before harvest (17 Aug.), whereas the single application was applied I week before harvest (31 Aug.). Fruit Soluble LB Time in RA Applications IEC firmness solids incidence Treatment' (d)t (no.) (1iL-L1)' (lbf)" (%) (%) Control 90 24.1 dv 15.6 ;1 a 16.7 a 2.5% EpiShield' TM 1 37.9 cd 15.4 ab 13.1 a 12.5 a' 1.5% PrimaFrcsft' 50-V 59.0 c 15.1 b 13.0 a 10.8 ab 5.0% Natural Shine 9000 39.6 cd 15.0 hc 12.6 h 4.6 b 2.5% EpiShieldtm1 3 85.01) 14.4 d 13_1 a 5.0 b 1.5%PrimaFresh"5O-V 64.7hc 14.7cd 13.4a 3.3h 5.0% Natural Shine' 9000 122.4 a 14.3 d 13.0 a 5.01) Control 180 157.7 c 13.1 a 12.7 ab 19.2 ab 2.5% FpiShicld'" 1 144.8 c 13.1 a 12.8 a 14.2 ab 1.5% PrimaFresh' 50-V 162.0 c 13.0 ab 12.5 ab 9.6 b 5.0% Natural Shine'" 9000 271.7 a 12.8 all12.3 b 14.2 ab 2.5% EpiShield' " 3 269.5 a 12.6 he 12.3 b 10.8 b 1.5% PrimaFresh' 50-V 228.0 h 12.2 c 12.5 ab 11.2 h 5.0% Natural ShincTM 9000 297.9 a 12.6 he 12.4 ab 6.7 h 'EpiShield I M PrimaFresh® 50-V. and Natural Shine I M 9000 arc products of Pace international (Seattle. WA). RA regular atmosphere storage. internal eth ylene concentration; 1 gb-I. 1.0 ppm "1 lbf= 4.4452 N. 'Valucs nit liii, .1 column is it), the same letter are not significantly ditkrent at I'S 0.05 using lukev's Studentizcd range test ( HSD) for normall y distributed data I JEC, fruit firmness, .i ml soluble solids) or the Kritska)-Wallis test for nonparametric distribution (1.11 incidence). lk,rI&linokgv October-December 2008 18(4) 693 TECHNOLOGY AND PRODUCT REPORTS treatment effects were observed as time in storage increased. After 90 d at -1 °C, fruit with three applications had higher I EC than those untreated or those receiving a single application (Table 2). Generally, fruit firmness followed this same ripening pattern, with the control and the single application and lowest lipid content treatment being the most firm and three applications being less firm. DifThrences in percentage of soluble solids were minor. After 180 d at -1 °C, similar patterns per- sisted, generally with less difference and variance among treatment means. '1 2 Ground color was unaffected by treatment (data not shown). Ag

FRUIT SURFACE EXAMINATION 2c lu" 14 2 USING SEM. At harvest and after 90 and 180 d in storage, cuticle samples from fruit receiving different treatments were examined using SEM. Representative images of cuticular surfaces from untreated fruit as well as from those receiving multiple applications of each treatment are shown in Figs. 3 and 4. The view field : in Fig. 3A is 1.0 mm. Typical of fruit growing in and regions, the fruit epicuticle shows significant microcracking. Magnification of the inset shows a lenticel with microcracking in various stages of "healing" (Fig. 3B). Because formulation and concentration varied among treatments, examination of treated surfices was completed to understand more fully the nature of the coatings in relation to the cuticular surface. Figure 4 shows cuticle plus lenticels from fruit surfaces 1 week after the third application of each respective treatment. Magnifica- tion for all images is identical. Fruit surfaces treated with EpiShield I M Fig. 4. Scanning electron micrographs (2.5%) and Natural Shine' 9000 Fig. 3. Scanning electron micrographs of 'Gale Gala' apple peel tissue sampled (5.0%) indicated a somewhat thicker of surface of untreated 'Gale Gala' and hardened coating that has contin- apple at harvest. Field of view (A) is 1 week after the third weekly ued to crack with fruit expansion application in 2006. The following about 1.0 mm 2 (0.00155 inch') and treatments, manufactured by Pace (Fig. 4, A and (). On the other hand, shows normal cuticular microcracking International (Seattle, WA), were 1.5% PrimaFresh 50-V shows more due to fruit enlargement. Magnification of inset in A indicated by applied to whole 'Gale Gala'/'Malling melding of the applied material with 106' apple trees with a low-pressure the cuticle. Examination of fruit sur- the dashed line shows a lenticel in the handgun: 2.5% EpiShield f (A), 1.5% face at 90 or 180 d in RA storage process of cracking and healing (B). PrimaFresh 50-V (B), and 5% Natural showed little difference, with regards Magnification of inset in B indicated by Shine iM 9000 (C). The bar in each to coating, than that observed at har- the dashed line shows typical image represents 100 p.m (100 microcrack "healing." The bar in each microns). vest (data not shown). Fruit surfaces image represents 100 pm (100 microns). receiving a single application were also similar to those receiving three applications, though less thick (data not 9000, SEM examination revealed fewer 2007, LINARES, CHILE. Differen- shown). Where the coating was exces- wax platelets protruding through the ces among treatmentswere apparent sivelv thick, such as that for three thickened build up after 90 d RA (data after 90 d in RA. With a single appli- applications of 5% Natural Shine I M not shown). cation, only 2.5% EpiShieldTM 694 Widnokgv . October-Dcccnibcr 2008 18(4) resulted in fewer fruit with LB (Table platelet regrowth. Under optimal con- treatment that was irrigated b y over- 3). Using four applications, all treat- ditions, this process allows the cuticle tree sprinklers. However, as the tem- ments resulted in fruit with less LB to enlarge while still maintaining perature rose and the irrigation ranging from 48% to 61% of the con- protection against cell desiccation. system was used often to cool the trol; there was no difference among However, under conditions of rapid fruit, it became obvious that the fruit values for treated fruit. Evaluation of fruit enlargement, high ambient tem- surface was accumulating significant fruit quality at 90 d RA storage indi- perature, and low relative humidity, residue from the water (data not cated no significant treatment effects "repairing" of the microcracks may shown). Although the treatments on measured parameters (data not lag fruit enlargement. Under such may have had similar benefits for shown). To minimize additional treat- conditions, cells closest to the micro- reducing incidence of LB, we decided ment factors, fruit were not treated cracks may tear and/or desiccate this was a variable for which we had with pre- or postharvest fungicide. beyond the point of recovery. Lend- little control, and we opted to use an This resulted in 60% ofthe fruit exhib- eels are often the source of multiple orchard with u ndcrtree irrigation iting sufficient rot after 180 d in RA as microcracks (Fig. 3) that may further instead. to he unusable for further evaluation. stress or induce injury to underlying Generally, multiple applications cells, leading to desiccation pre- and were more efThctive than single treat- Discussion postharvest (Maguire et al., 1999). ments for reducing incidence of LB. As in other tree fruit, the apple We assume the lipophilic applications This may have more to do with the maintains a cuticle to protect the reduce subcuticular cell damage by time of most severe desiccation pres- inner cells from desiccation, contam- covering or filling in some of the micro- sure during the final month before ination, and excessive water absorp- cracks to prevent moisture loss and harvest and the optimum time of appli- tion. Wax biosynthesis, the basis of possible desiccation -induced necrosis. cation. Further work is needed to better cuticle development, begins as soon Some of the variability of re- understand the relationship of micro- as the epidermal cells sense desicca- sponse between seasons is presumed climate and application timing and dos- tion pressure and continues through due to diffi.renccs in cultural and envi- age to maximize treatment efficacy. storage until cell necrosis (Belding ronmental factors. In addition, culti- et al., 1998; Morice and Shorland, vars differ in surface wax morphology 1973; Veraverheke et al., 2005). and chemical composition during Literature cited As the fruit enlarges, the cuticle development as well as during and Belding, RD., S.M. Blankenship, F. also grows b "shearing" or "cracking" after cold storage and subsequent Young, and R. B. I ,cidv. 1998. Composi- to accommodate the expansion Shelf life (Curry, 2005; Veraverbeke tion and variability of epicuticular waxes (Faust and Shear, 1972; Meyer, et al., 2001). Characteristics and in apple cultivars. J. Amer. Soc. Hort. Set. 1944). Hypodermal cells may un- composition of apple cuticular wax 123:348-356. dergo mitosis and also stretch in the also change in response to chemicals Curry, E.A. 2003. Factors associated with direction of enlargement, whereas (Curry, 2008), as well to environ- lenticel breakdown in apples. Proc. Wash- epidermal cells mainl y divide to main- mental stresses such as rain acidity ington State Hort. Assn. 5 June 2008. tain minimal surface area per cell (Rinallo and Mori, 1996), temper-

October-December 2008 18(4) 695 TECHNOLOGY AND PRODUCT REPORTS

accumulation of cpicuticular wax on i\lorice, I .M and F. B. Shorland. 1973. emulsion-based edible films. J. Membr. developing leaves. Photochem. Photo- Composition of the surface waxes of apple Sci. 4678:1-10. hiol. Sci. 2:861-866. fruits and changes during storage. J. Sci. Food Agr. 24:1331-1339. Rinallo, C. and B. Mon. 1996. Damage Kester, J.J. and 0. Fennema. 1989. An in apple (Mains domestica llorkh) fruit cdible film of lipids and cellulose ethers: Morillon, V., F. Debeaufort, G. Blond, exposed to different levels of rain acidity. Barrier properties to moisture vapor trans- M. Capelle, and A. Voilley. 2002. Factors J. Hurt. Sci. 71:17-23. iiission and structural evaluation. J. Food affecting the moisture permeability of Roy, S., A.E. Watada, W.S. Conway, E.F. ci. 54:1383-1389. lipid-based edible films: A review. Crit. Rev. Food Sci. Nutt. 42:67-89. Erbc, and W.P. Wergin. 1994. Low- [uric, S., E. Fallik, and J.D. Klein. 1996. temperature scanning electron micro- The effect of heat treatment on apple National Agricultural Statistical Service. scopy of frozen hydrated apple tissues cpicuticular wax and calcium uptake. 2007. Agri-Facts. 5 June 2008.

696 Iktdinokgy October-December 2008 18(4)