Ethylene nd chnges during ripening in Horvin plum (Prunus slicin Lindl.) fruits El etileno y los cmios durnte l mdurción en frutos de ciruel (Prunus slicin Lindl.) Horvin Ldy Ximen Rozo-Romero 1, Jvier Giovnni Álvrez-Herrer 1, nd Heler Enrique Blguer-López 1, 2 ABSTRACT The plum is fruit prized for its nutrceuticl properties ecuse of its high content of fier nd soritol, which id in digestion; furthermore, it is chrcterized s contining ntioxidnt pigments nd n ntiseptic ction with nthocynins. These fruits re clssified s climcteric nd continue the process of respirtion nd ripening fter hrvesting; ecuse of this, it is necessry to hrvest erly so they cn withstnd trnsport, which often cuses the fruits to not rech the consumption mturity required y consumers. The effect of ethylene on the ripening of plum fruits ws evluted, for which completely rndomized design with 1 tretments ws used, which resulted from the comintion of two fctors plus control without pplictions. The first fctor ws the ethylene dose (1; 1, nd 2, mg L -1 ) nd the second fctor ws the length of exposure to the ethylene (5, 1 nd 15 minutes). The fruits were stored t room temperture for 9 dys. In the fruits treted with ethylene, significnt increse in the respirtion index nd totl solule solids ws oserved. Additionlly, greter totl titrtle cids nd firmness vlues were otined with the control tretment thn with the ethylene; similrly, the ethylene ppliction incresed the fresh mss loss in the plum fruits. Overll, differences etween the fruits treted with ethylene nd the control were oserved, ut not etween the doses, indicting tht the lowest ethylene dose (1 mg L -1 ) cn otin the desired uniformity in plum fruits. Key words: posthrvest, storge, peel color, fruits. RESUMEN L ciruel es un fruto muy precido por sus propieddes nutrcéutics, y que por su lto contenido de fir y soritol yud l digestión, demás se crcteriz por contener pigmentos de cción ntioxidnte y ntiséptic como ls ntocinins. Estos frutos se clsificn como climtéricos, y continún su proceso de respirción y mdurción después de ser cosechdos, deido esto es necesrio cosechrlos en etps temprns, pr que puedn soportr el trnsporte, lo cul ocsion que muchs veces los frutos no lcncen l mdurez de consumo requerid por el consumidor. Se evluó el efecto del etileno sore l mdurción de frutos de ciruel, pr lo cul se utilizó un diseño completmente letorizdo con 1 trtmientos, los cules resultron de l cominción de dos fctores más un testigo (sin plicción). El primer fctor fue l dosis de etileno (1, 1. y 2. mg L -1 ) y el segundo fctor el tiempo de exposición l etileno (5, 1 y 15 minutos). Los frutos fueron lmcendos tempertur miente durnte 9 dís. En los frutos trtdos con etileno se oservó un umento significtivo en el índice de respirción y los sólidos solules totles. Adicionlmente, en ls vriles de cidez totl titulle y firmez se otuvieron vlores myores en el trtmiento testigo que en los trtmientos con etileno, del mismo modo l plicción de etileno umentó l pérdid de ms fresc en los frutos de ciruel. En generl se oservron diferencis entre los frutos trtdos con etileno y el testigo, pero no entre ls dosis, lo que indic que con l menor dosis de etileno (1 mg L -1 ) se puede otener l uniformidd desed en los frutos de etileno. Plrs clve: poscosech, lmcenmiento, color de l epidermis, fruts. Introduction The Horvin plum fruit vriety comes from deciduous fruit tree widely cultivted in Colomi (Cmpos, 213; Álvrez-Herrer et l., 215); the fruit is drupe tht usully presents wx on the epidermis (Bugher, 23). Plum fruits cn mesure etween 2 nd 8 cm nd the shpe cn e round, olong or ellipticl (Bugher, 23). Their principl component is wter nd they re enriched with phosphorus, clcium nd potssium (Clvo-Villegs, 29). They lso contin compounds tht re of nutritionl interest, including soritol, which promotes lxtive chrcteristic nd high fier content (Clvo-Villegs, 29). The sme uthor lso mentioned tht they hve ntiseptic, ntioxidnt Received for puliction: 27 Mrch, 215. Accepted for puliction: 3 June, 215. Doi: 1.15446/gron.colom.v33n2.49856 1 2 Agriculturl Reserch Group (Grupo de Investigciones Agricols in Spnish), Fculty of Agriculturl Sciences, Universidd Pedgogic y Tecnologic de Colomi (UPTC). Tunj (Colomi). jglvrezh@gmil.com Progrm of Biology, Fculty of Bsic Sciences, Universidd El Bosque. Bogot (Colomi). Agronomí Colomin 33(2), 228-237, 215
pigments, such s nthocynins. However, their consumption is low, which is ttriuted to under ripe when mrketed (Crisosto et l., 24) ecuse consumers vlue the fruits of plum in color, flvor nd rom (Louw nd Theron, 212) nd even though they re mny nutritionl enefits they provide plums, posthrvest hndling is not pproprite ecuse the fruits re often hrvested erly in order to fcilitte trnsport nd distriution (Adi et l., 22). At present, deciduous fruit crops present severl chllenges, some relted to the hndling of fruit in the pre- nd posthrvest periods, due to the high demnd for qulity in specilized mrkets (Fchinello et l., 211) tht oliges producers nd mrketers to implement pproprite technologies tht help conserve the physicl nd chemicl chrcteristics of fresh produce for longer period of time. Among the lterntives for fruit storge, the use of 1-MCP hs presented mjor effects in terms of the preservtion of the posthrvest shelf-life of fruits. Velrdo et l. (212) reported tht 1-MCP tretments did not ffect weight loss, ut retined flesh firmness; 1-MCP helped to mintin the chrcteristic fruit color regrdless of the temperture for more thn 3 d of shelf-life during storge. Dong et l. (21) reported in fruits of Red Ros plum ws treted 1-MCP low ethylene production nd softened more slowly thn untreted fruits. They lso showed lower exopolyglcturonse (exo-pg) nd endo-glucnse (EGse) ctivities nd the respirtion rtes, pectin esterse (PE) nd endo-pg were similr in 1-MCP-treted fruits nd control. Ozturk (215) reported the effects of pre-hrvest methyl jsmonte (MJ) tretments on the ethylene production, respirtion rte, ioctive compounds nd physicochemicl prmeters of plum fruits (Prunus slicin Lindl. cv. Fortune nd Frir); in oth plum cultivrs, 1,12 mg L -1 MJ incresed the hue ngle of the fruits. The fruit mss nd geometric men dimeter were lower in the MJ tretments, while the flesh firmness ws higher, except on the initil hrvest dte. The solule solids concentrtion incresed nd the titrtle cidity decresed with the MJ tretments. The MJ-treted fruits exhiited higher levels of ethylene production nd respirtion rtes. MJ ws more effective in incresing the wter-solule ntioxidnt ctivity, wtersolule phenolics nd individul phenolics. The chlorogenic cid, cffeic cid, rutin, ferulic cid, nringenin nd kempferol contents incresed significntly with 2,24 mg L -1 MJ. In plum crops, fruit hrvesting is done mnully sed on the fruit colortion, ccording to the proportion of color in the epidermis (green-red), which genertes different orgnoleptic chrcteristics when mrketing nd hrvest mturity plys very importnt role in determining the qulity nd shelf-life of the product nd consumer cceptnce (Singh nd Khn, 21). In climcteric fruits such s the plum, ethylene is one of the promoters nd coordintes the principl chnges during the growth period; this ction promotes fruit softening nd ccelertes the metolic processes (Plou et l., 23). The ction of this hormone is produced y the inding of the molecule nd the receptors locted in the endoplsmic reticulum memrne (Serek et l., 26). This process ctivtes receptor tht sends trnsduction signls tht generte physiologicl nd generic response (Pereir et l., 28). The ethylene presence efore hrvest improves the stimultion of mturtion, offering consumers etter tsting plums tht re fully ripened (Kder, 28), ecuse the mrketing of plum fruits re vlued for their color, flvor nd rom (Louw nd Theron, 212). The side effects of ethylene doses on plums is unknown; s perishle fruit, it cn diminish its shelf-life, ut, if the tretment is done fter prolonged refrigertion period or with crops recently hrvested t different mturity levels, they re not redy to e commercilized. It could e mngement option with greter opportunity for distriuting products in the interntionl mrket. Moreover, this study imed to ssess the effect of ethylene on hrvested Horvin vriety plums nd to estlish the ccelertion of fruit ripening through ethylene doses, s well s mintin the physicl nd orgnoleptic chrcteristics of plum fruits. Mterils nd methods This study ws performed t the Vegetl Physiology Lortory of the Universidd Pedgogic y Tecnologic de Colomi, in Tunj (Colomi). The plum fruit smples were tken from commercil crop locted t 2,6 m.s.l., 5 41 36 N nd 73 14 51 W in the Tut municiplity of the deprtment of Boyc. Furthermore, this loction hs n verge precipittion of 935 mm nd temperture etween 12 nd 14 C. The plum (Prunus slicin Lindl.) vriety Horvin ws used, which ws collected in four different mturity stges (2, 3, 4 nd 5) ccording to the clssifiction reported y Sánchez nd Svedr (213). The fruits were selected with homogenous sizes, lck of dmge nd clen conditions. A commercil ethylene ws used, known s Ethrel. The fruits were disinfected with 1% sodium hypochlorite solution, leving them to ir dry for 3 min, followed y Rozo-Romero, Álvrez-Herrer, nd Blguer-López: Ethylene nd chnges during ripening in Horvin plum (Prunus slicin Lindl.) fruits 229
immersion in n ethylene solution, depending on the dose nd time of the tretment. The storge of the plum fruits ws done t room temperture (18 C). A completely rndom design ws used, in which three different ethylene doses were used (1; 1, nd 2, mg L -1 ), ccording to the doses used y Arévlo-Glrz et l. (27) nd Blguer-López et l. (213), long with control without ny pplictions, for three different exposure times (5, 1 nd 15 min), for totl of 1 tretments with four replictions, corresponding to 4 experimentl units (EU). Ech EU ws composed of pproximtely 4 g of fruit. The mesurements were tken every 3 dys fter the hrvest (dh) using the methodology descried y Dequiz et l. (214); the color ws evluted with Minolt CR 3 digitl colorimeter (Minolt, Osk, Jpn). The CIELAB L, nd system prmeters were determined with three redings for ech fruit in the equtoril dimeter. L indictes the rightness, where is lck nd 1 white; vlues of < indicte tendency towrds green nd > towrds red; hs the sme rnge, ut vlues < indicte tendency towrds lue nd > towrds yellow. For this vrile, two fruits were leled per experimentl unit, with which the mesurements were tken over time, lwys with the sme fruits nd the sme re. The mss loss ws mesured with n Accul VIC 612 electronic scle with.1 g precision (Srtorius Group, Goettingen, Germny), the respirtory intensity (RI) ws mesured with lquest 2 (Vernier Softwre & Technology, Beverton, OR), the firmness ws mesured in the equtoril prt of the fruit with PCE-PTR2 digitl penetrometer digitl (PCE-Ieric, Torr, Spin), nd the totl titrtle cidity (TTA) ws determined using the formul: % cidity = (A * B * C) * 1/D, where: A = volume of spent NOH; B = normlity of NOH (.97); C = equivlent weight in g of the fruit s predominnt cid (.67 g meq citric mlic cid); nd D = weight in grms of the smple (5 g) nd totl solule solids (TSS) using refrctometer Hnn HI 9683 (Hnn Instruments, Eir, Spin). This phse process lsted 9 d, in which the plum fruits lost their orgnoleptic qulity. With the otined dt, normlity test nd homogeneity of vrince test (Brtlett) were crried out (Shpiro-Wilk). An nlysis of vrince (Anov) ws done to determine the sttisticl differences nd estlish etter tretments through the comprisons of Duncn (P.5). This nlysis nd the sttistics were done with the sttistic progrm SAS v. 9.2e (SAS Institute Inc., Cry, NC). Results nd discussion Respirtory intensity (RI) The vrince nlysis showed significnce differences etween the control nd the ethylene tretments (Fig. 1). Furthermore, t the eginning of the experiment, there were no significnt differences due to the fct tht ll of the fruits were t the sme ripening stge (stge 3: 5% V-5% R) with strting RI verge of 21.41 mg CO 2 kg -1 h -1. After the third dy, there ws n RI increse tht continued on dy 6 nd dy 9 of storge lthough some of the tretments hd decrese in their RI verge. Respirtory intensity (mg CO 2 kg -1 ) 5 45 4 35 3 25 2 15 1 5 NS mg L -1 1 mg L -1-5 min 1 mg L -1-1 min 1 mg L -1-15 min 1, mg L -1-5 min 1, mg L -1-1 min 1, mg L -1-15 min 2, mg L -1-5 min 2, mg L -1-1 min 2, mg L -1-15 min ** Time (dh) Figure 1. Effect of different concentrtions of ethylene (, 1; 1, nd 2, mg L -1 ) nd immersion times on the respirtory intensity of the plum fruits during the posthrvest period. * significnt t (P.5); ** significnt t (P.1); ns, no significnt ccording to the Anov. On the other hnd, the control tretment showed n RI increse of 19.1 mg CO 2 kg -1 h -1 fter the third dy of its storge, in contrst to the other tretments tht showed considerle increse in their respirtory rte, otining n verge of 35.9 mg CO 2 kg -1 h -1. It ws lso oserved tht the sme tendency occurred fter the sixth dy of storge of the control tretment, in which the RI ws lower (29.8 mg CO 2 kg -1 h -1 ) in comprison with the other tretments (39.18 mg CO 2 kg -1 h -1 ). After the ninth dy of storge, oth the control tretment nd the 1 mg L -1 tretment hd n RI tht decresed with 5 nd 1 min of immersion due the nturl ehvior of the climcteric fruits. Once fruits rech the highest climcteric, when the highest respirtory rte lso occurs, the ging process nd deth of fruits strts nd the RI decreses (Rodríguez nd Restrepo, 211). * ** 23 Agron. Colom. 33(2) 215
mg L -1 1 mg L -1 1, mg L -1 2, mg L -1 min 5 min 1 min 15 min Respirtory intensity (mg CO 2 kg -1 ) A c Respirtory intensity (mg CO 2 kg -1 ) B 45 4 35 3 25 2 15 1 5 Time (dh) 45 4 35 3 25 2 15 1 5 Time (dh) Figure 2. Respirtory intensity of Horvin plum fruits during the posthrvest period with ppliction ethylene. A, ethylene doses; B, immersion times. Mens with different letters in tretment indicte significnt differences ccording to the Duncn test (P.5) (n=4). Significnt differences etween the ethylene doses were oserved on the third dy of the fruit storge experiment, ut not so much t the eginning nor on the sixth dy or ninth dy of the fruit storge. Moreover, the Anov showed tht there ws not vrint etween the immersion time in which similr vlues were otined, contrry to the control test tht presented vrints (Fig. 2). Bsed on the oservtions, it ws cler tht the physicochemicl chnges tht took plce during the ripening process of the plum fruits were initited nd coordinted y ethylene. In generl, most of the fruits were very receptive to the endogenous ethylene nd exogenous ethylene in which plum fruit ws not different sed on the results cquired in this study. It is known tht the plum fruit is climcteric fruit tht strts its ripening process with the utoctlysis of ethylene production nd n increse in the respirtory rte (Prk et l., 26). In the eginning of the ripening phse, this trnsltes into physicl chnges, such s loss of firmness, loss of green color, decrese in cidity, development of scent nd irreversile ging (Plou et l., 23). In ddition, ccording to the ove, Prk et l. (26) confirmed tht the production of ethylene throughout the ctlysis effect of the endogenous ethylene process is well-known climcteric fruit trit found in kiwi nd plum fruits. In this study, the respirtory ehvior of the plum fruits treted with ethylene strted with prolonged increse during the first 6 d of storge, where it reched the climcteric pek; then, n RI decrese initition ws oserved, which is consistent with the ssertion of Fonsec et l. (22) tht the rte of respirtion in climcteric fruits is high in the erly stges of fruit development, reching peks, ut decreses s the fruit ripens, pproching senescence. Lrsen nd Vngdl (213) evluted the RI nd ethylene production in nine plum cultivrs tht showed reltively high rtes of respirtion nd were strongly influenced, more so y the storge temperture thn y the production of endogenous ethylene, confirming the ssertion of Zuzung et l. (21) tht most plum cultivrs exhiit typicl climcteric chnges of the RI; however, some cultivrs show different pttern clled suppressed climcteric, which is not the cse for the Horvin vriety, which presents the typicl climcteric pek of the species, rther premturely due pplictions of exogenous ethylene. Fresh mss loss There were no significnt differences etween the tretments; however, norml pttern occurred when the fruits were stored. As time pssed, the percentge of loss incresed 5.12% the first 3 d nd 12.42% fter 9 d of storge. On the other hnd, in the plum fruits tht were treted with 2, mg L -1, the lost mss decresed 5.87% within the first 3 d nd 14.34% fter 9 d of storge (Fig. 3). The increse in the mss loss of the fruits nd vegetles during storge is pttern tht origintes in the nturl process of trnspirtion nd respirtion, in which wter loss occurs (Znidrcic et l., 21), during the posthrvest period, more so in climcteric fruits such s plum fruits. In ddition, the use of exogenous ethylene cn reduce the qulity of fruits (Wills nd Wrton, 24) due to the fct tht it cuses degrdtion of the cellulr wlls, speeding up the trnspirtion nd respirtion processes nd leding to greter wter loss (Kder, 22). This gretly ffected Rozo-Romero, Álvrez-Herrer, nd Blguer-López: Ethylene nd chnges during ripening in Horvin plum (Prunus slicin Lindl.) fruits 231
mg L -1 1 mg L -1 1, mg L -1 2, mg L -1 min 5 min 1 min 15 min Mss loss (%) 16 14 12 1 8 6 A Mss loss (%) 16 14 12 1 8 6 B 4 4 2 Time (dh) 2 Time (dh) Figure 3. Mss loss of Horvin plum fruits during the posthrvest period with ppliction ethylene. A, ethylene doses; B, immersion times. Mens with different letters in tretment indicte significnt differences ccording to the Duncn test (P.5) (n=4). the qulity of the plum fruits tested due to the use of the ethylene (2, mg L -1 ), which cused greter mss loss over time. Firmness This vrile showed differences etween the control nd the ethylene tretment due to the fct tht the fruits treted with ethylene hd greter firmness loss over time, with 87.2% t 9 d of storge for 2, mg L -1, very similr to the dt from the tretments with doses of 1 nd 1, mg L -1 (87.34 nd 88.1%, respectively). For the control tretment, the loss of firmness ws less drmtic, with reduction in the firmness of 64.4% (Fig. 4). This ehvior during the plum fruit ripening process hs lso een oserved in severl kinds of fruits nd vegetles when treted with ethylene, its firmness ws reduced this ecoming in fruits cceptle to the mrket. However, when treted with ethylene for long periods of time, the ripening process could ecome more rpid nd the ging could occur fster, leding to fruit pulp tht is too soft nd n uncceptle product for consumers. The degrdtion of the polymer crohydrtes, more precisely cellulose nd pectin, wekened the cell wlls nd the cohesive forces tht keep the wlls together, producing firmness loss (Reid, 22). On this suject, Sánchez nd Svedr (213) greed tht Horvin fruits lose firmness t every stge of their mg L -1 1 mg L -1 1, mg L -1 2, mg L -1 min 5 min 1 min 15 min 7 A 7 B 6 6 Firmness (N) 5 4 3 2 1 c Time (dh) Firmness (N) 5 4 3 2 1 c c Time (dh) Figure 4. Firmness of Horvin plum fruits during the posthrvest period with ppliction ethylene. A, ethylene doses; B, immersion times. Mens with different letters in tretment indicte significnt differences ccording to the Duncn test (P.5) (n=4). 232 Agron. Colom. 33(2) 215
ripening process when the storge time is incresed. The following vlues were tken for 1% red plum fruits: 27.21 N t the eginning of hrvest nd 3.61 N 15 d fter they were hrvested. In contrst, the 1% green plum fruits showed greter firmness, with eginning vlue of 5 nd finishing vlue of 19 N t dy 29 fter the hrvest. When compring the ove mentioned vlues with the otined vlues in this study; it ws perceived tht, since the plum fruits were treted with ethylene, ll of the vlues were lower in ll of the tretments, except in the control tretment. In ddition, Prk et l. (26) oserved tht kiwi fruits treted with ethylene lost their firmness quickly during their ripening process. These vlues correlted with the results otined y Plou et l. (23) in pech fruits treted with ethylene doses of 1, 1 nd 1 µl L -1, which showed softening in their texture in contrst to the fruits tht were not treted. The occurrence of these chnges is importnt ecuse firmness is key prmeter in fruit qulity tht is directly relted to mturity nd is often good indictor of the potentil shelf-life in fruits such s plums (Prr- Corondo et l., 27; Vlero et l., 27). In the specific cse of plums, there hve een no studies on ethylene pplictions to promote mturtion, ut with respect to the firmness, Usenik et l. (214) stted tht, for good consumer cceptnce, the firmness of the plum fruit must e close to 15 N, ut lso tht these vlues depend not only on the cultivr ut lso to the environmentl conditions ecuse fruits hrvested t periods of high rinfll showed vlues inferior to those otined t periods of low rinfll. Color When compring the verges otined in the different tretments, it ws oserved tht there ws only differences etween the control tretment (without ethylene pplictions) nd the tretments with ethylene pplictions, regrdless of the dose used; therefore, it ws inferred tht either the lowest dose (1 mg L -1 ) or the highest dose (2 mg L -1 ) cn otin the sme results for the chnge in peel color (T. 1). The dt otined for the color index (CI = 1 x /L x ) indicted tht the ppliction of ethylene ccelerted the color chnge in the plum fruits, compring the verge of the control (33.79 nd 69.42) t 3 nd 6 d, respectively, with the verges otined in the tretment with n ethylene dose of 1 mg L -1 on the sme mesurement dy (84.3 nd 111.81). In the plum fruits, the nthocynin content incresed during development nd mturtion, reching mximum t full mturity (Hgen et l., 26). In this period, synthesis is stimulted y light through two mechnisms: one due to n increse in the photosynthetic ctivity nd the second y the ctivtion of phytochrome, which is n intermedite in vrious processes (Bstís nd Corelli-Grppdelli, 212). In the lst mesurement, no difference ws oserved etween the tretments; therefore, it ws inferred tht, regrdless of the ppliction of ethylene, the color index will e the sme s tht otined in the fruits without Tle 1. Effect of ethylene dose nd immersion time on the physicl vriles mesured in Horvin plum fruits. Vrile L CI Dh Ethylene dose (mg L -1 ) Immersion time (min) 1 1, 2, 5 1 15 52.74 42.69 34.1 c 38.48 c 52.74 38.1 39.55 37.7 3 37.5 21.21 2.21 22.91 37.5 2.91 22.35 21.7 6 23.53 19.32 2.28 21.65 23.53 19.41 21.81 2.3 9 19.49 2.46 2.29 21.55 19.49 2.5 22.48 19.31 1.25 17.78 22.65 22.61 1.25 23.27 18.14 21.63 3 21.43 22.99 17.7 22.16 21.43 21.76 2.63 2.46 6 24.9 12.74 9.48 11.32 24.9 11.72 1.87 1.94 9 18.14 7.14 7.17 7.28 18.14 7.6 7.4 6.95 8.85 21.25 18.28 17.9 38.85 19.58 19.73 18.12 3 2. 13.47 1.31 1.96 2. 12.57 11.52 1.65 6 14.88 6.29 4.36 c 4.77 c 14.88 5.57 5.5 4.79 9 9.64 3.53 2.84 2.99 9.64 3.61 2.68 3.8 6.92 26.56 42.99 39.67 6.925 37.88 32.28 38.16 3 33.79 84.3 92.54 9.69 33.79 88.84 82.79 95.63 6 69.42 111.81 19.18 115.48 69.42 118.28 1.22 117.98 9 96.83 15.92 11 115.32 96.83 19.4 12 129.84 dh: dys fter hrvest; L: rightness; : chromticity from green to red; : chromticity from lue to yellow; CI: color index. N: no dt on loss of orgnoleptic qulity. Mens with different letters in ech row indicte significnt differences ccording to the Duncn test (P.5) (n=6). Rozo-Romero, Álvrez-Herrer, nd Blguer-López: Ethylene nd chnges during ripening in Horvin plum (Prunus slicin Lindl.) fruits 233
pplictions. Therefore, ethylene pplictions induce color chnge more rpidly, coinciding with Dequiz et l. (214) who studied pithy fruits where the ppliction of ethylene ccelerted the color chnge. Totl solule solids (TSS) The Anov test only showed significnt differences etween the tretments with the 2, mg L -1 ethylene ppliction nd 1 min immersion, which hd difference in the mesurements tken t 6 d; in which, it showed lower verge thn the other tretments. On the third dy of the storge, difference ws oserved etween the control tretment with vlue of 15.37 Brix nd the 2, mg L -1 tretment with vlue of 14.3; the other two tretments (1 nd 1, mg L -1 ) do not show differences etween them or with the other ones. In this sme tendency, it ws oserved tht the mesurements tken on dy 6 of storge presented cler difference etween the control tretment nd the 2, mg L -1 tretment; however, the 1 mg L -1 tretment did not hve ny differences with the control. On dy 9 of storge, there ws not ny difference etween the verge vlues of ech tretment (Fig. 5). A similr ehvior ws oserved in degreening citrus fruits y eing exposed to ethylene where it does not ffect the qulity prmeters, when it s compred ginst the de degreening citrus fruits without ethylene (Sdiri et l., 212). Other studies gree tht fruits treted with ethylene present similr iochemicl nd physicl chnges s non-treted fruits (Plz et l., 24; Mrtínez-Jáveg et l., 28; Tietel et l., 21). A considerle increse ws noticed in the quntity of TSS otined on dy 3 of storge in ll of the tretments. On dy 6, there ws smll decrese in this vlue nd t the end of the experiment, ll of the tretment vlues hd similr tendency. This increse ws ttriuted to strch hydrolysis nd other crohydrtes during the produce ripening stge (Goñi et l., 1997). The increse in this vlue during the ripening stge coincided with the results otined y Prk et l. (26), who found tht the TSS ws significntly higher in kiwi treted with ethylene, while the TSS grdully decresed independent of the pplied tretments. This ehvior is importnt considering tht the clcultion of the TSS content is key vrile for fruit qulity (Di Miceli et l., 21; Infnte et l., 211), which, together with the cidity nd the mturity index (TSS/TTA), hs een estlished s one the most determining mturity indices for plums (Prsnn et l., 27; Csquero nd Guerr, 29). It ws lso oserved tht, the in the 2, mg L -1 ethylene tretment, the TSS levels were lower thn in the other tretments, which ws ttriutle to n excess ppliction; s stted y Att-Aly et l. (2), lrge mount of exogenous ethylene my inhiit proper mturtion system. In generl, excluding the dt otined in the tretment with the highest ethylene dose (2, mg L -1 ), there ws no significnt difference etween the tretments with ethylene nd the control, which coincided with the results of Plou et l. (23), where the internl qulity of fruits exposed to ethylene s climcteric (grpes) nd non-climcteric (stone fruits) were unffected y tretment with exogenous ethylene. Furthermore, Singh nd Singh (212) oserved tht there were no differences in the TSS of jpnese plums treted with 1-MCP in cool nd controlled tmospheres, mg L -1 1 mg L -1 1, mg L -1 2, mg L -1 min 5 min 1 min 15 min TSS ( Brix) 16. 15.5 15. 14.5 14. 13.5 13. A TSS ( Brix) 16. 15.5 15. 14.5 14. 13.5 13. B 12.5 12.5 12. Time (dh) 12. Time (dh) Figure 5. Totl solule solids (TSS) of Horvin plum fruits during the posthrvest period with ppliction ethylene. A, ethylene doses; B, immersion times. Mens with different letters in tretment indicte significnt differences ccording to the Duncn test (P.5) (n=4). 234 Agron. Colom. 33(2) 215
mg L -1 1 mg L -1 1, mg L -1 2, mg L -1 min 5 min 1 min 15 min TTA (%) 2. 1.8 1.6 1.4 1.2 1..8.6.4.2 A Time (dh) TTA (%) 2. 1.8 1.6 1.4 1.2 1..8.6.4.2 B Time (dh) Figure 6. Totl titrtle cidity (TTA) of Horvin plum fruits during the posthrvest period with ppliction ethylene. A, ethylene doses; B, immersion times. Mens with different letters in tretment indicte significnt differences ccording to the Duncn test (P.5) (n=4). s compred to the control. This contrsts with the report of Prk et l. (26) who showed tht the contents of fructose, glucose nd sucrose in ethylene-treted kiwi fruits incresed, s compred to the untreted smples, deducing tht the ethylene tretment improved the free sugr y incresing the metolism of the kiwis. Totl titrtle cidity (TTA) This vrile showed the sme ehvior s the respirtion, where, t the eginning of the experiment, there ws no significnt chnge etween the tretments; however, from dy 3 of storge, the fruit response ws different ccording to the pplied tretment. The comprison etween the results showed tht, t dy 3, there were significnt differences in the control tretment, with TTA of 1.18 %, while the 2, mg L -1 ethylene tretment otined.85%. In the other two tretments (1 mg L -1 nd 1, mg L -1 ), there ws no difference etween them or with the other two tretments (Fig. 6). Therefore, it ws demonstrted tht the highest ethylene dose helped to gretly reduce the TTA, fctor tht is very importnt ecuse plums contin high levels of cids, minly mlic cid, which decrese during ripening s they re used s respirtory sustrtes, nd with incresing IR y ethylene ction, e increse spend of cid tht re used in the respirtion process (Rodríguez et l., 25), which enefits the fruits due to the fct tht consumers prefer fruits with gret ppernce nd low levels of cids. These results gree Sdiri et l. (212) who evluted the result of comined of degreening tretments with ethylene for the qulity of clementines tngerines nd Nvelin ornges, oth of which showed n increse in the TSS nd reduction in the TTA during the entire shelf-life, in comprison to the initil hrvest results. With respect to the immersion time fctor, there ws no sttisticl difference for the TTA. Conclusions The ppliction of ethylene ccelerted the plum fruit ripening, especilly during the first dys of storge (dy 3 to 6). Moreover, the ppliction of ethylene incresed the mount of TSS, improved fruit color, nd decresed the TTA nd firmness. Otining good qulity plum fruits cn e chieved with the ppliction of dose of 1 mg L -1 ethylene. As for the immersion time, there ws no difference in ny of the vriles, so minimum of 5 min is recommended for tretments to e effective. Literture cited Adi, N., P. Holford, nd B. Mcglsson. 22. Appliction of twodimensionl gel electrophoresis to detect proteins ssocited with hrvest mturity in stonefruit. Posthrvest Biol. Technol. 26, 1-13. Doi: 1.116/S925-5214(1)197-1 Álvrez-Herrer, J.G., X. Rozo-Romero, nd A.J. Reyes. 215. Comportmiento poscosech de frutos de ciruel (Prunus slicin Lindl.) en cutro estdos de mdurez trtdos con etileno. Rev. Colom. Cienc. Hortic. 9(1), 46-59. Arévlo-Glrz, L., B. Butist-Reyes, C. Sucedo-Veloz, nd T. Mrtínez-Dmín. 27. Almcenmiento refrigerdo y plicciones de 1-metilciclopropeno (1-mcp) en frutos de chicozpote (Mnilkr spot (L.) p. royen). Agrocienci 41, 469-477. Att-Aly, M.A., J.K. Brecht, nd D.J. Huer. 2. Ripening of tomto locule gel tissue in response to ethylene. Posthrvest Biol. Technol. 19, 239-244. Doi: 1.116/S925-5214()99-5 Rozo-Romero, Álvrez-Herrer, nd Blguer-López: Ethylene nd chnges during ripening in Horvin plum (Prunus slicin Lindl.) fruits 235
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