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Application of vacuum and exogenous ethylene on Ataulfo mango ripening
LWT - Food Science and Technology 44 (2011) 2040e2046
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Application of vacuum and exogenous ethylene on Ataulfo mango ripening Beatriz Tovar a, Efigenia Montalvo a, Berenice M. Damián a, Hugo S. García b, Miguel Mata a, * a b
Laboratorio de Integral de Investigación de Alimentos, Instituto Tecnológico de Tepic, Apdo. Postal 634, Tepic, Nayarit, Mexico UNIDA, Instituto Tecnológico de Veracruz, M.A. de Quevedo 2779, Veracruz, Ver. 91897, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 December 2010 Received in revised form 31 May 2011 Accepted 8 June 2011
The limited industrial processing and export to European countries of fresh Mexican ‘Ataulfo’ mangoes is attributed in part to the lack of homogeneous ripening among fruit from the same lot. A viable technology to alleviate the situation is the application of exogenous ethylene. In this work, vacuum (34 kPa) was applied for 20 min to ‘Ataulfo’ mangoes that were later exposed to exogenous ethylene (500, 1000 and 1500 mL L1) for 30 min and ripening was monitored. Application of vacuum did not produce apparent visual damage to the fruit; when 1500 mL L1 ethylene were applied for 30 min after the vacuum, induced production of internal ethylene with a concomitant increase in respiration rate. Firmness and acidity loss proceeded faster after the fruits were exposed to vacuum and 1500 mL L1 ethylene; similarly, total soluble solids increased and pulp and peel color development was 100% in the whole lot. An overall reduction of three days from the normal ripening time was observed attributed to the treatments. It is proposed that short exposures to vacuum and ethylene could improve the uniformity in mango ripening. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: ‘Ataulfo’ mango Ethylene Vacuum Ripening
1. Introduction Mango fruit (Mangifera indica L) has increased its acceptance and trade in different international markets due to its sensory and nutritional qualities. The US and Canada signify the main markets for Mexican ‘Ataulfo’ mango with 80%, whereas Asian and European markets attract only ca. 1% of the exports (FAO, 2009). In climacteric fruits, application of ethylene stimulates and accelerates the ripening process, and has been employed as a treatment to both hasten and homogenize the ripening of several fruits (Salveit, 1999). The quality of fruit exposed to exogenous ethylene for ripening purposes is dependent upon the proper use of optimal levels of ethylene, CO2 and O2 concentrations, temperature, relative humidity and exposure time (Medlicott, N’Diaye, & Sigrist, 1990; Salveit, 1999). Several works have been published on ripening acceleration and homogenization of mango by ethylene exposure for 12e24 h (Centurión, González, Tamayo, Argumedo, & Sauri, 1998; Lagunes et al., 2007; Medlicott, N’Diaye, & Sigrist, 1990; Zamora, García, Mata, & Tovar, 2004). ‘Ataulfo’ mangoes bound for export markets must be transported refrigerated (13 C) in order to reach consumers in good physiological conditions. This type of handling produces uneven
* Corresponding author. Tel./fax: þ52 311 213 1891. E-mail address: [email protected] (M. Mata). 0023-6438/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2011.06.005
ripening of mangoes when the fruit arrive at the markets (Montalvo, García, Tovar, & Mata, 2007). In a previous study, we found that ‘Ataulfo’ mangoes which were refrigerated for 4 days at 13 C and then exposed to 100 mL L1 of ethylene for 12 h gained 4 days in their ripening process and had more homogeneous ripening indexes, thereby minimizing the effect of refrigerated storage; however, in terms of time, a treatment of 12 h could delay fruit trading at the peak of the season for fresh consumption or processing (Montalvo et al., 2007). Vacuum or modified atmosphere packing has been employed by the food industry several years ago, mainly to extend the shelf life of fruits and vegetables (Wang, Zhang, & Wang, 2001). On the other hand, the use of vacuum has been under study to develop new technologies that could facilitate mass transfer, as is the case of osmotic dehydration. In the case of fruits, osmotic dehydration favored gas exhaustion from intracellular spaces and enhanced solids transfer inside the fruit (Mújica, Valdez, López, Palou, & Welti, 2003; Rastogi & Raghavarao, 2004). Apples to which 10.1 kPa of vacuum was applied showed a 10-fold decrease in internal ethylene concentration (Dilley, 1972). Zapotoczny, Markowski, and Majewska (2003) utilized three levels of vacuum: 10, 50 or 100 kPa at a constant temperature and relative humidity conditions in cucumber. The results clearly showed that no changes in mechanical properties occurred after 30 days. Based on the reports described above, it may be interesting to apply vacuum to ‘Ataulfo’ mangoes and thus eliminate the vacuum by applying
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ethylene, with the subsequent hypothesis that ethylene entrance to the fruit could be improved and thus less exposure time could be required to homogenize mango fruit ripening. These two effects should lead to better market the fruit for either fresh consumption, or a faster utilization in processing plants. The objective of our work was to evaluate the effects of applied vacuum and exogenous ethylene on the ripening of ‘Ataulfo’ mangoes. 2. Materials and methods 2.1. Fruits and treatments Physiologically mature ‘Ataulfo’ mangoes were harvested at an orchard located in the village “5 de Mayo”, near Tepic, Nayarit, México. Four hundred mangoes were collected, and 50 mangoes were subjected to one of 8 treatment protocols. Protocols were as follows: 1. Control mangoes, no vacuum applied. 2. Mangoes subjected to a vacuum of 34 kPa (manometric) for 20 min (VP) at 25 1 C and 90 3% RH 3e5. Mangoes were exposed to exogenous ethylene at concentrations of 500 mL L1 (NP500), 1000 mL L1 (NP1000) or 1500 mL L1 (NP1500) at ambient pressure (100 kPa) for 30 min. 6e8. Mangoes were subjected to a vacuum of 34 kPa for 20 min, and then equilibrated at atmospheric pressure with exogenous ethylene at concentrations of 500 mL L1 (VP500), 1000 mL L1 (VP1000) or 1500 mL L1 (VP1500) for 30 min. After being subjected to one of the above-indicated treatments, the mangoes were stored at atmospheric pressure (100 kPa), 25 1 C (T) and 90 3% RH until fully ripened for 13 days of storage; samples were tested immediately after each treatment (storage day 1). 2.2. Application of exogenous ethylene with or with no vacuum on mango fruit Exposure to ethylene with no vacuum was made in 225 L sealed chambers for 30 min, fitted with a fan, gas inlet and outlet and a flow meter. CO2 absorbers were placed inside (tree containers with 500 mL of saturated NaOH). Certified ethylene in synthetic air (Etil-5Ò) was supplied by Praxair (Praxair, México S.A. de C.V.). Vacuum was applied in an experimental chamber, which was adapted with a vacuum gauge and a gas valve to effect air removal. Chambers were sealed after filled with fruit and the valve was hooked to a vacuum pump until 34 kPa were reached. The certified ethylene mixtures were placed inside 200 L containers that were sealed; then the mixture was transferred to the experimental chamber 20 min after the vacuum was applied to the fruit, through a flow meter until the desired ethylene concentration was reached as measured by GC. The mixture was allowed to stay in contact with the fruit for 30 min. 2.3. Respiration rate (RR) and ethylene production rate (EPR) Respiration rate (RR) and ethylene production rate (EPR) were measured daily by a method reported previously (Tovar, García, & Mata, 2001). A single fruit was placed inside a 3.5 L glass bottle fitted with a septum. One mango was kept for 1 h for RR and another fruit for 12 h for EPR; in the latter determination, 250 mL of saturated NaOH were included to absorb CO2. Samples of 1 mL from the headspace were withdrawn and injected to a gas chromatograph (HP model 6890). An HP-plot capillary column (15 m 0.53 mm, 40 mm film thickness) was used to detect both
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CO2 and ethylene; N2 was used as carrier gas at 7 mL min1. The FID detector was used for ethylene and the TCD detector for CO2. Injector port and detectors (FID and TCD) were maintained at 250 C, while oven temperature was kept at 50 C for 30 s and then heated at 30 C/min to 80 C. Air and H2 flows were 400 mL min1 and 30 mL min1, respectively. 2.4. Total soluble solids, titratable acidity, firmness, internal and external color Total soluble solids (TSS) were determined with a refractometer (Bellingham Stanley Ltd) with temperature compensation (AOAC, 1984, pp. 420e1073). Titratable acidity (TA) as milliequivalents of citric acid/100 g fresh weight (meq citric acid/100 g fw) was measured using 5 g of homogenized pulp sample and titrated with NaOH 0.1 mol equi/L using phenolphthalein as an indicator (AOAC, 1984). For textural firmness measurement mango was prepared by cutting the mesocarp parallel to and 1 cm from the flat side of the seed. Resistance to penetration was measured on both sides of the equatorial diameter with a Shimpo texture meter (Lincolnwood, IL) fitted with a 0.5 cm diameter cylindrical probe. Results were reported in N. Internal color determinations were made by triplicate measurements of the Hue angle on the surface of the samples prepared for textural firmness, using a Minolta CR-300 colorimeter. Samples were withdrawn every 4 days for physico-chemical analyses. Peel color was evaluated visually with the EMEX official quality standard for export mangoes (EMEX, 1998) that employs the following scale: 1 ¼ green, 2 ¼ green with yellow areas, 3 ¼ equally green and yellow, 4 ¼ yellow with green areas, 5 ¼ yellow, 6 ¼ yellow with orange areas. Results are reported as percent of fruits located at each particular stage of ripening. External color was monitored daily on 20 mangoes. 2.5. Statistical analysis Data were analyzed by ANOVA (GLM-ANOVA) using the statistical package SAS (The SAS System for WindowsÔ. Version 6.11, SAS Institute, Cary, NC). Means comparison was made by the least significant difference (LSD). All tests of significance were at the 0.05 level. 3. Results and discussion 3.1. Respiration rate and ethylene production rate Fruit treated only with vacuum (VP, see Fig. 1A) had greater RR values than control fruit between 4, 5, 6 and 7 days; however, in both samples, the climacteric was noted on day 8 with values of 110.29 and 118.25 mL CO2 kg1 h1, respectively. The increase in RR of VP fruit may be attributed to stress caused by the applied vacuum. Plaxton and Podestá (2006) proposed that under stress the mitochondrial electron transport relies on the functions of alternative oxidases (AOXs), which can bypass the blocked proton pumping complex III, thus keeping the electron flux. Such flexibility in plant respiration provides the capability to adapt better to stress conditions, such as hypoxia and mechanical wounding. Activation of this pathway could explain at least part of the elevation in RR in VP fruit. It has been reported that either mechanical damage or storage under atypical conditions could produce tissue stress that may lead to increased RR and EPR (Barry, Llop-Tous, & Grierson, 2000; Yang & Hoffman, 1984). Fig. 1B slows a concomitant elevation in EPR of VP fruit, which was more clearly noted from day 5 (0.073 mL kg1 h1), while in control fruit this shift was noted on day 6 (0.017 mL kg1 h1). From days 6e9, no differences in EPR of VP and control fruit were noted (p > 0.05); however, statistically
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140
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Ethylene production rate (µl/kg-h)
Respiration rate (ml CO2 /kg-h)
C
100 80 60 40 20 0 0 140
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*
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Days of storage *Means statistically different (p<0.05) Fig. 1. Respiration rate and ethylene production rate of “Ataulfo” mangoes that were stored at 25 1 C, control, with vacuum (VP); treated with exogenous ethylene at atmospheric pressure (NP), with vacuum and treated with exogenous ethylene at 25 C and 90 3% RH. Data points represent the mean of three replicates and their corresponding standard Control, VP, NP500, NP1000, NP1500, VP500, VP1500. deviation.
smaller EPR in VP fruit was measured from days 10e12. It has been reported that internal gas (CO2, ethylene and O2) expansion may occur in fruit when vacuum is applied. These gases could diffuse into intracellular spaces and outside the fruit, and could cause reversible tissue deformations (Barat, Fito, & Chiralt, 2001; Wang et al., 2001). On day 13, no significant difference was measured (p < 0.05) in EPR between VP and control fruit (1.41 and 1.40 mL kg1 h1, respectively). This means that at the end of the storage the auto-catalyzed production of ethylene in fruit was equalized. Fig. 1C contains data on the RR of fruit treated with ethylene at ambient pressure (NP500, NP1000 y NP1500). In all samples, the
climacteric peak was observed on the 8th day with 121.22, 124.28 and 124.11 mL CO2 kg1 h1, respectively and no significant differences were found between them. Although the climacteric peak of the treatments coincided with that of the control and VP fruit, these later samples had smaller values of RR. Additionally, from day 2, NP1500 fruit showed a clear increase in RR, which was followed by NP500 and NP1000 fruit, with respect to control and VP fruit. This trend suggests a particular sensibility of ‘Ataulfo’ mangoes to exogenous ethylene; thus, short exposures to small concentrations of this hormone may be enough to trigger a respiratory response by the fruit. It has been documented that exogenous ethylene increased RR, EPR and accelerated fruit ripening, the
B. Tovar et al. / LWT - Food Science and Technology 44 (2011) 2040e2046
extent of which depends on exposure time, type of fruit and its state of ripening (Prasanna, Parva, & Tharanathan, 2007; Salveit, 1999). In the present study, ethylene production was detected from day 6 in fruit treated with exogenous ethylene and stored at ambient pressure (NP500, NP1000 and NP1500; see Fig. 1D). At the end of storage, all treated samples had greater EPR than control and VP fruit: 2.00, 1.79 and 2.02 mL kg1 h1, for NP500, NP1000 and NP1500 fruit, respectively. This trend suggests that exogenous ethylene applied at different concentrations was able to increase the production of autocatalytic ethylene but produced no gain in the time to reach the climacteric peak. Ripening homogenization did not occur too, and this would explain the requirement of exposure of up to 12 h to attain this effect (Salveit, 1999). As it can be seen on Fig. 1E, fruit that were subjected to vacuum and then brought back to ambient pressure followed by ethylene exposure at 1500 mL L1 for only 30 min (VP1500), displayed greater RR on days 2e6 (p < 0.005) with respect to the other treatments. These fruits from the VP500 and VP1000 treatments showed their climacteric peak one day early and RR remained high from days 5e7 compared to control and VP fruits. Values of RR reached at the climacteric were 129.66, 129.69 and 130.64 mL CO2 kg1 h1 for VP500, VP1000 and VP1500 mangoes, respectively on day 7. Then, RR decreased faster in VP1500 mangoes. Previous research which report the application of vacuum apples, mango, and papaya (Barat et al., 2001; Fito & Pastor, 1993; Mújica et al., 2003) suggest that a deformation-relaxation phenomenon could develop under vacuum, and internal pressure buildup may happed due to gas expansion inside fruit tissue (Del Valle, Aránguiz, & Díaz, 1998; Fito, 1994). Vacuum favored gas transfer inside the fruit in a proportional rate with the concentration of ethylene of the atmosphere and may account for the increased RR in VP1500 fruit. This could also be due to the activation of AOXs as described above and the presence of greater ethylene concentrations. Fig. 1F shows that EPR increased during storage. It is clearly noted that VP1500 mangoes had increased EPR during most of the storage, except on days 10 and 11, with respect to the other treatments, until 3.0 mL kg1 h1 were reached. In a previous study and using the same mango variety, but after 12 h of ethylene exposure at ambient pressure we measured an EPR of 2.6 mL kg1 h1
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ethylene at the end of the storage (Montalvo et al., 2007). This implies that vacuum and ethylene (1500 mL kg1 h1) applied for only 30 min attained a similar extent of internal ethylene as longer exposures (12 h) with no vacuum employed, and both were able to start the ethylene-regulated ripening changes in the fruit. In VP1500 fruit, increased EPR is attributed to greater ethylene diffusion due to the effect of vacuum and then the pressure was reinstated by an ethylene-containing atmosphere with the highest concentration Ethylene promoted enhanced activities of enzymes involved in endogenous ethylene synthesis. Increased EPR was reported on refrigerated ‘Ataulfo’ mangoes treated with ethylene under atmospheric pressure (Montalvo et al., 2007). Molecular studies in other fruits have demonstrated that exogenous ethylene stimulated gene expression for endogenous ethylene synthesis. Increased mRNA for ACC oxidase and ACC synthase has also been reported (Barry et al., 2000; Lassere et al., 1996; López-Gómez, Campbell, Jiang-Guo, Shang-Fa, & Gómez Lim, 1997; Nakatsuka et al., 1998).
3.2. Compositional variables during ripening Table 1 show that TSS from day 5 and until the end of the experiment, VP fruit were different from control fruit with maximal values of 17.27 and 16.35 Brix, respectively. TSS was similar among all ethylene-treated fruit that were kept at normal pressure (NP500, NP1000 and NP1500) on days 5 at 13 (p < 0.05). This was irrespective from the ethylene concentration employed. This suggests that ethylene applied at atmospheric pressure for 30 min did not elicit any significant effect on TSS. Conversely, fruit exposed to vacuum and ethylene had similar (p < 0.05) values for TSS at day 13: 19.11, 19.28 and 19.38 Brix for VP500, VP1000 and VP1500, respectively (Table 1). These values were greater than those found for other treatments. Thus, VP and ethylene may be considered responsible of such changes. Table 1 shows that change rate on TSS of VP1500 fruit was greater than for the rate of the other treatments, probably due to a greater production of autocatalytic ethylene (Fig. 1f). Several authors have also reported that increased TSS at the same time that starch was hydrolyzed into sucrose,
Table 1 Physico-chemical values of ‘Ataulfo’ mangoes: control, with vacuum (VP); treated with exogenous ethylene at normal pressure (NP), and exposed to vacuum and treated with exogenous ethylene (500, 1000 or 1500 mL1 L1) at 25 C and 90% HR. Days post-harvest
Treatments Control
VP
500 mL L1 NP
Total soluble solids ( Brix) 4.97 0.25b 1 4.99 0.22b 5 8.52 0.12d 9.19 0.20c 9 14.38 0.23c 15.71 0.16b 13 16.35 0.12c 17.27 0.24b Titratable acidity (meq citric acid/100 g fw) 1 3.40 0.14a 3.33 0.31a 5 2.83 0.06b 2.54 0.02c 9 1.87 0.03a 1.20 0.07b 13 0.37 0.08a 0.29 0.12b Firmness (N) 174.40 5.1a 1 175.45 4.1a 5 129.88 3.4a 120.94 2.5b 9 46.31 1.4a 40.16 1.3c 13 13.45 0.6a 11.78 1.2b Hue Angle (h) 90.09 1.7ab 1 90.24 2.4ab 5 96.72 3.4a 93.05 2.7b 9 86.97 2.5a 79.03 2.8c 13 77.45 1.5a 77.58 1.3a
1000 mL L1 VP
NP
1500 mL L1 VP
NP
VP
5.19 9.39 14.83 16.44
0.55a 0.02c 0.25c 0.55c
5.74 10.77 16.10 19.11
0.20a 0.18b 0.24b 0.48a
5.90 9.49 14.86 16.70
0.28a 0.12c 0.21c 0.29c
5.92 10.57 16.26 19.28
0.21a 0.02b 0.18b 0.31a
5.75 9.37 14.86 16.78
0.20a 0.07c 0.21c 0.21c
5.98 13.19 17.20 19.38
0.25a 0.13a 0.12a 0.21a
3.20 2.79 1.89 0.37
0.04a 0.01b 0.12a 0.08a
3.18 2.07 1.05 0.29
0.08a 0.14d 0.02c 0.08b
3.18 2.84 1.89 0.36
0.05a 0.06ab 0.10a 0.09a
3.04 2.05 0.84 0.29
0.20a 0.01d 0.01d 0.06b
3.32 3.03 1.99 0.38
0.22a 0.09ab 0.01a 0.07a
3.25 2.06 0.44 0.27
0.29a 0.08d 0.09e 0.13c
174.13 117.45 44.85 11.46
5.42a 5.99bc 2.8b 1.52b
136.77 103.81 37.93 10.56
2.1c 1.8d 2.35d 1.3c
176.37 119.26 43.60 11.33
2.6a 2.3b 2.43b 1.6b
140.63 98.18 38.78 11.61
2.3b 2.1d 1.5cd 1.3b
176.45 117.40 43.93 11.41
3.1a 6.0bc 2.1b 1.5b
127.27 91.21 31.61 10.05
2.1d 1.6e 1.2e 1.81c
90.51 90.84 84.07 76.31
2.1ab 3.3b 2.38b 2.6a
93.03 89.16 81.78 74.24
2.5a 1.1c 3.0c 1.3c
92.08 96.71 84.25 75.95
3.42a 4.0a 2.2b 1.2b
92.49 89.03 83.23 73.42
3.1a 3.3c 3.22bc 2.12c
91.83 90.12 85.76 77.96
2.5a 4.11b 3.7ab 1.0a
92.90 84.50 75.21 70.48
2.6a 1.4d 2.1d 1.3d
Means with same letters within a row are not statistically different (Tukey a ¼ 0.05). Entries represent the means of six measurements.
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fructose and glucose (Hubbar, Pharr, & Huber, 1990; Montalvo et al., 2007; Zamora et al., 2004). TA decreased during mango ripening (Table 1). This is a normal event due to the reduction of organic acids content in this process (Plaxton, 1996). Both control and VP fruit had statistically different acidity values (P < 0.05) and reached acidities of 0.37 and 0.29 meq
citric acid/100 g fw, respectively, at the end of the storage. In a similar fashion as TSS, there were no differences in TA between NP500, NP1000 and NP1500 fruit, or with respect to the control fruit (Table 1) throughout all the days of storage. For day 9, acidity of VP1500 decreased considerably (0.44 meq citric acid/100 g fw) as compared to VP500 fruit (1.05 meq citric acid/100 g fw) and
Fig. 2. Number of fruits graded with color development held at 25 C (Control), with vacuum (VP); treated with exogenous ethylene at atmospheric pressure (NP), with vacuum and treated with exogenous ethylene (VP) at 25 C and 90 3% RH. (A)-Control; (B)-VP; (C)-NP500; (D)-NP1000; (E)-NP1500; (F)-VP500; (G)-VP100; (H)-VP1500.
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VP1000 fruit (0.84 meq citric acid/100 g fw) (see Table 1). Respiration is a process inversely related to TA due to the availability of organic acids (Tsouvaltziz, Gerasopoulos, & Siomos, 2007). The early drop in acidity of VP1500 fruit coincided with higher RR, greater TSS and the early detection of EPR (Fig. 1B). There were differences in textural firmness of VP fruit at the three ethylene concentrations (VP500, VP1000 and VP1500) with reference to the other treatments, with lower firmness at 5e9 days of storage (Table 1); although at the end of storage there were no differences between all the treatments (p < 0.01), the fastest rate of loss of firmness occurred in VP1500 fruit. It has also been reported that very low ethylene concentrations affect the textural firmness of the fruits; however, this is also dependent of ethylene exposure time (Mir & Beaudry, 2002). Thus, application of vacuum for 30 min, followed by ethylene exposure exerted a definite effect on textural hardness. Cheong et al. (2002) reported that many of the ethylene response transcriptions factors such as ethylene-responsive element binding proteins (EREBP) are rapidly induced by mechanical wounding. These transcriptional factors may directly participate in the activation of ethylene-responsive genes. In mango, vacuum could have caused similar gene expression and enhancement of this response could have been possible because of the higher concentration of ethylene used on VP1500 fruit. Then, loss of firmness may be attributed to the effect of ethylene on the synthesis of cell wall-degrading enzymes, since greater activities of pectinmethylesterase, polygalacturonase and b-galactosidase were measured on refrigerated ‘Ataulfo’ mangoes that were treated with ethylene for 12 h (Montalvo, Adame, García, Tovar, & Mata, 2009). Sane, Chourasia, and Nath (2005) reported the role of the expansines gene on softening of ‘Dashehari’ mango when exposed to 100 mL L1 ethylene for 24 h. Results indicated that softening of fruit pulp is associated to the expression of the expansine gene (MiExpA) and found that gene regulation was controlled by ethylene. Based on the above evidence, it is quite probable that the described enzymes and mechanisms could have been involved in the loss of textural firmness. Mean values for Hue angle from mango pulp post-harvest are shown on Table 1. These values decreased in all treatments as ripening proceeded. Similar to firmness there were differences between hue angle values. On day 13, both control and VP fruit, had a hue angle value of 77.45 and 77.58, respectively. For fruits NP500, NP1000 and NP1500 similar hue angle values to those of control fruit (p > 0.05) were found; while hue angle values of VP fruit treated with three different ethylene concentrations and the other treatments; lower values indicate pulp color development toward orange. VP1500 fruit reached a yellow-orange color (70.48) at day 13. Salveit (1999) described how application of exogenous ethylene promoted ripening by first degrading the green color with a concomitant development of yellow color marked by carotenoid synthesis. Fig. 2 depicts the number of mangoes graded with color development (%). After nine days of storage, more than 50% of the VP fruits, and 30% of control fruits had yellow-orange tones, regarded as normal for the consumption stage of ‘Ataulfo’ mangoes. At the end of storage, VP fruits were fully ripened while control fruits were not completely ripened since some fruits still had green areas. Fruit from treatments NP500, NP1000 and NP1500 contained ca. 80% of yellow-orange mangoes. For VP1500 fruit, all the mangoes were completely ripened on day 9; while at the same day VP500 and VP1000 fruit had 90 and 80% of ripened mangoes, respectively. Our results are consistent with the report for Kent mangoes by Zamora et al. (2004) and ‘Ataulfo’ mangoes by Montalvo et al. (2007). It is possible that exogenous ethylene activated enzyme activities linked to the metabolism and carotenoid synthesis in both pulp and peel. Results in apricot (Prunus armeniaca) fruit showed that carotenoid accumulation was correlated
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with post-transcriptional regulation, feed-back regulation by endproducts, and hormonal regulation (by ethylene) as other regulation mechanisms of carotenoid accumulation (Marty et al., 2005). 4. Conclusions Application of 34 kPa vacuum for 20 min, allowed for uniform ripening of ‘Ataulfo’ mangoes measured as internal and external color while compositional variables (TSS, TA, pH values, firmness) were not affected. Ethylene application at ambient pressure did not affect fruit ripening when applied by short times. Vacuum (34 kPa) for 20 min with 1500 mL L1 ethylene for 30 min, increased EPR and RR, which triggered the ripening process that proceeded in shorter time and these fruit had the same compositional quality as that of control fruit, but ripening was more homogenous in their external color and the edible stage was reached 3 days earlier than control mangoes. Acknowledgments The authors gratefully acknowledge the financial support of DGEST through the grant Nr. 317.06 and CONACyT of México through the grant 208035. The valuable contribution by Mr. Abelardo González Cabrera of fresh mangoes for the study is truly appreciated. References AOAC. (1984). Official methods of analysis (14th ed.). Arlington, Virginia, USA: Association of Official Analytical Chemists. Barat, J. M., Fito, P., & Chiralt, A. (2001). Modeling of simultaneous mass transfer and structural changes in fruit tissues. Journal of Food Engineering, 49(2e3), 77e85. Barry, C. S., Llop-Tous, M. I., & Grierson, D. (2000). The regulation of aminocyclopropane-1-carboxylic acid synthase gene expression during the transition from system-1 to system-2 ethylene synthesis in tomato. Plant Physiology, 123, 979e986. Centurión, A. R., González, N. S. A., Tamayo, C. J. A., Argumedo, J. J., & Sauri, D. E. (1998). The effect of Ethephon on the colour, composition and quality of mango (Mangifera indica, cv Kent). Food Science and Technology International, 4, 199e205. Cheong, Y. H., Chang, H. S., Gupta, R., Wang, X., Zhu, T., & Luan, S. (2002). Transcriptional profiling reveals novel interactions between wounding, pathogen, abiotic stress and hormonal responses in Arabidopsis. Plant Physiology, 129, 661e667. Del Valle, J. M., Aránguiz, V., & Díaz, L. (1998). Volumetric procedure to assess infiltration kinetics and porosity of fruits by applying a vacuum pulse. Journal of Food Engineering, 38(2), 207e221. Dilley, D. R. (1972). Hypobaric storage e a new concept for preservation of perishables. Proceedings Michigan State Horticultural Society, 102, 82e89. EMEX, A.C. (1998). Norma de calidad para mango fresco de exportación. Elaborada por Baéz-Sañudo, R., Bringas, E., Ojeda, J., Cruz, L., Ontiveros, S., Pellegrin, J. Boletín. 6. p. CIAD, A.C. FAO. (2009). Food and Agriculture Organization of the United Nations. http://faostat. fao.org. Fito, P., & Pastor, R. (1993). Non diffusional mechanisms occurring during vacuum osmotic dehydration. Journal of Food Engineering, 21, 513e519. Fito, P. (1994). Modeling of vacuum osmotic dehydration of food. Journal of Food Engineering, 22, 313e327. Hubbar, N. L., Pharr, D. M., & Huber, S. C. (1990). Role of sucrose phosphate synthase in sucrose biosynthesis in ripening bananas and its relationship to the respiratory climacteric. Plant Physiology, 94, 201e208. Lagunes, L., Tovar, B., Mata, M., Vinay-Vadillo, J. C., delaCruz, J., & García, H. S. (2007). Effect of exogenous ethylene on ACC content and ACC oxidase activity during ripening of Manila mangoes subjected to hot water treatment. Plant Foods for Human Nutrition, 62(4), 157e163. Lassere, E., Bouquin, T., Hernández, J. A., Pech, J. C., Bull, J., & Balangué, C. (1996). Structure and expression of three genes encoding ACC oxidase homologs from melon (Cucumis melo L). Gene, 3, 81e90. López-Gómez, R., Campbell, A., Jiang-Guo, D., Shang-Fa, Y., & Gómez Lim, M. A. (1997). Ethylene biosynthesis in banana fruit: isolation of a genomic clone to ACC oxidase and expression studies. Plant Science, 123, 123e131. Marty, I., Bureau, S., Sarkissian, G., Gouble, B., Audergon, J. M., & Albagnac, G. (2005). Ethylene regulation of carotenoid accumulation and carotenogenic gene expression in colour-contrasted apricot varieties (Prunus armeniaca). Journal of Experimental Botany, 56(417), 1877e1886.
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Medlicott, A. P., N’Diaye, M., & Sigrist, J. M. M. (1990). Harvest maturity and concentration and exposure time to acetylene influence initiation of ripening in mangoes. Journal of the American Society for Horticultural Science, 115(3), 426e430. Mir, N., & Beaudry, R. (2002). Atmosphere control using oxygen and carbon dioxide. In M. Knee (Ed.), Fruit quality and its biological basis (pp. 122e156). Boca Raton, Florida, USA: CRC Press. Montalvo, E., García, H. S., Tovar, B., & Mata, M. (2007). Application of exogenous ethylene on postharvest ripening of refrigerated ‘Ataulfo’ mangoes. Lebensmittel Wissenschaft und Technologie, 40, 1466e1472. Montalvo, E., Adame, Y., García, H. S., Tovar, B., & Mata, M. (2009). Changes of sugars, b-carotene and firmness of refrigerated Ataulfo mangoes treated with exogenous ethylene. Journal of Agricultural Science, 147, 193e199. Mújica, H., Valdez, A., López, A., Palou, E., & Welti, J. (2003). Impregnation properties of some fruits at vacuum pressure. Journal of Food Engineering, 56, 307e314. Nakatsuka, A., Murachi, S., Okunishi, H., Shiomi, S., Nakano, R., Kubo, Y., et al. (1998). Differential expression and internal feedback regulation of 1-aminocyclopropane1-carboxylate synthase, and ethylene receptor genes in tomato fruit during development and ripening. Plant Physiology, 118, 1295e1305. Plaxton, W. C. (1996). The organization and regulation of plant glycolysis. Annual Reviews on Plant Physiology and Plant Molecular Biology, 47, 185e214. Plaxton, W. C., & Podestá, F. E. (2006). The functional organization and control of plant respiration. Critical Reviews in Plant Sciences, 25, 159e198. Prasanna, V., Parva, T. N., & Tharanathan, R. N. (2007). Fruit ripening Phenomena-An overview. Critical Reviews in Food Science and Nutrition, 47, 1e19.
Rastogi, N. K., & Raghavarao, K. S. M. S. (2004). Mass Transfer during osmotic dehydration of pineapple: considering Fickian diffusion in cubical configuration. Lebensmittel Wissenschaft und Technologie, 37, 43e47. Salveit, M. E. (1999). Effect of ethylene on quality of fresh fruits a vegetables. Postharvest Biology and Technology, 15, 279e292. Sane, A. V., Chourasia, A., & Nath, P. (2005). Softening in mango (Mangifera indica cv. Dashehari) is correlated with the expression of an early ethylene responsive, ripening related expansin gene, MiExpA1. Postharvest Biology and Technology, 38, 223e230. Tovar, B., García, H. S., & Mata, M. (2001). Physiology of pre-cut mango I. ACC and ACC oxidase activity of slices subjected to osmotic dehydration. Food Research International, 34(2e3), 207e215. Tsouvaltziz, P., Gerasopoulos, D., & Siomos, A. (2007). Effects of base removal and heat treatment on visual and nutritional quality of minimally processed leeks. Postharvest Biology and Technology, 43, 158e164. Wang, L., Zhang, P., & Wang, S. J. (2001). Advances in research on theory and technology for hypobaric storage of fruit and vegetable. Storage and Process, 5, 3e6. Yang, S. F., & Hoffman, N. E. (1984). Ethylene biosynthesis and its regulation in higher plants. Annual Reviews in Plant Physiology, 84, 520e525. Zapotoczny, P., Markowski, M., & Majewska, K. (2003). The quality of cucumbers stored under hypobaric conditions. Acta Horticulturae, 600, 193e196. Zamora, E., García, H. S., Mata, M., & Tovar, B. (2004). Ripening enhancement of refrigerated “Kent” mango. Revista Fitotecnia Mexicana, 27(4), 359e366.
Contents lists available at ScienceDirect
LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt
Application of vacuum and exogenous ethylene on Ataulfo mango ripening Beatriz Tovar a, Efigenia Montalvo a, Berenice M. Damián a, Hugo S. García b, Miguel Mata a, * a b
Laboratorio de Integral de Investigación de Alimentos, Instituto Tecnológico de Tepic, Apdo. Postal 634, Tepic, Nayarit, Mexico UNIDA, Instituto Tecnológico de Veracruz, M.A. de Quevedo 2779, Veracruz, Ver. 91897, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 December 2010 Received in revised form 31 May 2011 Accepted 8 June 2011
The limited industrial processing and export to European countries of fresh Mexican ‘Ataulfo’ mangoes is attributed in part to the lack of homogeneous ripening among fruit from the same lot. A viable technology to alleviate the situation is the application of exogenous ethylene. In this work, vacuum (34 kPa) was applied for 20 min to ‘Ataulfo’ mangoes that were later exposed to exogenous ethylene (500, 1000 and 1500 mL L1) for 30 min and ripening was monitored. Application of vacuum did not produce apparent visual damage to the fruit; when 1500 mL L1 ethylene were applied for 30 min after the vacuum, induced production of internal ethylene with a concomitant increase in respiration rate. Firmness and acidity loss proceeded faster after the fruits were exposed to vacuum and 1500 mL L1 ethylene; similarly, total soluble solids increased and pulp and peel color development was 100% in the whole lot. An overall reduction of three days from the normal ripening time was observed attributed to the treatments. It is proposed that short exposures to vacuum and ethylene could improve the uniformity in mango ripening. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: ‘Ataulfo’ mango Ethylene Vacuum Ripening
1. Introduction Mango fruit (Mangifera indica L) has increased its acceptance and trade in different international markets due to its sensory and nutritional qualities. The US and Canada signify the main markets for Mexican ‘Ataulfo’ mango with 80%, whereas Asian and European markets attract only ca. 1% of the exports (FAO, 2009). In climacteric fruits, application of ethylene stimulates and accelerates the ripening process, and has been employed as a treatment to both hasten and homogenize the ripening of several fruits (Salveit, 1999). The quality of fruit exposed to exogenous ethylene for ripening purposes is dependent upon the proper use of optimal levels of ethylene, CO2 and O2 concentrations, temperature, relative humidity and exposure time (Medlicott, N’Diaye, & Sigrist, 1990; Salveit, 1999). Several works have been published on ripening acceleration and homogenization of mango by ethylene exposure for 12e24 h (Centurión, González, Tamayo, Argumedo, & Sauri, 1998; Lagunes et al., 2007; Medlicott, N’Diaye, & Sigrist, 1990; Zamora, García, Mata, & Tovar, 2004). ‘Ataulfo’ mangoes bound for export markets must be transported refrigerated (13 C) in order to reach consumers in good physiological conditions. This type of handling produces uneven
* Corresponding author. Tel./fax: þ52 311 213 1891. E-mail address: [email protected] (M. Mata). 0023-6438/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2011.06.005
ripening of mangoes when the fruit arrive at the markets (Montalvo, García, Tovar, & Mata, 2007). In a previous study, we found that ‘Ataulfo’ mangoes which were refrigerated for 4 days at 13 C and then exposed to 100 mL L1 of ethylene for 12 h gained 4 days in their ripening process and had more homogeneous ripening indexes, thereby minimizing the effect of refrigerated storage; however, in terms of time, a treatment of 12 h could delay fruit trading at the peak of the season for fresh consumption or processing (Montalvo et al., 2007). Vacuum or modified atmosphere packing has been employed by the food industry several years ago, mainly to extend the shelf life of fruits and vegetables (Wang, Zhang, & Wang, 2001). On the other hand, the use of vacuum has been under study to develop new technologies that could facilitate mass transfer, as is the case of osmotic dehydration. In the case of fruits, osmotic dehydration favored gas exhaustion from intracellular spaces and enhanced solids transfer inside the fruit (Mújica, Valdez, López, Palou, & Welti, 2003; Rastogi & Raghavarao, 2004). Apples to which 10.1 kPa of vacuum was applied showed a 10-fold decrease in internal ethylene concentration (Dilley, 1972). Zapotoczny, Markowski, and Majewska (2003) utilized three levels of vacuum: 10, 50 or 100 kPa at a constant temperature and relative humidity conditions in cucumber. The results clearly showed that no changes in mechanical properties occurred after 30 days. Based on the reports described above, it may be interesting to apply vacuum to ‘Ataulfo’ mangoes and thus eliminate the vacuum by applying
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ethylene, with the subsequent hypothesis that ethylene entrance to the fruit could be improved and thus less exposure time could be required to homogenize mango fruit ripening. These two effects should lead to better market the fruit for either fresh consumption, or a faster utilization in processing plants. The objective of our work was to evaluate the effects of applied vacuum and exogenous ethylene on the ripening of ‘Ataulfo’ mangoes. 2. Materials and methods 2.1. Fruits and treatments Physiologically mature ‘Ataulfo’ mangoes were harvested at an orchard located in the village “5 de Mayo”, near Tepic, Nayarit, México. Four hundred mangoes were collected, and 50 mangoes were subjected to one of 8 treatment protocols. Protocols were as follows: 1. Control mangoes, no vacuum applied. 2. Mangoes subjected to a vacuum of 34 kPa (manometric) for 20 min (VP) at 25 1 C and 90 3% RH 3e5. Mangoes were exposed to exogenous ethylene at concentrations of 500 mL L1 (NP500), 1000 mL L1 (NP1000) or 1500 mL L1 (NP1500) at ambient pressure (100 kPa) for 30 min. 6e8. Mangoes were subjected to a vacuum of 34 kPa for 20 min, and then equilibrated at atmospheric pressure with exogenous ethylene at concentrations of 500 mL L1 (VP500), 1000 mL L1 (VP1000) or 1500 mL L1 (VP1500) for 30 min. After being subjected to one of the above-indicated treatments, the mangoes were stored at atmospheric pressure (100 kPa), 25 1 C (T) and 90 3% RH until fully ripened for 13 days of storage; samples were tested immediately after each treatment (storage day 1). 2.2. Application of exogenous ethylene with or with no vacuum on mango fruit Exposure to ethylene with no vacuum was made in 225 L sealed chambers for 30 min, fitted with a fan, gas inlet and outlet and a flow meter. CO2 absorbers were placed inside (tree containers with 500 mL of saturated NaOH). Certified ethylene in synthetic air (Etil-5Ò) was supplied by Praxair (Praxair, México S.A. de C.V.). Vacuum was applied in an experimental chamber, which was adapted with a vacuum gauge and a gas valve to effect air removal. Chambers were sealed after filled with fruit and the valve was hooked to a vacuum pump until 34 kPa were reached. The certified ethylene mixtures were placed inside 200 L containers that were sealed; then the mixture was transferred to the experimental chamber 20 min after the vacuum was applied to the fruit, through a flow meter until the desired ethylene concentration was reached as measured by GC. The mixture was allowed to stay in contact with the fruit for 30 min. 2.3. Respiration rate (RR) and ethylene production rate (EPR) Respiration rate (RR) and ethylene production rate (EPR) were measured daily by a method reported previously (Tovar, García, & Mata, 2001). A single fruit was placed inside a 3.5 L glass bottle fitted with a septum. One mango was kept for 1 h for RR and another fruit for 12 h for EPR; in the latter determination, 250 mL of saturated NaOH were included to absorb CO2. Samples of 1 mL from the headspace were withdrawn and injected to a gas chromatograph (HP model 6890). An HP-plot capillary column (15 m 0.53 mm, 40 mm film thickness) was used to detect both
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CO2 and ethylene; N2 was used as carrier gas at 7 mL min1. The FID detector was used for ethylene and the TCD detector for CO2. Injector port and detectors (FID and TCD) were maintained at 250 C, while oven temperature was kept at 50 C for 30 s and then heated at 30 C/min to 80 C. Air and H2 flows were 400 mL min1 and 30 mL min1, respectively. 2.4. Total soluble solids, titratable acidity, firmness, internal and external color Total soluble solids (TSS) were determined with a refractometer (Bellingham Stanley Ltd) with temperature compensation (AOAC, 1984, pp. 420e1073). Titratable acidity (TA) as milliequivalents of citric acid/100 g fresh weight (meq citric acid/100 g fw) was measured using 5 g of homogenized pulp sample and titrated with NaOH 0.1 mol equi/L using phenolphthalein as an indicator (AOAC, 1984). For textural firmness measurement mango was prepared by cutting the mesocarp parallel to and 1 cm from the flat side of the seed. Resistance to penetration was measured on both sides of the equatorial diameter with a Shimpo texture meter (Lincolnwood, IL) fitted with a 0.5 cm diameter cylindrical probe. Results were reported in N. Internal color determinations were made by triplicate measurements of the Hue angle on the surface of the samples prepared for textural firmness, using a Minolta CR-300 colorimeter. Samples were withdrawn every 4 days for physico-chemical analyses. Peel color was evaluated visually with the EMEX official quality standard for export mangoes (EMEX, 1998) that employs the following scale: 1 ¼ green, 2 ¼ green with yellow areas, 3 ¼ equally green and yellow, 4 ¼ yellow with green areas, 5 ¼ yellow, 6 ¼ yellow with orange areas. Results are reported as percent of fruits located at each particular stage of ripening. External color was monitored daily on 20 mangoes. 2.5. Statistical analysis Data were analyzed by ANOVA (GLM-ANOVA) using the statistical package SAS (The SAS System for WindowsÔ. Version 6.11, SAS Institute, Cary, NC). Means comparison was made by the least significant difference (LSD). All tests of significance were at the 0.05 level. 3. Results and discussion 3.1. Respiration rate and ethylene production rate Fruit treated only with vacuum (VP, see Fig. 1A) had greater RR values than control fruit between 4, 5, 6 and 7 days; however, in both samples, the climacteric was noted on day 8 with values of 110.29 and 118.25 mL CO2 kg1 h1, respectively. The increase in RR of VP fruit may be attributed to stress caused by the applied vacuum. Plaxton and Podestá (2006) proposed that under stress the mitochondrial electron transport relies on the functions of alternative oxidases (AOXs), which can bypass the blocked proton pumping complex III, thus keeping the electron flux. Such flexibility in plant respiration provides the capability to adapt better to stress conditions, such as hypoxia and mechanical wounding. Activation of this pathway could explain at least part of the elevation in RR in VP fruit. It has been reported that either mechanical damage or storage under atypical conditions could produce tissue stress that may lead to increased RR and EPR (Barry, Llop-Tous, & Grierson, 2000; Yang & Hoffman, 1984). Fig. 1B slows a concomitant elevation in EPR of VP fruit, which was more clearly noted from day 5 (0.073 mL kg1 h1), while in control fruit this shift was noted on day 6 (0.017 mL kg1 h1). From days 6e9, no differences in EPR of VP and control fruit were noted (p > 0.05); however, statistically
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140
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Days of storage *Means statistically different (p<0.05) Fig. 1. Respiration rate and ethylene production rate of “Ataulfo” mangoes that were stored at 25 1 C, control, with vacuum (VP); treated with exogenous ethylene at atmospheric pressure (NP), with vacuum and treated with exogenous ethylene at 25 C and 90 3% RH. Data points represent the mean of three replicates and their corresponding standard Control, VP, NP500, NP1000, NP1500, VP500, VP1500. deviation.
smaller EPR in VP fruit was measured from days 10e12. It has been reported that internal gas (CO2, ethylene and O2) expansion may occur in fruit when vacuum is applied. These gases could diffuse into intracellular spaces and outside the fruit, and could cause reversible tissue deformations (Barat, Fito, & Chiralt, 2001; Wang et al., 2001). On day 13, no significant difference was measured (p < 0.05) in EPR between VP and control fruit (1.41 and 1.40 mL kg1 h1, respectively). This means that at the end of the storage the auto-catalyzed production of ethylene in fruit was equalized. Fig. 1C contains data on the RR of fruit treated with ethylene at ambient pressure (NP500, NP1000 y NP1500). In all samples, the
climacteric peak was observed on the 8th day with 121.22, 124.28 and 124.11 mL CO2 kg1 h1, respectively and no significant differences were found between them. Although the climacteric peak of the treatments coincided with that of the control and VP fruit, these later samples had smaller values of RR. Additionally, from day 2, NP1500 fruit showed a clear increase in RR, which was followed by NP500 and NP1000 fruit, with respect to control and VP fruit. This trend suggests a particular sensibility of ‘Ataulfo’ mangoes to exogenous ethylene; thus, short exposures to small concentrations of this hormone may be enough to trigger a respiratory response by the fruit. It has been documented that exogenous ethylene increased RR, EPR and accelerated fruit ripening, the
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extent of which depends on exposure time, type of fruit and its state of ripening (Prasanna, Parva, & Tharanathan, 2007; Salveit, 1999). In the present study, ethylene production was detected from day 6 in fruit treated with exogenous ethylene and stored at ambient pressure (NP500, NP1000 and NP1500; see Fig. 1D). At the end of storage, all treated samples had greater EPR than control and VP fruit: 2.00, 1.79 and 2.02 mL kg1 h1, for NP500, NP1000 and NP1500 fruit, respectively. This trend suggests that exogenous ethylene applied at different concentrations was able to increase the production of autocatalytic ethylene but produced no gain in the time to reach the climacteric peak. Ripening homogenization did not occur too, and this would explain the requirement of exposure of up to 12 h to attain this effect (Salveit, 1999). As it can be seen on Fig. 1E, fruit that were subjected to vacuum and then brought back to ambient pressure followed by ethylene exposure at 1500 mL L1 for only 30 min (VP1500), displayed greater RR on days 2e6 (p < 0.005) with respect to the other treatments. These fruits from the VP500 and VP1000 treatments showed their climacteric peak one day early and RR remained high from days 5e7 compared to control and VP fruits. Values of RR reached at the climacteric were 129.66, 129.69 and 130.64 mL CO2 kg1 h1 for VP500, VP1000 and VP1500 mangoes, respectively on day 7. Then, RR decreased faster in VP1500 mangoes. Previous research which report the application of vacuum apples, mango, and papaya (Barat et al., 2001; Fito & Pastor, 1993; Mújica et al., 2003) suggest that a deformation-relaxation phenomenon could develop under vacuum, and internal pressure buildup may happed due to gas expansion inside fruit tissue (Del Valle, Aránguiz, & Díaz, 1998; Fito, 1994). Vacuum favored gas transfer inside the fruit in a proportional rate with the concentration of ethylene of the atmosphere and may account for the increased RR in VP1500 fruit. This could also be due to the activation of AOXs as described above and the presence of greater ethylene concentrations. Fig. 1F shows that EPR increased during storage. It is clearly noted that VP1500 mangoes had increased EPR during most of the storage, except on days 10 and 11, with respect to the other treatments, until 3.0 mL kg1 h1 were reached. In a previous study and using the same mango variety, but after 12 h of ethylene exposure at ambient pressure we measured an EPR of 2.6 mL kg1 h1
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ethylene at the end of the storage (Montalvo et al., 2007). This implies that vacuum and ethylene (1500 mL kg1 h1) applied for only 30 min attained a similar extent of internal ethylene as longer exposures (12 h) with no vacuum employed, and both were able to start the ethylene-regulated ripening changes in the fruit. In VP1500 fruit, increased EPR is attributed to greater ethylene diffusion due to the effect of vacuum and then the pressure was reinstated by an ethylene-containing atmosphere with the highest concentration Ethylene promoted enhanced activities of enzymes involved in endogenous ethylene synthesis. Increased EPR was reported on refrigerated ‘Ataulfo’ mangoes treated with ethylene under atmospheric pressure (Montalvo et al., 2007). Molecular studies in other fruits have demonstrated that exogenous ethylene stimulated gene expression for endogenous ethylene synthesis. Increased mRNA for ACC oxidase and ACC synthase has also been reported (Barry et al., 2000; Lassere et al., 1996; López-Gómez, Campbell, Jiang-Guo, Shang-Fa, & Gómez Lim, 1997; Nakatsuka et al., 1998).
3.2. Compositional variables during ripening Table 1 show that TSS from day 5 and until the end of the experiment, VP fruit were different from control fruit with maximal values of 17.27 and 16.35 Brix, respectively. TSS was similar among all ethylene-treated fruit that were kept at normal pressure (NP500, NP1000 and NP1500) on days 5 at 13 (p < 0.05). This was irrespective from the ethylene concentration employed. This suggests that ethylene applied at atmospheric pressure for 30 min did not elicit any significant effect on TSS. Conversely, fruit exposed to vacuum and ethylene had similar (p < 0.05) values for TSS at day 13: 19.11, 19.28 and 19.38 Brix for VP500, VP1000 and VP1500, respectively (Table 1). These values were greater than those found for other treatments. Thus, VP and ethylene may be considered responsible of such changes. Table 1 shows that change rate on TSS of VP1500 fruit was greater than for the rate of the other treatments, probably due to a greater production of autocatalytic ethylene (Fig. 1f). Several authors have also reported that increased TSS at the same time that starch was hydrolyzed into sucrose,
Table 1 Physico-chemical values of ‘Ataulfo’ mangoes: control, with vacuum (VP); treated with exogenous ethylene at normal pressure (NP), and exposed to vacuum and treated with exogenous ethylene (500, 1000 or 1500 mL1 L1) at 25 C and 90% HR. Days post-harvest
Treatments Control
VP
500 mL L1 NP
Total soluble solids ( Brix) 4.97 0.25b 1 4.99 0.22b 5 8.52 0.12d 9.19 0.20c 9 14.38 0.23c 15.71 0.16b 13 16.35 0.12c 17.27 0.24b Titratable acidity (meq citric acid/100 g fw) 1 3.40 0.14a 3.33 0.31a 5 2.83 0.06b 2.54 0.02c 9 1.87 0.03a 1.20 0.07b 13 0.37 0.08a 0.29 0.12b Firmness (N) 174.40 5.1a 1 175.45 4.1a 5 129.88 3.4a 120.94 2.5b 9 46.31 1.4a 40.16 1.3c 13 13.45 0.6a 11.78 1.2b Hue Angle (h) 90.09 1.7ab 1 90.24 2.4ab 5 96.72 3.4a 93.05 2.7b 9 86.97 2.5a 79.03 2.8c 13 77.45 1.5a 77.58 1.3a
1000 mL L1 VP
NP
1500 mL L1 VP
NP
VP
5.19 9.39 14.83 16.44
0.55a 0.02c 0.25c 0.55c
5.74 10.77 16.10 19.11
0.20a 0.18b 0.24b 0.48a
5.90 9.49 14.86 16.70
0.28a 0.12c 0.21c 0.29c
5.92 10.57 16.26 19.28
0.21a 0.02b 0.18b 0.31a
5.75 9.37 14.86 16.78
0.20a 0.07c 0.21c 0.21c
5.98 13.19 17.20 19.38
0.25a 0.13a 0.12a 0.21a
3.20 2.79 1.89 0.37
0.04a 0.01b 0.12a 0.08a
3.18 2.07 1.05 0.29
0.08a 0.14d 0.02c 0.08b
3.18 2.84 1.89 0.36
0.05a 0.06ab 0.10a 0.09a
3.04 2.05 0.84 0.29
0.20a 0.01d 0.01d 0.06b
3.32 3.03 1.99 0.38
0.22a 0.09ab 0.01a 0.07a
3.25 2.06 0.44 0.27
0.29a 0.08d 0.09e 0.13c
174.13 117.45 44.85 11.46
5.42a 5.99bc 2.8b 1.52b
136.77 103.81 37.93 10.56
2.1c 1.8d 2.35d 1.3c
176.37 119.26 43.60 11.33
2.6a 2.3b 2.43b 1.6b
140.63 98.18 38.78 11.61
2.3b 2.1d 1.5cd 1.3b
176.45 117.40 43.93 11.41
3.1a 6.0bc 2.1b 1.5b
127.27 91.21 31.61 10.05
2.1d 1.6e 1.2e 1.81c
90.51 90.84 84.07 76.31
2.1ab 3.3b 2.38b 2.6a
93.03 89.16 81.78 74.24
2.5a 1.1c 3.0c 1.3c
92.08 96.71 84.25 75.95
3.42a 4.0a 2.2b 1.2b
92.49 89.03 83.23 73.42
3.1a 3.3c 3.22bc 2.12c
91.83 90.12 85.76 77.96
2.5a 4.11b 3.7ab 1.0a
92.90 84.50 75.21 70.48
2.6a 1.4d 2.1d 1.3d
Means with same letters within a row are not statistically different (Tukey a ¼ 0.05). Entries represent the means of six measurements.
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fructose and glucose (Hubbar, Pharr, & Huber, 1990; Montalvo et al., 2007; Zamora et al., 2004). TA decreased during mango ripening (Table 1). This is a normal event due to the reduction of organic acids content in this process (Plaxton, 1996). Both control and VP fruit had statistically different acidity values (P < 0.05) and reached acidities of 0.37 and 0.29 meq
citric acid/100 g fw, respectively, at the end of the storage. In a similar fashion as TSS, there were no differences in TA between NP500, NP1000 and NP1500 fruit, or with respect to the control fruit (Table 1) throughout all the days of storage. For day 9, acidity of VP1500 decreased considerably (0.44 meq citric acid/100 g fw) as compared to VP500 fruit (1.05 meq citric acid/100 g fw) and
Fig. 2. Number of fruits graded with color development held at 25 C (Control), with vacuum (VP); treated with exogenous ethylene at atmospheric pressure (NP), with vacuum and treated with exogenous ethylene (VP) at 25 C and 90 3% RH. (A)-Control; (B)-VP; (C)-NP500; (D)-NP1000; (E)-NP1500; (F)-VP500; (G)-VP100; (H)-VP1500.
B. Tovar et al. / LWT - Food Science and Technology 44 (2011) 2040e2046
VP1000 fruit (0.84 meq citric acid/100 g fw) (see Table 1). Respiration is a process inversely related to TA due to the availability of organic acids (Tsouvaltziz, Gerasopoulos, & Siomos, 2007). The early drop in acidity of VP1500 fruit coincided with higher RR, greater TSS and the early detection of EPR (Fig. 1B). There were differences in textural firmness of VP fruit at the three ethylene concentrations (VP500, VP1000 and VP1500) with reference to the other treatments, with lower firmness at 5e9 days of storage (Table 1); although at the end of storage there were no differences between all the treatments (p < 0.01), the fastest rate of loss of firmness occurred in VP1500 fruit. It has also been reported that very low ethylene concentrations affect the textural firmness of the fruits; however, this is also dependent of ethylene exposure time (Mir & Beaudry, 2002). Thus, application of vacuum for 30 min, followed by ethylene exposure exerted a definite effect on textural hardness. Cheong et al. (2002) reported that many of the ethylene response transcriptions factors such as ethylene-responsive element binding proteins (EREBP) are rapidly induced by mechanical wounding. These transcriptional factors may directly participate in the activation of ethylene-responsive genes. In mango, vacuum could have caused similar gene expression and enhancement of this response could have been possible because of the higher concentration of ethylene used on VP1500 fruit. Then, loss of firmness may be attributed to the effect of ethylene on the synthesis of cell wall-degrading enzymes, since greater activities of pectinmethylesterase, polygalacturonase and b-galactosidase were measured on refrigerated ‘Ataulfo’ mangoes that were treated with ethylene for 12 h (Montalvo, Adame, García, Tovar, & Mata, 2009). Sane, Chourasia, and Nath (2005) reported the role of the expansines gene on softening of ‘Dashehari’ mango when exposed to 100 mL L1 ethylene for 24 h. Results indicated that softening of fruit pulp is associated to the expression of the expansine gene (MiExpA) and found that gene regulation was controlled by ethylene. Based on the above evidence, it is quite probable that the described enzymes and mechanisms could have been involved in the loss of textural firmness. Mean values for Hue angle from mango pulp post-harvest are shown on Table 1. These values decreased in all treatments as ripening proceeded. Similar to firmness there were differences between hue angle values. On day 13, both control and VP fruit, had a hue angle value of 77.45 and 77.58, respectively. For fruits NP500, NP1000 and NP1500 similar hue angle values to those of control fruit (p > 0.05) were found; while hue angle values of VP fruit treated with three different ethylene concentrations and the other treatments; lower values indicate pulp color development toward orange. VP1500 fruit reached a yellow-orange color (70.48) at day 13. Salveit (1999) described how application of exogenous ethylene promoted ripening by first degrading the green color with a concomitant development of yellow color marked by carotenoid synthesis. Fig. 2 depicts the number of mangoes graded with color development (%). After nine days of storage, more than 50% of the VP fruits, and 30% of control fruits had yellow-orange tones, regarded as normal for the consumption stage of ‘Ataulfo’ mangoes. At the end of storage, VP fruits were fully ripened while control fruits were not completely ripened since some fruits still had green areas. Fruit from treatments NP500, NP1000 and NP1500 contained ca. 80% of yellow-orange mangoes. For VP1500 fruit, all the mangoes were completely ripened on day 9; while at the same day VP500 and VP1000 fruit had 90 and 80% of ripened mangoes, respectively. Our results are consistent with the report for Kent mangoes by Zamora et al. (2004) and ‘Ataulfo’ mangoes by Montalvo et al. (2007). It is possible that exogenous ethylene activated enzyme activities linked to the metabolism and carotenoid synthesis in both pulp and peel. Results in apricot (Prunus armeniaca) fruit showed that carotenoid accumulation was correlated
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with post-transcriptional regulation, feed-back regulation by endproducts, and hormonal regulation (by ethylene) as other regulation mechanisms of carotenoid accumulation (Marty et al., 2005). 4. Conclusions Application of 34 kPa vacuum for 20 min, allowed for uniform ripening of ‘Ataulfo’ mangoes measured as internal and external color while compositional variables (TSS, TA, pH values, firmness) were not affected. Ethylene application at ambient pressure did not affect fruit ripening when applied by short times. Vacuum (34 kPa) for 20 min with 1500 mL L1 ethylene for 30 min, increased EPR and RR, which triggered the ripening process that proceeded in shorter time and these fruit had the same compositional quality as that of control fruit, but ripening was more homogenous in their external color and the edible stage was reached 3 days earlier than control mangoes. Acknowledgments The authors gratefully acknowledge the financial support of DGEST through the grant Nr. 317.06 and CONACyT of México through the grant 208035. The valuable contribution by Mr. Abelardo González Cabrera of fresh mangoes for the study is truly appreciated. References AOAC. (1984). Official methods of analysis (14th ed.). Arlington, Virginia, USA: Association of Official Analytical Chemists. Barat, J. M., Fito, P., & Chiralt, A. (2001). Modeling of simultaneous mass transfer and structural changes in fruit tissues. Journal of Food Engineering, 49(2e3), 77e85. Barry, C. S., Llop-Tous, M. I., & Grierson, D. (2000). The regulation of aminocyclopropane-1-carboxylic acid synthase gene expression during the transition from system-1 to system-2 ethylene synthesis in tomato. Plant Physiology, 123, 979e986. Centurión, A. R., González, N. S. A., Tamayo, C. J. A., Argumedo, J. J., & Sauri, D. E. (1998). The effect of Ethephon on the colour, composition and quality of mango (Mangifera indica, cv Kent). Food Science and Technology International, 4, 199e205. Cheong, Y. H., Chang, H. S., Gupta, R., Wang, X., Zhu, T., & Luan, S. (2002). Transcriptional profiling reveals novel interactions between wounding, pathogen, abiotic stress and hormonal responses in Arabidopsis. Plant Physiology, 129, 661e667. Del Valle, J. M., Aránguiz, V., & Díaz, L. (1998). Volumetric procedure to assess infiltration kinetics and porosity of fruits by applying a vacuum pulse. Journal of Food Engineering, 38(2), 207e221. Dilley, D. R. (1972). Hypobaric storage e a new concept for preservation of perishables. Proceedings Michigan State Horticultural Society, 102, 82e89. EMEX, A.C. (1998). Norma de calidad para mango fresco de exportación. Elaborada por Baéz-Sañudo, R., Bringas, E., Ojeda, J., Cruz, L., Ontiveros, S., Pellegrin, J. Boletín. 6. p. CIAD, A.C. FAO. (2009). Food and Agriculture Organization of the United Nations. http://faostat. fao.org. Fito, P., & Pastor, R. (1993). Non diffusional mechanisms occurring during vacuum osmotic dehydration. Journal of Food Engineering, 21, 513e519. Fito, P. (1994). Modeling of vacuum osmotic dehydration of food. Journal of Food Engineering, 22, 313e327. Hubbar, N. L., Pharr, D. M., & Huber, S. C. (1990). Role of sucrose phosphate synthase in sucrose biosynthesis in ripening bananas and its relationship to the respiratory climacteric. Plant Physiology, 94, 201e208. Lagunes, L., Tovar, B., Mata, M., Vinay-Vadillo, J. C., delaCruz, J., & García, H. S. (2007). Effect of exogenous ethylene on ACC content and ACC oxidase activity during ripening of Manila mangoes subjected to hot water treatment. Plant Foods for Human Nutrition, 62(4), 157e163. Lassere, E., Bouquin, T., Hernández, J. A., Pech, J. C., Bull, J., & Balangué, C. (1996). Structure and expression of three genes encoding ACC oxidase homologs from melon (Cucumis melo L). Gene, 3, 81e90. López-Gómez, R., Campbell, A., Jiang-Guo, D., Shang-Fa, Y., & Gómez Lim, M. A. (1997). Ethylene biosynthesis in banana fruit: isolation of a genomic clone to ACC oxidase and expression studies. Plant Science, 123, 123e131. Marty, I., Bureau, S., Sarkissian, G., Gouble, B., Audergon, J. M., & Albagnac, G. (2005). Ethylene regulation of carotenoid accumulation and carotenogenic gene expression in colour-contrasted apricot varieties (Prunus armeniaca). Journal of Experimental Botany, 56(417), 1877e1886.
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