ORIGINAL ARTICLE
https://doi.org/10.1007/s10341-019-00444-2
Pre-harvest Micronized Calcium and Postharvest UV-C Treatments
Extend the Quality of ‘Crimson Seedless’ (
Vitis vinifera L.) Grapes
Ferhan K. Sabir1· Ali Sabir1Received: 16 August 2018 / Accepted: 21 June 2019 / Published online: 9 July 2019 © Springer-Verlag GmbH Deutschland, ein Teil von Springer Nature 2019
Abstract
Certain postharvest disorders such as rachis desiccation, weight loss, accelerated softening and biochemical changes limit the postharvest life of table grapes. The present study was conducted to evaluate the effect of pre-harvest micronized calcium pulverizations, postharvest UV-C treatment and their combined applications on extending postharvest quality of table grapes cv ‘Crimson Seedless’. Pre-harvest micronized calcium pulverization was performed to improve rachis greenness and berry resistance while postharvest UV-C was aimed to induce physiological resistance and delay senescence in grape berries. Ca treatments significantly increased chlorophyll concentrations of rachis while Ca plus UV-C was the best treatment to maintain rachis chlorophyll concentration. UV-C with or without pre-harvest Ca treatment effectively delayed the weight loss during the storage. Ca delayed the increase of SSC during the storage. All the treatments, particularly postharvest UV-C, significantly delayed the berry senescence by delaying the decrease in acidity. UV-C with or without Ca, with the lowest values, significantly retarded the changes in phenols and decreased the berry decay. Ca plus UV-C treatment also effectively maintained the skin rupture force during the storage. Overall, pre-harvest micronized Ca pulverizations plus postharvest UV-C treatment can be recommended to extent the quality of table grapes cv. ‘Crimson Seedless’ up to 120 days at cold storage.
Keywords ‘Crimson Seedless’ · Table grape · Quality maintenance · Postharvest physiology
Behandlungen mit mikronisiertem Calcium vor der Ernte und UV-C-Bestrahlung nach der Ernte
verbessern die Qualität der Tafeltraubensorte ‘Crimson Seedless‘ (Vitis vinifera L.)
Schlüsselwörter ‘Crimson Seedless’ · Tafeltrauben · Haltbarkeit · Nachernte-Physiologie
Introduction
‘Crimson Seedless’ (Vitis vinifera L.), a late season grape cultivar with attractive, red seedless berries, is currently a very popular table grape cultivar across the world. The popularity of this cultivar is ascribed to its very unique sweet (high SSC (Soluble Solid Content) around 18 °Brix), juicy, crisp and elongated pink berries. ‘Crimson Seedless’ is a late maturing grape which is resistant to berry crack thus allowing for a longer ripening period, and clusters main-tained in cold storage tend to remain in good conditions
Ferhan K. Sabir fkbasmaci@selcuk.edu.tr
1 Agriculture Faculty Horticulture Department, Selcuk University, Konya, Turkey
(Human2010). However table grapes, including ‘Crimson Seedless’ experience undesired changes during storage in-cluding biochemical and physical modifications in acidity, total soluble solids, sugars, pH, total polyphenols, and dif-ferent sensorial attributes. The ratio between sugars/acids is regarded to be the prime factor affecting taste and end quality of grapes and this ratio is highly exaggerated dur-ing prolonged storage (Sen et al.2016). Grape berries are perishable and highly susceptible to fungal infections such as Botrytis, Aspergillus, Alternaria, etc. that adversely af-fect the quality attributes of fruits (Pedreschi et al. 2013). Grey mold and stem browning caused by Botrytis cinerea, are a major biological disorders of horticultural produces. B. cinerea can grow even below at –0.5 °C and has the tendency to reproduce rapidly on berries skin (Liu et al. 2016). Several strategies have been introduced to minimize the postharvest losses of grapes. The typical practice is
fumigation of the berries after being harvested with con-ventional sulfur dioxide gas (SO2) but severe health issues
of its residues specifically to the people that are allergic to sulfites have been reported (Sabir and Sabir2009). For reasonably concrete estimates of postharvest quality exten-sion of produces, attention has to be devoted to harvesting and packaging strategies, effectiveness of various chemi-cals, and consideration of residuals of applications. Many studies are available for the investigation of certain meth-ods or applications to supply the grape year-round. Among them, utilization of calcium salts are a well experienced ex-ample to replace conservative fungicide sprays in control-ling the postharvest antimicrobial decay of fruiting berries (Romanazzi et al.2012). Calcium salt has been shown to play an eccentric part in upholding the cell wall of the fruit cells for its role as preservative and firming agent. Posthar-vest application of different salts pretreatments including calcium chloride (Yousefi et al. 2015), sodium carbonate and bicarbonates (Nigro et al.2006), calcium lactate (Javed et al. 2016) have been shown to be promising treatments for maintaining the quality characteristics of fruits. In a re-cent study, studying on extension of postharvest quality of ‘Thompson Seedless’ grapes by pre-harvest micronized cal-cite sprays, Sabir and Sabir (2017a) indicated that pre-har-vest calcite treatments may be an environmental-friendly, healthy and sustainable strategy for extending postharvest quality of table grapes, without adverse effect on posthar-vest physiology of produces, and thus may be considered as an effective alternative for common chemical treatments. Although, pre-harvest calcite spray resulted in good results compared to control, decay rate was at considerable lev-els (approx. 17%) after a three-month-storage. Therefore, it was presumed that combined employment of pre-harvest calcite with a healthy disinfection methodology performed after harvest would be more effective to extend the storage life of table grapes. Recently, postharvest use of UV-C as disinfectant was proposed to extend postharvest quality in perishable products such as grapes (Akbudak and Karabulut 2002), tomatoes (Charles et al.2005), peaches and apples (Lu et al.1991). Therefore, the purpose of this study was to evaluate the effect of pre-harvest micronized calcium pul-verization, postharvest UV-C treatment and their combined application on extending postharvest quality of grapes cv ‘Crimson Seedless’.
Materials and Methods
Plant Materials and Treatments
The pharvest treatments were performed in the re-search and implementation glasshouse of Selcuk Univer-sity, Konya, Turkey, during the 2017 growing season. The
experimental soilless grown grapevines were individually cultivated in 70 L (solid volume) pots filled with sterile peat (1.034% N, 0.94% P2O5, 0.64% K2O Klassman®) and
perlite mixture in equal volume. At the beginning of the vegetation period, the vines were spur pruned to leave 12–14 buds per plant. The summer shoots were tied with thread to wires 2.2 m above the pots to let shoots grow on a perpendicular position to ensure equally benefiting from the sunlight (Sabir 2013). The vines received the same annual amount of fertilizer (approx. 50 g N, 30 g P, 50 g K, and equal mixture of microlements per vine) from April to July. Drip irrigation system was regulated according to soil water matric potential using soil tensiometers (The Irrometer Company, Riverside, CA) to ensure and maintain optimum irrigation.
Twenty four uniform vines, free from various physiolog-ical and visible pathologphysiolog-ical disorders were selected for the study. The vines were divided into two rows one of which received micronized calcium treatment while the other was non-treated control group. The spray of micronized calcium solutions at 0.1% dose (2.3 g per vine for each application) was applied after full bloom, when the berry diameter was around 3 mm and repeated two weeks later using a hand pressure sprayer on fruit and the entire vine canopy.
Procurement of Raw Material
About 30 kg grape clusters belonging to each group (Ca-sprayed and control) were freshly harvested sepa-rately at commercial maturity stage from the experimental glasshouse and immediately transported to the laboratory. The clusters, selected based on uniformity in size and ma-turity, free from diseases and visual blemishes, were further sorted into two equal groups one of which was subjected to the postharvest UV-C treatment. For UV-C irradiation, two subsets of berries (Ca-treated or non-treated) were irradiated for 5 min using two germicidal low pressure mer-cury-vapor discharge lamps emitting quasi-monochromatic UV radiation at 254 nm as described by El Ghaouth et al. (2000). The berries were placed in metal trays in a single layer approximately 12 cm from the surface of the lamp.
For each group, twelve packages (three replications × four storage times) were prepared by placing about 500 g of ta-ble grapes inside 30 cm × 40 cm polyamide/polyethylene plastic bags. Samples were stored for up to 120 d in a cold room at 1 °C (80–90% R.H.). For quality analyses, samples were taken at harvest, 30th, 60th, 90th and 120th days of storage.
Weight Loss and Biochemical Assessments
To calculate weight loss, individual samples were weighed initially and after each storage period. Total soluble solids
content (SSC) expressed as °Brix was measured with a portable refractometer (Atago, Tokyo, Japan) in grape juice obtained by whisking the berries from each replica-tion in a blender (1 min, 14,000 rpm) and then filtering the juice. Titratable acidity (TA) was determined by titrating 10 mL of juice using NaOH 0.1 mol L–1to pH 8.1 (AOAC 1984). Results were expressed as g tartaric acid per 100 g fresh weight (FW). Maturity index (MI) was calculated as SSC/TA ratio. The pH was measured using a pH meter (Crison, Barcelona, Spain).
Rachis Chlorophyll Concentration, Berry Detachment Force and Skin Rupture Force
A total of forty five representative berries per treatment were randomly taken from the top, middle, and bottom of each clusters and rachis sections were prepared by cutting the rachis with shears. A berry from each section was then cradled in a jig attached to a force gauge (DPS-11; Imada, Northbrook, IL), and the rachis section was slowly pulled away from the berry until it detached. The force required to detach each berry from the rachis in kilogram-force was recorded as the BDF (Berry Detachment Force) (Fidelibus et al. 2007). Total chlorophyll off rachis was determined spectrophotometrically as described by Agar et al. (1997) with slight modifications. One gram of blended rachis tis-sue was homogenized with 15 mL chloroform–methanol (2:1, v/v) for 1 min. Extracts were filtered with filter pa-per and solutions supplemented with chloroform–methanol to 25 mL final volume. Total chlorophyll was determined by measuring the absorbance of solution in the spectropho-tometer at 663 and 645 nm against chloroform–methanol blank. Results were calculated using the McKinney equa-tion and expressed as mg kg–1.
Total Phenols and Antioxidant Activity
Grape berry extracts for antioxidant and phenol analyses were prepared using method described by Thaipong et al. (2006) with slight modifications. After removing the stem caps of berries, 5 g grape tissue from a mixture of fifteen berries without seeds was homogenized in methanol us-ing Ultra-Turrax homogenizer (IKA, T18 digital, Staufen, Germany) for 1 min and then centrifuged at 4000 × g for 30 min at 5 °C. The supernatants were recovered and stored at –20 °C in dark color bottles until analysis. The antiox-idant capacity of the sample was found using a ferric re-ducing antioxidant potential (FRAP) assay according to the method defined by Benzie and Strain (1996). The FRAP reagent was a mixture of 25 mL acetate buffer pH 3.0, 2.5 mL 10 mM 2,4,6-trioyridyl-1,3,5-triazine (TPTZ) and 2.5 mL 20 mM ferric chloride hexahydrate. The mixture re-action was started when 0.5 mL of the supernatant added
into 5 mL of FRAP solution. The reaction solution was in-cubated at ambient temperature for 30 min and then the absorbance was measured at 630 nm. The antioxidant ca-pacity was expressed as micro moles of Trolox equivalents per gram fresh weight (μmole Trolox equivalent/g FW). Total phenols were determined according to the method of Singleton et al. (1999). A 100 μL aliquot of each extract was mixed with 1.58 mL of water, 100 μL of Folin-Cio-calteu’s reagent and 300 μL of sodium carbonate solution (200 g L–1). The absorbance at 760 nm was read after 2 h.
The content of total phenols was calculated on the basis of the calibration curve of gallic acid and was expressed as mg gallic acid 100 g–1FW.
Decay Incidence
The decay rate of grapes was evaluated at the end of storage because there was no visual decay symptom up to the end of storage. Decay rate was quantified by counting the decayed berries in each cluster, multiplying the total number of de-cayed berries per replication by the average berry size, and calculating the percentage of decayed berries with respect to the weight of the entire replication. The decay rate was then obtained by the formula: Decay rate (%) = (Number of decayed berries/Total number of berries) × 100 (Youssef et al.2015).
Statistical Analyses
Statistical analyses were performed in triplicate on three different batches. The mean values and standard deviation were calculated. The data shown in the figures are the aver-age of all repetitions, where the error bars are the standard deviations. Experimental data were submitted to one-way analysis of variance and Student’s t-test (PÄ 0.05) using the software SPSS 13.0 for windows.
Results and Discussion
Steady increase in the weight loss was observed in all treat-ments with the progression in the storage period (Fig.1). Weight loss drastically increased in the first 30 d of stor-age and afterwards the treatment effects begun to exhibit significant differences. Grapes belonging to control or Ca alone treatments suffered from greatest weight loss during the storage, while UV-C with or without pre-harvest Ca treatment significantly delayed the weight loss. Studying on postharvest storage of table grapes, Akbudak and Karabulut (2002) also recorded a significant delay in weight loss of table grapes subjected to UV-C treatment during cold stor-age. Weight loss, a critical problem affecting the postharvest quality of table grapes, is one of easy and objective
mea-0 1 2 3 4 5 6 7 8 9 0 30 60 90 120 Weight loss (%) Storage duraon (d) LSD%5=0.15
Control Ca UV-C Ca+UV-C
Fig. 1 Weight loss changes of berries during the prolonged storage as influenced by treatments. Error bar stands for the standard deviation of the mean of triplicate determinations
sures often used to score storage success (Sabir and Sabir 2017b). Percent loss of fresh weight is therefore used to de-scribe freshness of horticultural products. Perishable fresh produces like table grapes continuously lose water during the postharvest handling. As stated by Kader (2002), rel-atively small moisture losses are enough to cause berry shriveling, wilting and undesirable texture changes.
Table 1 SSC, TA, MI and pH changes of berries during the prolonged storage as influenced by treatments Treatments Storage time (days)
0 30 60 90 120
SSC (°Brix)
Control 19.80 ± 0.12h 22.07 ± 0.12bc 20.80 ± 0.20e-h 23.53 ± 0.64a 22.53 ± 0.50b Ca 18.93 ± 0.12i 20.73 ± 0.64e-h 20.13 ± 0.23gh 21.40 ± 0.53c-f 20.87 ± 0.23efg UV-C 19.80 ± 0.12h 21.13 ± 1.10def 20.67 ± 0.99fgh 21.47 ± 0.42cde 22.07 ± 0.12bc Ca + UV-C 18.93 ± 0.12i 22.49 ± 0.37b 20.07 ± 0.31h 22.53 ± 0.15b 21.87 ± 0.23bcd TA (%) Control 0.527 ± 0.011a 0.428 ± 0.010bcd 0.411 ± 0.020de 0.318 ± 0.012h 0.290 ± 0.013i Ca 0.532 ± 0.010a 0.434 ± 0.030bcd 0.418 ± 0.016cd 0.349 ± 0.011g 0.302 ± 0.014hi UV-C 0.527 ± 0.011a 0.444 ± 0.012bc 0.434 ± 0.019bcd 0.374 ± 0.030fg 0.355 ± 0.028g Ca + UV-C 0.532 ± 0.010a 0.446 ± 0.010b 0.422 ± 0.008bcd 0.386 ± 0.015ef 0.356 ± 0.002g MI (SSC/TA) Control 38.10 ± 0.81f 51.54 ± 1.48e 50.74 ± 2.39e 74.05 ± 2.99a 77.75 ± 2.57a Ca 35.61 ± 0.56f 47.95 ± 4.67e 48.20 ± 1.49e 61.32 ± 2.72cd 69.13 ± 2.44b UV-C 38.10 ± 0.81f 47.69 ± 3.56e 47.68 ± 2.45e 57.68 ± 3.78d 62.49 ± 4.87c Ca + UV-C 35.61 ± 0.56f 50.42 ± 0.97e 47.61 ± 0.20e 58.46 ± 2.39cd 61.45 ± 1.05cd pH Control 3.74 ± 0.02a 3.63 ± 0.06b-e 3.63 ± 0.04bcd 3.64 ± 0.01bc 3.41 ± 0.06g Ca 3.78 ± 0.05a 3.66 ± 0.04b 3.56 ± 0.06ef 3.58 ± 0.04c-f 3.42 ± 0.02g UV-C 3.74 ± 0.02a 3.62 ± 0.04b-e 3.64 ± 0.06bc 3.64 ± 0.05bcd 3.43 ± 0.01g Ca + UV-C 3.78 ± 0.05a 3.74 ± 0.02a 3.58 ± 0.06def 3.54 ± 0.03f 3.47 ± 0.04g Means of triplicate measurements are presented with standard deviations. Data with different letters are significantly different (PÄ 0.05)
Changes in SSC, TA, MI (SSC/TA) and pH of the grapes throughout the storage period are shown in Table1. At har-vest, SSC values were 18.9 and 19.8 °Brix for Ca treat-ment and control grapes, respectively. A significant and treatment-dependent increase occurred along with the pro-longed storage time. Although the grape is classified as one of nonclimacteric fruits (Kader 2002), the increase in SSC indicates progressive ripening of grapes during stor-age, as reported by various researchers for different culti-vars (Sabir and Sabir2013). Some of other reasons for SSC increase may also relate with gradual increase in solute con-centration due to the water loss from the berry cell (Pretel et al.2006), rapid conversion of complex starch molecules into simpler sugars (Gallo et al. 2014), glycogenesis and metabolism of fruiting tissues that becomes partially inac-tive due to changes in glucose and fructose (Imlak et al. 2017) during postharvest life the SSC increment. Nonethe-less, it is worth to bear in mind that the SSC concentration might also remain stable under different storage conditions in certain circumstances as Crisosto et al. (2002) and Sabir and Sabir (2017a) have already reported a steady course in SSC content of different table grapes during cold stor-age. From the beginning of the storage up to the end, Ca treatment alone significantly delayed the increase of SSC. Such delaying effect of Ca treatment performed via posthar-vest immersing the grape clusters in aqueous solutions of calcium chloride was also reported by Imlak et al. (2017)
0 2 4 6 8 10 12 14 16 0 30 60 90 120 Rachis chlorophyll (mg 100 g -1 ) Storage duraon (d) LSD%5=1.10
Control Ca UV-C Ca+UV-C
Fig. 2 Rachis chlorophyll concentration changes during the prolonged
storage as influenced by treatments. Error bar stands for the standard deviation of the mean of triplicate determinations
studying on ‘Thompson Seedless’ cultivar. Considering the findings on SSC of the present and the mentioned studies, calcium applications therefore seem particularly useful for Aegean Region vineyards where ‘Thompson Seedless’ and sometimes ‘Crimson Seedless’ vineyards are covered with nets or plastics to artificially delay the harvest period. In contrast to increase in SSC, TA level of grapes decreased during the storage time. Decline in acidity seemed to be sig-nificantly retained by postharvest UV-C treatment although, statistically irrespective of pre-harvest Ca pulverizations. Such decrease in concentration of total acids are mainly due to cell wall degradation (Guerra and Casquero2008) and irreversibly conversion back of organic acids to sug-ars (a pathway called gluconeogenesis) (Sung et al.1988). At harvest, MI values significantly differed among the pre-harvest treatments due to differences in SSC values. MI gradually increased with progression in storage period and postharvest UV-C treatment significantly delayed the MI. Generally, grapes with high SSC (>15%) had a high level of consumer preference regardless of their level of titrat-able acidity. It has been claimed, however, that the use of either SSC or TA alone as a maturity index is limited by a pronounced variation among the rape cultivars, cultiva-tion condicultiva-tions and season. Instead, the sugar-to-acid ratio (SSC:TA) has been proven to be more closely and precisely related to fruit quality than TA or SSC alone. Nonetheless, there is still a lack of well-defined maturity indices based on these parameters. Therefore, it remains difficult to de-termine the optimal time for harvest. pH value of the must was not significantly affected by treatments although slight differences were observed during the storage.
The green rachis is an important determinant of the fresh-ness of the table grapes after storage as it mainly affects
1,0 1,5 2,0 2,5 3,0 0 30 60 90 120 Be rry d e tacment force (N) Storage duraon (d) LSD%5=0.06
Control Ca UV-C Ca+UV-C
Fig. 3 Berry detachment force changes during the prolonged storage as influenced by treatments. Error bar stands for the standard deviation of the mean of triplicate determinations
consumer preference. As illustrated in Fig. 2, pre-harvest Ca treatments significantly increased total chlorophyll centrations of rachis. Expectedly rachis chlorophyll con-centration gradually decreased probably due to dehydration and ethylene biosynthesis along with the prolonged storage. Rachis chlorophyll degradation was accompanied by loss in weights as indicated by several researchers (Lichter et al. 2011; Sabir and Sabir2017a,2017b). Loss in total chloro-phyll concentration of rachis during the storage was also greatest in clusters of non-treated control group, whereas Ca plus UV-C was the best treatment to retain rachis chloro-phyll concentration. So far, browning of rachis has been controlled by the use of SO2which bleaches the rachis and
turns them from green to a khaki-beige-like color (Nelson 1985). Although, the bleached rachis is more acceptable than brown ones but, undoubtedly less appealing than the green color of fresh grapes.
As depicted in Fig. 3, berry detachment force (BDF) gradually decreased during the first month of storage with the greatest change in non-treated control grapes. In the first month, all the treatments had significantly positive effects on BDF compared to control clusters. Ca plus UV-C treat-ment was pioneering with its remarkably high BDF value, followed by Ca alone and UV-C. As previously reported by Marzouka and Kassem (2011) and Sabir and Sabir (2017a), Ca treatment might have strengthened the berry adherence to rachis. Berry shattering, a serious problem in grape mar-ket, was effectively delayed by Ca pulverization with or without UV-C radiation, probably. However, BDF dramat-ically decreased after the first month and the effects of the treatments were insignificant at the end of the storage.
At harvest, skin rupture force of Ca-treated berries was significantly higher than that of control berries (Fig. 4).
1,0 1,5 2,0 2,5 3,0 3,5 4,0 0 30 60 90 120
Skin rupture force
(N)
Storage duraon (d)
LSD%5=0.06
Control Ca UV-C Ca+UV-C
Fig. 4 Skin rupture force changes during the prolonged storage as in-fluenced by treatments. Error bar stands for the standard deviation of the mean of triplicate determinations
Berry skin rupture force (SRF) decreased during the stor-age, with a just opposite course to weight loss, indicating the existence of a tight negative relationship between them. Periodical analyses indicated Ca plus UV-C treatment ef-fectively maintained the SRF during the storage. At the end of the 120 d storage, all the treatments had significantly higher values of SRF with the maximum value obtained from Ca plus UV-C. Previous studies have shown that cal-cium preserve the membrane integrity of plant cell by de-laying senescence-related membrane lipid changes and en-hancing membrane restructuring processes (Picchioni et al. 1996), thereby conferring the rigidity to the cell wall and conserving the wall from hydrolytic enzymes produced by decay-causing microorganisms. There was no decay inci-dence in berries during the first 90 d of storage. At the end of the storage, with a significant difference among the treat-ments, the greatest decay rate was determined in control grapes (6.1%), while the lowest decay occurred in Ca plus UV-C treatment (2.2%) (Fig.5). Decayed grape amounts of all the treatments were markedly lower than control grape. These results are in agreement with data in the literature on the effect of low UV-C doses in reducing postharvest dis-eases of different commodities such as grapefruit (Droby et al. 1993), peach and apple (Stevens et al. 1996), and black carrots (Turkmen and Takci 2018). Prohibitive fea-ture of UV-C is most probably due to its effect on inducing a defense system through enhancing activities of antiox-idant matters as was seen in the present study, resulting in improved resistance against pathogen attack in treated grapes. On the other hand, Vicente et al. (2009) has already been well-documented that calcium improves and protects cell wall components and may protect the pectic backbone from polygalacturonase-mediated depolymerisation (Wehr
0 1 2 3 4 5 6 7
Control Ca UV-C Ca+UV-C
Decay rate
(%
)
Treatment
LSD%5=0.34
Fig. 5 Decay rate of berries as influenced by treatments. Error bar stands for the standard deviation of the mean of triplicate determina-tions
et al.2004). Such a protective effect of Ca might have re-sulted in decrease in decay incidence.
Consumer demand for fresh grapes or their derivatives have been increasing due to their rich composition in pheno-lic compounds, giving them a great nutritional value with high antioxidant activity (Solari-Godiño et al. 2017). Re-taining the content of phenolic compounds is an important issue to maintain postharvest quality of grapes. Changes in total phenol content of ‘Crimson Seedless’ grapes during storage is illustrated in Fig.6. At harvest, total phenol con-tent did not significantly differed among the treatments. Af-ter a slight increase up to the 60th d of storage, total phenol
100 200 300 400 500 600 700 800 0 30 60 90 120 Storage duraon (d) LSD%5=24.50
Control Ca UV-C Ca+UV-C
Fig. 6 Total phenol changes during the prolonged storage as influ-enced by treatments. Error bar stands for the standard deviation of the mean of triplicate determinations
0,0 0,5 1,0 1,5 2,0 2,5 3,0 0 30 60 90 120 Storage duraon (d) LSD%5=0.10
Control Ca UV-C Ca+UV-C
Fig. 7 Antioxidant activity changes during the prolonged storage as influenced by treatments. Error bar stands for the standard deviation of the mean of triplicate determinations
underwent an apparent and treatment-dependent increase. At the end of the storage, control grapes had the greatest phenol content and were followed by Ca treatment. How-ever, UV-C with or without Ca, with the lowest values, significantly retarded the changes in phenols. Prohibiting the loss in phenols during storage is one of major chal-lenge in preservation of grape and its derivatives (Genova et al.2012). Antioxidant activity increased with prolonged storage duration (Fig.7). But, neither pre-harvest Ca pul-verization nor postharvest UV-C treatment have significant effect on antioxidant activity.
Conclusion
The postharvest life of table grape is limited by quality de-terioration between harvest and retail, mainly due to weight loss, rachis desiccation and accelerated softening and senes-cence. Green rachis is one of the most appealing features for consumer acceptance. In the present study, pre-har-vest micronized calcium pulverization was performed to improve rachis greenness and berry resistance while UV-C was aimed to induce physiological resistance and de-lay senescence in grape berries. Pre-harvest Ca treatments significantly increased total chlorophyll concentrations of rachis and Ca plus UV-C was the best treatment to retain rachis chlorophyll concentration. UV-C with or without pre-harvest Ca treatment significantly delayed the weight loss during the storage. Ca delayed the increase of SSC during the storage. All the treatments, particularly posthar-vest UV-C, significantly delayed the berry senescence by delaying the decrease in acidity. UV-C with or without Ca, with the lowest values, significantly retarded the changes
in phenols and reduced the decay incidence. Ca plus UV-C treatment also effectively maintained the SRF during the storage. Considering the general results, pre-harvest mi-cronized Ca pulverizations plus postharvest UV-C treat-ment can be recommended to extent the quality of table grapes cv. ‘Crimson Seedless’ up to 120 days at cold stor-age.
Conflict of interest F.K. Sabir and A. Sabir declare that they have no
competing interests.
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