Postharvest application of salicylic acid enhanced antioxidant enzyme activity and maintained quality of peach cv. ‘Flordaking’ fruit during storage

Scientia Horticulturae 142 (2012) 221–228

Contents lists available at SciVerse ScienceDirect

Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti

Postharvest application of salicylic acid enhanced antioxidant enzyme activity and maintained quality of peach cv. ‘Flordaking’ fruit during storage Muhammad Javed Tareen a , Nadeem Akhtar Abbasi b,∗ , Ishfaq Ahmad Hafiz b a b

Agriculture Research Institute, Quetta, Balochistan, Pakistan Department of Horticulture, PMAS-Arid Agriculture University, Rawalpindi, Pakistan

a r t i c l e

i n f o

Article history: Received 7 December 2011 Received in revised form 19 April 2012 Accepted 24 April 2012 Keywords: Peach Antioxidant enzyme Free radicals pH

a b s t r a c t Peach fruit has become very popular among stone fruits in Pakistan with increasing production. The main area of peach production in Pakistan is Swat, in the northern part of the country. Significant fruit losses occur during harvest temporary storing, and transport to market. Objective of this study was to determine the effectiveness of salicylic acid (SA) at different concentrations (0, 0.5, 1.0, 1.5 or 2.0 mmol L−1 ) on postharvest life of peach fruit (cv. ‘Flordaking’). Fruits were treated with SA immediately after harvest and stored at 0 ◦ C for 5 weeks. Generally, all of the SA concentrations gave a higher activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) during five weeks of storage. The 2.0 mmol SA concentrations showed the highest activity for enzymatic antioxidants. The fruit browning enzyme polyphenol oxidase (PPO) activity decreased in SA treated fruits. SA treated fruits exhibited higher radical scavenging activity (RSA) than control fruits. The SA 2.0 mmol concentration resulted in increased fruit weight, firmness, and decreased juice pH. The higher concentration of SA (2.0 mmol) proved to be the most effective in keeping peach fruit quality intact along with maintained skin color and delayed fruit surface decay during storage. Conclusively amongst all treatments SA 2.0 mmol application exhibited maximum antioxidants enzymatic activities, minimum weight loss, stored firmness and decreased pH during storage period. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Peaches (Prunus persica L. Batsch) are second to apricots in production among stone fruits in Pakistan. Peaches are one of the most well-liked fruits in the world because of their flavor, dietary value, attractive color and medicinal worth. Peach fruit are enriched with ascorbic acid, carotenoids (provitamin A), phenolic compounds and are considered prime sources for antioxidants (Tomas-Barberan et al., 2001; Byrne, 2002). Efforts have been made to find natural alternatives to synthetic chemicals in order to reduce bacterial and fungal growth in minimally processed fruits (Robert et al., 2003) and to improve overall keeping quality of fruits (Akhtar et al., 2010) during postharvest storage has been the focal point of interest for researchers. Food grade phytochemicals or phenolic compounds are typically used for maintaining postharvest quality. Such strategies also include cold storage (Crisosto et al., 2001), modified atmosphere storage (Akbudak and Eris, 2004), controlled atmosphere storage (Garner et al., 2001), hot water dips (Jemric et al., 2011), intermittent

∗ Corresponding author. Tel.: +92 51 9290771; fax: +92 51 9290160. E-mail address: [email protected] (N.A. Abbasi). 0304-4238/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scienta.2012.04.027

warming (Fernandez-Trujillo and Artes, 1998), gamma irradiation (Kim et al., 2010), 1-methylcyclopropene (1-MCP) (Dal Cin et al., 2006), polyamines (PA) (Liu et al., 2006), aminoethoxyvinylglycine (AVG) (Hayama et al., 2008), nitric oxide (NO) (Zhu et al., 2006), Pichia membranaefaciens combined with salicylic acid (SA) (Xu et al., 2008) and SA (Wang et al., 2006) have been tried in order to extend peach fruit postharvest life and keep quality intact for possible longer period. Salicylic acid (SA), a phenolic compound which is found in a wide range of plant species, has been reported to play a vital role in regulating plant growth and development (Wang et al., 2006). SA is involved in stoma movement, seed germination, ion absorption, sex expression, and stimulation of disease resistance (Raskin, 1992). SA treatment reduced chilling injury in maize (Janda et al., 1999), tomato fruit (Ding et al., 2002), banana seedlings (Kang et al., 2003). SA induces H2 O2 accumulation at high temperatures while reducing H2 O2 at lower temperatures. SA is involved in chilling tolerance through H2 O2 metabolism mediation (Kang et al., 2003). In another study SA significantly reduced chilling injury in ‘Beijing 24 peaches by stimulating antioxidant synthesis during cold storage (Wang et al., 2006). SA has also been reported to reduce spoilage in peach fruit by controlling cell membrane electrolyte leakage, decreasing respiration and ethylene production, maintaining flesh

222

M.J. Tareen et al. / Scientia Horticulturae 142 (2012) 221–228

firmness, and increasing antioxidant enzymes activities (Han et al., 2003). SA has been reported to regulate antioxidants and maintain dietary value during storage (Huang et al., 2008). The regulation of antioxidants as a result of SA application is not clear. It may be due to activation of antioxidant system in response to signaling SA which results in systemic acquired resistance in the cells. SA treated strawberry fruit showed less weight loss than untreated fruit (Shafiee et al., 2010), the color of peach and strawberry fruits were significantly regulated by SA (Abbasi et al., 2010; Karlidag et al., 2009; Babalar et al., 2007). SA has been shown to enhance soluble solids content and titratable acidity of apple fruit during storage (Han and Li, 1997). Two vital antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) play significant roles in scavenging free radicals produced as a result of metabolic processes. SOD converts OH− into H2 O2 which is converted into H2 O and O2 by CAT (Scandalios, 1993). Higher POD activity resulted in lower browning incidence in treated peach fruits compared with control (Meng et al., 2009). It is understood that flesh browning or discoloration in several fruits is because of catalytic activity of polyphenol oxidase (Jiang et al., 2004; Lurie and Crisosto, 2005; Nguyen et al., 2003; Frank et al., 2007). Enzymatic modifications of the pectic molecules are responsible for major chemical, physiological and textural changes, which are mostly associated with changes in cell wall composition and structure (Brummell et al., 2004). In fruits, spoilage occurs mainly due to dehydration, faster respiration rate, development of physiological disorders, and attack of microorganism. Because of minimal postharvest life peaches are subject to fast ripening and microbial decomposition (Cao et al., 2010). These characteristics lead to considerable changes in fruits like texture, firmness, fruit skin color, aroma and total soluble solids. Therefore, considering the magnitude of post harvest losses and effectiveness of SA treatments on fruits as reported by various researchers, this study was designed to evaluate the postharvest role of SA through estimation of sensory and quality attributes such as percent weight loss of fruit, soluble solids content (SSC), FRSA and antioxidant enzymes (SOD, CAT, POD and PPO) in peach cultivar ‘Flordaking’. 2. Materials and methods 2.1. Plant materials Peach fruit (Prunus persica L. Batsch. cv. ‘Flordaking’) were selected of uniform size and maturity, free from diseases and visual blemishes from a commercial orchard in village Madrotta (33◦ 40 50.93 N latitude; 73◦ 07 51.29 E longitude) district Attock, Pakistan. Fruit of this early maturing cultivar were sampled at commercial maturity stage (SSC 8.87; N 72.86). Peach trees grafted on Peshawar local rootstock were planted in a north–south direction (7 m between rows and 7 m within rows) and trained on a central open leader system. After harvesting fruit were transported in an air conditioned vehicle to the Postharvest Laboratory of Horticulture Department, PMAS-Arid Agriculture University Rawalpindi. 2.2. Fruit treatments Firstly, peach fruits were washed with distilled water for removal of dust and other pollutants. Then 1260 fruits were divided into five lots, each lot consisting of 252 fruits. For measurement of weight loss and skin color changes a separate lot of 135 fruits were divided into three groups and then each group was further divided into five parts for application of different treatments. Then the same were dipped in different concentrations of aqueous solutions of 0.5,

1.0, 1.5 or 2.0 mmol L−1 of salicylic acid for 5 min while fruits dipped in distilled water served as control. After drying excessive water from surface of fruits were placed treatment wise in corrugated cartons in cold store at 0 ± 0.3 ◦ C and 90 ± 4% relative humidity. 2.3. Fruit skin color and fruit surface decay Changes in fruit skin color as affected by different treatments were recorded including parameters L*, C* and h◦ during cold storage time. The observations were recorded with the help of chromameter (CR-400 Konica Minolta Sensing, Inc., Japan) from the opposite cheeks of each fruit. C* and h◦ were calculated from a* and b* according to McGuire (1992). Fruit surface decay was assessed by using the Browning Index method as described by Wang et al. (2005). 2.4. Weight loss of fruit, fruit firmness, soluble solids content and fruit juice pH Separate samples of fruit in 3 replications from each treatment were kept for the evaluation of fruit weight loss (%) till the end of experiment. Fruit firmness (N) was measured by using a penetrometer (Wagner Fruit Firmness Tester model FT-327). An 8 mm plunger tip was used after removing the epidermis from the opposite equatorial sides of each fruit with the help of a peeler. The soluble solids content of peach fruit was recorded with the help of a digital refrectrometer (Atago-Palette PR 101; Atago Co., ItabashiKu, Tokyo, Japan). Readings were noted from a composite sample after homogenizing five fruits per replicate from each treatment in a juicer machine. The readings for SSC were expressed as ◦ Brix. Hydrogen-ion concentration of peach fruits was determined with the help of a pH meter from the homogenized juice as prepared earlier. 2.5. Preparation of cell free extracts and assays of antioxidant enzymes (SOD, CAT, PPO and POD) A 5–6 g sample from randomly selected five peach fruits per replicate per treatment was used to get cell free extract. The sample was ground in liquid nitrogen to make a very fine powder using mortar and pestle according to the method described by Abbasi and Kushad (2006). The ground tissues were suspended in 15 mL of 100 mM L−1 KPO4 buffer (pH 7.8) containing 0.5% (v/v) Triton x100 and 1 g polyvinyl polypyrrolidone (PVPP). Then homogenates were centrifuged at 16,000 × g for 30 min at 4 ◦ C. The supernatant was collected from centrifuged material and stored at −50 ◦ C for further analysis. Superoxide dismutase (SOD) activity was assayed spectrophotometrically by measuring the 50% inhibition of the photochemical reduction of nitro blue tetrazolium (NBT) according to the method described by Abbasi et al. (1998). Two sets of five cuvettes, each containing 13 mM methionine, 75 ␮M NBT, 0.1 mM EDTA, 2 ␮M riboflavin as a substrate. Then 0, 50, 100, 200, or 300 ␮L enzyme extract was added to each reaction cuvette. Out of two sets one set of reaction cuvettes was kept in a dark box as control while the second set was kept in a box illuminated with fluorescent lamps for 10 min. The absorbance was recorded at 560 nm by using Optima® 300 plus UV/V spectrophotometer. One unit of SOD was defined as the amount of enzyme. Units were presented as U g−1 protein. Catalase (CAT) activity was recorded according to the method mentioned by Abbasi et al. (1998). Two buffer solutions (A and B) were used to carry out the catalase enzyme reaction. A 50 ␮L enzyme extract was added to each of two cuvettes, one containing 1 mL buffer A and the other containing 1 mL buffer B. The change in optical density (OD) at 240 nm was recorded by means of a spectrophotometer after 45 s and 60 s at the time when the extract was

M.J. Tareen et al. / Scientia Horticulturae 142 (2012) 221–228

223

added to the cuvettes. The difference in optical density between the 45 s and 60 s reading was used to calculate the CAT activity. CAT activity was expressed as U g−1 protein. Peroxidase (POD) activity was analyzed using the method of Abbasi et al. (1998) with some modification. The reaction mixture was containing 1.7 mL (15 mM NaKPO4 buffer having pH 6.0), substrates 0.5 mL (1 mM H2 O2 ) and 0.5 mL (0.1 mM guaiacol) and enzyme 0.3 mL to a total volume of 3 mL in a cuvette. The absorbance of the reaction mixture was recorded at 470 nm using a spectrophotometer. Change in optical density over a 3 min period and expressed as unit g−1 protein. Polyphenol oxidase (PPO) activity was measured using the method as described by Abbasi et al. (1998). For this purpose reaction mixture was consisted of 2.5 mL of 0.1 M sodium citrate buffer (pH 5.0), 0.3 mL of 0.02 M catechol in sodium citrate buffer (pH 5.0) and 0.2 mL enzyme extract in a total volume of 3 mL cuvette. The change in OD of reaction mixture was noted at 420 nm by means of a spectrophotometer. PPO activity was calculated according to a change in OD over a period of 3 min and expressed as OD min−1 g−1 protein. 2.6. Protein determination activity assay The Bradford (1976) method was followed for total protein determination of peach fruit skin and pulp tissues while bovine serum albumin was used as a standard. 2.7. Radical scavenging activity of DPPH Method for radical scavenging activity of 2,2-diphenyl-2picrylhydrazyl hydrate (DPPH) was followed as described by Brand-Williams et al. (1995). Frozen 5 g of peach fruit tissues were ground and homogenized then extracted in methanol (10 mL) for 2 h. The same extract was used for assay of radical scavenging activity against stable DPPH prepared in methanol. The measurements were recorded at 515 nm with the help of Optima® 300 plus UV/V spectrophotometer. Percent inhibition of DPPH radical was calculated according to the following formula: % inhibition =

AB − AA × 100 AB

where AB , absorption of blank sample (t = 0 min) and AA , absorbance of tested extract solution (t = 30 min). 2.8. Statistical analysis The experimental design was completely randomized consisting of two factor factorial that is chemical treatments and storage period having three replications. The data were subjected to twoway analysis of variance (ANOVA). The effects of treatments and cold storage duration in experiment on different parameters were assessed within ANOVA. Duncan’s multiple range tests were used for significant differences at p ≤ 0.05 according to Steel et al. (1996) using MSTAT-C software (Michigan State University, 1991). All the assumptions of ANOVA were checked to ensure the validity of statistical analysis. 3. Results 3.1. Fruit skin color and fruit surface decay All SA concentrations showed significantly higher L* values than control for skin color of peach fruit (Fig. 1A). Fruits treated with salicylic acid at 1.5 mmol were recorded with highest skin luminosity amongst the SA concentrations during storage time. Lowest skin brightness was registered by control. The interaction between

Fig. 1. Effects of different concentrations of salicylic acid (SA) on skin L* (A), C* (B) and h◦ (C) of peach fruit cv. ‘Flordaking’ during five weeks of storage at 0 ± 0.3 ◦ C. Vertical bars indicate ±SE of the mean values.

treatments and weekly intervals show that L* values remained higher during first two weeks then the same started decreasing continually until last week of the experiment. The shift of gray towards chromatic color is known as chroma (C*) (McGuire, 1992) and this shift indicates the magnitude of color intensity or saturation. In this study when comparison was made with control higher SA (2.0 mmol) concentration exhibited significantly lower shift towards chromatic color from gray (Fig. 1B). Higher SA concentrations showed least changes for C* and were found statistically at par (p < 0.05). Results for weekly intervals indicated that generally

224

M.J. Tareen et al. / Scientia Horticulturae 142 (2012) 221–228

3.2. Percent weight loss, fruit firmness, soluble solids content and fruit juice pH

Fig. 2. Effects of different concentrations of salicylic acid on fruit surface decay of peach fruit cv. ‘Flordaking’ during five weeks of storage at 0 ± 0.3 ◦ C.

decreasing trend was recorded in C* during storage period except an increase during third week. While, hue angle (h◦ ) values were significantly higher in fruits treated with 1.5 mmol SA when compared with control. Five weeks intervals for treatments showed that SA concentrations had no difference amongst them for hue angle. Generally, the trend was decreasing with a brief increase during week 4 for h◦ in the skin of peach fruits treated with SA during the storage period (Fig. 1C). All the SA treatments were noted with surface fruit decay during the third week while control fruits showed the same a week earlier (Fig. 2). Lower concentrations of SA were recorded with greater surface decay than higher concentrations. Fruits treated with 2.0 mmol SA showed greater resistance against fruit decay when compared with control and other concentrations.

Percent weight loss was observed with increasing trend in all the treatments during storage time (Fig. 3A). However, least weight losses were observed in 2.0 mmol SA treated fruits with respect to other SA concentrations and control during five weeks storage. As shown in figure for weight loss, weekly intervals for fruit weight loss revealed a continual increase in peach fruit throughout the experiment. Highest weight loss was observed in untreated fruits (control) during week 5 while during the same least weight losses were observed in fruits treated with 2.0 mmol SA. Fruit firmness was found significantly higher in treated fruits when compared with control (Fig. 3B). Amongst treated fruits, salicylic acid at the concentration of 2.0 mmol was recorded with highest fruit firmness during storage period. Despite consistent decrease in firmness of all treatments during the storage period but still all SA concentrations helped in retaining higher fruit firmness when compared with control. Peach fruit treated with higher SA concentrations had increased SSC levels as compared with control and lower concentrations (Fig. 3C). SA 2.0 mmol was recorded with highest SSC levels SA concentrations 0.5, 1.0 mmol L−1 and control fruits remained non significant (p < 0.05). The interaction between treatments and weekly intervals showed stability in SSC changes during week 1, later on it started increasing for rest of the weekly intervals. Only control declined at the end of experiment. The highest SA (2.0 mmol) concentration was recorded with minimum pH of juice than other treatments including control after five weeks storage period (Fig. 3D). The interaction for treatments and weekly intervals was observed with significant increase in fruit juice pH during week 2 then it stayed stagnant during weeks 2 and 3 afterwards it kept increasing until end of the experiment.

Fig. 3. Effects of different concentrations of salicylic acid (SA) on weight loss (A), firmness (B), soluble solids content (C) and fruit juice pH (D) of peach fruit cv. ‘Flordaking’ during five weeks of storage at 0 ± 0.3 ◦ C. Vertical bars indicate ±SE of the mean values.

M.J. Tareen et al. / Scientia Horticulturae 142 (2012) 221–228

225

Fig. 4. Effects of different concentrations of salicylic acid on SOD activity (A), CAT activity (B), POD activity (C) and PPO activity (D) of peach fruit cv. ‘Flordaking’ during five weeks of storage at 0 ± 0.3 ◦ C. Vertical bars indicate ±SE of the mean values.

3.3. Changes in antioxidant enzymes (SOD, CAT, POD and PPO) Generally, in the beginning all the treatments showed increase for SOD activity in peach fruits during five weeks of storage period (Fig. 4A). This increase peaked during third week then started decreasing till end of the storage period while 2.0 mmol SA treated fruits peaked for SOD activity a week later and then dropped at the end of storage period. On the other hand untreated fruits (control) showed least SOD activity during most of the storage period as compared to SA treated fruits. Intervals for storage period depicted that there was increase in SOD activity until week 3 then this trend was inhibited and declined till the end of the experiment. The CAT activity also started increasing from the beginning of storage period afterwards it fluttered in all SA concentrations including control. However, 2.0 mmol SA treated fruits had increasing trend for CAT up till fourth week then tilted at the end of storage. CAT activity remained lower throughout the storage period in control peach fruit than SA treated fruits. CAT activity was observed with increasing trend in control fruits till second week then it started exhaustion till fourth week and again showed slight increase at the end of storage period (Fig. 4B). Results pertaining to weekly intervals showed that activity increased until week 4 and then it decreased towards end of the experiment. A steady increase for POD activity was found in all treatments during first and second weeks then an abrupt increase was observed up to fourth week, and then the same declined at the end of storage period. Peach fruits treated with higher concentration of SA (2.0 mmol) had significantly higher POD activity compared with rest of the treatments (Fig. 4C). Weekly intervals for POD activity were initially observed with stability then it increased till fourth week and thereafter a decline was conspicuous. PPO activity was found stable during first two weeks then tended to increase till fifth week (Fig. 4D). Salicylic

acid at 0.5 mmol was noted for highest PPO activity followed by control and remained statistically at par (p < 0.05). Whereas, higher SA (2.0 mmol) concentration showed significantly least levels of PPO activity compared with all other treatments during five weeks storage period. For treatments and weekly intervals interaction PPO activity trend remained more or less same as of POD activity. 3.4. Changes in free radical scavenging activity of DPPH Free radical scavenging activity (FRSA) of DPPH was found significantly different among the treatments (Fig. 5). During first two weeks FRSA increased and peaked during third and fourth weeks then decreased during fifth week. Fruits treated with 2.0 mmol SA concentration were recorded with highest FRSA

Fig. 5. Effects of different concentrations of salicylic acid on radical scavenging activity of peach fruit cv. ‘Flordaking’ during five weeks of storage at 0 ± 0.3 ◦ C. Vertical bars indicate ±SE of the mean values.

226

M.J. Tareen et al. / Scientia Horticulturae 142 (2012) 221–228

levels when compared with rest of concentrations and control. However, lowest FRSA was found in control fruits during five weeks of storage period. There was a gradual increase in FRSA up till week 3 and remained stable during week 4 then declined during the fifth week of experiment.

4. Discussion It is a common practice that peaches are harvested on the basis of ground color, and consumers are also attracted by its red and yellow skin. The results of our study showed that fruits treated with salicylic acid had higher L* values as compared with control and our these results are in agreement with the findings of Delwiche and Baumgardner (1983) who reported that water loss from the surface of peach fruit caused decreased luminosity. Least values of L* were noted in the skin of control fruits which caused dark appearance of the fruits. This may be due to color saturation caused by more transpiration from fruit surface which is evident from percent weight loss parameter of this study. On other hand, increased L* values in SA treated fruits may be in result of decreased chlorophyll degradation and reduced fruit weight losses during storage period. Peach fruits having high L* values were reported with good visual quality (Jia et al., 2005). The changes in peach fruit skin for C* and h◦ were also noted with significance among all the treatments. Fruits treated with higher SA concentrations significantly decreased C* while increased h◦ when compared with lower SA concentrations and untreated fruits. In tomatoes red color development was inhibited when treated with SA (Ding and Wang, 2003), and fresh-cut Chinese water chestnut showed delayed discoloration with increased SA concentrations (Peng and Jiang, 2006). In our study, the interaction between treatments and weekly intervals show a quivered trend for C* during last three weeks of storage period. Fruits treated with edible chemicals have protected tissues from decay and remain intact longer from diseases and infections which negatively harm fruit life and quality (Tareen et al., 2012). Our study showed that higher concentration of SA (2.0 mmol) played significant role in delaying the decay occurrence in peach fruit during five weeks storage period. Our results are in agreement with the outcome of Wang et al. (2006) in peaches and Sayyari et al. (2009) in pomegranates that higher SA concentrations significantly lowered the fruit decay. Fruit weight losses are known for most significant physiological disorder during postharvest life. In this study, SA significantly decreased percent weight loss, fruit softening and fruit pH during five weeks of storage period. SA has been reported to reduce fruit weight losses by closing stoma in Vicia feba and ‘Ponkan’ mandarin fruit (Manthe et al., 1992; Zheng and Zhang, 2004). Minimum weight loss in SA treated fruits resulted in high firmness and maintained lower pH levels of peach fruits of cv. ‘Flordaking’. This is because SA might have reduced respiration rates this phenomenon has also been reported by some other researchers (Han et al., 2003; Srivastava and Dwivedi, 2000; Wolucka et al., 2005). Thus, our results showed less weight losses in SA treated fruits than untreated fruits. Strawberry fruits showed less fruit weight loss than control when salicylic acid was supplied with nutrients (Shafiee et al., 2010). Fruits treated with higher SA concentrations were recorded with higher levels of SSC. Our finding is supported by the findings of Peng and Jiang (2006) who reported that fresh-cut of Chinese water chestnut treated with SA increased SSC, titratable acidity and ascorbic acid in addition to this similar results have also been reported by Karlidag et al. (2009) when banana fruits were treated with SA. Softening starts due to the conversion of insoluble protopectin into water-soluble pectin (Pressey and Avants, 1973), which eventually results in cell wall deterioration (Fishman et al., 1993). Mango fruits treated with SA showed increased fruit

firmness and in result decreased activity of cell wall degrading enzymes (Srivastava and Dwivedi, 2000). In present study firmer peach fruits with low pH levels treated with SA might be due to decrease in pectin solubilization. Superoxide dismutase has front line role in the fruit antioxidative defense mechanism. Our present experiment revealed that all SA concentrations induced higher activities of antioxidant enzymes (SOD, CAT and POD) and this might be attributed to lowered activity of lipoxygenase (LOX) which is partly responsible for superoxide radicals formation. These superoxide radicals are converted into hydrogen peroxide in result of SOD activity and the same is disintegrated into H2 O and O2 by CAT and POD activities. SA 2.0 mmol concentration was recorded with highest SOD activity during the five weeks of storage period. Previously documented research work have also reported similar results that peach fruits treated with SA exhibited increased SOD activity (Tian et al., 2007). In the present investigation, SA increased CAT activity in peach fruit cv. ‘Flordaking’ as compared with the control fruit. This might be due to SA which has been reported to enhance the transcription and translation of the CAT gene in treated peach fruit (Tian et al., 2007). Researchers have also showed that sugar apple fruit treated with SA had increased CAT activity (Mo et al., 2008). Decreased CAT activity suggests weakened capability of cell to scavenge H2 O2 (Ng et al., 2005). POD is an important antioxidant enzyme and has similar role as of CAT. SA treated fruit were observed with increased POD activity throughout the storage period. Higher SA (2.0 mmol) concentration induced higher POD activity than the control fruit. Numerous researchers have documented increased POD activity in fruits when treated with SA such as sugar apple fruits (Mo et al., 2008), mandarin fruits (El-hilali et al., 2003) and papaya (Setha et al., 2000). Higher SA (2.0 mmol) concentration effectively inhibited PPO activity responsible for browning in fruits and vegetables whereas rest of the SA concentrations including control had increased PPO activity in peach fruit. Enzymatic browning due to higher PPO activity is caused during ripening; senescence or stress condition coincided with membrane damage in fruits (Mayer, 1987). Different concentrations of SA regulated PPO activity in peaches and apples during storage (Han et al., 2003). Our results are in agreement with the findings of Ding et al. (2009) who stated that 2.0 mmol SA effectively lowered the PPO activity in peach fruits during storage at 0 ◦ C. Antioxidant activities can be altered by harvest time, storage techniques and duration between fruits picked and consumed; further pinpointing that postharvest life of peaches has deep impact on their antioxidants capability (Vaio et al., 2008). SA in present study enhanced FRSA, however, the effect was found proportional

Fig. 6. The Pearson linear correlation coefficients between free radicals scavenging activity and salicylic acid concentrations.

M.J. Tareen et al. / Scientia Horticulturae 142 (2012) 221–228

to its applied concentration on fruits. When analyzed the possible correlation between SA concentrations and FRSA, the Pearson linear correlation coefficients were recorded highly significant (p < 0.05), being r = 0.9411 (Fig. 6). From this, it can be inferred that increase in SA concentration helped in increasing the free radicals scavenging activity. SA being an important phenolic compound contributes to the fruit defense systems and in the biosynthesis of nutrition components including antioxidant enzymes activity (Huang et al., 2008). Fruit internal quality and pace of senescence during storage are correlated to its antioxidants potential (Lurie, 2003). SA has been reported having similar results when strawberry fruits treated with higher concentration of SA (2.0 mmol). The interaction between treatments and weekly intervals showed that FRSA started increasing from the beginning of storage period and maintained same trend up till week 4 then it tended to decline at the end. 5. Conclusion The results of this work recommend the use of salicylic acid on peach fruit, on the basis of its proved superiority when compared with the control fruit for some fruit quality parameters, such as skin color, weight loss, firmness and fruit juice pH. SA treated peach fruits had brighter skin (L*), and delayed shift of gray or white to chroma (C*), and fruit decay. Moreover, positive effects of SA on fruit postharvest life and quality are evidently confirming from our study findings. Thus, in the present study SA demonstrated its ability to maintain peach fruit quality with acceptable color and these all above mentioned quality attributes may be attributed to its capability to maintain high antioxidant enzymes activity under cold storage conditions. Amongst the salicylic acid different concentrations 2.0 mmol proved the best. Acknowledgments The authors are thankful to the Agriculture Department Balochistan for support and acknowledge the cooperation of Department of Horticulture, PMAS-Arid Agriculture University, Rawalpindi, for providing research facilities. We are also grateful to Dr. David H. Picha, Louisiana State University, USA, for his critical reading of this manuscript. References Abbasi, N.A., Kushad, M.M., Endress, A.G., 1998. Active oxygen-scavenging enzymes activities in developing apple flowers and fruits. Sci. Hortic. 74, 183–194. Abbasi, N.A., Kushad, M.M., 2006. The activities of SOD, POD and CAT in ‘Red Spur Delicious’ apple fruit are affected by DPA but not calcium in postharvest drench solutions. J. Am. Pomolog. Soc. 60, 84–89. Abbasi, N.A., Hafeez, S., Tareen, M.J., 2010. Salicylic acid prolongs shelf life and improves quality of ‘Maria Delicia’ peach fruit. Acta Hortic. 880, 191–197. Akbudak, B., Eris, A., 2004. Physical and chemical changes in peaches and nectarines during the modified atmosphere storage. Food Control 15, 307–313. Akhtar, A., Abbasi, N.A., Hussain, A., 2010. Effect of calcium chloride treatments on quality characteristics of loquat fruit during storage. Pak. J. Bot. 42 (1), 181–188. Babalar, M., Asghari, M., Talaei, A., Khosroshahi, A., 2007. Effect of pre- and postharvest salicylic acid treatment on ethylene production, fungal decay and overall quality of Selva strawberry fruit. Food Chem. 105, 449–453. Bradford, M., 1976. A rapid and sensitive method for the quantification of microgram quantities of protein utilizing the principle of protein–dye binding. Anal. Biochem. 72, 248–254. Brand-Williams, W., Cuvelier, M.E., Berset, C., 1995. Use of free radical method to evaluate antioxidant activity. Lebensmittel Wissenschaft Techno 28, 25–30. Brummell, D.A., Dal Cin, V., Crisosto, C.H., Labavitch, J.M., 2004. Cell wall metabolism during the development of chilling injury in cold-stored peach fruit: association of mealiness with arrested disassembly of cell wall pectins. J. Exp. Bot. 55, 2041–2052. Byrne, D.H., 2002. Peach breeding trends. Acta Hortic. 592, 49–59. Cao, S., Hua, Z., Zheng, Y., Lua, B., 2010. Synergistic effect of heat treatment and salicylic acid on alleviating internal browning in cold-stored peach fruit. Postharvest Biol. Technol. 58, 93L 97.

227

Crisosto, C.H., Gugliuzza, G., Garner, D., Palo, L., 2001. Understanding the role of ethylene in peach cold storage life. Acta Hortic. 553, 287–288. Dal Cin, V., Rizzini, F.M., Botton, A., Tonutti, P., 2006. The ethylene biosynthetic and signal transduction pathways are differently affected by 1-MCP in apple and peach fruit. Postharvest Biol. Technol. 42, 125–133. Delwiche, M., Baumgardner, R.A., 1983. Ground color as a peach maturity index. J. Am. Soc. Hortic. Sci. 110, 53–57. Ding, C.K., Wang, C.Y., Gross, K.C., Smith, D.L., 2002. Jasmonate and salicylate induce the expression of pathogenesis-related protein genes and increase resistance to chilling injury in tomato fruit. Planta 214, 95–901. Ding, C., Wang, C.Y., 2003. The dual effects of methyl salicylate on ripening and expression of ethylene biosynthetic genes in tomato fruit. Plant Sci. 164, 589–596. Ding, Z., Tian, S., Meng, X., XU, Y., 2009. Hydrogen peroxide is correlated with browning in peach fruit stored at low temperature. Front. Chem. Eng. 3, 363–374. El-hilali, F., Ait-Oubahou, A., Remah, A., Akhayat, O., 2003. Chilling injury and peroxidase activity changes in fortune mandarin fruit during low temperature storage. Bulg. J. Plant Physiol. 29, 44–54. Fernandez-Trujillo, J.P., Artes, F., 1998. Chilling injuries in peaches during conventional and intermittent warming storage. Int. J. Refrig. 21, 265–272. Fishman, M.L., Levaj, B., Gillespie, D., Scorza, R., 1993. Changes in the physicochemical properties of peach fruit pectin during on-tree ripening and storage. J. Am. Soc. Hortic. Sci. 118, 343–349. Frank, C., Lammertyn, J., Tri Ho, Q., Verboven, P., Verlinden, B., Nicolaï, B.M., 2007. Browning disorders in peach fruit. Postharvest Biol. Technol. 43, 1–13. Garner, D., Crisosto, C.H., Otieza, E., 2001. Controlled atmosphere storage and minoethoxyvinylglycine postharvest dip delay post cold storage softening of ‘Snow King’ peach. Hortic. Technol. 11, 598–602. Han, T., Li, L.P., 1997. Physiological effect of salicylic acid on storage of apple in short period. Plant Physiol. Commun. 33, 347–348. Han, T., Wang, Y., Li, L., Ge, X., 2003. Effect of exogenous salicylic acid on postharvest physiology of peaches. Acta Hortic. 628, 383–389. Hayama, H., Tatsuki, M., Nakamura, Y., 2008. Combined treatment of minoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) reduces melting-flesh peach fruit softening. Postharvest Biol. Technol. 50, 228–230. Huang, R., Xia, R., Lu, Y., Hu1, L., Xu, Y., 2008. Effect of pre-harvest salicylic acid spray treatment on post-harvest antioxidant in the pulp and peel of ‘Cara cara’ navel orange (Citrus sinenisis L. Osbeck). J. Sci. Food Agric. 88, 229–236. Janda, T., Szalai, G., Tari, I., Paldi, E., 1999. Hydroponic treatment with salicylic acid decreases the effects of chilling injury in maize (Zea mays L.) plants. Planta 208, 175–180. Jemric, T., Ivic, D., Fruk, G., Matijas, H.S., Cvjetkovic, B., Bupic, M., Pavkovic, B., 2011. Reduction of postharvest decay of peach and nectarine caused by Monilinia laxa hot water dipping. Food Bioprocess Technol. 4, 149L 154. Jia, H.J., Araki, A., Ang, G., Okamoto, 2005. Influence of fruit bagging on aroma volatiles and skin coloration of ‘Hakuho’ peach (Prunus persica Batsch). Postharvest Biol. Technol. 35, 61–68. Jiang, Y.M., Duan, X.W., Joyce, D., Zhang, Z.Q., Li, J.R., 2004. Advances in understanding of enzymatic browning in harvested litchi fruit. Food Chem. 88, 443–446. Kang, G.Z., Wang, Z.X., Sun, G.C., 2003. Participation of H2 O2 in enhancement of cold chilling by salicylic acid in banana seedlings. Acta Bot. Sin. 45, 567–573. Karlidag, H., Yildirim, E., Turan, M., 2009. Exogenous applications of salicylic acid affect quality and yield of strawberry grown under antifrost heated greenhouse conditions. J. Plant Nutr. Soil Sci. 172, 270–276. Kim, K.H., Kim, M.S., Kim, H.G., Yook, H.S., 2010. Inactivation of contaminated fungi and antioxidant effects of peach (Prunus persica L. Batsch cv Dangeumdo) by 0.5–2 kGy gamma irradiation. Radiat. Phys. Chem. 79, 495–501. Liu, J.H., Nada, K., Pang, X.M., Honda, C., Kitashiba, H., Moriguchi, T., 2006. Role of polyamines in peach fruit development and storage. Tree Physiol. 26, 791–798. Lurie, S., 2003. Antioxidants: Postharvest Oxidative Stress in Horticultural Crops. Foods Products Press. The Howerth Press, Binghampton, NY, pp. 131–150. Lurie, S., Crisosto, C.H., 2005. Chilling injure in peach and nectarine. Postharvest Biol. Technol. 37, 195–208. Manthe, B., Schulz, M., Schnabl, H., 1992. Effects of salicylic acid on growth and stomatal movements of Vicia faba L.: evidence for salicylic acid metabolization. J. Chem. Ecol. 18, 1525–1539. Mayer, A.M., 1987. Polyphenol oxidase and peroxidase in plants recent progress. Phytochemistry 26, 11–20. McGuire, R., 1992. Reporting of objective color measurements. Hortic. Sci. 27 (12), 1254–1255. Meng, X., Han, J., Wang, Q., Tian, 2009. Changes in physiology and quality of peach fruits treated by methyl jasmonate under low temperature stress. Food Chem. 114, 1028–1035. Mo, Y., Gong, D., Liang, L., Han, R., Xie, J., Li, W., 2008. Enhanced preservation effects of sugar apple fruits by salicylic acid treatment during post-harvest storage. J. Sci. Food Agric. 88, 2693–2699. Ng, T.B., Gao, W., Li, L., Niu, S.M., Zhao, L., Liu, J., Shi, L.S., Fu, M., Liu, F., 2005. Rose (Rosa rugosa)-flower extract increases the activities of antioxidant enzymes and their gene expression and reduces lipid peroxidation. Biochem. Cell Biol. 83, 78–85. Nguyen, T.B.T., Ketsa, S., Doorn, W.G., 2003. Relationship between browning and the activities of polyphenoloxidase and phenylalanine ammonia lyase in banana peel during low temperature storage. Postharvest Biol. Technol. 30, 187–193. Peng, L., Jiang, Y., 2006. Exogenous salicylic acid inhibits browning of fresh-cut Chinese water chestnut. Food Chem. 94, 535–540. Pressey, R., Avants, J.K., 1973. Separation and characterization of endopolygalacturonase and exopolygalacturonase from peaches. Plant Physiol. 52, 252–256.

228

M.J. Tareen et al. / Scientia Horticulturae 142 (2012) 221–228

Raskin, I., 1992. Role of salicylic acid in plants. Annu. Rev. Plant Physiol. Mol. Biol. 43, 439–463. Robert, C., Soliva, F., Martın, O.B., 2003. New advances in extending the shelf life of fresh-cut fruits: a review. Trends Food Sci. Technol. 14, 341–353. Sayyari, M., Babalar, M., Kalantari, S., Serrano, M., Valero, D., 2009. Effect of salicylic acid treatment on reducing chilling injury in stored pomegranates. Postharvest Biol. Technol. 53, 152–154. Scandalios, J.G., 1993. Oxygen stress and superoxide dismutase. Plant Physiol. 107, 7–12. Setha, S., Kanlayanarat, S., Srilaong, V., 2000. Changes in polyamine levels and peroxidase activity in ‘Khakdun’ papaya (Carica papaya L.) under low temperature storage conditions. In: Johnson, G.I., LeVan To, Duc, N.D., Webb, M.C. (Eds.), Quality Assurance in Agricultural Produce, ACCIAR Proceedings, vol. 100. , pp. 593–598. Shafiee, M., Taghavi, T.S., Babalar, M., 2010. Addition of salicylic acid to nutrient solution combined with postharvest treatments (hot water, salicylic acid, and calcium dipping) improved postharvest fruit quality of strawberry. Sci. Hortic. 124, 40–45. Srivastava, M.K., Dwivedi, U.N., 2000. Ripening of banana fruit by salicylic acid. Plant Sci. 158, 87–96. Tareen, M.J., Abbasi, N.A., Hafiz, I.A., 2012. Effect of salicylic acid treatments of storage life of peach fruits cv. ‘Flordaking’. Pak. J. Bot. 44 (I), 119L 124. Tian, S., Qin, G., Li, B., Wang, Q., Meng, X., 2007. Effects of salicylic acid on disease resistance and postharvest decay control of fruits. Stewart Postharvest Rev. 6 (2), 1–7.

Tomas-Barberan, F.A., Gil, M.I., Cremin, P., Waterhouse, A.L., Hess-Pierce, B., Kader, A.A., 2001. HPLC–DAD–ESIMS analysis of phenolic compounds in nectarines, peaches, and plums. J. Agric. Food Chem. 49, 4748–4760. Vaio, C.D., Graziani, G., Marra, L., Cascone, A., Ritieni, A., 2008. Antioxidant capacities, carotenoids and polyphenols evaluation of fresh and refrigerated peach and nectarine cultivars from Italy. Eur. Food Res. Technol. 227, 1225–1231. Wang, Y.S., Tian, S.P., Xu, Y., 2005. Effects of high oxygen concentration on pro- and anti-oxidant enzymes in peach fruits during post harvest periods. Food Chem. 91, 99–104. Wang, L., Chen, S., Kong, W., Shaohua, L., Douglas, D., 2006. Salicylic acid pretreatment alleviates chilling injury and affects the antioxidant system and heat shock proteins of peaches during cold storage. Postharvest Biol. Technol. 41, 244–251. Wolucka, B.A., Goossens, A., Inze, D., 2005. Methyl jasmonate stimulates the de novo biosynthesis of vitamin C in plant cell suspensions. J. Exp. Bot. 56, 2527–2538. Xu, X., Chan, Z., Xu, Y., Tian, S., 2008. Effect of Pichia membranaefaciens combined with salicylic acid on controlling brown rot in peach fruit and the mechanisms involved. J. Sci. Food Agric. 88, 1786–1793. Zheng, Y., Zhang, Q., 2004. Effects of polyamines and salicylic acid postharvest storage of ‘Ponkan’ mandarin. Acta Hortic. 632, 317–320. Zhu, S., Liu, M., Zhou, J., 2006. Inhibition by nitric oxide of ethylene biosynthesis and lipoxygenase activity in peach fruit during storage. Postharvest Biol. Technol. 42, 41–48.