(Solanum melongena) fruits

LWT - Food Science and Technology 74 (2016) 420e426

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Carnauba wax-based edible coating enhances shelf-life and retain quality of eggplant (Solanum melongena) fruits Sudhir Singh a, *, Priti Khemariya a, Ashutosh Rai b, Avinash Chandra Rai b, Tanmay K. Koley a, Bijendra Singh b a b

Division of Vegetable Production, Indian Institute of Vegetable Research, Shahanshapur, P.O. Jhakhini, Varanasi, U. P. 221305, India Division of Vegetable Improvement, Indian Institute of Vegetable Research, Shahanshapur, P.O. Jhakhini, Varanasi, U. P. 221305, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 28 April 2016 Received in revised form 6 August 2016 Accepted 7 August 2016 Available online 9 August 2016

Eggplant has limited shelf-life of only 3 days under ambient storage conditions. The functional quality of carnauba wax (CW) is assessed with various additives for shelf-life related attributes in eggplant during ambient storage (20 ± 1 C and RH 52e54%) in both unpackaged and packaged in 35m polypropylene pouches. Minimum decrease (8.56 N-6.92 N and 8.56 N-5.63 N) in firmness was recorded in Poly ethylene glycol (PEG) and 0.5% Sodium alginate (SA) in diluted (1:4) CW emulsion (T2) while maximum decrease (8.56 N-5.54 N and 8.56 N-3.57 N) in control (T4) packaged and unpackaged eggplants after 12 days of storage, respectively. Maximum antioxidant activity (67.63 and 51.52 mmol Trolox equivalent antioxidant capacity (TEAC)/100 g FW) was observed in T2 treatment and minimum antioxidant activity (23.61 and 20.60 mmol TEAC/100 g FW) in control fruits in packaged and unpackaged respectively after 12 days. The minimum decrease (2.64e2.20 and 2.64e2.24) mmol tetraguaiacol (TG)/min/100 g FW) of peroxidase activity was recorded in T2 treated fruits in packaged and unpackaged eggplant respectively and maximum decrease (2.64e1.37 and 2.64e1.63 mmol TG/min/100 g FW) was obtained in control unpackaged and packaged eggplant respectively after 12 days. Packaged eggplant treated with PEG and SA in CW emulsion remained acceptable upto 12 days. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Antioxidant activity Firmness Nutritional quality Poly ethylene glycol Total phenolic content

1. Introduction Eggplant or brinjal (Solanum melongena L.) is an important solanaceaeous vegetable of South East Asian origin, commercially cultivated in most parts of the world for the immature fruits having 12 ± 2 days of anthesis which is used for preparation of various types of cuisines. Fruits of eggplant are rich source of various vitamins, minerals as well as bioactive compounds like phenolics and flavonoids which provide immunity against diseases (Esteban, Molla, Robredo, & Lopez-Andreu, 1992). The regular consumption of eggplant has been reported to decrease low density lipoprotein (LDL) in human blood leading to improved heart function mainly due to hypolipidemic effects of flavonoids (Kashyap et al., 2003; Sudheesh, Presannakumar, Vijayakumar, & Vijayalakshmi, 1997). The beneficial effects of eggplant also include reduction in tumor growth metastasis (Matsubara, Kaneyuki, Miyake, & Mori, 2005),

* Corresponding author. E-mail address: [email protected] (S. Singh). http://dx.doi.org/10.1016/j.lwt.2016.08.004 0023-6438/© 2016 Elsevier Ltd. All rights reserved.

and prevention of antherosclerosis by inhibiting inflammation (Han et al., 2003). Nasunin, an anthocyanin isolated from the peel of purple eggplant has been reported to cause inhibition of both hydroxyl radical generation and superoxide scavenging activity (Noda, Kneyuki, Igarashi, Mori, & Packer, 2000). In South and Southeast Asia, the region of domestication of eggplant a wide variability exists for fruit color (purple, green, white), shape (long, oval, round), and size (Doganlar, Frary, Daunay, Lester, & Tanksley, 2002; Nothmann, Rylski, & Spigelman, 1976). In Northern India, white-fruited variety is grown and maintained as land races by farmers, and is liked for its medicinal properties as well as delicacy. Generally, eggplant fruits are transported from field to market in moist gunny bags, still during long distance transport and handling in market, fruits suffer from various quality losses like rapid surface shrinkage, loss of skin glossyness, loss of color, and drying of pedicel. All these factors reduce the shelf-life of fruits to only 2e3 days under ambient conditions (Hemalatha, Jayajasmine, & Ponnuswami, 2000). Traders many times use fraudulent unhygienic practices like sprinkling of water and application of petroleum based oil to make them attractive. Such malpractices are

S. Singh et al. / LWT - Food Science and Technology 74 (2016) 420e426

harmful to human health. Often brinjal fruits get rotten and infected with microbes during storage. This calls for an urgent need for safer technology to aim reduction in transpiration, physiological processes related to maturation and senescence and reduction in the initiation and microbial growth rate so as to provide fruit vila-Avin ~ a de without compromising its freshness and quality (Da Jesús et al., 2011). Among various post-harvest treatments, the use of an edible coating is a safe and suitable alternative for retaining the marketable and nutritional quality of eggplant for longer period. Edible coating is a thin layer of edible material applied to the fruit surface for acting as barrier for moisture, oxygen, carbon-dioxide, water vapor, aroma compounds and solute movement (Asrey, Patel, Singh, & Sagar, 2008; Spotti, Cecchini, Spotti, & Carrara, 2016) thus decreasing the respiration and transpiration rate, ripening and preserving the texture and flavor of fruits for considerably longer period (Olivas and Barbosa-Canovas, 2008). In the case of eggplant fruits, loss of moisture and glossiness are major concerns in postharvest management. The application of lipid-based edible coating is considered as the most suitable treatment. Carnauba wax (CW) as edible coating under the lipid group has been amply utilized to enhance the shelf-life in many fruits and vegetables. Carnauba wax is recovered from the leaves of Brazilian palm tree (Copernica cerifera) and has been mainly applied to reduce water loss and maintain glossy appearance (Baldwin, 1994). A commercial carnauba - shellac coating is reported to delay ripening in pears due to evolution of higher CO2 concentrations than non waxed fruit thus resulting in retention of firmness and delayed color changes (Drake and Nelson, 1990). Similarly Chimarelli and Hubinger (2014) also reported the suitability of film formulation containing (3%, w/ w) cassava starch, glycerol (1.5%, w/w), carnauba wax (0.2%, w/w) and stearic acid (0.8%, w/w), which resulted in films with a cohesive matrix, better mechanical properties and good barrier to moisture and gas in apple slices. In recent past, efforts have been made to increase the shelf-life and maintain the freshness of tomato and chilli using edible coating (Chitravathi, Chauhan, & Raju, 2014; Gonzalez-Aguilar, Villa-Rodriguez, Ayala-Zavala, & Yahia, 2010), but in the case of eggplant such information is scanty. In the present work, different treatments with carnauba wax as an edible coating were tried with eggplant fruits so as to enhance the shelf-life and maintain the freshness of fruits. For this purpose, additives such as poly ethylene glycol (PEG) as humectant, sodium alginate (SA) as thickener and sodium dodecyl sulfate (SDS) as surfactant were made different formulations of carnauba wax. Additionally, fruits were also coated with commercial ‘Niprofresh’ formulation for comparing the efficacy of edible coating on various physicochemicals and antioxidant properties during the storage of fruit. 2. Materials and methods

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sodium hypochlorite (150e200 mg/L) sanitized BOD incubator. 2.2. Preparation of emulsion Carnauba wax (10.0 g) was melted in water bath at 90e95 C and oleic acid (7.5 mL/100 g) was added as emulsifier with constant stirring at high temperature (90e95 C) and the suspension was agitated at 1200 rpm for 3 min using a centrifuge (MA 102, Remi, Pune, India). The stable emulsion was standardized by addition of 1.0e1.2 mL of 20 g/100 mL hot (90e95 C) sodium hydroxide solution. The pH of the emulsion was neutralized to pH 7.0 by adding 1.0e1.2 mL/100 mL of hot (90e95 C) acetic acid solution. Finally, 100 mL hot water was added to obtain a clear suspension, which was agitated at 10,000 rpm for 5 min to assess formation of sediments, and finally formulation contained 8.97 g/100 mL CW. Commercial ‘Niprofresh’ VCW50 emulsion (Nipro Technologies Ltd., Panchkula, Haryana, India) was used to compare the efficacy of carnauba wax formulation. Various chemical additives such as PEG 4000 (2.5 g/100 mL), SA (0.5 g/100 mL) and SDS (2 g/100 mL) were added in carnauba wax emulsion to improve the functional quality. 2.3. Experimental treatments The carnauba wax dipping solutions consisted of diluted 1 mL:4 mL commercial Niprofresh carnauba wax (CW) emulsion (T1), CW emulsion 1 mL:4 mL þ 2.5 g/100 mL PEG þ 0.5 g/100 mL SA (T2), CW emulsion 1 mL:4 mL þ 2.0 g/100 mL SDS (T3), non-coated eggplant fruits were used as control (T4). Eight eggplant fruits were dipped in different carnauba wax emulsion treatments (T1-T3) for 2 min at 20 ± 1 C followed by drying at ambient temperature (20 ± 1 C) with relative humidity of 50e55% for 30 min. All the treated and control fruits were divided into two sets; one set of fruits were packaged in polypropylene (pp) pouches (35 mm thick), while other was not packaged. The packaged and unpackaged fruits were stored in perforated plastic trays for up to 12 days at 18e21 C and RH of 50e55% in a BOD incubator. Data was recorded on eight fruits from each treatment at 0, 4, 8 and 12 days of storage. 2.4. Analysis of storage properties Changes in physical properties, like loss in fruit weight, firmness, skin color, moisture were recorded by visual observations as well as quantitation (Fig. 1). Changes in nutritional properties in terms of total phenolic content (Singleton, Orthofer, & LamuelaRaventos, 1999), total antioxidant activity (Brand-Williams, Cuvelier, & Berset, 1995) along with their correlation and changes in expression of peroxidase activity (Castillo, Penel, & Greppin, 1984) were also calculated packaged and unpackaged conditions (Fig. 2).

2.1. Materials White-fruited eggplant was obtained from the farm of Indian Institute of Vegetable Research, Varanasi. Carnauba wax was procured from the local market of Varanasi. Oleic acid, acetic acid, sodium hydroxide, poly ethylene glycol (PEG), sodium alginate (SA) and sodium dodecyl sulfate (SDS) were procured from SD Fine Chemicals, Mumbai, India. Fruits were manually harvested at around 12 ± 2 days of anthesis having ~13 cm length, ~4.56 cm diameter and individual weight of about 60 g. Any fruit with blemishes or infested with fruit and shoot borer was discarded. For treatment, fruits were first thoroughly washed in running tap water and then disinfected by dipping in 100 mg/L sodium hypochlorite solution for 5 min. Thereafter, fruits were rinsed 3e4 times with distilled water and stored at 20 ± 1 C for surface drying in prior

2.4.1. Physiological loss in weight (PLW) The weight of all the eight fruits in an individual treatment was recorded on scientific weighing machine (Denver Instrument APX60; d ¼ 0. 1 mg) at 0 day and thereafter 2 days interval, and it was expressed as the g/100 g loss of the initial weight as per the method of Chitravathi et al. (2014). 2.4.2. Fruit firmness The firmness of all the unpeeled eight fruits in an individual treatment having three replicates during storage was estimated using texture analyzer using needle probe (P2N) of 50 kg load cell having pre-test speed of 2.0 mm/s and post-test speed of 1.0 mm/s (Texture Expert Exceed, Ver. 2.64, Stable Microsystem, U.K.).

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Fig. 1. Changes in physical properties in carnauba wax treated eggplants during ambient storage of 18e21 C, RH 91% Max and 52% Min (n ¼ 3). T1 (:): 1 mL:4 mL Commercial Niprofresh carnauba wax emulsion, T2 (;): 1 mL:4 mL Carnauba wax emulsion þ 2.5 g/100 mL PEG þ 0.5 g/100 mL SA, T3 (C): 1 mL:4 mL Carnauba wax emulsion þ 2.0 g/100 mL SDS, T4 (-): 1 mL:4 mL Control fruit, (*) indicates statistically significant change at p 0.05. Data are mean of three replicates ± SE. A. Changes in PLW (g/100 g) of carnauba wax treated eggplants in (a) packaged and (b) unpackaged during storage; Changes in moisture (g/100 g) of carnauba wax treated eggplants in (c) packaged and (d) unpackaged during storage. B. Changes in firmness (N) of carnauba wax treated eggplants in (a) packaged and (b) unpackaged during storage; Changes in lightness (L value) of carnauba wax treated eggplants in (c) packaged and (d) unpackaged during storage.


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Fig. 2. Changes in nutritional properties in carnauba wax treated eggplants during ambient storage of 18e21 C, RH 91% Max and 52% Min (n ¼ 3). T1 (:): 1 mL:4 mL Commercial Niprofresh carnauba wax emulsion, T2 (;): 1 mL:4 mL Carnauba wax emulsion þ 2.5 g/100 mL PEG þ 0.5 g/100 mL SA, T3 (C): 1 mL:4 mL Carnauba wax emulsion þ 2.0 g/100 mL SDS, T4 (-): 1 mL:4 mL Control fruit, (*) indicates statistically significant change at p 0.05. Data are mean of three replicates ± SE. A. Changes in total phenol content (mg GAE/ 100 g FW) of carnauba wax treated eggplants in (a) packaged and (b) unpackaged during storage; Changes in antioxidant activity (mmol TEAC/100 g FW) of carnauba wax treated eggplants in (c) packaged and (d) unpackaged during storage. B. Correlation between total phenol content and antioxidant activity of carnauba wax treated eggplants in (a) packaged (Y ¼ 0.67 85.45; R2 ¼ 0.940) and (b) unpackaged (Y ¼ 0.67 86.45; R2 ¼ 0.930) during storage; Changes in peroxidase activity (mmol TG/min/100 g FW) of carnauba wax treated eggplants in (c) packaged and (d) unpackaged during storage.

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2.4.3. CIE LAB color measurement Color attributes of unpeeled skin fruit surface in terms of the CIE LAB value of white eggplants was measured using a color meter (Color-Tec PCM™ Colorimeter, USA) based on CIELAB values. The instrument was calibrated with a standard white and black plate and measurement was taken in triplicate. 2.4.4. Peroxidase activity The peroxidase activity (POX) in fruits after storage was determined by the method as described by Castillo et al. (1984). Peroxidase activity was measured at 470 nm spectro-photometrically (UV-1601, Shimadzu, Japan) as a product of guaiacol oxidation. Reaction was recorded for 5 min at every 30 s interval and the values were expressed as mmol tetraguaiacol/min on a fresh weight basis in per 100 g of pulp. 2.4.5. Total phenolic content (TPC) Total phenolic content was estimated spectrophotometrically using FolineCiocalteu reagent (Singleton et al. 1999) and the values were expressed as gram of mg Gallic acid equivalent per 100 g fresh weight of pulp. 2.4.6. Trolox equivalent antioxidant capacity (TEAC) The antioxidant activity in different treatments during storage was studied through the evaluation of free radical scavenging effect on stable DPPH (2, 2-diphenyl-1-picrylhydrazine) radical (BrandWilliams et al., 1995) with minor modifications, and values were expressed as mmol TEAC/100 g FW. 2.4.7. Statistical analysis Each experiment was setup with triplicates and the data were represented as mean ± standard error. Data was analyzed by ANOVA (p 0.05) followed by Student's t-test using GraphPad Prism version 5.0 for Windows, GraphPad Software, La Jolla California USA.

oil-based commercial ‘Stafresh’ carnauba wax coated tomato. 3.2. Moisture content For marketing purpose, moisture content is considered to be the most important parameter of fruits and vegetables. Excess moisture loss leads to shrinkage of fruit surface thus reducing its market value. To solve this problem, using edible coating to reduce moisture loss is the most suitable method of choice. In the present study, moisture loss occurred during storage in eggplants in all the treatments but was the highest in untreated fruits (Fig. 1A). After 12 days of storage, moisture content was the maximum (84.42 g/100 g and 81.60 g/100 g) in T2 formulation while it was the minimum (75.91 g/100 g and 70.56 g/100 g) moisture content in control eggplants with polypropylene packaged and unpackaged fruits, respectively. Higher moisture retention in coated fruits could be attributed to the moisture barrier properties of carnauba wax. novas (2003) also reported that Olivas, Rodriguez, and Barbosa-Ca edible coating acts as barrier for water loss causing high relative humidity in microclimate surrounding fruit surface leading to reduced moisture gradient to the exterior. 3.3. Fruit firmness Carnauba wax coating significantly (p < 0.05) prevented the reduction in fruits firmness during storage in all treatments. Initially, the firmness in all the treatments was 8.56 N which decreased to the minimum level of 5.54 and 3.57 N in control packaged and unpackaged eggplants after 12 days of storage (Fig. 1B). However, a minimum decrease in firmness of 8.56e6.92 N and 8.56e5.63 N was recorded in T2 formulation followed by T1 (8.56e6.02 N) and (8.56e4.72 N) and T3 formulation (8.56e5.71 N) and (8.56e4.45 N) in packaged and unpackaged eggplants after 12 vila-Avin ~ a de Jesús et al. (2011) also days of storage, respectively. Da reported that edible coating of carnauba and mineral oil reduced the firmness in tomato at breaker and pink stage of harvest.

3. Results and discussion 3.4. Color 3.1. Physiological loss in weight All the treated fruits showed a significant (P < 0.05) reduction in the physiological loss in weight compared to that of untreated fruits. The treatment 2 under packaged conditions showed the minimum (2.24 g/100 g) weight loss compared to 3.11 g/100 g weight loss in unpackaged conditions after 4 days of storage at 20 C. In contrast, untreated fruits were recorded 3.22 g/100 g and 5.76 g/100 g weight loss in packaged and unpackaged conditions, respectively after 4 days of storage at ambient (Fig. 1A). The commercial Niprofresh CW (T1) treated fruits showed a loss of 2.41 g/ 100 g and 4.4 g/100 g after 4 days of storage in packaged and unpackaged conditions, respectively, which further increased to 6.80 g/100 g and 15.81 g/100 g at 12 days of storage, respectively (Fig. 1A). Several studies revealed the beneficial effects of low temperature storage and edible coating on reducing the respiration rate which can be attributed to their good oxygen barrier properties (Olivas and Barbosa-Canovas, 2005). Increase in weight loss had also been observed in dark purple American eggplants during storage at 10 C compared to the storage at 0 C, and further it was observed 4.2 g/100 g loss at 10 C as compared to 1.6 g/100 g in 0 C n, Zaro, Chaves, & Vicente, 2012). after 14 days of storage (Concello Another report of Gajewski, Kowalczyk, Bajer, and Radzanowska (2009) also supported these findings that dry matter content in eggplants decreased significantly (6.1e5.8 g/100 g) during storage ~a of 1 week at 16 C due to sugar loss during respiration. D avila-Avin de Jesús et al. (2011) reported a minimum weight loss using mineral

During storage, no specific trend was observed for red (a*) and yellow (b*) fruit core (data not shown). However, a definite gradient was observed for lightness (L). Lightness is a good indicator of browning in eggplants. Eggplants of T2 treatment retained the maximum L-value (82) in packaged fruits while control had the minimum in unpackaged (77) and packaged (80) fruits after 12 days of storage (Fig. 1B). However, Concellon, Anon, and Chaves (2007) reported that there had been no change in L-value during 15 days of storage at 10 C in eggplants, but there had been a gradual decrease in L-value during storage at 0 C. The lower L-value indicates severe browning of seed and pulp in eggplants. 3.5. Phenolics The antioxidant activity of vegetables is attributed to the total phenolic concentrations (Olajire & Azeez, 2011). Eggplants are good sources of total phenols and it has the ability to scavenge the free radicals (Cao, Sofic, & Prior, 1996). In the current experiment, no definite pattern of changes in TPC was observed in control and coated eggplants during storage. Initially an increasing trend was observed for TPC up to 4 days of storage followed by decreasing trend up to 8 days of storage and again, an increasing trend up to 12 days was assessed. Minimum TPC were observed in control eggplants in packaged (542.28 mg GAE/100 g) and unpackaged (334.86 mg GAE/100 g) condition respectively, after 12 days of storage (Fig. 2A). Similar trend hypothesized that the degradation


of phenolic compounds in eggplants possibly might be due to compartmentalization of the enzymes and substrates (Concellon et al., 2012). Liu and Jiang (2006) have also reported that the loss of soluble phenolics occur in some commodities in association with lignifications. The fate of phenolic compounds could be reflected due to lignin deposition in fibres, xylem vessels and seed coats (Concellon et al., 2012). The increase in TPC in later stage may be related to stress response of stored eggpant. Shiri, Ghasemnezhad, Bakhshi, and Dad (2011) have reported the increase in TPC in fresh cut table grapes during storage as phenolic compounds are generally synthesized by the Shikimate pathway in which phenylalanine ammonialyase is the key enzyme during physical damage and during stress condition. The increase in TPC may also be reflected due to decomposition of lignin by lignin hydrolyzing enzymes thus subsequently release of soluble phenols. However, phenolic pathway is very complex thus further detailed investigation is essential for proving our present hypothesis. 3.6. Antioxidant activity The antioxidant activity in CW treated eggplants also did not follow any definite pattern during storage. However, maximum antioxidant activity (67.63 and 51.52 mmol TEAC/100 g FW) was observed in T2 treatment and minimum antioxidant activity (23.21 and 20.60 mmol TEAC/100 g FW) was observed in control fruits in packaged and unpackaged fruits respectively after 12 days of storage (Fig. 2A). A similar trend was also reported by others in eggplants (Concellon et al., 2012). It is interesting to see that trend of changes in antioxidant activity is similar to the changes of total phenolics. Thus, it can be interpreted that changes of antioxidant activity was due to gain and loss of TPC in eggplants during storage. The increase in antioxidant activity significantly indicates the increase in nutritional value of fruits and potentially benefits with consumption of antioxidants rich fruits (Concellon et al., 2012). Several others reports also carried out on the effects of phenolic compounds on total antioxidant activity and correlations between phenolic compounds and total antioxidant activity (Jagadish, Krishnan, Shenbhagaraman, & Kaviyarasan, 2009; Kim, Beppu, & Kataoka, 2009; Li, Wong, Cheng, & Chen, 2008). To see the relationship between total phenolics and antioxidant activity Pearson correlation was performed. A strong positive correlation was observed between antioxidant activity and TPC in carnauba wax treated eggplants during storage (Fig. 2B). Similarly patterns of good linear correlation between the total phenolic content and the scavenging of DPPH radical was observed in extract of Nigerian vegetables (Olajire & Azeez, 2011). 3.7. Peroxidase activity Peroxidases belong to enzymes involved in growth, development and senescence processes of plants (Asada, 1992). Peroxidase activity gradually decreased in carnauba wax treated eggplants during storage which is reflected in the metabolic processes. After 12 days of storage, minimum decrease of peroxidase activity was recorded in T2 treated fruits in packaged (2.64e2.20 mmol TG/min/ 100 g FW) and unpackaged (2.64e2.24 mmol TG/min/100 g FW) eggplants whereas maximum decrease was obtained in control fruits both in packaged (2.64e1.63 mmol TG/min/100 g FW) and unpackaged (2.64e1.37 mmol TG/min/100 g FW) eggplants (Fig. 2B). Similar pattern was also reported in enzyme activity in broccoli ska, Leja, & Mareczek, 2003). flower buds during storage (Starzyn 4. Conclusion The developed carnauba wax emulsion coating showed good

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commercial attributes such as glossiness, early drying nature and reduced physiological weight loss. Effectiveness of additives such as PEG, SA and SDS in CW emulsion coating could extent shelf life and enhanced antioxidant activity of packaged eggplants at maximum storage period during ambient temperature. Reduced Firmness, moisture, lightness as well as lower PLW were observed in PEG and SA based CW coated eggplants in packaged condition showed enhancement of storage capability of those eggplants. TPC and antioxidants activity showed no definite pattern during storage upto 12 days. However, maximum TPC and antioxidant activity were retained in PEG and SA based CW treated packaged eggplants during storage for 12 days, indicating more nutrition and antioxidant activity with a positive correlation. This treatment can ideally be adopted for enhancing storage life of highly perishable vegetables like eggplant to restrict use of unhygienic practices by the farmers and traders. Further, much more work may be carried out to investigate antimicrobial and antifungal properties of this CW coated eggplants with effectiveness on long storage stability, retention and activeness of other useful physiochemical and bioactive compounds. Acknowledgements The work has been carried out at Indian Institute of Vegetable Research, Varanasi funded by ICAR, New Delhi. The authors sincerely acknowledge the help rendered by Dr. Sanjeev Kumar, ICAR-IISR, Lucknow for language improvement of manuscript. There has been no conflict of interest; the contributions of all the authors are equal. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.lwt.2016.08.004. References Asada, K. (1992). Ascorbate peroxidase e A hydrogen peroxide-scavenging enzyme in plants. Physiologia Plantarum, 85(2), 235e241. Asrey, R., Patel, V. B., Singh, S. K., & Sagar, V. R. (2008). Factors affecting fruit maturity and maturity standards-A review. Journal of Food Science and Technology-Mysore, 45(5), 381e390. Baldwin, E. A. (1994). Edible coating in fresh fruits and vegetables. Edible Coating and Films. Lancaster, PA: Technomic. Brand-Williams, W., Cuvelier, M. E., & Berset, C. L. W. T. (1995). Use of a free radical method to evaluate antioxidant activity. LWT-Food Science and Technology, 28(1), 25e30. Cao, G., Sofic, E., & Prior, R. L. (1996). Antioxidant capacity of tea and common vegetables. Journal of Agricultural and Food Chemistry, 44(11), 3426e3431. Castillo, F. J., Penel, C., & Greppin, H. (1984). Peroxidase release induced by ozone in Sedum album leaves Involvement of Ca2þ. Plant Physiology, 74(4), 846e851. Chitravathi, K., Chauhan, O. P., & Raju, P. S. (2014). Postharvest shelf-life extension of green chillies (Capsicum annuum L.) using shellac-based edible surface coatings. Postharvest Biology and Technology, 92, 146e148. Chiumarelli, M., & Hubinger, M. D. (2014). Evaluation of edible films and coatings formulated with cassava starch, glycerol, carnauba wax and stearic acid. Food Hydrocolloids, 38, 20e27. Concellon, A., Anon, M. C., & Chaves, A. R. (2007). Effect of low temperature storage on physical and physiological characteristics of eggplant fruit (Solanum melongena L.). LWT-Food Science and Technology, 40(3), 389e396. n, A., Zaro, M. J., Chaves, A. R., & Vicente, A. R. (2012). Changes in quality Concello and phenolic antioxidants in dark purple American eggplant (Solanum melongena L. cv. Lucía) as affected by storage at 0 C and 10 C. Postharvest Biology and Technology, 66, 35e41. ~ a de Jesús, J. E., Villa-Rodríguez, J., Cruz-Valenzuela, R., RodríguezD avila-Avin Armenta, M., Espino-Díaz, M., Ayala-Zavala, J. F., et al. (2011). Effect of edible coatings, storage time and maturity stage on overall quality of tomato fruits. American Journal of Agricultural and Biological Sciences, 6(1), 162e171. Doganlar, S., Frary, A., Daunay, M. C., Lester, R. N., & Tanksley, S. D. (2002). Conservation of gene function in the Solanaceae as revealed by comparative mapping of domestication traits in eggplant. Genetics, 161(4), 1713e1726. Drake, S. R., & Nelson, J. W. (1990). Storage quality of waxed and nonwaxed ‘Delicious’ and ‘Golden Delicious’ apples. Journal of Food Quality, 13, 331e341.

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