Influence of salicylic acid and storage durations on sensory evaluation of sweet orange cv . blood red

Citrus is a perishable commodity and is one of the most important fruit of Pakistan after apple. Losses occur during storage either due to disease attack or any other problem. Salicylic acid is one of the antioxidant which is responsible for minimizing the disease attack in many fruits. Hence the present study was designed to investigate “Influence of salicylic acid (SA) and storage durations on sensory evaluation of sweet orange Cv Blood Red”. The experiment was performed at Post Harvest Laboratory, Department of Horticulture, The University of Agriculture Peshawar during 2013. The experiment was laid out using Completely Randomized Design (CRD) with three repeats. Sweet orange fruit Cv. Blood Red were treated with different concentration of salicylic acid (O (control), 1, 2, and 3 mML), stored at room temperature for about 60 days, at 15 days of intervals. The experimental results showed that the salicylic acid concentration and storage durations significantly influenced all the sensory attributes. The Salicylic Acid concentration at the rate of 2 mML significantly retained Taste (4.08) and Aroma (6.07), while 3 mM SA L showed highest appearance (6.20) and texture (6.20). Sweet orange fruits stored for more than 30 days showed decrease in taste (4.33), aroma (5.83), texture (5.17), and appearance (6.25). It is concluded from the present study that salicylic acid at the rate of 2 and 3mML significantly retained the sensory attributes of sweet orange upto 30 days which is acceptable for consumer use of Peshawar valley.


Introduction
Sweet orange (Citrus sinensis L.) fruits are classified as non-climacteric fruits [1] belongs to family Rutaceae [2].The fruit of citrus botanically is a hespresidium, [1, 3] Citrus fruit is considered as true fruit generally developed from a superior ovary having all the tissue derived from ovary [4].The growth and development of citrus fruit up to harvesting takes about 6-18 months depending upon the type of cultivar [5].Morphologically, citrus composed of two main regions, the first region known as pericarp the peel or rind, while the second region known as endocarp, the pulp which is the edible portion [3].It is generally believed that South East Asia is center of origin of citrus species and since prehistoric, it spread over all the world.Sanskrit literature referred the appearance of citrus before 800 BC  Citrus fruit due to large scale production and health benefits is considered to be one of the important fruit crops in the world.It is consumed either fresh fruit or for juice purpose.Citrus having many commercial species which includes grape fruit (Citrus paradise), lemon and Lime (Citrus lemon and Citrus aurantifolia) mandarin and tangerine (Citrus unshi and Citrus reticulata) pamelo (Citrus grandis), oranges (Citrus sinensis) [6].Post-harvest diseases play a major role in reducing the post-harvest life of citrus fruits, common disease includes the green mold and blue mold in all the production area of citrus [13].Post-harvest treatments are helpful in order to reduce the post-harvest fungal attack and weight loss from the fruits, some postharvest treatments like application of salicylic acid, calcium chloride, coatings and other antioxidants are helpful in reducing such problems [14,15].Salicylic acid is among the phenolic compound which is safe and natural compound and is helpful in maintaining the post-harvest losses of horticultural produce.Besides its postharvest importance it is used as a pre-harvest treatment where it induces the defense resistance system, which on commercial basis significantly helpful in retaining the post-harvest decay.Many studies revealed that salicylic acid was applied in combination with other post-harvest treatment were helpful in increasing storage life of horticultural produce by reduction of postharvest losses [16].In order to reduce the injurious effect of chemicals e.g fungicides used for the control of post-harvest disease it had adverse effects on health of human.Safe and alternative methods are required to control the post-harvest disease and minimizing the effects of chemicals on human [17].By the application of natural compounds like salicylic acid fruits are improved, as it helps in resistance of fruits against fungal attack and also control weight loss of horticultural commodity.This is a very safe and effective strategy for enhancing the quality and shelf life for horticultural commodity [15].Salicylic acid when exogenously applied moves inside the plant in a systematic way and creating defense against the different kinds of pathogens by induction into expression of defense genes [15,18].Keeping the importance of salicylic acid and post-harvest problems of sweet orange, the present study was designed to investigate the influence of salicylic acid (SA) on fruit quality of sweet orange during storage.To find out the best storage duration for storability of sweet orange and to find out the interactive effect of salicylic acid concentration and storage duration to enhance the shelf life of sweet orange.

Materials and methods
To study the "Influence of salicylic acid and storage durations on sensory evaluation of Sweet Orange (Citrus sinensis L) cv Blood

Collection of fruit samples
The sweet orange fruits were transported from Citrus Research Institute (CRI) Sargodha, Punjab, to the Post Harvest Laboratory Peshawar Department of Horticulture, The University of Agriculture Peshawar in December 2013.The fruits of same size and maturity were selected for experimental trial, while the injured or diseased fruits were discarded.Procedure for preparation of salicylic acid Concentrations of salicylic acid 1, 2, and 3mML -1 of the weighted samples 0.138, 0.276 and 0.414 were prepared by dissolving them (powder form) in distilled water.As salicylic acid is hardly soluble in water so for this vary reason magnetic stirrers were used and the solutions were left on stirrers for 24 hours, so that it can completely dissolved in water.There were 60 treatments, each treatment contained 10 numbers of fruits, and so 600 total fruits were used.The sweet orange fruits were divided into four groups each group contained 150 fruits and each group was dipped in solution of different concentration 0 (control), 1, 2 and 3 mML -1 of salicylic acid for about 5 minutes.The treated fruits were than air dried for about 30 minutes and then the fruits were stored at room temperature (10-15 ο C) with Relative Humidity of 70-80% for 2 months.

Parameters studied
The following parameters were studied during the course of the experiment.1. Taste 2. Texture 3. Aroma 4. Appearance

Taste
The mean data table clearly showed that there exists a significant difference among the various levels of salicylic acid and storage durations while their interaction was found non-significant.(Table 1).The good taste (4.80) was recorded for fruits dipped with 2mML -1 of salicylic acid closely followed by taste (4.33 and 4.27) of sweet orange fruit dipped in 3 and 1mML -1 respectively, while the poor taste (3.47) was recorded in fruits which were untreated.As regards storage duration it also influenced the fruit taste of sweet orange significantly, The good taste was recorded in the fruits which were freshly harvested (6.33), followed by taste (4.92 and 4.33) of sweet orange fruits stored for 15 and 30 days of intervals respectively, while poor taste (2.08) was recorded in fruits stored for 60 days of intervals.With the increase in storage duration the taste of sweet orange decreased.Similar results were quoted by [19] he reported that taste of apples and mangoes significantly declined with increase in storage duration.Similar results regarding taste were quoted by [20] in strawberry fruit, where the application of polyamines was affective in maintaining the taste of fruits.
[21] also concluded the effect of salicylic acid in maintaining the taste of apricot fruit, while similar results regarding effect of salicylic acid in controlling taste were concluded by [22] in kiwi fruits.

Texture
The mean data table clearly showed that there exists a significant difference among the various levels of salicylic acid and storage durations while their interaction was found non-significant.(Table 1).The high quality textured fruits (5.23) were obtained from 3mML -1 of salicylic acid, followed by the texture of sweet orange fruits (4.47 and 4.28) was recorded In fruits dipped in 2mML -1 and 0mML -1 (control) respectively, while the poor quality textured fruits (4.10) were obtained from 1mML -1 of salicylic acid.As concerned to storage durations, it also influenced significantly the texture of sweet orange fruit during storage.The high quality textured fruits (7.00) were obtained from the fruits which were freshly harvested, which is at par with the value of texture (6.67) which were stored for 15 days of interval, while the poor textured fruits (1.61) were obtained from fruits stored for 60 days of intervals.With the increase in evaporation, wrinkling and loss of firmness resulted in poor textured fruits and thus continuous as the storage duration proceeds.By application of salicylic acid slows down the rate of moisture loss and maintained its firmness which ultimately improved the texture of fruits .Similarly the application of polyamines maintained the texture of strawberries [20] during storage.The application of salicylic acid significantly maintained the kiwi fruit structure during storage [22] Aroma The mean data table clearly showed that there exists a significant difference among the various levels of salicylic acid, and storage durations while their interaction was found non-significant.(Table 1).The highest aroma (6.07) was recorded in fruits dipped in 2mML -1 of salicylic acid followed by (5.20 and 5.67) was recorded in fruits dipped in 3 and O mML -1 of salicylic acid respectively.While the least aroma (4.80) was recorded in fruits dipped in 1mML -1 of salicylic acid.In case of storage duration aroma was significantly influenced by storage duration.However the highest aroma (7.92) was recorded in fruits which were freshly harvested, which is statistically similar with fruits stored for 15 days of interval (7.33), while the least aroma (2.08) recorded in fruits stored for 60 days of intervals.Similar findings were quoted by [19] in apples and [23] in mangoes.Salicylic acid application significantly maintained the aroma of sweet orange fruit during storage.The results are supported by the finding of [22] who also reported that the salicylic acid helped to maintain the aroma of kiwi fruit during storage.

Appearance
The mean data table clearly showed that there exists a significant difference among the various levels of salicylic acid and storage durations while their interaction was found non-significant (Table 1).The good appearance (6.20) was recorded in fruits dipped in 3mML -1 of salicylic acid, which is at par with value of appearance (6.07) shown by sweet orange fruits dipped in 2mML -1 of salicylic acid.While the bad appearance (5.13) was shown by sweet orange fruits dipped in 1mML -1 of salicylic acid.As concerned to storage durations it also significantly influenced the appearance of sweet orange fruits.The good appearance (6.67) was shown in sweet orange fruits, stored for 15 day of intervals.Which is statistically similar with (6.58 and 6.25) of sweet orange fruit which were freshly harvest and stored for 30 days of intervals.While the bad appearance (4.17) was shown by sweet orange fruits stored for 60 days of intervals.This might be due to moisture loss from the fruit during the process of respiration or it might be due to loss of other components during the metabolic activities.By application of salicylic acid it significantly reduced the appearance of sweet orange fruits during the storage by lowering down the process of respiration and other related metabolic activities.The results of present study are supported by the findings of [22] who reported the similar results by application of salicylic acid helpful in maintaining the appearance of kiwi fruit.The application of polyamines to strawberry fruit significantly maintained the physical appearance during storage [20].

Conclusions and recommendations
Based on the results obtained, it is concluded that Salicylic acid helped effectively in maintaining the sensory attributes of sweet orange fruits, by sustaining aroma, appearance, texture and taste.The salicylic acid treatment 2 mML -1 was efficient in controlling the taste and aroma, while, 3 mML -1 salicylic acid was efficient in retaining texture and appearance of sweet orange fruits during storage.As regards the different storage intervals, the sweet orange sustained its quality attributes up to 30 days of storage interval at room conditions (12±1 o C and RH of 70-80%) while after 30 days the gradual decline was noticed in quality parameters.

Authors' contributions
Conceived and designed the experiments: FU Red".An experiment was conducted at Post Harvest Laboratory, Department of Horticulture, The University of Agriculture, Peshawar in December 2013 in normal room temperature (12±1 o C and RH of 70-80%) in open environment.The experimental was laid out in Completely Randomized Design (CRD) with two factor factorial arrangements repeated three times.Fruits of Sweet orange cv.Blood Red were dipped in salicylic acid concentrations (0, 1, 2 and 3 mML -1 ) which were stored for 60 days with 15 days interval (0, 15, 30, 45 and 60 days).