Effects of preharvest fruit bagging on postharvest quality and shelf life of mango cv. Amrapali

Fruit fly and other organisms attack during growth and development of mango fruits which causes severe postharvest losses. Therefore, it is necessarily important to explore some technologies to protect fruits and reduce postharvest losses. This experiment was conducted in order to study the effects of preharvest fruit bagging on the postharvest quality and shelf life of mango cv. Amrapali. Five bagging materials viz., i) non-bag, control, ii) brown paper, iii) white paper, iv) white polythene and v) black polythene bag were used in this study. The single factor experiment was laid out in randomized complete block design with three replicates. Significant variations were noticed among the preharvest bagging materials in relation to physio-chemical quality attributes and shelf life of mango cv. Amrapali. The attributes such as weight and size of fruits, skin color, moisture, dry matter, vitamin C, sugar (reducing, non-reducing and total), total soluble solids (TSS) contents and shelf life were significantly influenced by the bagging materials. A significant difference was observed in the shelf life of bagged and non-bagged fruits. The longest shelf life (15 days) was found in brown paper bagged whereas the shortest shelf life (8 days) was in non-bagged control fruits. Considering the findings it was observed that brown and white paper bagged fruits appeared to be the superior in respect of skin color, moisture, dry matter, vitamin C, TSS, titratable acidity and extending shelf life in mango cv. Amrapali. Article history: Received: 10 October 2019 Accepted: 04 February 2020 Published: 31 March 2020


Introduction
Mango (Mangifera indica L.) belongs to the family Anacardiaceae is considered as the king of fruit of the tropics and sub-tropics and one of the most common, widely cultivated fruit of Bangladesh. The mango is native to south Asia, from where it has been distributed to worldwide to become one of the most cultivated fruit in tropics. During the period of 2017-2018, it occupied 0.44 million hectares of land and total production was 1.17 million tons and ranks first in terms of total area and production among the fruit crops in Bangladesh (BBS, 2018). But the yield is very low compared to India, Pakistan and other countries of the world (Hossain and Ahmed, 1994).
Mango is grown in almost all districts of Bangladesh, but it is commercially cultivated in the greater districts of Chapainawabganj, Rajshahi, Dinajpur, Natore, Rangpur, Kushtia, Jessore and Satkhira. The world mango fruit market is very competitive, with quality and price being the determinants. Producers should aim at producing high quality mango fruits and reducing postharvest damages to survive in the competition. Preharvest cultural practices and environmental conditions during fruit development profoundly influence postharvest performance and final quality (Lechaudel and Joas, 2007). Mango fruit skin, flesh and stone have specific compositions that appear to accumulate water and dry matter at different rates, depending on environmental conditions (Lechaudel and Joas, 2007). Mango fruit is harvested at early or late mature green stage depending on the distance of the market (Esguerra and Lizada, 1990).
After harvest, mango fruit ripens by undergoing many physicochemical changes that determine the quality of the fruit. Appearance and eating quality are the major attributes of mango that determine consumer acceptance (Mtebe et al., 2006). Fruit appearance is influenced by absence/presence of physical, pathological and physiological disorders. These disorders are also the main causes for postharvest loss of fruits and vegetables due to their detrimental effect on the physiological and biochemical changes during postharvest handling. The disorders induce rotting and early senescence leading to poor flavor and aroma (Mtebe et al., 2006).
The magnitude of postharvest losses in fresh fruit ranging from 5 to 25% in developed countries and 20 to 50% in developing countries. For example, Hassan (2010) found 27.4% postharvest loss of mango in Bangladesh. The postharvest loss in terms of quality and quantity of fruits occur in all stages of the postharvest system from harvesting to consumption. Mango showed highly prominent postharvest loss because of its high perishability and climacteric pattern of respiration. Postharvest loss of mango fruits varied from 0 to 16.3% with an average loss of 12.5% from variety to variety (Quroshi and Meah, 1991). It also depends on transport distance from production site to retail location.
Mango is known to be the suitable host for fruit fly. It adversely affects mango fruit especially during April-May. Usually premature fruits (at about ten weeks old) are vulnerable to fruit fly infestation (Vayssieres et al., 2010). Moreover, intensity of fruit fly infestation in mango fruit varied based on agro-ecological zones, varieties, physical, biochemical and ecological factors (Nankinga et al., 2014). Besides, some fungal diseases (anthracnose, stem end rot, powdery mildew etc.) and bacterial fruit rot also affects mango (Ploetz, 2003;Sharma et al., 2009;Sarwar, 2015). As a result, the quality and shelf life of mango fruits deteriorates after harvest. Postharvest diseases cause considerable losses of harvested fruits during transportation and storage (Sharma et al., 2009). Bagging, a physical protection technique, not only protects fruits from pests and diseases but also affects the quality of the produce by changing microenvironment of fruit during development Amarante et al., 2002;Leite et al., 2014;Sharma et al., 2014;Zhang et al., 2015). The preharvest bagging reduces agrochemical residual effects, prevents sunburn, decreases the mechanical damage and controls insect pest infestation in fruits (Sharma et al., 2014;Ehteshami et al., 2015). However, no noticeable research works have been conducted on the effect of different bagging materials on postharvest quality and shelf life of mango in Bangladesh. Considering the above facts this study has been undertaken to find out the effects of different bagging materials on postharvest quality of mango and to reduce the postharvest spoilage and increase the shelf life of mango.

Experimental site
The study was conducted at Bangladesh Agricultural University Germplasm Centre (BAU-GPC), Mymensingh, during February to July 2016. The experimental area was under the sub-tropical climate characterized by heavy rainfall during May-September and scanty rainfall during the rest period of the year.

Experimental design and treatments
The experiment was conducted following randomized complete block design with three replications. Five bagging treatments were applied in this study namely T0: non-bag, control; T1: brown paper bag; T2: white paper bag; T3: white polythene bag and T4: black polythene bag. The size of bags was 25cm × 20cm. Before bagging a small perforations (≤ 4 mm diameter) were made at the bottom of all bags for proper ventilation. The particular bag was stapled properly at the stalk of each fruit of respective treatment so that it would not be fall down as well as there would not be open space. The white and black polythene bags were tied with the help of thread. Five uniformly grown fruits (30 days after fruit set) were selected for bagging.
Fruits were harvested at full mature stage and transferred to the postgraduate laboratory of the Department of Horticulture for study different physico-chemical traits during storage. Chemical analyses were carried out in the laboratory of the Department of Biochemistry & Molecular Biology, Bangladesh Agricultural University, Mymensingh.

Methods used for measuring different parameters
Skin color of fruits was measured using color chart. Fresh weight of fruits was measured using digital balance (KERN, PCB 250-3, KERN & Sohn GmbH, Germany) and expressed in gram (g). Fruit length and breadth were measured by slide calipers in centimeter (cm).

Moisture and dry matter content
Fruit samples were taken in porcelain crucible and oven dried at 80°C till the weight become constant. Percent moisture content was calculated according to the following formula: % moisture 100 (g) ht Fresh weig (g) Dry weight -(g) ht Fresh weig   Dry matter content was calculated according to the following formula: Dry matter content = 100-%moisture TSS (%Brix) TSS content was determined by Hand-Held Refractometer (ATAGO Company Ltd., Japan). A drop of juice was squeezed on the surface of the prism of the refractometer and percent total soluble solids were obtained from direct reading of the instrument. Temperature corrections were made by using the temperature correction chart.

Titratable acidity
Titratable acidity of fruit was determined by titration method described by Ranganna (1986).

Total sugar content
Total sugar content of mango fruit was determined colorimetrically by the anthrone method (Jayaraman, 1981).

Reducing sugar
Reducing sugar content of mango fruit was determined by dinitro salicylic acid (DNS) method (Miller, 1972).

Vitamin C (Ascorbic acid) content
It was determined by titration method. In brief, ten grams of fresh pulp was taken in 100 ml beaker with 50 ml 3% metaphosphoric acid and then it was transferred to a blender and homogenized with same concentration of metaphosphoric acid. After blending, it was filtered and transferred to a 100 ml volumetric flask and was made upto the mark with 3% metaphosphoric acid. Then 5 ml of the aliquot was taken in a conical flask and titrated with 2, 6-dichlorophenol indophenol dye. Phenolphthalein was used as indicator which gave a pink coloured end point and persisted at least 15 seconds. The ascorbic acid content of the sample was calculated by following formula: Shelf life of mango fruits as influenced by different postharvest treatments was calculated by counting the number of days required to ripen fully with retained optimum marketing and eating qualities.

Statistical analysis
Data on various parameters were statistically analyzed using MSTATC statistical package. The means for all the treatments were calculated and analyses of variances (ANOVA) for all the parameters were performed by Ftest. The significance of difference between the pairs of means was compared by least significant difference (LSD) test at the 1% and 5% levels of probability (Gomez and Gomez, 1984).

Skin colour
Apparently significant variations were observed in respect of skin colour among the fruits of bagged and non-bagged before and after storage.
Plate 1. External appearance of fruits after a week of storage in the laboratory Table 1. Effects of preharvest bagging on changes in skin colour of fruit at harvesting and ripening stage.

Treatment
After harvesting After ripening T0 (Non-bag, Control) Green Yellow green T1 (Brown paper bag) Yellow green Dark orange yellow T2 (White paper bag) Light green Yellow green T3 (White polythene bag) Green Light yellow green T4 (Black polythene bag) Green Brown green The most attractive colour was found in brown paper bagged fruits and the worst colour was found in nonbagged control fruits at the harvesting and at 12 th day of storage (Plate 1 and Table 1).

Fresh weight, length and breadth of fruit
Preharvest fruit bagging had significant influence on fresh weight, length and breadth of fruit. The maximum fruit fresh weight, length and breadth were found in black polythene bag (175.54g, 8.77 cm and 6.63 cm, respectively) followed by white paper bag (162.81g, 8.67 cm and 6.38 cm, respectively), white polythene bag (162.08 g, 8.55 cm, and 6.27 cm, respectively), brown paper bag (160.66 g, 8.40 cm and 6.29 cm, respectively) and the lowest fruit fresh weight, length and breadth were recorded in non-bagged control fruit (149.18g, 8.23 cm and 5.94 cm, respectively) ( Table 2).

Moisture content
It was observed that the statistically significant variations were found in moisture content after storage due to different treatments. The highest moisture content of mango fruit was observed in white polythene bag (82.90 %) and the lowest moisture content was recorded in white paper bag (79.37%) (Fig. 1).  T1  T2  T0  T3  T4  0

Dry matter content
Dry matter content of mango varied significantly due to the effect of different preharvest fruit bagging treatments. The highest dry matter content was found in white paper bagged fruit (20.63%) and the lowest dry matter content was in white polythene bagged fruit (17.10%) (Fig. 2).

TSS content
Preharvest fruit bagging treatments also showed significant effect on TSS content of mango. The maximum TSS content (22.87% Brix) was found in nonbagged control fruits while the minimum TSS content (17.97% Brix) was found in white polythene bagged after ripening (Fig. 3).

Vitamin C content
After ripening vitamin C content of mango pulp was significantly influenced by preharvest bagging treatments of mango. The highest vitamin C content (29.72mg/100g) was found in non-bagged control fruit and the lowest vitamin C content (19.67 mg/100g) was in brown paper bag (Fig. 4). There was a decreasing trend in vitamin C content of fruit pulp in bagged fruit than that of non-bagged control fruit. The white paper bag, black polythene bag and white polythene bag showed 24.49, 23.31 and 22.29mg/100g, respectively (Fig. 4).

Reducing sugar content
The preharvest bagging treatments used in this study showed statistically significant effect on reducing sugar content of mango during storage. The maximum reducing sugar content (10.68%) was recorded in white polythene bagged fruit at the 12 th day of storage while the minimum reducing sugar content (8.99%) was found in white paper bagged fruit at the same day of storage (Table 3).

Non-reducing sugar content
It was noticed that non-reducing sugar content increased at storage. The preharvest fruit bagging treatments showed significant variation in non-reducing sugar content during storage period. At 12 th day of storage, the highest non-reducing sugar content (11.21%) was observed in non-bagged control fruits while the lowest non-reducing sugar content (10.15%) was found in brown paper bagged fruit (Table 3).

Total sugar content
The preharvest fruit bagging treatments showed significant variation in respect of total sugar content during storage. Results showed that the higher amount of total sugar content (21.13%) was present in non-bagged control fruits followed by white polythene bagged fruit (20.89%), black polythene bagged fruits (20.24%), brown paper bagged fruit (19.32%), while the lower amount of total sugar (19.31%) was recorded in white paper bagged fruit (Table 3).

Titratable acidity
The preharvest fruit bagging showed statistically significant difference in terms of titratable acidity content at storage. It was observed that white paper bagged fruit contained the highest amount of titratable acidity (2.58%) and black polythene bagged fruit contained the lowest (1.78%) at storage period (Fig. 5).

Shelf life
The effects of different preharvest fruit bagging treatments were statistically significant in respect of extending shelf life of mango cv. Amrapali. The shelf life of mango fruits ranged from 10 to 15 days. The shortest (8 days) and longest (15 days) shelf life was observed in non-bagged control fruits and brown paper bagged fruits, respectively. The shelf life of mango fruits were extended by 2.40, 3.27, 4.33 and 7.00 days in white polythene bag, black polythene bag, white paper bag and brown paper bag treatments, respectively over non-bag control (Fig. 6).

Discussion
Fruit skin colour is the key factor of any fruit that attracts consumers. An attractive skin colour improves the physical appearance of fruit, which enhance to get better price in the domestic and export markets. Several studies have indicated that preharvest fruit bagging improve or inhibit fruit skin colour development. The changes in colour of mango skin from green to breaker are the most obvious change which occurs during storage of fruits. Change of skin colour during ripening and senescence of fruits involves chlorophyll degradation or qualitative and quantitative alteration of the green pigment into other pigments. In this study, we observed that brown paper bagged fruits showed the most attractive yellow green and dark orange yellow colour at harvest and after ripen, respectively. It is reported that bagging improves the skin colour of fruit by increasing their anthocyanin content. In litchi, semitransparent-CP bags resulted in excellent skin colour in fruit (Tyas et al., 1998;Chen and Li, 1999). In earlier studies, fruit bagging had been reported to inhibit colour development in apple. However, it has now been recognized that fruit bagging is an effective way to improve fruit colour in apple (Fallahi et al., 1997).
Preharvest fruit bagging with different bagging materials significantly improved physical traits of fruit viz., weight, length, diameter and pulp weight over nonbagged control fruits. The bagged fruits produced the highest fruit weight (175.54 g), length (8.77 cm) and breadth (6.63cm) as compared to non-bagged control fruit. Covering fruit with a bag at a particular developmental stage (30 days after fruit setting) may influence their growth and size. It is reported that fruit size and weight are determined by the type of bag used, fruit and cultivar (Sharma et al., 2014). Bagging of 'Nam Dok Mai' mango fruit with two-layer paper bags, newspaper, and golden paper bags increased fruit weight (Watanawan et al., 2008). In this study we also noticed that fruit bagging significantly increases fruit weight and size. Chonhenchob et al. (2011) claimed that fruit bagging increased fruit weight, size over non-bagged control fruits. Fallahi et al. (2001) reported that preharvest fruit bagging significantly increase fruit weight of BC-2, Fuji Apple. Bagging promoted longan fruit development, resulting in larger-sized fruit (Yang et al., 2009).
It was reported that bagged fruit retained higher moisture content during storage period (Yang et al., 2009). In our experiment we found that the moisture content was higher (82.90%) in polythene bagged fruit. Dry matter content (20.63%) was also higher in white paper bagged fruit. The dry matter content was higher might be due to fruit bagging. The result of the present study is in support of the findings of . He stated that due to preharvest bagging dry matter content increased from 17.14 to 20.83% during storage.
TSS of all bagged mango fruits showed lower value than non-bagged control fruits. The result is in agreement with the finding of Signes et al. 2007, they found lower TSS in bagged grape. In our study, we observed higher TSS content (22.87 % Brix) in non-bagged control fruit and lower (19.10 % Brix) in black polythene bagged fruit.
We recorded higher vitamin C content (29.72mg/100g) in non-bagged control fruit as compared to bagged fruits. The bagging led to lower content of chemical components such as Vitamin C, phenols and organic acids in most of peach varieties (Lima et al., 2013). The preharvest bagging showed significant effect on total sugar, reducing sugar and non-reducing sugar content of fruits at harvest. White polythene bagged fruit showed the highest reducing sugar content (10.69%). The variation observed in chemical composition of mango fruits can be attributed to the changed microenvironment around fruit during its growth and development. The bagged fruits showed highest content of vitamin C, sucrose, glucose and fructose over non-bagged control in Zill mango (Hongxia et al., 2009); date palm (Harhash and Al-Obeed, 2010). Ding and Syakirah (2010) reported that different colour bag did not affect the titratable acidity of mango. But in this study, we found variations in titratable acidity content in bagged fruits. The maximum titratable acidity (2.58%) was reported in white paper bag while the minimum (1.98%) in black polythene bagged fruits.
The shelf life of mango fruits was found to be extended by 7.00, 4.33, 2.40 and 3.27 days in bagging with brown paper, white paper, white polythene and black polythene, respectively as compared to non-bagged fruits. It is assumed that non-bagged fruits affected by insects and diseases earlier giving the shortest shelf life during storage. The greater storability of the bagged fruits was might be due to the reduced level of disease both in terms of incidence and severity. And this reduced disease may be due to the effects of antimicrobial components in sap that were not allowed to remove from the fruits. The antimicrobial properties of sap had been extensively investigated by Hassan (2010). Singh et al. (2007) reported that pre harvest bagging delayed ripening resulting in extended shelf life of Perla, a black grape. The bagging modified the microenvironment near fruit especially in respect to air temperature and humidity (Yang et al., 2009). The longer shelf life of bagged fruits indicated that the effect of bagging persisted during ripening of fruits in storage.  noticed that the infestation of anthracnose and stem end rot reduced in mango cv. Keitt with white paper bag used at approximately 100 days before harvest. Bagging provided physical barrier between fruit and pests which resulted in longer shelf life of mango.