1 Introduction

Apple (Malus domestica Borkh.) is an economically important fruit plant in family Rosaceae. Apple fruits have colorful appearance, crispy flesh, pleasant flavor and sweet taste. It has been originated in Central Asia, where its wild ancestor Malus sieversii is still found today (Hancock et al., 2008). Apples have been grown for thousands of years in Asia and Europe; were brought to Indian sub-continent by European colonists. There are more than 7 500 cultivars and it is one of the most grown fruit in the temperate zones of all over the world (Martinelli et al., 2008). Apples have religious and mythological significance in Norse, Greek, Christian traditions and European cultures. The proverb “An apple a day keeps the doctor away” addresses the health benefit of fruit. Consumption of apple has shown better health to prevent a variety of chronic diseases and lung cancer, asthma, diabetes and ischemic heart disease which is mainly due to large content of structural cell walls and polysaccharides along with the various phyto-chemical antioxidants (Device et al., 2010). Red delicious, Royal Delicious and Golden Delicious cultivars are leading the deciduous fruit grown successfully in high hill areas from east to far west of Nepal. Royal Delicious is a widely adapted commercial cultivar of apple used as a pollinizer in apple orchards. In Nepal, apple can be grown in 54 districts; however, only 12 districts grow apple commercially of which Jumla district ranked the number one in terms of area and production (Subedi et al., 2012). Climate is very much suitable for the production of apple. Efforts have been made to increase production in high hills and mountains. However, because of transportation problems, the produced fruits do not reach to the market in normal condition. Postharvest losses due to inappropriate packaging are very high. Despite of great potentiality for production, at present 99.0% of the apple fruits in the market are imported from China and India. To replace import, Nepal has to develop its own packaging and transportation mechanism.

Apple growers of Nepal have not been receiving anticipated level of income because of higher postharvest loss due to inappropriate traditional postharvest handling practices. Large amount of fruit losses occurs after harvest and minimizing this loss could save over 25% of produce (Gurung, 1998). Gautam et al. (2004) reported that 58.2% apple fruits damage during harvesting, handling, transportation and distribution due to inadequate postharvest handling technology.

All the apple production areas located in higher hills, from where usually the fruits are harvested and transported to collection centers on conical bamboo baskets by the porters and thereafter to distance market in different CFB boxes and gunny sacks. Fruits bruise easily due to scratch, compression, impact and vibration forces during transportation also lead to damages. The damages may not be apparent and visible to naked eyes immediately after transport; however become visible after storage. Moreover scratches and wounds created during transport are the avenue for the entry of microorganism for the development of disease and rotting. Thus, damaged fruits have short storage life as compared to undamaged healthy fruits (Subedi et al., 2016; Subedi et al., 2017).

In Nepal, present packaging system for apple fruit is unsuitable and unscientific. The use of traditional forms of packages like bamboo baskets; reused Beer cartons, noodle cartons, Chinese apple cartons and gunny sacks are still prevalent which are not convenient containers for packaging, handling, transporting and marketing of fresh apple for distant market. Rough surface and sharp edge of bamboo baskets cause bruising and scaring; inconvenience in handling and stacking during transportation.

Among different packaging containers, CFB boxes are capable of withstanding various shipping and transportation hazards (impact, compression and vibration damages), attractive, light weight; provide cushioning and good stacking strength and excellent cushioning for product protection, offers better retention of shelf life, quality of product and better printability which helps in efficient marketing (Salunkhe et al., 1995). One of the important functions of CFB boxes is to provide crush resistance/product protection and adequate strength for stacking in warehouses. The use of CFB boxes is being made to limited extent in Nepal. Some traders and cooperatives have initialed to use CFB boxes for packaging and transportation of apple to long distance market; however packaging containers and packaging methods have not been standardized yet.

Apple growers, cooperatives and traders still use 3 ply Beer cartons and 7 ply CFB boxes of 20 kg capacity recommended by Fruit Development Directorate (FDD) to pack and transport apples. At present, nearest cold storage is located in Kohalpur, Banke, Nepal which is far from the production site. Fruits are usually stored in cold storage by traders and released periodically for marketing. Postharvest brushing damage on Standard cultivars of apple fruits is a serious problem for the growers. To overcome this problem, research has been undertaken to identify appropriate packaging materials for transportation of Royal Delicious apple fruits from the production center to the distant market and thereafter on storage in a prime form and fresh condition so that bruising process can be managed or controlled more effectively.

2 Material and Methods

Studies were carried out for two consecutive years (2013-2014) to identify appropriate packaging material for transportation of Royal Delicious apple from HRS, Rajikot, Jumla, Nepal to Kohalpur, Banke, Nepal. Fruits were harvested at commercial maturity stage from HRS, Rajikot, Jumla (2390m a.s.l., 29^°17’N, 82^°13’E) and transported to Kohalpur, Banke, Nepal in different types of CFB boxes. To compare with conventional and other methods, two existing practices were also included as treatments; these were 7 ply CFB box of 20 kg capacity recommended by FDD and 3 ply Beer carton as local practice. Six different types of 10 kg capacity CFB boxes (300mm x 250mm x 295mm) having different plies with different bursting strength were manufactured at Sahara packaging private limited, Jorpati, Kathmandu, Nepal. They were; 5 ply CFB boxes with 140 psi, 160 psi, 180 psi bursting strength, 7 ply CFB boxes with 140 psi, 160 psi, 180 psi bursting strength.

To compare with conventional and other methods, two existing practices were also included as treatments; these were 7 ply CFB box of 20 kg capacity recommended by FDD and 3 ply Beer carton as local practice. Four holes of 20mm diameter were made on both sides of the CFB boxes at 5.5mm and 18.5mm height for exchange of gases. Uniform sized 64 and 140 apple fruits were arranged in 4 layers separated by five deck plates in 10kg and 20kg capacity CFB boxes respectively. CFB boxes were sealed with carton tape first, then diagonally sealed by carton sealing and strapping machine (Golden Eagle); transported to truck (200m walking distance) by porters on their head. CFB boxes were loaded randomly; stacked in 4 layers inside truck after spreading of HDPE tarpaulin at the base; shipped by truck to Kohalpur, Banke, Nepal (215 km mountainous gravel road, 48 hours) and then stored for one month in cold storage at 5±1°C and 95% RH.

Since the effect of packing material is not prominent immediately after transportation, the fruits were stored for one month for observation. After one month storage, consumer’s acceptability (Juyun Lim, 2011) was recorded by a panel of 10 judges on the basis of hedonic rating (9-like extremely; 8-like very much; 7-like moderately; 6-like slightly; 5-neither like nor dislike; 4-dislike slightly; 3-dislike moderately; 2-dislike very much; 1-dislike extremely). Firmness of fruit was measured with hand penetrometer (FT-327, Italy) having plunger diameter of 11mm. Total soluble solids (brix) was recorded with hand refractometer (Erma, Japan) calibrated at 20°C. Titratable acidity was determined by titrating a 5 ml juice with 0.1N sodium hydroxide using phenolphthalein as an indicator (AOAC, 1990). Starch iodine test was performed to determine the conversion pattern of starch into sugars (M.S. Reid et al., 1982). Iodine solution was prepared by dissolving 10g of iodine crystals and 25 g of potassium iodide in 1 liter of distilled water.

Fruits (n=10) were cut at right angles to the core, approximately halfway from stem to calyx end; Iodine solution was applied to cut surface, drained away any excess and rated fruit staining after two minutes by using 0-6 scales [0-all tissue zones stained (all starch); 1-clearing within the core flesh, particularly between adjacent seed carpel; 2-clearing has extended to the core line and started to extend into the regions between core line vascular bundles; 3-clearing has continued between the core line vascular bundles, while tissue surrounding the core line vascular bundles and in the outer cortex remain stained; 4-clearing has continued into the outer cortex, but not to the skin. Most core line vascular bundles and associated tissue which remain stained are surrounded by unstained cortical tissue; 5-clearing has extended to within a few mm of the skin and unstained zones around the core line vascular bundle, where they exist, started to contract; 6-no staining (no starch)].

The experiment was designed as eight treatments randomized completely with three replications, each replication comprising of 64 and 140 fruits according to capacity of CFB box. Observations were recorded for PLW, damage incurred due to bruising and spoilage during transportation and subsequent storage. Spoilage was considered for unacceptable fruit loss while some fruits which were damaged partially were accepted at 50% lower price, an equivalent loss were calculated. Economic analysis of best and existing packing methods were calculated assuming 50% lower price of damaged fruits in the market. Physicochemical studies on quality parameters were performed at RARS, Khajura, Banke, Nepal. Data were pooled and analyzed statistically using Gen Stat software version 10.3 (VSN, 2011).

3 Results and Discussion

3.1 PLW (%)

PLW of apple fruits among the tested packaging containers was highly significant during transportation and storage. Minimum PLW (1.6%) was observed in 7 ply 180 psi CFB boxes while maximum (4.4%) in 3 ply Beer carton (Table 1). Maximum PLW in 3 ply Beer carton might be due to inadequate strength which increased damage to carton surface resulted more water loss due to higher evapo-transpiration and respiration (Gautam and Bhattarai, 2012; Subedi et al., 2017). Mohammed et al. (2016) reported that moisture loss of a single bruised apple may be increased by as much as 400% compared to that of an intact apple.

3.2 Total damage, spoilage loss, acceptable damage, equivalent loss and total postharvest loss

Total number of damaged fruits among the tested CFB cartons due to bruising, scaring and spoilage during transportation and storage was highly significant (Table 2). Minimum number of total damaged fruits was observed in 7 ply 180 psi CFB boxes (6.6%) followed by 7 ply 160 psi CFB boxes (7.7%) while maximum in 3 ply Beer cartons (22.4%). Likewise, minimum spoilage loss or unacceptable damage (2.2%) was observed in 7 ply 180 psi CFB boxes followed by 7 ply 160 psi CFB boxes (3.1%) while maximum in 3 ply Beer cartons (13.5%). Minimum acceptable or partially damaged fruits were observed (5.4%) in 5 ply 180 psi CFB boxes followed by 7 ply 180 psi CFB boxes (5.5%) while maximum (8.9%) in 3 ply Beer cartons. Minimum equivalent loss (50% of acceptable or partially damaged fruits) was observed (2.7%) in 5 ply 180 psi CFB while higher (4.5%) in 3 ply Beer cartons other treatments. Total postharvest loss was maximum in 3 ply Beer cartons (22.4%) followed by 7 ply FFD CFB boxes (16.9%) while minimum in 7 ply 180 psi CFB boxes (6.6%).

Maximum damages in 3 ply Beer carton might be due to inadequate cushioning and strength which increased the damage to internal tissues during transportation. Seven ply CFB box of 20 kg capacity recommended by FDD was not acceptable container for packaging of apple fruits because of high postharvest loss; inconvenience in handling during transportation, storage and marketing; and unaffordable price for the consumers.  CFB Box of 10 kg capacity having 7 ply 180 psi bursting strength was easily accepted by the farmers groups, cooperatives, traders and consumers in Nepalese context because of convenience in handling; minimum brushing, scaring, spoilage damage; high storability, affordable price, better retention of fruit quality.

Scratches or minor wounds may not be apparently visible immediately after transportation however it has significant influence during storage. The fruit skin in apples consists of the cuticle, epidermis and several layers of hypodermis. Both skin and its waxy coat are of significant importance during transportation and storage (Subedi et al., 2016; Subedi et al., 2017). Most important function of epidermis and cuticle is to protect fruit surface against environmental stresses such as wind, temperature, drought, chemicals, insects, and microorganisms throughout the fruit life on the tree and later, after harvest, during transportation and storage (Babos et al., 1984). Compression damage may occur in lower depth of the container as a result of load of upper fruits, while impact damage may occur due to rough handling on the surface of fruits, and vibration forces usually occur during transportation. Packaging container might have effect on damage of fruits. Fruits are compressed in the bottom layers as well as sides of carton during transportation and storage which caused damages. There have been several other studies related to the damage caused by transportation hazards. Highest bruising damage and spoilage on 3 ply Beer cartons obtained from this study are also supported by the finding of Shrestha (1996); Gautam et al. (2004); and Subedi et al. (2017). Paudel et al. (2016) reported that maximum damage (32.5%) was observed on control while minimum (17.5%) on paper wrapped fruits after 60 days of storage.

3.3 Hedonic rating and juice content

At maturity stage, mean overall preference was 8.6 (Figure 1). Minimum overall preference (8.4) was recorded in 3 ply Beer cartons followed by 7 ply FFD CFB boxes (8.6) while maximum (8.8) in other treatments due to ripening which increase the appearance, crispiness, taste and aroma of fruits. Minimum sensory score maintained by 3 ply Beer cartons might be due to inadequate strength and cushioning which increased the physical damage to apple fruits during transportation. 7 ply CFB boxes of 20 kg capacity recommended by FFD was not appropriate container because of more postharvest losses, inconvenience in handling and unaffordable price for the consumers.

At maturity stage, mean juice content was 69.5% (Figure 1) while juice content of apples decreased during storage ranging from 60.5-66% irrespective of packaging materials; it was higher in 7 ply 140 psi CFB boxes while lowest in 3 ply Beer cartons. Minimum juice content in 3 ply Beer carton might be due to inadequate strength and cushioning which increased physical damage to apple fruits resulted more water loss due to higher evapo-transpiration and respiration during transportation. Another reason for low juice content of fruits packed in 3 ply Beer carton is due to Softening of fruits due to lack of ventilation which is an undesirable ripening process as firmer apples tend to be juicier, crispier, crunchier and less mealy than softer fruit. CFB Box of 10 kg capacity having 7 ply 180 psi bursting strength was easily accepted by the farmers groups, cooperatives, traders and consumers because better retention of physical appearance, crispiness, taste, aroma, firmness and juice content. Of the different stages of development (growth, maturation, ripening, and senescence), apple fruits are considered horticulturally mature during maturation and early stages of ripening (Watada et al., 1984).

3.4 Total soluble solids (tss), titratable acidity (ta) and tss:ta ratio

At maturity stage, TSS, TA and TSS/TA of fruits were 10.6%, 0.25% and 43.1 respectively (Figure 2). TSS of fruits increased during transportation and storage (Figure 2). Highest TSS was noticed in 3 ply Beer cartons and 7 ply FFD CFB boxes (14.6%) while lower in other treatments (14.2-14.4%). TSS of apple is a major quality parameter which is positively correlated with texture and composition. Increase in TSS could be attributed to breakdown of starch into sugars or hydrolysis of cell wall polysaccharides (Weibel et al., 2004). Level of TA decreased during transportation and storage.

Lowest TA was recorded in 3 ply Beer cartons (0.20%) which may be due to more physical damage to fruits resulting faster ripening while highest in other treatments (0.23-0.24%). Reduction of TA during transportation and storage might be due to conversion of organic acid into reducing sugars during fruit ripening process (Figure 2). Malic acid is the major acid in apple juice plays a major role in flavor attribute (Ben et al., 1985).

Level of TSS: TA ratio increased during transportation and storage (Figure 2). Higher TSS: TA ratio (74.7) was recorded 3 ply Beer cartons while lower (59.0-62.2) in others treatments. This might be due to conversion of organic acid into sugars during fruit ripening process. Excessive increase in TSS: TA ratio in 3 ply Beer cartons may cause imbalance resulting poor sensory rating due to development of slight bitterness and mealiness. Due to absence of ventilation in 3 ply Beer cartons, anaerobic condition favors quick fermentation of fruits. Mahajan (1994) reported that many biochemical changes take place during storage which disturbs the TSS: TA ratio ultimately rendering the fruit unacceptable.

3.5 Fruit firmness, starch index and blush intensity

At maturity stage, fruit firmness was 8.1 kg/cm². Firmness of fruits decreased after transportation and storage (Figure 2). Lowest firmness was recorded in 3 ply Beer cartons (5.8 kg/cm²) while higher in other treatments. This evidence indicates that fruits packed in 3 ply Beer cartons degraded faster due to low aeration as well as more physical damage during transportation. A major quality problem of apples in the market is soft fruit which is typically assessed using a puncture test also known as flesh firmness. Softening is generally considered an undesirable ripening process in apple fruit, as firmer apples tend to be juicier, crispier, crunchier and less mealy than softer fruit. Softening of flesh during storage could be due to degradation of soluble pectin by high activity of endo-poly-galacturonase enzyme in fruits (Jason et al., 2002; and Harker et al., 2002). Jaeger et al. (1998) reported that apples that have crisp, juicy texture and prolong shelf life are highly preferred by the consumers.

At maturity stage, average starch index of apple fruits was 4.1. Starch content decreased during transportation and storage (Figure 2). Higher starch index (5.9) was recorded in 3 ply Beer cartons followed by 7 ply FDD CFB boxes (5.6) while lower (5.5) in other treatments. Higher starch index in fruits packed in 3 ply Beer cartons might be due to more physical damage resulted more conversion of starch into reducing sugars. At maturity stage, blush intensity was 65.0% with respect to packaging materials. Blush intensity increased during transportation and storage (Figure 2). Highest blush intensity (80.0%) in 3 ply Beer cartons while lowest (75.0-77.5%) in other treatments, this might be due to absence of ventilation by which anaerobic condition favors fermentation and conversion of chlorophyll into colored pigments.

3.6 Economic analysis

Minimum postharvest loss (6.6%) was observed in 7 ply 180 psi CFB boxes (improved practice) while maximum (22.4%) in 3 ply Beer cartons (existing practice). Lowest net return (NRs 185000 per truckload) was observed in 3 ply Beer cartons while highest (NRs 263750 per truckload) in 7 ply 180 psi CFB boxes. With prospects of loss reduction, improved packaging method sounds the best technology. PLW (4.4%), spoilage loss (13.5%), losses due to 50% decrease in the market value of fruits was 4.5% in 3 ply Beer cartons making a total of 22.4% loss which was reduced to 6.6% in 7 ply 180 psi CFB boxes. Economic analysis shows that higher BC Ratio (1.8) was obtained in 7 ply 180 psi CFB boxes while lower (1.6) in 3 ply Beer cartons. If the traders replace conventional system of packaging fruits in 3 ply Beer carton by improved one, they can gain additional benefit of NRs 78750 (USD 757) per truckload (Table 3).

4 Conclusions

Based on above evidence, we can conclude that CFB box recommended by FFD (7 ply CFB boxes of 20 kg capacity) was not acceptable container because of more postharvest loss, inconvenience in handling and unaffordable price for the consumers. CFB box of 10 kg capacity with 7 ply 180 psi bursting strength was identified as most desirable, efficacious and appropriate container easily accepted by farmers groups, cooperatives, traders and consumers in Nepalese context for packaging and long distance transportation of fruits from production sites to distant markets by truck in rough road because of convenience in handling and stacking; minimum scratching, brushing and spoilage damages; high shock bearing capacity, high storability; better retention of appearance, crispiness, taste, aroma and fruit firmness; high BC ratio and affordable price for consumers.

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