Effect of Post-Harvest Handling and Ripening Methods on Quality and Shelf-Life of Banana

Banana (Musa spp.) is a highly perishable fruit that requires special handling. In Eritrea, post-harvest handling practices are characterized to be poor and as a result, poor fruit quality and high post-harvest loss are common. Thus, the purpose of this study was to evaluate the effect of different post-harvest handling and ripening methods on quality and shelf-life of banana. A Complete Randomized Design (CRD) was used for evaluating a combination of two levels of post-harvest handling and four ripening methods in a factorial combination conducted in the laboratory of Horticulture at Hamelmalo Agricultural College. Peel colour change, physiological weight loss, pulp to peel ratio, total soluble solids (TSS), pulp pH, ripening period and shelf life were parameters studied. The results showed fruits treated with ripened tomato showed improved characteristics in all parameters compared to those treated with smoke from kerosene burning or mixed with moringa leaf. Similarly, fruits brought directly from the farm were better than those collected from the ripening room after passing the conventional post-harvest handling. Based on the results of this study, it can be concluded that ripening of banana with the help of tomato improves fruit quality and shelf life. Thus, it can be a safe and better alternative to smoking from kerosene burning. While moringa leaf has no potential as an alternative.


Introduction
Banana is one of the most economical and important fruits of the world, which undergoes rapid physiological deterioration after harvest [1]. Globally, it is the fourth most important crop in food market next to rice, wheat, and maize [2]. Banana constitutes significant roles in food security, employment, economic development, and nutrition for many developing countries [3]. In Eritrea, the banana is one of the most important fruit crops. It is mainly grown in the western lowlands of the country and it covers the highest area than any other fruit crop predominantly harvested year-round [4]. In 1964 banana production in Eritrea was at its highest level and was exported to Europe, the Middle East, and neighboring East African countries. However, it ceased in 1974 [5] because of the war for independence, drought, low-quality production, and failure to compete with other exporting countries [6].
Bananas are highly perishable climacteric fruits usually harvested at their mature green stage and artificially ripen in a ripening room [7]. As the fruit is harvested at its green mature stage artificial ripening is a very important aspect at commercial levels [8]. The ripening process of banana fruits involves numerous biochemical and physiological changes [8]. Under natural fruit ripening conditions, ethylene gas is auto-stimulated by the ripening fruits. However, the fruits ripen slowly and unevenly, leading to high weight loss and failure to develop good colour and aroma [9]. Thus unripe bananas need to be exposed to an exogenous source of ethylene gas for the assurance of firm pulp texture, good flavour, and bright peel colour [10].
In Eritrea, the post-harvest handling of banana is very poor, with few treatments being given to control damage, diseases, and quality, as a result, poorquality bananas with external bruising are sold in the local markets [5]. Results of a survey carried out in 2017/2018 (unpublished data) showed, majority of the harvested fruits are transported to wholesaler markets located mainly in Asmara and other major cities of the country which are far from the production areas.
Fruits are transported long distance using inappropriate means of transportation on mostly rough roads and are stored under poor storage conditions. Bunches are loaded on open trucks and then covered with banana leaves for transportation [11]. Such kind of transportation system leads to mechanical damages and post-harvest losses in banana supply chains [12] [13] and [14]. During loading and unloading of bunches, laborers usually stand, sit, or walk on the fruits. As a result, most of the fruits get damaged leading to reduced fruit quality, and shelf life is also affected [11]. Then they are stored under poor storage conditions for ripening purposes with less attention is given to control the temperature, relative humidity, and air circulation of ripening rooms. The farmers and sellers also have limited knowledge of post-harvest handling practices of bananas. All these have aggregated negative impacts on the post-harvest losses and delivery of poor quality and external bruised fruits to the local markets [4]. This poor handling reflects lack of awareness in the whole post-harvest handling system including lack of appropriate harvesting technology, transportation, storage, and ripening facilities [11].
The 2017/2018 survey results (unpublished data) also show that the ripening system followed in Eritrea in which smoke generated from kerosene burning  In this smoke-based system, banana fruits   are separated from the bunch during unloading and packed into wooden boxes   and kept in air-tight rooms where kerosene stove is burned for about 24 to 48 hrs depending on the external environmental conditions. Less attention is given to controlling temperature, relative humidity and air circulation inside the ripening rooms. All these will have a cumulative effect on the fruit quality and shelf life of bananas. On the other hand, lack of infrastructure facilities has limited the implementation of improved ripening systems and storage practices.
Banana ripening with ethylene is a well-known process; while the effectiveness of the traditional ripening methods practiced in Eritrea has not yet been evaluated from the fruit quality and shelf life point of view [11]. Under the current economic situation and lack of improved technologies in Eritrea, ethylene-based ripening methods are unlikely to be expanded. In addition to that, cheaper alternatives such as ethephon and acetylene which are widely used in many other poor countries have been banned due to the negative effects on human health [15]. Therefore, it is important to search for better alternative methods that have no negative effect on human health and at least can be applied at a small-scale ripening system which may have collective contribution towards improving the quality of banana fruits displayed in local markets. Thus, this study was designed to assess the currently practiced post-harvest handling method and the smoke from kerosene burning-based ripening methods compared to other methods and find out a better and safer alternative for improving the quality and shelf life of banana.

Site Description
The experiment was conducted in the Horticulture Laboratory of Hamelmalo Agricultural College (HAC), located 13 km north of Keren, Eritrea. Average daily temperature and relative humidity in the laboratory were recorded using a digital Thermo hygrometer (Model IM397, Temp Tec). The temperature and relative humidity ranged from 20.01˚C to 25.79˚C and 58.25% to 71.5% respectively during the ripening period.

Banana Fruit
Banana fruits of Dwarf Cavendish were collected from two sources. The first group of fruits (PH1) was harvested by the researcher directly from the farm and was handled properly until it has reached the laboratory in the college in a way that post-harvest damage was avoided or kept as minimum as possible. The second group of fruits (PH2) was of the same variety and from the same farm, but harvested by the farmer and transported by the wholesalers to the ripening room in Keren (the nearest city to the laboratory). This allowed the fruits to pass all the common post-harvest handling practices applied in Eritrea. As soon as the fruits reached the ripening room, samples were collected and transported to

Grading, Packaging and Storage of Banana in the Laboratory
When the banana fruits reached the laboratory, they were carefully unloaded, and to remove the field heat they were stored in a cool place (at 20˚C) for about two hours. Then fruits were graded based on size, maturity stage, and level of damage. Following that, damaged fruits were removed to avoid spoilage of the other fruits, and the remaining good fruits were assigned to the treatments.

Experimental Design
The

Data Collection
Observations were recorded three times from three sample fingers during the storage period. They were collected on the first, seventh, and fourteenth day starting from the first storage date to determine the quality parameters of fruits as follows: Peel colour change: The number of days taken to reach different stages of colour during storage and ripening was recorded daily and total days taken to reach the sixth stage of peel colour were counted to determine the progress. A Where: 1 = green; 2 = green with yellow tracks; 3 = more green than yellow; 4 = more yellow than green; 5 = yellow with green tips; 6 = all yellow and 7 = yellow flecked with black spots [16].
Physiological Weight Loss (PWL): Randomly selected hands of fruits from each treatment were weighted on day one to determine the initial weight, then the same hands of fruits were weighted again after seven and fourteen days of storage to determine the percentage of weight losses due to storage which was calculated as the difference between initial and final weight determined by [17].
A digital balance (Model Adventurer Pro Av4101, BLANC-LABO S.A.) was used for weighing the fruits.
Pulp to peel ratio: The pulp to peel ratios of bananas were recorded by weighting the pulp, and peel of the fruits separately at days one, seven and 14 after storage. The ratio was determined by dividing pulp weight to the peel weight [16].
Total Soluble Solids (TSS): Total soluble solids of banana pulp were measured three times at days one, seven and 14. According to [18], banana juice was

Data Analysis
Data recorded for the different variables from the experiment was subject to the analysis of variance (ANOVA) using GENSTAT Discovery Edition 4 software,

Peel Colour Change
Peel colour change from green to yellow is a result of chlorophyll degradation and is the most important eating criterion used by consumers to determine fruit ripening [1] and [19]. The results of the current study showed significant differences (p < 0.001) among the different ripening methods for attaining stage 6, the  Figure 2). Fruits ripened using smoking from kerosene burning attained the acceptable peel colour change after six days of storage followed by bananas treated with moringa leaf with a mean of 6.17 days after storage. The difference between the smoking and moringa treatments was not significant. Fruits ripened using ripened tomato was the slowest (7.67 days) to reach stage six ( Table 1). The results are in agreement with [20] and [10] who used smoke from kerosene and straw respectively. Similarly, [2] reported faster peel colour change (7 days after storage) of fruits treated with kerosene smoking compared to ethrel treated. [20] related the faster colour change in smoke-treated banana fruits to increased temperature from the kerosene burner in addition to ethylene. However, this is in contrast to the known fact that chlorophyll degradation slows or stops at high temperature [1]. [21] also found no effect of temperature and applied ethylene on colour change.
During ripening, there is a link between chromoplast development and ethylene. This is due to the carotenoid pathway being under positive control of ethylene [22]. The amount of ethylene required to start ripening is as little as 0.01 uL/L, however; the magnitude varies by the amount applied [19] and [23].
Therefore, the faster colouration observed on smoking from kerosene is probably due to the higher amount of ethylene combusted from kerosene burning compared to the other sources. On the other hand, [24] reported that an in-   There was a significant difference (p < 0.001) in peel colour change between the two post-harvest handling methods (Table 1). Fruits collected from the ripening room (PH2) were faster to reach the 6 th stage of colour (6.25 days) compared to fruits brought directly from the farm with reduced post-harvest damage (PH1) which reached the 6 th colour stage in an average of 7.08 days from storage ( Table 1). The difference is due to post-harvest handling of bananas in Eritrea which includes few treatments to control damage resulting in fruits reaching ripening room with external bruising [5]. Since fruits collected from the ripening room (PH2) passed the conventional handling conditions, they normally are subject to more physical damage compared to those handled with care (PH1). Consequently, fruits from PH2 are expected to produce more ethylene during the climacteric phase leading to earlier coloration.  (Table 1). This indicates that limited amount of ethylene is produced by the natural ethylene generating fruits like tomato to initiate ripening process.

Physiological Weight Loss (PWL)
The result in Table 2 shows both ripening and post-harvest handling methods had significant effects on physiological weight loss recorded at 7 th (p < 0.001 and p = 0.007) and 14 days (p < 0.001) after storage. Table 2 also shows the interaction between the ripening method and post-harvest handling had significant effect (p < 0.001) on physiological weight loss at14 but not at seven days after storage. We observed ripening with smoking using kerosene burning with mean values of 11% and 16.15% at seven and 14 days after storage respectively was the highest in physiological weight loss among all ripening methods in both postharvest handling methods tested in this study. While fruits ripened with the help of ripened tomato with a mean value of 7.8% at seven days after storage and 11.83% at 14 days after storage was the lowest ( Table 2). Physiological weight loss of fruit is a direct result of water loss which is due to external and internal factors such as temperature, relative humidity, and peel permeability [1]. [21] reported an increase in weight loss in banana due to the interaction effect of applied ethylene and increased temperature. This may interpret the highest weight losses recorded by the kerosene burning ripening method of the current study  where burning of kerosene resulted in higher temperature. In addition to that amount of ethylene from combusting kerosene is higher than tomato and moringa leaf. Besides, kerosene combusting might have increased ethylene production and ethylene gas intern triggered the initiation of ripening and senescence [7]. However, the effect of smoking from kerosene burning on physiological weight loss percentage in this study was different from previous studies. It was much lower than [20] who reported 15% at seven days and 20% at 14 days, but higher than the 8.10% after seven days of storage reported by [2].
Except for fruits treated with moringa leaf at seven and smoking from kerosene burning at 14 days after storage, fruits collected from the ripening room (PH2) had significantly higher weight loss in all treatments. Accelerated weight loss is due to the breakdown of cellular walls and increased permeability of the outer tissues to water vapour as a result of mechanical injuries [1]. This explains the higher loss in PH2 in which fruits had higher probability of mechanical damage between harvest and reaching the ripening room in city [5]. Similarly, [13] reported that inappropriate transportation, loading, and unloading methods cause mechanical damages and subsequently PWL.

Pulp to Peel Ratio
Significant difference (p < 0.001) was observed among the different ripening methods after 7 th and 14 days of storage. The highest pulp to peel ratio (1.96 and 3.18) measured at 7 and 14 days respectively was on fruits treated with smoking from kerosene burning. The lowest ratio after 7 and 14 days of storage (1.67 and 2.50 respectively) was recorded on fruits treated with ripened tomato (Table 3).
Similar results were reported by [20] who found a higher pulp to peel ratio of bananas ripened with smoking from kerosene burning. The increase in pulp to peel ratio during ripening is related to an increased sugar concentration of the pulp tissues [25] and losses of water from the peel to the air and moving towards the fruit pulp [26] [27] and [28].
Post-harvest handling methods showed significant difference (p < 0.001) only at 14 days after storage in which the ratio was higher in the PH2 treatment (3.01) compared to a ratio of 2.63 in PH1 ( Table 3). The interaction between ripening methods and post-harvest handling also had significant effect on pulp to peel ratio at 7 th (p < 0.001) and 14 (p = 0.017) days after storage. The highest pulp to peel ratio (3.22) was obtained after 14 days of storage in fruits treated with smoking from kerosene burning and brought from the ripening room (PH2) followed by fruits treated by the same method and brought directly from the farm (PH1) which scored a ratio of 3.14. While the lowest pulp to peel ratio on each of the two post-harvest handling practices (2.31 and 2.70) was obtained from fruits treated with ripened tomato after 14 days of storage (Table 3).
In the present study, with the advance of ripening the peel weight continued to decrease whereas the pulp weight continued to increase causing an increase in pulp to peel ratio (from 47.58% to 54.10%). This was in agreement with previous B. M. Abraham et al.  results obtained by [29], who found an increase in pulp to peel ratio with the advance from ripening stage five to stage seven in which an increase in pulp moisture content was observed indicating to movement of water from peel to  [28] and [29]. Higher storage temperature, lower humidity, and applied ethylene were also found to increase pulp to peel ratio [21] and [28]. Bananas treated with smoke from kerosene burning are expected to have higher temperature and ethylene compared to the other treatments. While the conventional post-harvest handling method (PH2) in which banana fruits were subject to various damages during harvesting, loading, unloading and transportation until it reaches the ripening room [5] is expected to have more moisture content loss from the peel [20]. This explains the high pulp to peel ratio in the smoke treated and the conventional post-harvest handling method (PH2) applied in the current study.

Total Soluble Solids (TSS)
The results in the current study (Table 4) Table 4).
The highest reading after seven days of storage was observed on fruits treated with smoke from kerosene burning (15.28 ˚Brix), while the lowest reading was observed on fruits treated with moringa leaf (12.77 ˚Brix). On the other hand, fruits treated with smoking from kerosene burning showed the highest TSS change percentage (58.67%) between the initial and seven days after storage and the lowest (6.74%) during the storage period from the seventh to 14 th days of storage compared to the rest three methods (Table 4). This is due to the conversion of starch to sugar in banana that occurs during the climacteric phase [1] and the increase in TSS during ripening is a result of an increase in the concentration of organic solutes as a consequence of water loss and hydrolysis of starch into soluble sugars such as sucrose, glucose, and fructose [29]. Therefore, this interprets the higher (initial to seven days after storage) and the lower (between seventh and 14 th days of storage) differences shown by the smoke from kerosene burning ripening method which ripened earlier and it entered the senescence stage where no more starch to be converted to sugar. Similar results were reported by [20] who found TSS values in smoke treated dwarf Cavendish bananas to increase early in the second day and start declining after eight days. The faster change in TSS of the smoke-treated bananas is due to the exogenous ethylene and the heat from kerosene burning [20]. However, other studies showed source of ethylene [30] and temperature and ethylene [21] had no effect on TSS at 6 th colour stage.

Pulp pH
The effect of ripening methods on pulp pH of banana at both the 7 th and 14 th days of storage was significant (p < 0.001). Post-harvest handling methods and their interaction with ripening methods had no effect (p > 0.05) on pulp pH at both the 7 th and 14 th days of storage (Table 5). On the seventh day of storage, the highest pH value (5.63) was obtained from fruits treated with plastic cover while   (Table 5). On the 14 th day of storage, the highest value (4.87) was obtained from fruits treated with ripened tomato, and the lowest value (4.37) was obtained from fruits treated with moringa leaf ( Table 5). The lower pH of the banana treated with smoking from kerosene could be due to the faster advance in ripening [20] and the effect of temperature [23].
In banana pulp pH quickly declines in response to increasing ripeness, however, the magnitude differs according to variety [16]. The increase in titratable acidity and decrease of pulp pH occurs until peel colour stage three and then acidity drops and pH increases and this coincides with the climacteric respiration [19], however, number of days to reach maximum titratable acidity may vary based on difference in ripening methods. [20] found it to be 4 and 6 days for smoking from kerosene and ethephon treated bananas respectively and more than eight days for other ripening methods, while [2] recorded maximum titrable acidity and lowest pH by treating bananas with smoking from kerosene burning at 7 days after storage. With aging, depletion of sugars as a respiratory substrate and the switch to catabolism of proteins occurs, and this leads to release of free amino groups resulting in a shift to a more alkaline pH in the cell sap [19]. However, in the current study, the pH of the pulp steadily decreased with the increase in storage periods from mean initial pH of 6.58 to 5.58 (17.92%) after seven days and 4.87 (14.58%) after 14 days after storage for fruits treated with ripened tomato (Table 5). In agreement with this finding, [31] reported a pulp pH decrease of plantain from 6.18 to 4.92 during the ripening process. The decline in pH with an advance in ripening is in agreement with [2].
Similarly, [27] found in bananas treated with different concentrations of ethrel the pH gradually decreased with the advance in ripening and when the fruit reached optimum ripening six days after storage, the pH was 4.8. [32] found the increase and decrease in pH and titrable acidity to depend on banana variety.
They observed different trends, some varieties showed a complete decrease in pH from green stage to fully yellow stage (this is the case of the current study), others showed first decrease and then an increase at full ripe, while the last group increase, decrease and again increase. Some previous studies showed ethylene source has no effect on titrable acidity and pH of banana pulp [23] and [30].

Ripening Period and Shelf Life
There were significant differences (p < 0.001) of ripening period and shelf life among all the ripening methods. The shortest ripening period (3.83 days) and shelf life (9.34 days) were observed on fruits treated with smoking from kerosene burning, while fruits treated with ripened tomato attained full ripening stage after 5.5days of storage and had the highest shelf life of 12.5 days (  (Table 6). The interaction effect of post-harvest handling and ripening methods was not significant on the ripening period (p = 0.610) however, it was affected significantly for shelf life (p = 0.045) ( Table 6).
The results of the current study were in agreement with the finding of [20] who found banana fruits treated with smoke from kerosene to have a shorter ripening period and referred that to the effect of exogenous ethylene and high temperature resulted from kerosene burning which may enhance the physico-chemical changes. The smoke from burning kerosene increases the temperature inside the chamber [27] and releases ethylene and other trace gases like acetylene and carbon monoxide [7]. Similarly, [21] found the storage period to decrease with increased temperature and the application of ethylene. This indicates that the difference in the length of both ripening period and shelf life of banana fruits treated with different ripening methods is due to differences in the amount of ethylene and temperature. Fruits treated with ripened tomato produced relatively limited amount of ethylene [19], which is expected to delay the ripening process [15]. [30] also found difference in the effect of sources of exogenous ethylene application on the ripening period of banana, where avocado with higher ethylene releasing capacity had more impact compared to tomato  Mechanical damage is one of the major factors leading to the post-harvest deterioration of banana. This is a result of poor packaging and handling of packed fruits during loading and unloading, shaking during transportation, and other factors [16]. Post-harvest handling in Eritrea includes few treatments to control damage [5]. Mechanically damaged banana fruits generally ripen earlier than non-damaged fruits [16]. This explains why ripening period and shelf life in the current study was shorter in the commonly followed post-harvest handling practices (PH2) compared to the fruits collected by the researcher from the farm and transported directly to the laboratory with proper packaging and all possible care to reduce mechanical damage (PH1).

Conclusion
From the results of this study, it can be concluded that the currently practiced post-harvest handling and smoking-based ripening methods have negative impacts on quality and shelf life of banana. On the other hand, the use of ripened tomato as a ripening agent combined with the application of proper handling that reduces damage on fruits during harvesting, packing, transportation, loading, and unloading can improve both internal and external fruit quality as well as shelf life. Therefore, tomato can serve as a better and safer alternative to the use of kerosene burning in banana ripening at least for small local ripening rooms.
In contrast, moringa leaf may not have any potential to serve as an alternative to kerosene burning-based ripening methods.