ABSTRACT
Tomato (Lycopersicon esculentum Mill.) is one of the most widely cultivated and extensively consumed horticultural crops in Ethiopia. Tomato has a limited shelf life at ambient conditions, is highly perishable fruit and it changes continuously after harvesting. There are many postharvest technologies that extend the marketable life of fruits and vegetables. The study was to evaluate the effect of packing materials on shelf-life and quality of tomato fruit at Samara, Northeastern rift valley of Ethiopia. Three types of packaging material were taken, that is, low density perforated and non-perforated polyethylene bag, carton and without packaging as a control. Physiological weight loss, decay percentage, color score, overall acceptability and percentage marketability were assessed for every three days of storage. The result revealed that packaging had a significant effect on physiological weight loss, decay percentage, color score, overall acceptability and marketability. The lowest physiological weight loss of 0.29 and 1.72% was recorded from non-perforated polyethylene bag at 3 and 6 days of storage, respectively; further increase in the storage period with the lowest physiological weight loss (24.57%) was recorded from perforate polyethylene bag. Moreover, the lowest (0.00%) decay percentage and the highest (60%) marketability were recorded from perforated polyethylene bag on day 9 of storage. Decay loss of tomato fruits at the end of storage was much (60%) higher on non-perforated polyethylene bag than the perforated and carton (0.00%). Color and overall acceptability score of tomato fruit was also maximum on perforated polyethylene bag and the lowest was obtained from control treatment at the end of storage. It can, thus, be concluded that packaging of tomato fruits in perforated polyethylene bags resulted in extending storage-life with better-quality of the produce in samara area.
Key words: Tomato fruit, packaging material, storage life, quality.
Tomato is one of the most popular and widely grown vegetable crops in the world. It belongs to the family Solanaceae. According to Mohan et al. (2016) and FAOSTAT (2015), tomato (Solanum lycopersicum Mill.), with a total production of around 160 million tons per year, is the second most important source of nourishment (after potatoes) for the World’s population. In Ethiopia, there is no exact information as to when tomato was first introduced; however, the crop is cultivated in different major growing areas of the country. In 2015 cropping calendar, tomato production in Ethiopia was about 22,788 tons from harvested area of 3,677 ha (CSA, 2015). Despite the importance of this crop, the production and productivity is constrained by different biophysical and socio-economic reasons, such as lack of adapted and improved tomato technologies, land shortage, inadequate knowledge on production and management (processing) systems, poor extension services, poor marketing system and proper utilization of the crop are a few to mention (Mersha, 2008).
Tomato is one of the very perishable fruit and it changes continuously after harvesting. Depending on the humidity and temperature it ripens very soon, ultimately resulted in poor quality as the fruit become soft and unacceptable (Ullah, 2009). Hence, it must be harvested at the right time because overripe tomato is more susceptible to physical injury than ripe and pink ones (Ullah, 2009). After harvest, ripening continues and tomatoes can became overripe very rapidly. Tomato is a climacteric fruit, having respiratory peak during their ripening process. Being a climacteric and perishable vegetable, tomatoes have a very short life span usually 2 to 3 weeks. The post-harvest (post production) and marketing system is a chain of interconnected activities from the time of harvest to the delivery of the food to the consumer often referred to as “farm to fork” (Zorya et al., 2011). Post-harvest losses refer to the measurable quantitative and qualitative food loss in the postharvest system (Aramyan and van Gogh, 2014; FAO, 2013). Losses in fresh horticultural produce are directly related to quality degradation. Quality loss is the result of improper handling and transportation in marketing of produce (Kumar et al., 2015).
Postharvest losses which average between 24 and 40% in developing countries, and between 2 and 20% in developed countries are a major source of waste. High levels of waste result in higher prices for fresh produce, and the farmer increasingly facing poverty (Rosa, 2006). Thus, the reduction of post-harvest losses of perishables is of major importance when striving for improved food security in developing countries (Kader, 2005). Gustavsson et al. (2011) revealed that world postharvest losses of fruits and vegetables range from 30 to 40% or even greater in developing countries. High quality tomatoes have a firm, uniform and shiny color, and good appearance, without signs of mechanical injuries, shriveling and bruise. The major causes of post-harvest losses are decay of fruit, external injury during harvesting, handling and storage of tomato fruits. In addition, environmental factors such as soil type, temperature, frost and rainy weather during harvest can cause severe effect on storage life and quality of tomatoes (Bachmann and Earles, 2000).
Water comprises 90% of the fresh weight of tomato fruit and the size of the fruit is influenced by the availability of water to the plant. The large amount of water also makes the fruit perishable. Also, quality of most fruits and vegetables is affected by water loss during storage, which depends on the temperature and relative humidity conditions (Perez et al., 2003). The rapid quality loss at relatively short period of 4 to 7 days is an efficient means of storing the fruits to reduce post-harvest losses and improve the quality and acceptability in the consumer market. Tomato fruit kept within sealed packages resulted in an atmosphere with high CO2 and low O2 content. These conditions retained flesh firmness, low acidity and soluble solids concentration and delayed fruit lycopene (Sabir and Agar, 2011). Among the various techniques developed to extend fruit postharvest life, the use of plastic film is growing in importance because it is convenient in the many different conditions throughout the chain of handling from producer to consumer. In Ethiopia, research experience on tomato was started in along times at major research centers. Postharvest losses are often more significant than fresh fruit and vegetables losses that occur in the field.
During storage, fruit and vegetables deteriorate through the action of spoilage microorganisms, which become activated because of the changing physiological state of the fruit and vegetables. The quality of fresh tomatoes is mainly determined by appearance (colour, visual aspects), firmness, flavour and nutritive value (Giovannoni, 2001). Consumers measure the quality of tomato fruit primarily by three factors: Physical appearance (color, size, shape, defects, and decay), firmness, and flavor. Fruit quality is significantly affected by stage of ripeness when removed from the plant, number of times handled, and storage temperature and time. However, the research developed in the past and current time mainly focused on varietal development, fertilizer trial and agronomic practices in different centers. As a result, the quality of fruits is reduced and considerable amount is wasted, from harvesting to final consumption. Weight loss, decay and rapid deterioration are often major factors that determine the storage and marketability duration of fruit and vegetables.
These factors depend among others on fruit quality and physiological stage and the atmosphere surrounding the fruit. Therefore, it is evident from different scholars that, even though these pre-harvest practices are compulsory for its quality, they must be coupled with the postharvest management practices. Premature harvesting, poor storage facilities, lack of infrastructure, lack of processing facilities, and inadequate market facilities cause high food losses in developing countries along the entire food supply chain (Aulakh et al., 2013). This loss can be kept in minimum by improving mature management practices. Premature harvesting, poor storage facilities, lack of infrastructure, lack of processing green stage at Samara, Northeastern rift valley of Ethiopia. extend the storage life of tomato fruits harvested at study was to evaluate the different packaging materials to appropriate packaging materials. The objective of this postharvest handling techniques through the use of appropriate packaging materials. The objective of this study was to evaluate the different packaging materials to extend the storage life of tomato fruits harvested at mature green stage at Samara, Northeastern rift valley of Ethiopia.
Descriptive of study area
The study was conducted at Samara University, College of Dry Land Agriculture, Samara, Ethiopia. It is located at an altitude of 426 m.a.s.l, latitude of 11.430 E and longitude of 41°Northeastern rift valley of Ethiopia. Samara is the hottest place in Ethiopia which is located 588 km north of Addis Ababa which is characterized by an arid and semi-arid climate with low and erratic rainfall. The mean annual rainfall of the area is below 500 mm and the average annual temperature is about 19 to 35°C; whereas, in the hottest months (May, June, July, August and September) the temperature may reach up to 46°C.
Experimental materials and design
At mature green stage of local cultivar of tomatoes, fruits were purchased at Logia market from the wholesaler at Logia (Samara) market. The fruit was selected by considering uniformity with regard to color, shape, and size and free from defect. The treatment consisted of 3 different packaging of carton, a low density perforated and non-perforated polyethylene bag and control (without packaging). The experiment was having a total of 12 numbers of observations. The design of the experiment used was complete randomized design (CRD) with three replications. In each treatment there were 10 tomato fruits with a total of 120 fruits per the experiment. In accordance with specifications of the design, each treatment was assigned randomly to the experimental units within a replication.
Sample preparation
Washing the fruit was done with water containing sodium hypochlorite (NaOCl) solution with a concentration of 100 mg/L at 20°C for 5 min to reduce microbial population. After surface drying with clean cloth, 10 tomato fruits per treatments were weighted by sensitive balance. The weighted tomato fruits were packed in different packaging treatments with three replications at ambient condition (35°C).
Methods of analysis
Physiological weight loss, decay percentage, color score; overall acceptability and percentage marketability were collected during the experiment period from the total population for every 3 days of interval (0, 3, 6 and 9 days). Physical and subjective data was taken from the population of tomato fruits during the storage period as follows.
Physiological weight loss (PWL):
The physiological weight loss was determined using the methods described by Workneh et al. (2011a). The following formula was used to calculate successive weight loss expressed as percentage for the respective treatments.
Decay loss: Any decay loss during storage was assessed and the type of the loss was identified. The percentage of decayed fruits was determined by dividing number of decayed fruits to number of unmarketable fruits. The disease type was also identified by the help of colored photographs found in Dadzie and Orchard (1997).
Color and overall acceptability score: Color was measured by comparing with the color chart described by Dadzie and Orchard (1997). It was determined by counting (20 respondents) the number of respondents from 0 to 5 scoring. A 1-5 rating with 0 = poor, 2 = fair, 3 = good, and 4 = very good and 5 = excellent and finally the mean data was analyzed. On the same way, overall acceptability was also assessed by the above selected respondents and the result was taken by the 1-5 rating similar with marketability.
Percentage of marketability: The marketable quality of fruits was subjectively assessed by procedure of Workneh et al. (2011a, b) with a slight modification. These descriptive quality attributes were determined subjectively by observing the level of visible mould growth, decay, shriveling, smoothness, and shininess of fruits with (20 respondents). A 1-5 rating, with1 = unusable, 2 = usable, 3 = fair, 4 = good, 5 = excellent was used to evaluate the fruit quality. Fruits receiving a rating 3 and above were considered as marketable. The numbers of marketable fruits were used as a measure to calculate the percentage of marketable fruits during storage. After subjectively assessing the product, it was calculated using the following formula.
Statistical analysis
The data obtained was statistically analyzed for analysis of variance (ANOVA) using General Linear Model (GLM) in SAS 9.1 version; whereas mean separation was made based on LSD at 5% level of significance (SAS, 2002).
Effect of packaging materials on shelf life and quality of tomato fruits
Physiological weight loss (PWL)
PWL (%) was significantly influenced by packaging treatments. On the first 3 to 6 days of packaging, the highest PWL (5.23 and 8.04) was recorded from control treatment and it was similar with carton (5.21 and 7.65%); on the same days of packaging the lowest PWL (0.29 and 1.72%) was recorded on fruits packed in non-perforated polyethylene bag. Moreover, on day 9 of packaging, the highest PWL (57.22%) was recorded with control treatment whereas, the lowest was recorded from perforated plastic (Table 1). At 3 to 6 days of storage, fruits kept in perforated and non-perforated plastic films had the lowest weight loss than carton and control. Control not only displayed rapid increase in weight loss (%) showing highest weight loss percentage at the end of storage period as compare to all other treatments at that stage. This is due to the uncontrolled ripening in control fruits as ripening in tomatoes is climacteric which showed a sudden increase in ethylene production and respiration rate (Anon, 2004a). This higher respiration rate also resulted in higher transpiration of water from the fruit surface which led to increase in percentage of weight loss (Sabir et al., 2004).
Thus, physiological weight loss in tomato fruits was influenced by packaging. The lowest PWL was recorded from non-perforated polyethylene bag at 3 to 6 days of storage and from perforated plastic in 9 days of storage. This might be due to the fact that, polyethylene plastic protects the fruits from adverse conditions by avoiding mechanical damage, reducing moisture loss, providing beneficial modified atmosphere and preventing pilferage as cited by Basel et al. (2002). Similarly, Thompson (2001) reported that weight loss of fruits in polyethylene bags was far low than from unpackaged fruits in which after 4 weeks of storage the weight loss was found as 1.8 and 2.1%, respectively, for fruit stored in 0.0375 and 0.05 mm bags and 12.2% for fruit stored without wrapping. Moreover, as cited by Prolux et al. (2005), high storage temperature leads to accelerated water loss and subsequently to shriveling and softening of the fruit. Furthermore, lower weight loss of fruits in the package could be due to slow rate of ripening and prevention of excessive moisture loss (Tilahun and Kebede, 2004).
Decay percentage
Table 2 revealed that, until 3 days of packaging, none of the tomato fruits became decayed which could be due to the low relative humidity of the storage room (56%) which limits the multiplication of microorganism. Decay percentage was significantly influenced by the different packaging materials. The highest decay percentage of 36.67 and 60% was recorded from non-perforated polyethylene bag on 6 and 9 days of storage, respectively. The lowest (0.00%) decay percentage was recorded from perforated polyethylene bag (Table 2). The result of the present study showed that, un-marketability of fruits from these packages was totally due to decay losses caused by decay microorganisms. Similarly, Mir and Beaudry (2000) revealed that, packaging isolates the product from the external environment and helps to ensure conditions that, at least reduce exposure to pathogens and contaminants there extends the shelf life of the produce but it does not reduce the distribution of microorganism inside the packaging materials.
In addition, Paull (1993) showed that, the termination of shelf life of tomato stored at ambient environment was determined by shriveling, over ripening, discoloration and mold growth. Shriveling and mold growth were predominant on the control fruits and polyethylene packaged fruits, respectively, with mold growth being more in non-perforated plastics. Faster transpiration rate at relatively higher temperature (35°C) may result in shriveling of non-packaged fruits. Furthermore, higher respiration rate at higher temperature (35°C) may lead to senescence because the stored food reserve which provides energy could be exhausted. On the other hand, condensation of water vapor, which may lead to the build-up of mold growth, may occur in the polyethylene bag due to the lower permeability of the film to water vapor (Thompson, 2001).
Color (scores)
It is evident from Table 3 that, color of tomato fruits was remained getting better with advances in ripening. It is clearly shown that as the ripening preceded the color of fruits changed from mature green to red on the base of tomato fruit classifying ripening stages as green, mature green, breaker, turning, pink red and red. From mature green to turning stage, the color of fruits changed with poor to fair. At this stage the chlorophyll pigment start to disappear and beta carotene production was initialized and at maximum (Chiesa et al., 1998a). When stage advances from pink to pink-red, the color of all fruits was in the range of good to very good (scoring above 3 and below 4). At this stage lycopene production has started producing red color and masking the yellow color of beta carotene (Salunkhe and Desai, 1984). However, when fruits advanced from pink red to red stage, the color acceptability of control fruits is shorten (between 4 to 5 days of their storage) as compared to the carton and perforated plastic packed fruits (between 8 to 9 days of their storage), that is, in the range of very good to excellent especially perforated plastic packed tomato fruits showed excellent color scores. This change was due to the action of treatments on the fruits as polyethylene packaging (perforated) helps the color retention as described by Badshah et al. (1997).
Overall acceptability (scores)
Table 3 showed the overall acceptability range of control and treated tomato fruits with respect to the consumer’s preference (trained judges). The present study revealed that control fruits showed, lower overall acceptability as compared to that of treated tomato fruits at 9 days of storage period. At the red stage of ripening (4-5 days), control fruits showed a below overall acceptability scores (3.2), which was due to its rapid turning of unacceptable color and loss of its content due to high temperature (35° C even more) of the surrounding environment. On basis of the overall acceptability, the fruits treated with perforated plastic showed the excellent overall acceptability followed by both carton packed and non-perforated plastic packaging. The results led to a conclusion that the main reason behind this improvement was due to the prevention of fruit from decay organism and the fruit will have stored reserve which is protected from adverse condition (Mir and Beaudry, 2000).
Percentage of marketability
The percentage of marketability of tomato fruit was significantly (p < 0.05) affected by the packaging materials on 9 days of storage period. Table 4 indicated that, highest percentage marketability was recorded on perforated polyethylene bags (80%) and the lowest was obtained from control treatment (46.67%). However, with increase in storage period (9 days) tomato fruits packed only with perforated polyethylene bags and carton were marketable; whereas the highest (60%) percentage of marketability in this period was recorded in perforated polyethylene bags (Table 4). At the beginning of the storage period, the difference between the plastic packaging was insignificant. But, starting from day 6, a significant difference was observed. This may be due to the difference in permeability of plastic films. At the end of the storage period, perforated polyethylene bags maintained marketability of tomato fruits to 60% whereas carton kept to 40% (Table 4).
This difference in marketability of tomato fruits is due to percentage of decayed fruits obtained from non-perforated polyethylene bags. This result is in line with the study of Ben-Yenonshuna (1985) who reported that, packaging of climacteric fruits in low density polyethylene bags delay ripening and softening, and hence improves marketability. These beneficial effects can be explained by the modified atmosphere created inside the package as well as the reduction in water loss (González et al., 2003). Lower respiration and ethylene production rates, reduced ethylene action, delayed ripening and senescence, retarding the growth of decay causing pathogens and insects due to modification of the gas atmosphere inside the package could be possible reason to extend the storage life of fruits (Kader and Rolle, 2004).
Packaging had a significant effect on physiological weight loss, decay percentage, color score, overall acceptability and marketability of tomato fruits. Based on the result of this study it can be concluded that packaging of tomato fruits in perforated low density polyethylene bags resulted in longer shelf life with better-quality of the tomato produce.
The authors have not declared any conflict of interests.
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