Tomatoes (Solanum lycopersicum L.) have a relatively poor storage capability. Green mature fruit can be held for up to two weeks at 18–20 oC and 90–95% Relative Humidity, but for less time under ambient tropical temperatures. Fully ripe tomatoes have only 4 to 7 days' storage life, at 13–15 oC and 90–95% Relative Humidity.13 Thus, affordable and easily applicable preservation technology is highly demanded by small and large holding farmers.
The selection of appropriate PHT demands the understanding of the existing challenge as millions of Ethiopian smallholder farmers produce fruit and vegetable crops for food and income.7 The vegetable crops such as tomato, onion, potato are susceptible for spoilage. Since vegetable crops possessed short life span, technological alternatives are vital. The ultimate intention of this investigation is to select the best technology or technique for preservation tomatoes considering house hold consumption of Ethiopian community from the producer to consumer. Figure 1 elucidates the hierarchical model of decision making process showing the criteria and sub-criteria to select preservation technique for tomato. The post-harvest experts recommended that upon selecting the technique for tomato preservation it is highly desirable to consider Economic feasibility, market opportunity, energy consumption. As per the expert suggestion, we considered economic viability, energy consumption, applicability and value addition as criteria to rank the preservation technologies.
Pairwise comparison of the main-criteria
The pair wise comparison of each criterion was done. The economic viability of a particular technology accounts highest weight (43.9%) and applicability takes 22.6% weight (Fig. 2). Further, energy consumption and value addition account 18.0% and 15.6% respectively. Thus, based on the current practices in Ethiopia one should consider the economic feasibility and applicability of a preservation technology to solve Post-harvest loss of perishable agricultural produces.
Pairwise comparison of the sub-criteria
Figure 3 depicts the pair wise comparison of the sub criteria with respect to the main criteria based on the expert evaluation. In one way or the other, the each preservation technology was evaluated and ranked with respect to the sub criteria. To implement a particular PT capital cost takes highest weight (34.0%) followed by personal skill (15.4%).
For the sustainable benefit of small holding farmers, the PT should be easy to operate with reduced capital cost. The obtained result is in line with the existing situation in Ethiopia. In the country, top priority is given to food security and post-harvest loss management with an intention to get nutritional and healthy food. Besides, sustainability (14.2%) and health impact (9.9%) are the second most important criteria to select the tomato processing technology. Furthermore, maintenance cost, service year, and shelf life account 9.8%, 7.2% and 5.6% respectively.
Alternatives with respect to the sub-criteria
Since most of the Ethiopian communities are rural dwellers access to electric city is impossible. Cold house storage which requires electricity is not affordable by the rural community. Therefore, low cost and energy saving cooling devices are recommended to keep agricultural produces longer time. Such storage systems are suitable for house hold consumption or transportation to market place. Places with cold climatic conditions are preferable to preserve and demand-driven transportation mechanisms could be devised for distribution when necessary.
Pairwise comparison of the alternatives with respect to each sub criteria is summarized in Fig. 1–7 and Table 2. In comparison, the capital cost takes 34.00% and whereas maintenance cost accounts 9.80%. In terms of capital cost, fermentation which accounts 43.70% is much more preferable followed by hot water treatment, cold house storage, Map and solar dryer constitute 31.30%, 15.80%, 5.60%, and 3.60% respectively. Whereas in terms of maintenance cost, hot water treatment technology with 49.00% weight is much more preferable than fermentation (31.10%), cold house storage (10.90%), Map(4.80%) and solar dryer (4.00%).
Table 2
Hierarchy of the alternatives with consolidated sub-criteria weights (Weighted sum method)
Sub-criteria/ Alternatives | pGlb (%) | SD (%) | CHS (%) | MAP (%) | FRM (%) | HWT (%) |
Capital cost | 34.00% | 0.035925 | 0.157825 | 0.055455 | 0.437394 | 0.313401 |
Maintenance cost | 9.80% | 0.039595 | 0.108556 | 0.048435 | 0.311493 | 0.491921 |
Sustainability | 14.00% | 0.517271 | 0.244868 | 0.041679 | 0.126829 | 0.069353 |
Environmental impact | 3.80% | 0.513415 | 0.075327 | 0.140008 | 0.235052 | 0.036198 |
Personal skill | 15.80% | 0.038367 | 0.092432 | 0.076795 | 0.476626 | 0.315779 |
Service year | 7.10% | 0.519548 | 0.244277 | 0.071798 | 0.046287 | 0.118089 |
Shelf life | 5.60% | 0.501147 | 0.146138 | 0.257198 | 0.062404 | 0.033114 |
Health impact | 9.90% | 0.266271 | 0.144532 | 0.070166 | 0.03837 | 0.480662 |
Group Result | 100% | 20.7% | 15.6% | 7.3% | 29.0% | 27.3% |
Where pGlb stands for global priority vector |
Alternatives with respect to the main citeria
Pairwise comparison of the alternatives with respect to individual main-criteria is presented in Fig. 8–11 and Table 3. In accordance with Fig. 2, for the successful implementation of these preservation technologies economic viability takes 43.90% weight followed by applicability, energy consumption and value addition which account 22.60%, 18.00% and 15.60% respectively. In terms of economic viability, hot-water treatment technology which accounts 40.30% is much more preferable than fermentation (37.40%), cold house storage (13.40%), Map (5.20%) and solar dryer (3.80%). In terms of energy consumption, the implementation of solar dryer (4.00%) is desirable than fermentation (18.00%), cold house storage (16.00%), Map (9.10%) and hot-water treatment (5.30%). In this regard, HWT technology requires additional energy source hardly available in rural areas. Considering the applicability of these preservation technologies, one can give first priority for SD with 27.90% weight followed by FRM (26.20%), HWT (21.70%), CHS (16.80%), and MAP (7.40%) correspondingly. In accordance with value addition, SD which contributed 38.40% weight is much more superior than HWT (27.70%), MAP (16.40%), CHS (14.50%), and FRM (5.00%). The reason behind SD top rankinng is that drying tomato is easier technique and can be stored for longer time simply by teating with vinegar.
Table 3
Alternatives with consolidated main-criteria weights (Weighted sum method)
Main Criteria/ Alternatives | pGlb (%) | SD | CHS | MAP | FRM | HWT |
Economic viability Energy consumption Applicability Value addition | 43.90% | 3.80% | 13.30% | 5.20% | 37.40% | 40.30% |
18.00% | 51.50% | 16.00% | 9.10% | 18.0% | 5.30% |
22.60% | 27.90% | 16.80% | 7.40% | 26.20% | 21.70% |
15.60% | 38.40% | 14.50% | 16.40% | 5.00% | 27.70% |
Where pGlb stands for global priority vector and alternatives refer to the preservation technologies such as SD, CHS, MAP, FRM, and HWT |
In general, as per the current practices in Ethiopia Solar dryer (SD) for Drying, Modified Atmosphere Packaging (MAP), Cold house storage (CHS) such as Mud Brick), Fermentation (FRM) and Hot water treatment (HWT) were selected to prolong the shelf life of tomato.
Previous study pointed out that the moisture content of tomatoes was reduced by 94.4% in 12 h as compared to the open sun drying, which took 74 h, respectively. Moreover, the quality and texture of dried tomatoes produced from solar dryer are superior compared to that of open sun drying.12 Solar powered cold storage house are recommended for large holding farmers with the possibility of commercializing higher quality food products.22
However, these technologies may not be affordable for house-hold consumption and small holding farmers. This investigation mainly encompasses the lower income farmers and small scale house hold consumption. Accordingly, Simple evaporative cooler (EC) or zero-energy cooling chamber (ZECC) as it does not use electricity is economically advantageous. On the basis of the demand of user, such low cost cold storage brick-walled of different capacity could be constructed in rural areas.23
Table 4
Ranking of the selected tomato preservation technologies based expert evaluation
Ranking | Preservarion Technologies | Weight (%) |
1 2 3 4 5 | Fermentation (FRM) Hot-water treatment (HWT) Cold house storage (CHS) Solar drayer (SD) Modified atmosphere packaging (MAP) | 29.0% 27.3% 20.7% 15.6% 7.3% |
Hot water treatment increases shelf life better than the control by three and half days on average. With regard to chemical quality attributes, 50°C treatment for 20 min is better for higher lycopene content compared to other treatments.26 This technique could be applied at house hold and small holding farmers as it is cost effective, inhibit the growth of microorganisms and extends the shelf life of tomato fruit.
Fermented tomato juice has showed a promising antimicrobial activity and are recommended as alternatives to dairy based probiotics to get health benefits, especially in lactose intolerance persons.27 According to the earlier publication, the optimized conditions of fermented tomato juice are determined to be pH 6.2, temperature of 37ºC, inoculum size of 7.58 log CFU/mL, sucrose concentration of 10% and fermentation for 24 h. Fermented juices exhibited good sensory attributes and could possibly be used as probiotic drinks.
From Table 1, we concluded that by using AHP as multi criteria decision making process fermentation ranked at the top followed by hot-water treatment, SD, CHS and MAP. The ranking of these technologies is based on the pairwise comparison of economic viability, energy consumption, applicability and value addition.