2. A REVIEW OF LITERATURE ON THE POSTHARVEST CHARACTERISTICS,
2.8 Discussion and Conclusion
Stage Challenges Probable Solutions
1c
Fruit undergo a basic wash and chlorine disinfection. Chlorine treatments are more effective when used in combination with other pre-packaging treatments, such as hot water treatments (Boyette et al., 1993).
Include other suitable treatments as part of the pre- packaging process of kumquats.
2
Groupage requires kumquats to be transported with other horticultural commodities due to the small volumes harvested.
Make use of smaller transport vehicles.
Transport kumquats with commodities that are not detrimental to the fruit.
4
Transport by sea can take up to 21 days.
Extended shipping times can result in pathogenic infections, decay and quality deterioration.
Effective pre-packaging treatments need to be applied early in the supply chain to enhance the shelf life and maintain fruit quality, such as hot water treatments (Rodov et al., 1995), and waxes (Hagenmaier and Baker, 1994).
Effective packaging treatments need to be applied to enhance the shelf life and maintain fruit quality.
5
There are few small-scale farmers contributing to the export market (Department of Agriculture, Forestry and Fisheries, 2012;
2015a).
Develop resources to assist small-scale farmers to contribute to export markets, such as a mobile packhouse to reduce investments in large packhouses.
Fruit packhouses are the hub at which majority of the postharvest handling occurs, such as pre-packaging treatments, packaging and storage. This implies that fruit are typically transported some distance from the orchards to the packhouse before any treatments can be applied. Currently, the main pre-packaging treatments identified within the citrus industry are postharvest fungicides, hypochlorite disinfection and waxing (Ladaniya, 2008). However, the relative efficacy of other treatments, such as hot water, biocontrol agents and anolyte water on citrus fruit have not been fully explored. Hot water treatments have a significantly positive effect on the postharvest citrus quality, particularly kumquat fruit, in terms of reduced decay as a result of the Penicillium pathogens, reduced weight loss and firmer fruit, (Schirra et al., 1995; Ben-Yehoshua et al., 2000; Porat et al., 2000;
Rodov et al., 2000; Fallik, 2004; Sapitnitskaya et al., 2006; Strano et al., 2014). Schirra et al. (1995), Ben-Yehoshua et al. (2000) and Rodov et al. (2000) found 53°C for 120 or 30 seconds to be the optimum temperature and time combination for kumquat heat treatments. Hot water treatments do not contain any chemicals and are, therefore, recommended for kumquat fruit due to the manner in which the fruit is consumed (Rodov et al., 1995; Schirra et al., 1995; Ben-Yehoshua, 2000; Schirra et al., 2011). Waxes were found to reduce the moisture loss and create shiny fruit surfaces; however, excessive waxing can result in the development of off-flavours due to suppressed gas exchange (Njombolwana et al., 2013). The use of hypochlorite as a disinfectant is common practice in the postharvest fruit industry. The current hypochlorite treatment of kumquats at packhouses in South Africa uses a 1% chlorine solution or chlorine dioxide. Biocontrol agents have been presented as an environmentally friendly alternative to fungicides. The yeast strain B13 provided positive results in preventing P. digitatum decay in oranges and lemons in South Africa (Abraham et al., 2010). Further studies are required to determine the feasibility of using B13 as a biocontrol agent for kumquat fruit. Excessive UV-C irradiation (˃0.5 kJ.m-2) or too high salt content (5%) can result in damage to the citrus fruit peel (D’hallewin et al., 2000; Obagwu and Korsten, 2003; Canale et al., 2011).
Combined pre-packaging treatments have been recommended, compared to individual treatments, due to their higher overall efficacy in reducing decay and maintaining fruit quality (Obagwu and Korsten, 2003; Sen et al., 2007). An effective pre-packaging treatment combination should include a disinfectant (hypochlorite or anolyte water), curative (hot water) and a preventative agent (biocontrol). Many studies have focused on
et al., 2001; Sen et al., 2007). However, these treatments did not combine disinfection, curative and preventative modes of action (Ben-Yehoshua et al., 2005; Sen et al., 2007).
Insufficient data is available on anolyte water as a pre-packaging treatment in citrus, particularly in kumquats. Therefore, a portion of this study was dedicated to determining the efficacy of anolyte water as a disinfectant of kumquat fruit.
The equipment used in industry focussed primarily on brushes and spray nozzles to remove dirt and clean the fruit surface. Hydraulic sprayers or water baths have been used for the application of hot water and chlorine treatments. Fallik (1999) developed a hot water brushing and rinsing unit for sweet peppers. However, this equipment was aimed at operation within a packhouse. Electricity and diesel were found to be the main sources of energy in packhouses. The energy utilisation among South African packhouses varies from 15 kW.h.ton-1 to 44 kW.h.ton-1 (Bouwer, 2011). Efficient equipment and management practices are essential to introduce and manage energy saving.
Ideally, an in-field integrated pre-packaging unit would address these concerns by pre- treating the fruit on-site, immediately after harvest, a concept that has not been previously documented. The unit could incorporate disinfection, curative and preventative pre- packaging treatments. This unit could be described as ‘condensing’ the packhouse processes into a mobile unit that could be operated on-site at the orchard. Mobile units for small-scale farmers are likely to reduce their financial investment in large packhouses.
South African kumquat yields are lower than other major citrus varieties, such as oranges (Beghin, 2014c). This allows for the unit to be taken directly to the orchard, where treatment of small quantities of fruit can be carefully managed. More importantly, the damaging delay between harvest and pre-packaging treatments would be greatly reduced, which would improve fruit quality and reduce decay.
Innovative and convenient techniques of treating kumquat fruit after harvest are required to reduce losses that occur when the fruit is transported untreated to packhouses. It is envisioned that by developing the South African kumquat industry, a larger export market can be created, as well as providing small-scale kumquat farmers with a niche in this export arena. The availability of literature pertaining to the pre-packaging treatment of kumquat fruit, particularly in South Africa, is limited. Therefore, postharvest kumquat
research is required to improve and extend the shelf life, by developing an in-field pre- packaging treatment unit.