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Development of postharvest UV light therapy technology for extended preservation of fresh organic fruits and vegetables

Activity summary

Fruits and vegetables are perishables since they maintain an active metabolism in the postharvest phase. The factors causing early termination of their storage life are relatively high respiration rates and senescence, transpiration, and high susceptibility to fungal infection. Storage diseases are responsible for substantial postharvest losses. Currently, the most important means of maintaining quality and prolonging the shelf-life of organic produce is low temperature storage, as organic producers have no access to chemical programs, unlike the growers and storage operators of regular crops. Pre-storage treatment with hormetic (hormesis is the stimulation of beneficial responses by low levels of stressors which are otherwise harmful) doses of UV-C has been shown to control diseases and delay senescence in fresh fruits and vegetables by the induction of natural defense mechanisms of the produce. In addition, UV-C induced responses typically persist even when the treated produce is subsequently exposed to other stresses during storage. However, UV-induced effects are localized and not systemic, which necessitates the exposure of the entire surface of crops of varying sizes and shapes to elicit the beneficial responses. Overcoming this challenge can lead to an effective preservation technology, as an adjunct to refrigeration, for fresh crops.

The objective of this research activity is to develop a postharvest UV light therapy technology for extended preservation of fresh organic fruits and vegetables by induction of disease resistance and delayed senescence. Initial efforts will be directed towards the design and construction of a prototype UV light exposure system and a working model capable of high throughput. The system will be tested for uniform light exposure using a number of products, selected for their size and shape (blueberry, strawberry, tomato, bell pepper, carrot and broccoli). The system will be modified, if necessary, to achieve the goal of exposing the entire surface of the products to UV, and a working model will be constructed. In parallel, studies will be carried out to determine the hormetic doses for selected produce based on UV-induced disease resistance and delayed senescence. Further work will involve the determination of the effects of cultivar and physiological age of the produce on the hormetic doses and UV-induced responses. Subsequently, the conditions for UV treatment (hormetic UV dose and fluence rate, and tissue orientation and temperature) will be evaluated. The next phase of investigation will involve the evaluation of the persistence of UV-induced effects in the treated produce during storage. The evaluation will include disease resistance and defense mechanisms, senescence-related changes, anti-oxidant capacity and health-promoting secondary metabolites. The final phase of the work will involve the evaluation of the shelf-life of produce, product quality and sensory attributes under both laboratory and commercial conditions, as well as the techno-economical feasibility of the treatment.

The organic sector, which emphasizes sustainability and is dedicated to minimizing waste, can benefit significantly from this environmentally-friendly technology. The ability to preserve crops longer than low temperature alone will allow and the reduced economic losses arising from postharvest losses could encourage growers to increase production of their crops and serve expanded and farther markets, leading to improved profitability of the sector. In addition, there is also a potential to enhance health-promoting phyto-compounds in the treated produce that could lead to increased consumer demand for organic produce. The proposed technology can also be beneficial to the regular fresh produce sector, which is also seeking alternative approaches to chemicals to control storage diseases.

Materials and Results to Date

• • Acta Horticulturae (2015) 1079: 159-164
• • Journal of the Science of Food and Agriculture (2015) 95: 2996-3002
• • LWT Food Science and Technology (2016) 65: 557-564
• • Acta Horticulturae (2015) 1079: 589-592
• • Plant Physiology and Biochemistry (2016) 108: 337-343
• • Journal of Plant Physiology (2017) 218: 265-274

Activity researchers

Contributing partners

• Additional partners to be confirmed