Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2013
Publication Date: 1/1/2014
Citation: Syamaladevi, R.M., Lupien, S.L., Bhunia, K., Sablani, S.S., Dugan, F.M., Rasco, B., Killinger, K., Dhingra, A., Ross, C. 2014. UV-C light inactivation kinetics of Penicillium expansum on pear surfaces: Influence on physicochemical and sensory quality during storage. Postharvest Biology and Technology. 87:27-32. Interpretive Summary: Fruit is often routinely disinfested with chlorine bleach (sodium hypochlorite) to reduce the numbers of fungi that can induce postharvest decay. Disinfestation with ultraviolet light is a potential commercial alternative to standard disinfestion of fruit with chlorine bleach. However, in addition to effects on fungal postharvest pathogens such as Penicillium, treatment with UV light may cause changes in fruit physiology and appearance, thereby affecting consumer preference. In this series of experiments, UV light reduced numbers of Penicillium spores on pear fruit, and had no negative effects on weight of product. However, color and flavor were impacted in ways resulting in diminished consumer preference relative to controls.
Technical Abstract: Postharvest quality and storage life of fresh pear are often limited by fungal growth caused by Penicillium expansum. Ultraviolet-C light (UV-C 254 nm) is a promising alternative disinfestation method to reduce fruit spoilage by fungi. In this study, UV-C inactivation kinetic data of Penicillium expansum on intact and wounded pear surfaces were obtained. P. expansum conidia were spot inoculated onto intact and wounded pear surfaces with skin (excised disks) and treated with UV-C doses ranging 0.101-3.06 kJ/m2 at 23C. The UV-C treated and untreated (control) pear discs were washed with sterile water, conidia recovered, and enumerated after 72-96 hours on potato dextrose agar and colony forming units (CFU) were counted. Subsequent changes in total soluble solids, firmness, color, and pear flavor following UV-C treatment were determined immediately after treatment and at 4 and 8 weeks of storage at 4C. The population of P. expansum was decreased by 2.8 log CFU/g (P value < 0.05) after 1.7 kJ/m2) on intact pear surfaces and 2.7 log CFU/g (P value < 0.05) after 3.1 kJ/m2 on wounded pear surfaces, respectively. No significant difference (P = 0.05) in % weight loss, or Brix and texture was observed between UV-C treated and untreated pears. However, browning was observed on UV-C treated pear surfaces after 4 and 8 weeks along with changes in flavor and texture, with an increase in consumer preference for the untreated control observed after 4 weeks storage.