DEVELOPMENT OF NON-CHEMICAL POSTHARVEST TREATMENTS FOR DISINFESTING AGRICULTURAL PRODUCTS

Thesis (Ph.D.), Department of Biological Systems Engineering, Washington State UniversityChemical fumigation disinfestation treatments bring more and more concerns due to its hazard to environment and human health, it is necessary to develop alternative non-chemical disinfestation treatments for agricultural products. Radio frequency (RF) and low pressure (LP) technologies have been explored as disinfestation treatments for several agricultural commodities. The aim of the current study was to develop RF and LP disinfestation treatments for legumes and fresh fruits, respectively.Black-eyed peas and mung beans were being considered as surrogate host legumes to be infested by cowpea weevils to validate RF treatment protocol, since they are better hosts for cowpea weevil compared with target legumes (chickpeas and lentils). The resistance of cowpea weevils at different life stages was investigated under RF treatments. RF treatment with 60°C and more than 5 min holding time can completely kill insects without product quality degradation. A computer simulation model was developed and validated, which can be used to investigate RF heating process to get better heating uniformity and efficiency. Industrial scale-up tests were conducted to make RF technology available for industry application. The current studies indicated RF energy can be applied to control insects in legumes without quality degradation, industrial-scale continuous RF disinfestation treatment was effective and could be used for practical applications.To investigate the potential of using LP technology in disinfestation study for fresh fruits, LP system stability and performance was evaluated in the first step. Results showed LP system maintained temperature, pressure and relative humidity very stable and at good levels with low chamber leakage rates. The tolerance of coding moth with different life stages was investigated as a next step. Weight loss, color, firmness, titratable acidity (TA), and soluble solid content (SSC) were selected as quality parameters to evaluate the quality changes of "Red Delicious" apples. Large larvae were found to be the most resistant life stage of codling moth in LP treatments. The insect mortality reached to 98% after 12 days LP treatment, and apple quality was maintained well after 15 days LP treatments, which indicated LP technology has the potential to be an alternative non-chemical disinfestation treatment method.Department of Biological Systems Engineering, Washington State Universit