Effect of high-pressure hot-water washing treatment on fruit quality, insects, and disease in apples and pears: Part III. Use of silicone-based materials and mechanical methods to eliminate surface pests

Surface arthropods on pome fruits can cause export problems and disrupt commercial markets. Eliminating insects and mites on the packing line would be the last opportunity to provide for pest-free produce. In this study, an experimental packing line was used to evaluate techniques using different surfactant baths, pressurized water sprays, and styles of rotating brushes to remove field-collected and laboratory-reared grape mealybug, Pseudococcus maritimus (Ehrhorn) (Homoptera: Pseudococcidae), the diapausing two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and the woolly apple aphid, Eriosoma lanigerum (Hausman) (Homoptera: Aphididae). The organosilicone Silwet L-77 was no more effective than a silicone-based food grade defoamer in aiding removal. Mechanical methods, such as the style of rotating brushes and pressurized sprays, were significantly effective in removing surface arthropods. No improvement in removal occurred when pressure was increased beyond 420 kPa. These techniques can be easily adapted to commercial facilities and will reduce the incidence of surface arthropods on marketed fresh fruits.     

Effect of high-pressure hot water washing treatment on fruit quality, insects, and disease in apples and pears: Part II. Effect on postharvest decay of d’Anjou pear fruit

A hot water pressure process (HWP) was evaluated for its effect on conidia of Penicillium expansum and on development of blue mold, gray mold, and mucor rot of d’Anjou pear fruit. Spores were removed from the water system through dilution and also as a result of hot water in the system that was lethal to the spores. When the system was heated, viable spores were not detected after 2–4 h of operation. Reductions in decay in the HWP system were 36, 29, and 13% for Botrytis cinerea, Mucor piriformis, and P. expansum, respectively. The response of P. expansum appeared related to the length of time fruit was in cold storage. Heat injury was observed on fruit treated with 40 and 50 °C water but not on fruit at 30 °C nozzle temperature. The HWP system described in this study should be considered as a component of an integrated decay control strategy.     

Effect of high-pressure hot-water washing treatment on fruit quality, insects, and disease in apples and pears: Part I. System description and the effect on fruit quality of ‘d’Anjou’ pears

A manually operated high-pressure hot-water washing system consisting of a boiler, hot-water mixing tank, contact loop, heat exchanger, spray mixing tank, high-pressure hot-water washing manifold, low-pressure fresh water rinse manifold, and pressure pump was constructed and installed in a packingline. The system developed 20–50 °C washing water at pressures up to 980 kPa. ‘d’Anjou’ pears (Pyrus communis L.), shortly after harvest, and after storage for 3 and 4 months in regular air (RA) or for 4, 7 and 8 months in controlled atmosphere (CA) at −1 °C were washed through the packingline with different wetting agents (0.1% Silwet, 0.01 and 0.1% Defoamer, and water), water pressures (regular and high-pressure (210–980 kPa)), water temperatures (control (tap water, 4–22 °C), 40 °C, and 50 °C), and brushes (soft and firm), respectively. The effect of the washing conditions on fruit quality was investigated after 1 month of storage at −1 °C to simulate shipping condition, and then again after 1 week at 20 °C to simulate marketing condition. Hot-water caused severe heat scald. When nozzle temperature was 50 °C, the incidence of heat scald increased to over 50% for the fruit stored in RA for 3 months. Combined with hot-water, 540 kPa high-pressure washing increased the incidence of friction discoloration. There were lower incidences of friction discoloration and heat scald for fruit stored in CA for 7 months, in comparison to that in RA for 3 months. However, those fruit did not ripen properly as indicated by a high extractable juice content. Fruit washed at harvest had minor incidences of friction discoloration regardless of different brushes, water pressures, and wetting agents. Fruit washed after storages in either 4 months RA or 4 or 8 months CA suffered a high incidence of friction discoloration including scuffing symptoms and pressure marking. The firm brushes caused a higher incidence of friction discoloration mainly because of scuffing symptoms. However, no differences were found between different water pressures and wetting agents with respect to friction discoloration. Fruit stored for 4 months RA suffered 26–28% friction discoloration in comparison to 16–18% in CA stored fruit with firm brush washing. Extended CA storage increased friction discoloration even with soft brush washing. The results suggest that a washing system with high-pressure spray, <30 °C warm water, wetting agent Defoamer and rotating soft brushes were significantly effective in removing surface pests and decay control without causing internal or external damage of fruit.