Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 8, 1997
Publication Date: N/A
Interpretive Summary: Regulatory agencies in many countries enforce established quarantine protocols for marketed fresh produce to ensure that infested fruit do not introduce fruit flies into fly-free production regions. Quarantine protocols include preharvest measures, such as sterile-fly-release and fly-free growing periods, and postharvest measures, such as commodity heat treatments. The objective of this research was to identify a non-damaging hot water or high temperature forced-air treatment for navel orange that could provide quarantine security against Mexican fruit fly (Anastrepha ludens Loew). Experiments were conducted in the 1994, 1995, and 1996 citrus seasons. During the first year of experiments, the oranges were immersed in 46 degrees C water for 3 hours, exposed to 46 degrees C forced-air for 4 hours, or 50 degrees C forced-air for 2 hours. Results from these tests showed that the least damaging heat treatment was 46 degrees C forced-air. In the second and third years of experiments the length of time and effect of fruit maturity on tolerance to 46 degrees C forced-air as investigated. Results from these experiments showed that early, mid, and late season navel orange can tolerate exposure to 46 degrees C force-air for up to 4.5 hours without deleterious effects on fruit quality. A heat treatment of this severity will most likely provide quarantine security against Mexican fruit fly.
Technical Abstract: Navel oranges [Citrus sinensis (L.) Osbeck] were exposed to 46 degrees C moist, forced-air for up to 4.5 hours, 50 degrees C moist, forced-air for 2 hours or immersed for 3 hours in 46 degrees C water. The quality attributes of heat-treated fruit were compared to that of oranges that were not heated. The flavor of oranges immersed in 46 degrees C water was rated dby panelists as significantly inferior to that of fruit that was not heated. The appearance of navel oranges exposed to 50 degrees C forced-air was rated as significantly inferior to that of nonheated controls. Oranges exposed to 46 degrees C forced-air for up to 4.5 hours had identical quality attributes as oranges not exposed to a heat treatment. The quality attributes of early, mid, and late season fruit exposed to 46 degrees C forced-air could not be distinguished from nonheated, control fruit. Results from this study suggest that navel orange tolerance to high temperature forced-air is short (<10 minutes) when fruit center temperatur reaches 48 degrees C, but fairly long (>90 minutes) at center temperatures of 45 degrees C. Fruit quality can be best maintained during high temperature forced-air treatments for disinfestation of Mexican fruit fly (Anastrepha ludens Loew) by extending the duration of exposure to 46 degrees C forced-air rather than exposing fruit to forced-air temperatures in excess of 46 degrees C.