Tolerance of grapefruit and Mexican fruit fly larvae to heated controlled atmospheres

The potential for disinfesting grapefruit ( Citrus paradisi Macf.) of Mexican fruit fly by heating the fruit in a controlled atmosphere was evaluated by comparing larval mortality and fruit quality after heat treatments with or without altered levels of oxygen and carbon dioxide. The mortality of third instar, Anastrepha ludens (Loew) larvae was significantly higher when larvae were heated at 44 °C in 1% oxygen for 2 h than when larvae were heated for the same amount of time at the same temperature in air or in air enriched to 20% carbon dioxide. Reducing the concentration of oxygen to 1 from 21% (air) during a heat treatment resulted in a 30% shorter exposure time (3.5 vs. 5 h) to achieve 100% larval mortality. The concentrations of oxygen and carbon dioxide inside the grapefruit during exposure to 46 °C were significantly different when the fruit were exposed to low oxygen, air, or high carbon dioxide during heating. Inconsistent fruit quality results warrant further study to optimize controlled atmosphere conditions during heating.