Performance of controlled atmosphere/heating block systems for assessing insect thermotolerance

• The new CA–HBS had a stable and low leakage rate.
• Chamber temperature variations were not influenced by adding gas or heating rates.
• The CA–HBS could be used for rapid assessment of pest thermotolerance.

Heated controlled atmosphere (CA) treatments have potential as alternatives to chemical fumigation for disinfesting postharvest fresh and stored products. To determine accurately the minimal thermal requirements to kill target insects over a wide range of temperatures and CA conditions, it is desirable to develop a model system to assess quickly the target insect thermotolerance. This study evaluated the gas tightness of the new controlled atmosphere/heating block system (CA–HBS) and the stability of gas concentrations, and determined temperature variations in the treatment chamber with and without added gas and under different gas channel designs and heating rates. The results showed that the new CA–HBS had a relatively constant leakage rate and kept O2 and CO2 concentration variations to within ±0.067% and ±0.167% at three set points (1% O2:15% CO2, 2% O2:17% CO2, and 2% O2:20% CO2), resulting in relatively stable gas compositions. With the long gas channel design, temperature variations in the treatment chamber were not influenced by the addition of gas or by heating rates. The performance of the CA–HBS indicated that this model system could be used for rapid assessment of pest thermotolerance.