Determination of the respiration rate of tomato fruit using flow analysis

A continuous-flow method using a conductometric detector was developed to measure CO2 resulting from respiration tomato fruit (Lycopersicon esculentum var. Santa Clara). The fruit are inserted into a 3.4-1 vessel and the atmosphere in the vessel continuously monitored for CO2, using a closed-loop system. The CO2 produced from fruit respiration diffuses through a Teflon (R) membrane, dissociates in the acceptor stream of deionized water, and the conductivity (mainly of H+ and HCO3-) is monitored. The conductance increase in the acceptor stream is proportional to the carbon dioxide concentration in the gaseous sample. Each determination is performed in 7 min, a time interval short enough to prevent respiration inhibition due to high levels of CO2 inside the respiration vessel. The relative error of measurement is - 3.0% (n = 7) for a CO2 level of 589 ppmv. Average respiration rates for the tomatoes var. Santa Clara of various stages of maturity ranged from 40 to 120 mg kg(-1) h(-1) evolved CO2. These results had low levels of variance between measurements, were consistent between repetitions, and were comparable with published data. (C) 2001 Elsevier Science B.V. All rights reserved.