Modular sensor-based respirometer for real-time monitoring of respiration rate

Monitoring and maintenance of optimal O-2 and CO2 composition inside packaging and storage systems of fresh produce is the key to extending their shelf life. Gas composition and, therefore, respiration rates of fresh produce are mostly measured by gas chromatography or headspace gas analysers. Such measurement involves an ex-situ environment where the sample needs to be taken out of storage room for gas analysis. This study reports the development of a special design leak proof compact modular respirometer (free volume of 3.3 L) and of a modular sensor system called respiration measuring sphere (RMS88). The RMS88 ( diameter: 88 mm, mass: 191 g) consists of one O-2 (0-25%), two CO2 sensors (0-0.5 and 0-5%), and temperature and relative humidity sensors. A 256 kByte F-RAM is used to store raw data and a transmitter is provided for wireless data transfer and communication with a PC. Using a LabVIEW based program, all results (gas compositions, respiration rates and respiratory quotient) can be viewed in real-time graphs on the PC screen. The newly developed modular respirometer along with the RMS88 was tested to measure respiration rate and respiratory quotient of strawberries in real-time. Such modular system can be used in DCA storage systems for remote, real-time and in-situ measurement of respiration rate and respiratory quotient. This will help for continuous and non-invasive monitoring of the physiological conditions of stored fresh produce.