Journal of the Science of Food and Agriculture vol:87 issue:10 pages:1858-1867
Gas diffusion properties of pear tissue are important in relation to gas exchange of the fruit with its environment during storage. In this contribution, a set-up for measuring tissue diffusivity using fluorescent optical probes was developed. O-2 and CO2 diffusivities were determined simultaneously based on a finite element model describing simultaneous O-2 and CO2 gas transport as well as respiration in the tissue. The effect of variations on the diffusion set-up conditions such as the volume of the measurement chamber and thickness of the sample on the accuracy of the estimated diffusivities was investigated using a sensitivity analysis on simulated data. The optical sensors produced good informative O-2 and CO2 partial pressure versus time profiles. The average O-2 and CO2 diffusivity of pear cortex tissue was (2.56 +/- 0.48) X 10(-10) m(2) s(-1) and (3.8 +/- 1.1) x 10(-9) m(2) s(-1), respectively. The coefficient of variation of diffusivity of O-2 and CO2 in pear tissue due to bias, variation of the sample thickness and volume of the measurement chamber was 2.0-2.3% and 2.1-2.4% for a measurement chamber volume between 7.5 and 15 mL and a tissue thickness of 1-2.5 mm, respectively. The variability of estimated diffusivities due to measurement errors was eight times smaller than the biological variability.