Estimation of effective diffusivity of pear tissue and cuticle by means of a numerical water diffusion model

An estimation procedure of effective diffusivity in pear tissue by means of a numerical water diffusion model is presented. Conference pears (Pyrus communis cv. Conference) of different picking date and different storage period and temperature were investigated. The moisture diffusivity of different tissues like outer cortex, inner cortex and cuticle was estimated. Results showed that the effective diffusion coefficients of water are slightly larger in late picking date pears than those of early picking date, but the effect of storage time was unclear and a large biological variability was observed. Temperature had different effects on the different tissues. The diffusion coefficients increased by a factor 2 in case of cuticle and by a factor 3.6–9.6 in the case of inner cortex tissue when the temperature increased from 1 °C to 20 °C. The value of the diffusion coefficient decreased dramatically from inner cortex tissue (123.0 × 10−13 m2 s−1 at 1 °C; 435.9 × 10−13 m2 s−1 at 20 °C) to outer cortex tissue (5.3 × 10−13 m2 s−1 at 1 °C; 10.5 × 10−13 m2 s−1 at 20 °C) and cuticle (0.55 × 10−13 m2 s−1 at 1 °C and 1.28 × 10−13 m2 s−1 at 20 °C). These values are comparable with those in literature obtained for other horticultural products such as apple.