Oilseeds sorption isoterms, mechanical properties and pressing: Global view of water impact

• We investigate seeds sorption isotherms, drying behaviour, mechanical properties linking to oil expression.
• Rapeseed, linseed & sunflower sorption isotherms are established and modelled (GAB).
• Embryos and hulls sorption isotherms are established and modelled.
• Correlation between sorption isotherms, drying behaviour, seeds mechanical properties and expression is proposed.
• Unidirectional expression yield is related to continuous pressing yield.

The aim of this study was to investigate the interaction between water and oleaginous seeds (rapeseed, flaxseed and sunflower) and its consequence on processing (pressing). Sorption isotherms of whole seeds, hulls and embryos were established and highlight the uniform behaviour of seed fractions towards water. Seed expression is highly influenced by seed moisture content and water activity in unidirectional and screw presses. Transposability of discontinuous pressing to continuous screw presses has been assessed. Seed mechanical properties are affected by water activity and moisture content. Moreover, fracturability evolution according to moisture content gives indication about oil yield dependency from water content and minimal elasticity corresponds to maximal oil yield for flaxseed. The relations established between sorption isotherms, drying behaviour, mechanical properties and pressing (unidirectional and continuous) leads to global view of water impact on seed processing.