Abstract
Seeds of five Citrus taxa: Citrus suhuiensis cv. limau langkat, Citrus suhuiensis cv. limau madu, Citrus limonia, Citrumelo and Citrus hystrix were equilibrated over various saturated salt solutions at 25 degrees C. Water desorption isotherms were constructed using the simplified sorption model. The relationships between seed total lipid content (expressed on a percentage dry weight basis) and water desorption isotherms and sorption parameters were investigated. The differences between the five Citrus taxa in terms of seed volume, fresh weight and total lipid content were highly significant (P <= 0.001). Negative linear correlations were detected amongst the taxa between seed total lipid contents and equilibrium water contents attained at RH greater than 78%. For all taxa investigated, the relationship between seed water content at equilibrium and water activity displayed a hyperbolic shape rather than the typical sigmoidal shape characterizing orthodox seeds. However, prominent differences in water desorption isotherms were observed due to differences in their lipid content. Negative linear correlations were found between seed total lipid content and water sorption parameters that related to the weakly binding site and to water binding sites at the multimolecular layer. Positive linear correlation was observed between seed lipid contents and the activity of multimolecular water.