Quantitative 1H magnetic resonance (MR) imaging was used to determine relaxation changes at regular intervals during growth and (T 1 , T 2 -CPMG) ripening of kiwifruit (Actinidia deliciosa var deliciosa). Temporal trends and differences between Ñesh, locule and core tissue were found for both relaxation parameters. However, no consistent associations were found between nondestructive measurements and those for individual free sugars, soluble solids content (SSC) and macronutrients and micronutrients determined on dissected companion samples. Increases of 200% in total free sugar concentration in Ñesh and 68% in SSC accompanied starch hydrolysis after harvest. Despite the magnitude of these changes, relaxation times remained unaltered. These observations were repeated in a second investigation using A arguta fruit and T 1 , T 2 , T 2 and self-di †usion image contrasts. Here, SSC increased 125% during a CPMG compressed 15-day ripening period, while MR parameters like self-di †usion declined only 7È14% from harvest values.
relaxation was also investi-T 2 -CPMG gated in aqueous solutions containing individual organic acids, sugars or pectate and juice from ripening fruit (4É7È15É5% SSC). Analysis of solutions and juices showed relaxation is indeed sensitive to increases in sugar composition but relatively insensitive to changes in organic acids and soluble pectin at concentrations normally found in fruit. Results imply that relaxation parameters determined from MR images may not be appreciably inÑuenced by processes that cause solution composition to vary dramatically, even though these changes are reÑected in the relaxation properties of the juice itself. Possible reasons for this are discussed with regard to the impact of cell structure and magnetic Ðeld strength on relaxation processes.