A Stable Isotope Approach to Assessing Water Loss in Fruits and Vegetables during Storage

Plant tissue water is the source of oxygen and hydrogen in organic biomatter. Recently, we demonstrated that the stable hydrogen isotope value (delta H-2) of plant methoxyl groups is a very reliable and easily available archive for the delta H-2 value of this tissue water. Here we show in a model experiment that the delta H-2 values of methoxyl groups remain unchanged after water loss during storage of fruits and vegetables under controlled conditions, while delta H-2 and delta O-18 values of tissue water increase. This enhancement is plant-dependent, and the correlation differs from the meteoric water line. The delta O-18 value is better correlated to the weight decrease of the samples. Therefore, we postulate that the delta H-2 value of methoxyl groups and the delta O-18 value of tissue water are suitable parameters for checking postharvest alterations of tissue water, either addition or loss.