ANALYSIS BY PROTON NMR OF CHANGES IN LIQUID-PHASE AND SOLID-PHASE COMPONENTS DURING RIPENING OF BANANA

Changes in both solid-phase and liquid-phase components were observed by proton (H-1) nuclear magnetic resonance (NMR) on intact samples of edible banana tissue (pulp) during ripening. Solid-selective cross-relaxation NMR showed that rigid components dominated by starch decreased from 20% of fresh weight in the mature green stage to 2.0% in the ripe yellow stage. Transverse relaxation measurements and wide-line NMR verified that starch in banana is as rigid as in isolated hydrated granules from banana. A less rigid component was also detected. On the same samples, liquid-phase components were measured by low-speed magic angle spinning NMR. Resonances of water, sucrose, fructose, glucose, fatty acyl chains of mobile lipids, and organic acids were easily detected. During ripening, sucrose concentration changed from 2.2 to 8.5% fresh weight, fructose from 0. 5 to 5.3%, and glucose from 0.4 to 4.3%. Also, conversion of starch to sugars was quantified. NMR analysis was conducted without tissue disruption, separations, chemical treatment, or other spectrometry. The potential applications of NMR for fruit and fruit product quality assessment and processing applications are discussed.