A 5.40-MHz NMR system was used for measuring the self-diffusion coefficient of water (Dw) and the spin-spin relaxation constant (T2) in apple (Malus ×domestica Borkh.) tissue. The pulsed field gradient spin echo (PFGSE) technique was used to measure Dw, and the Carr-Purcell-Meiboom-Gill (CPMG) technique was used to measure T2. T2 and Dw values were compared for apples with differing amounts of soluble solids concentration (SSC) and with and without internal defects, such as bruising, watercore, and internal browning. `Granny Smith', `Golden Delicious', and `Delicious' apples were tested. In `Golden Delicious', Dw highly correlated with apple tissue SSC (P < 0.002, r 2 = 0.68). This indicates that Dw could potentially be used for sorting `Golden Delicious” apples based on SSC, but the coefficient of determination needs to be improved before it would be commercially viable. There were no measurable differences in Dw among healthy apple tissue and tissue affected by either watercore or internal browning. T2 values showed no relationship between healthy apple tissue and bruised tissue in `Golden Delicious' and `Granny Smith'. However, in `Delicious' tissue, T2 values were statistically different between healthy and bruised tissue (P < 0.02). Further comparisons in `Delicious' between watercore and healthy apple tissue showed no differences. But, there were statistical differences found between T2 in healthy apple tissue and tissue with internal browning (P < 0.01). These results indicate that T2 could potentially be used for separating `Delicious' apples with internal browning or with bruising from healthy apples. Titratable acids and pH were correlated for `Golden Delicious' (P < 0.08). This correlation is significant because one may be able to noninvasively measure pH in `Golden Delicious' apples using NMR, which could then be correlated to titratable acids.
Kevin M. Keener, Richard L. Stroshine, and John A. Nyenhuis
R. Roger Ruan, Paul L. Chen, and Simon Almaer
This paper describes the relationship between the maturity stages and nuclear magnetic resonance (NMR) characteristics of sweet corn (Zea mays L.). The NMR parameter T2, which is the spin–spin relaxation time constant, and two conventional maturity parameters, moisture content and alcohol insoluble solids (AIS), of sweet corn samples during maturation, were determined and correlated with reference maturity indices, namely, heat units and sensory maturity scores. The relationships between T2 and the heat unit and sensory maturity score of the samples were linear, suggesting that T2 can be used to establish mathematical models for the prediction of sweet corn maturity to determine harvest time. The major advantages of using NMR are the nondestructive nature, the speed, and the simplicity of the method.
A. A. Gardea, P. B. Lombard, R. L. Kohnert, A. N. Azarenko, Y. M. Moreno, and L. S. Daley
Changes in water content of `Pinot Noir' endo- and ecodormant primary buds were gravimetrically partitioned into extracellular (ECW) and intracellular water (ICW). During endodormancy, water status remained unchanged with values of 0.6 and 0.1 mg/mg dw for ICW and ECW, respectively. Ecodormant buds, prior to budbreak, increased in ICW from 0.5 to 4.4 mg/mg dry weight for Jan. and Apr., respectively. Liquid water in the buds was determined by H-NMR. The spin-spin relaxation time (T2) at -30C represented the bound fraction, which peaked in Jan. at 0.3 mg/mg dw followed by a decrease to 0.2 mg/mg dw in March. During the dormant season the free fraction was always larger than the bound fraction. No vascular connection between bud and stem was observed by mid Jan. Changes in bound water indicated that there is a transient fraction changing to the free form. These changes were not strictly related to the bud's dormancy status.