Assessment of pomegranate postharvest quality using nuclear magnetic resonance

作者：Zhang Lu; McCarthy Michael J^*

来源：Postharvest Biology and Technology, 2013, 77: 59-66.

DOI：10.1016/j.postharvbio.2012.11.006

• Pomegranate
• Quality
• Brix
• Acidity
• pH
• NMR

Fruit quality parameters, soluble solids content (Brix), total titratable acidity, pH, and Brix/acid ratio, are often used as indicators of fruit maturity and palatability. Measurement of these fruit quality parameters requires a series of destructive methods, which can only be conducted on extracted fruit juice. The aim of this study is to investigate the relationship between spin spin relaxation time and pomegranate quality attributes and the potential of MRI for quantitative analysis of pomegranate quality. Spin spin relaxation time, T-2, measured using a low magnetic field (0.04T) showed correlation with the soluble solids content of pomegranate. The T-2 relaxation time ranged from 837 ms to 1024 ms for the fruit with soluble solids content from 15.3 degrees Brix to 18.7 degrees Brix. However, accurate prediction was not achieved. In the MRI experiment, six MR images with varying contribution to total signal intensity from proton density, relaxation rates, and diffusion weighing were obtained for pomegranate fruit using a 1 T MR imaging system with 0.22 T/m gradient strength. The pH, Brix, total titratable acidity, and Brix/acid ratio of pomegranate were also measured by traditional destructive methods. Partial least square (PLS) analysis was applied to the statistical features of the voxel signal intensities in the MR images and quality parameters to examine the correlation between MR images results and destructive measurements: The MR image based PLS model have a R-2 of 0.54, 0.6, and 0.63 for predicting titratable acidity, pH, and soluble solids/acidity levels, respectively. The correlation between MR image statistical features and soluble solids content of pomegranate was poor. In these models, T-2 weighted Fast Spin Echo, diffusion weighted image, and Spin Echo image with short TE and moderate TR are the most important images in predicting the pomegranate quality attributes. Unlike traditional destructive methods, MR imaging is capable of evaluating multiple quality parameters in a single measurement.

• 出版日期2013-3