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United States Department of Agriculture

Agricultural Research Service

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Location: Sugarbeet and Bean Research

2010 Annual Report

1a. Objectives (from AD-416)
1) Evaluate NIR spectra in diffuse reflectance, transmittance, and scattering modes for determination of potato density/specific gravity. 2) Evaluate NIR spectra in diffuse reflectance, transmittance, and scattering modes for determination of specific sugars levels in potatoes. 3) Determine optimal sensing configuration (mode and wavelengths) for moving toward development of a prototype device for potential real-time field-based measurement.

1b. Approach (from AD-416)
Potatoes covering a range of density and sugar levels will be obtained from the potato industry. Samples will be collected and evaluated at multiple intervals over the length of the storage season. Each cleaned and intact potato tuber will be measured with the laboratory instrumentation set-up under the following three modes: diffuse reflectance over the visible and NIR region from 500-1700 nm; transmittance over the range of 500-1300 nm; and scattering over the range of 500-1300 nm. The transmittance and scattering ranges do not extend as far into the NIR range due to absorption. Following whole (intact) tuber measurement, a tissue sample will be cut from the same tuber and the same spectroscopic measurements will be obtained on this controlled and uniform sized sample. Additionally, each potato will be measured for density and specific sugars using conventional hydrometer and wet chemistry techniques to provide a baseline to which the spectroscopic measurements will be compared and correlated. A local company, Techmark Inc., specializes in potato handling and analysis and is supportive and willing to assist with conventional analysis (as a no cost collaborator). While the goal is to successfully measure whole/intact tubers, additionally evaluating samples of tissue will provide the opportunity to compare the results of this study against published results and also tissue versus whole tuber measurement. Several potato varieties will be included in the study to determine robustness or specificity of findings. Data analysis will involve determining portions of the spectra and the mode, or combinations of spectra and modes, capable of best predicting density and sugars levels. The progression of the research would include the first year of broad spectral measurement of whole tubers and tissue samples and critical analysis of data. A second year would be important (similar budget) to validate first year findings and, in parallel, focus on a particular sensing configuration based on what we learned from year one. This sensing configuration would be a step toward a prototype device incorporating dedicated electronics for real-time in-field measurements.

3. Progress Report
Based on the results obtained for the 08-09 harvest and follow-up consultations with our project’s industry advisor, a few changes were made for the 09-10 season of harvest, experimentation, and analysis. While the leaf primordial correlations were the most promising in the first season of study, it was dropped from this study year due to the desire to focus on sugars measurement; the time and expertise required to measure bud leaves; and some concern that there existed some secondary relationships that may have led to the high primordial predictions. In the 09-10 season, the sample measurement of transmittance was replaced by reflectance while interactance and scattering measurements remained the same. In attempt to obtain the best possible sample set covering a range of sugars and to evaluate a range of spectral measurements and spectral properties, the following extensive set of data was collected. Potato Sample Set: Two cultivars (Frito Lay and Russet Burbank) were grown at two locations having varying growing conditions. Between two and four vine kill dates, depending on location, at one week intervals were conducted covering the early to late harvest window. Samples were harvested 7, 14, and 21 days following vine kills. Each unique vine kill/harvest date combination was separated and stored at either 4, 7, or 10 deg. C for storage periods of 0, 30, 60, 120, or 150 days. These treatments yielded 360 different conditions in attempt to develop a broad, uniform, and extensive sucrose and glucose distribution. Electronic/Spectral Data Collection: The following electronic/spectral measurements were conducted on each unique sample condition: 1) Interactance (500-1000 nm) on both whole tuber and uniform slice (1/2 inch thickness); 2) Scattering (measured with hyperspectral imaging) (500 – 1000nm) on slice only; 3) Reflectance (900-1350nm) on both whole tuber and slice. Wet Chemistry-based Sugars Data Collection: Following non-destructive and subsequently destructive electronic measurement, cores from within each potato were collected and juiced to obtain a unique sample for each potato and immediately frozen at minus 80 C for later analysis. The subsequent sugars analysis was conducted with wet chemistry utilizing the Megazyme analysis kit. The project has completed the wet chemistry analysis for this large sample set. The current activity is identifying, extracting, and preprocessing the parameters from the electronic measurements for which to evaluate for correlation against the wet chemistry sugars analysis. A complete statistical analysis and correlation of the electronic measurements to glucose and sucrose is to be conducted to determine the potential for electronic measurement to resolve sugar level differences and changes at the levels desired by the potato industry. This research will continue under project number 3635-43640-001-01S. Project progress was monitored via meetings, emails, and joint sessions on planning, execution, and analysis of research with the collaborating researchers.

4. Accomplishments

Last Modified: 05/24/2017
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