Dielectric spectroscopy for evaluating dry matter content of potato tubers

Abstract The present study investigated the application of dielectric spectroscopy as a method for evaluating the dry matter content of potato tubers. Sample specific factors determining the precision of this application were investigated by studying the prediction of the dry material content in agar gel based model systems with known dry matter content. Dielectric spectra were measured with a large custom-made open-ended coaxial probe in the frequency interval from 0.01 GHz to 3 GHz. Both univariate linear models motivated by a two phase mixture model and cross-validated multivariate partial least squares regression (PLSR) models were applied to predict the dry matter content. Results showed that the PLSR models gave markedly better prediction of the dry matter content from the dielectric response in most of the investigated systems compared to the univariate linear models. The highest precision of the predicted dry matter content was observed in chemically and spatially uniform systems, with a root mean square error (RMSE) of the predicted dry-matter content of 0.64 percentage points observed in agar gels containing refined potato starch. A marked decrease in precision is observed in model systems which include chemical variations between potato tuber samples. The added dry material content was predicted with a RMSE of 0.94 percentage points in agar gels with added dried material extracted from separate potato tubers. The local dry matter content from a region within 2 cm of the center location of the dielectric measurement on potato tubers was predicted with a RMSE of 1.21 percentage points. The dry matter content of total potato tubers were predicted with a RMSE of 1.93 percentage points. The difference between the precision of the local and total potato tuber dry matter prediction indicated that spatially non-uniform dry matter distributions were the largest contribution to the observed prediction errors. Variations in chemical composition and air space tissue was also found to be possible factors contributing to the prediction error for potato tubers.

[1]  W. Schilz,et al.  A microwave method for density independent determination of the moisture content of solids , 1980 .

[2]  Takaaki Sato,et al.  Dielectric Relaxation Processes in Ethanol/Water Mixtures , 2004 .

[3]  H. L. Lucas,et al.  Specific gravity — Dry matter relationship in potatoes , 1951, American Potato Journal.

[4]  Stuart O. Nelson,et al.  Microwave moisture meter for in-shell peanut kernels , 2016 .

[5]  Udo Kaatze,et al.  Techniques for measuring the microwave dielectric properties of materials , 2010 .

[6]  Stuart O. Nelson,et al.  Nondestructive sensing of bulk density and moisture content in shelled peanuts from microwave permittivity measurements , 2006 .

[7]  Michio Miyakawa,et al.  A numerical study on the measurement region of an open-ended coaxial probe used for complex permittivity measurement , 2001 .

[8]  H. B. Sifton.  Air-space tissue in plants , 1945, The Botanical Review.

[9]  J. Donovan.  Phase transitions of the starch–water system , 1979 .

[10]  Max Kuhn,et al.  caret: Classification and Regression Training , 2015 .

[11]  S. Wold,et al.  PLS-regression: a basic tool of chemometrics , 2001 .

[12]  G. Ramsay,et al.  The three-dimensional distribution of minerals in potato tubers. , 2011, Annals of botany.

[13]  Stuart O. Nelson,et al.  Dielectric spectroscopy measurements for moisture prediction in Vidalia onions , 2011 .

[14]  W. B. Westphal,et al.  Dielectric Behavior of a Semi-Solid Food at Low, Intermediate and High Moisture Contents , 1980 .

[15]  Reinhard Knöchel,et al.  Resonant microwave sensors for instantaneous determination of moisture in foodstuffs , 2001 .

[16]  Ljubomir J. Buturovic,et al.  Cross-validation pitfalls when selecting and assessing regression and classification models , 2014, Journal of Cheminformatics.

[17]  J. Barthel,et al.  The dielectric relaxation of water between 0°C and 35°C , 1999 .

[18]  Samir Trabelsi,et al.  Dielectric Spectroscopy of Honeydew Melons for Quality Sensing , 2006, 2006 IEEE Instrumentation and Measurement Technology Conference Proceedings.

[19]  Ronald Pethig,et al.  Dielectric and electronic properties of biological materials , 1979 .

[20]  W. Pace,et al.  Dielectric Properties of Potatoes and Potato Chips , 1968 .

[21]  A. Blennow,et al.  Testing properties of potato starch from different scales of isolations - A ringtest , 2007 .

[22]  R. Davis.  Tissue air space in the potato; Its estimation and relation to dry matter and specific gravity , 1962, American Potato Journal.

[23]  M. Nissen.  The weight of potatoes in water: Further studies on the relation between the dry matter and starch content , 1967, European Potato Journal.

[24]  D. Meissner,et al.  Polymerdynamics of cellulose and other polysaccharides in solid state-secondary dielectric relaxation processes , 2001 .

[25]  M. Kent,et al.  Dielectric studies of added water in poultry meat and scallops , 1996 .

[26]  Zulkifly Abbas,et al.  Determination of Moisture Content in Oil Palm Fruits Using a Five-Port Reflectometer , 2011, Sensors.

[27]  M. McCarthy,et al.  Determination of quality parameters of tomato paste using guided microwave spectroscopy , 2014 .

[28]  B. Makower,et al.  Radio-frequency dielectric properties of dehydrated carrots; application to moisture determination by electrical methods. , 1945, The Journal of physical chemistry.

[29]  Hu Lizhi,et al.  Discrimination of olive oil adulterated with vegetable oils using dielectric spectroscopy , 2010 .

[30]  P. Domich,et al.  Analysis of an open-ended coaxial probe with lift-off for nondestructive testing , 1994 .

[31]  M. Stone.  Cross‐Validatory Choice and Assessment of Statistical Predictions , 1976 .

[32]  C. Jun,et al.  Performance of some variable selection methods when multicollinearity is present , 2005 .

[33]  N. W. Simmonds,et al.  Relations between specific gravity, dry matter content and starch content of potatoes , 1977, Potato Research.

[34]  C C Davis,et al.  Microwave dielectric measurements of erythrocyte suspensions. , 1994, Biophysical journal.

[35]  M. Kent,et al.  Composition of foods using microwave dielectric spectra , 2000 .

[36]  Stuart O. Nelson,et al.  Free-space measurement of dielectric properties of cereal grain and oilseed at microwave frequencies , 2003 .

[37]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[38]  M. Edelenbos,et al.  Prediction of Starch, Soluble Sugars and Amino Acids in Potatoes (Solanum tuberosum L.) Using Hyperspectral Imaging, Dielectric and LF-NMR Methodologies , 2016, Potato Research.

[39]  Rasmus Bro,et al.  Variable selection in regression—a tutorial , 2010 .

[40]  M. L. Weaver,et al.  Anatomy and compositional variations within potatoes. IV. Total solids distribution in different cultivars , 1971, American Potato Journal.

[41]  G. Downey,et al.  Exploration of microwave dielectric and near infrared spectroscopy with multivariate data analysis for fat content determination in ground beef , 2016 .

[42]  R. Clarke,et al.  Dielectric metrology with coaxial sensors , 2007 .

[43]  Y. Feldman,et al.  A microwave sensor for the characterization of bovine milk , 2016 .

[44]  G. P. De Loor,et al.  The dielectric constant of foods and other materials with high water contents at microwave frequencies , 2007 .

[45]  A. Getchell,et al.  The chemical composition of white potatoes , 1951, American Potato Journal.

[46]  M. Stuchly,et al.  Coaxial Line Reflection Methods for Measuring Dielectric Properties of Biological Substances at Radio and Microwave Frequencies-A Review , 1980, IEEE Transactions on Instrumentation and Measurement.

[47]  S. Kays,et al.  10-1800-MHz dielectric properties of fresh apples during storage , 2007 .