Evaluating on-farm methods for measuring dry matter content of potatoes

Monday, July 21, 2014
Exhibit Hall AB (Kansas City Convention Center)
Richard J. Norell , University of Idaho, Idaho Falls, ID
J. Benton Glaze, Jr. , University of Idaho, Twin Falls, ID
Mireille Chahine , University of Idaho, Twin Falls, ID
Nora L. Olsen , University of Idaho, Kimberly, ID
Abstract Text:

Measuring dry matter content is critical for pricing cull potatoes and for effectively managing potato feeding rates on livestock operations.  In this study, dry matter determinations from three on-farm methods (microwave, dehydrator, and Koster Moisture tester) were compared with a laboratory oven.  Twenty lots of potatoes were obtained for the study (1 blue, 3 red, 3 yellow, and 14 burbank varieties).  Ten potatoes from each lot were cleaned then sliced horizontally into 7mm thick slices.  Duplicate 100g sub-samples were run with each drying method.  Lab (L) samples were dried for 24 h at 55 C.  Equipment for the on-farm methods included two 1000-watt microwaves (M), four 500-watt Nesco FD60 food dehydrators (D) set at 68 C, and two Koster Moisture Testers (K).  Samples were weighed at specified time intervals during the drying process with the on-farm methods and a run was deemed complete when two identical weights were obtained.  Drying time and dry matter (DM) data were analyzed as a completely randomized block design.  Drying time differed significantly between on-farm methods (p<0.001) and averaged 8.6, 248.5, and 428.6 minutes for M, K, and D, respectively.  Mean DM was significantly higher (p<0.05) for M (23.4%) and D (23.5%) than K (22.6%) or L (22.7%).   A Bland-Altman assessment for agreement was used to compare difference in DM between each on-farm method and L.  A range of agreement was defined as mean bias + or – 2 SD.  The 95% limits of agreement between the lab oven and M, K, and D were: -0.7% to 1.5%; -1.6% to 1.4%; -1.0% to 1.6%, respectively.  Overall, the three on-farm methods provided closely corresponding DM to L.  The trend lines between Bland-Altman differences and oven DM were not statistically significant (p>0.75) for D and K but was significant (p<0.05) for M with a negative slope across the range of DM in the study.  Drying potatoes with all three on-farm methods did not create objectionable odors and can therefore be conducted indoors if desired.  This study indicates that the three on-farm methods are effective tools for measuring DM content of potatoes. 

Keywords: potatoes, dry matter, on-farm testing