Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2007
Publication Date: 11/9/2007
Citation: Butts, C.L., Kandala, C., Sorensen, R.B., Lamb, M.C. 2007. In-shell Bulk Density as an Estimator of Farmers Stock Grade Factors. Peanut Science 34(2)135-141.
Interpretive Summary: Bulk density of a product can be determined by obtaining is weight, then pouring it into a container of known size and measuring the product depth. The bulk density is then calculated by dividing the weight by the product volume. This research was conducted to determine if bulk density of in-shell peanuts can be used to estimate the factors currently used to establish peanut value. Data was obtained over a 4-year period and for several peanut cultivars, and for all four peanut types (runner, spanish, valencia, and virginia). Bulk density averaged 19.7 lb/ft3 for runner, 26.6 lb/ft3 for spanish, 30.6 lb/ft3 for valencia, and 16.1 lb/ft3 for virginia peanuts. The relationship between bulk density and marketing grade factors was very dependent on location, peanut variety, and the year. Bulk density cannot be used to accurately determine the peanut value when sold by the grower.
Technical Abstract: The objective of this research was to determine whether or not bulk density can be used to accurately estimate farmer stock grade factors such as total sound mature kernels and other kernels. Physical properties including bulk density, pod size and kernel size distributions are measured as part of the cooperative Uniform Peanut Performance Tests (UPPT). Using physical property data from three years (2002-2004) of UPPT, analysis of variance were performed to determine the effect of bulk density, location, year, peanut type, and cultivar on percent total sound mature kernels (TSMK), other kernels (OK), and farmer stock value (FSV). Results indicated that all effects in the model were significant in predicting both TSMK and FSV and accounted for most of the variation (R2=0.80). Linear regressions of the UPPT data with bulk density as a single factor showed that TSMK and FSV increased as bulk density increased with poor R2 values (R2=0.2). A second set of data collected during the 2005 peanut harvest by Federal State Inspection Service (FSIS) had similar results. Location and peanut type were highly significant factors in the variation of TSMK, OK, and FSV. Overall correlation of grade factors with bulk density, location, and type was poor (R2<0.5). Based on these data, bulk density cannot be used to accurately estimate TSMK and OK for marketing farmer stock peanuts. Observed bulk density averaged 316 kg/m3 for runner, 427 kg/m3 for spanish, 491 kg/m3 for valencia, and 258 kg/m3 for virginia peanuts.