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2015/2016 Sorghum Early Harvest Report

Contents

  1. Harvest Quality Highlights
  2. Introduction
  3. Quality Test Results
  4. Chemical Composition
  5. Physical Factors
  6. Testing Analysis Methods
  7. Moisture
  8. Chemical Composition
  9. Physical Factors
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D.Physical Factors

Physical factors include other quality attributes that are neither grading factors nor chemical composition. Tests for physical factors provide additional information about the processing characteristics of sorghum for various uses, as well as its storability and potential for breakage in handling. The storability, the ability to withstand handling, and the processing performance of sorghum are influenced by sorghum’s morphology. Sorghum kernels are morphologically made up of three parts, the germ or embryo, the pericarp or outer covering, and the endosperm. The endosperm represents about 82 to 86% of the kernel, and consists of soft (also referred to as floury) endosperm and of hard (also called vitreous) endosperm, as shown to the right. The endosperm contains primarily starch and protein whereas the germ contains oil and some proteins. The pericarp is comprised mostly of fiber with a small coating of waxy material.

SUMMARY: PHYSICAL FACTORS

  • For the Early Harvest sorghum samples in 2015, kernel diameter averaged 2.54 mm, 1000-k weights averaged 25.97 g and kernel volume averaged 19.22 mm3, all typical values for kernels from any sorghum samples, except 1000-k weights which are on the lower end of typical values cited in literature.
  • In the 2015 Early Harvest samples, kernel true densities averaged 1.350 g/cm3, which is within the range of feed sorghum.
  • Kernel hardness index averaged 68.5 for Early Harvest sorghum in 2015, a typical value for any sorghum sample.

1. Kernel Diameter

Kernel diameter directly correlates with kernel volume, affects size reduction behavior and material handling practices, and may indicate maturity of kernels. Size reduction refers to reducing kernels (large particles) to ground material (small particles), commonly through grinding/milling. Size reduction, energy consumption, decortication efficiency and yield of kernel components depend on diameter. Decortication refers to the removal of the pericarp and germ from a kernel by attrition or abrasion with minimal removal of endosperm before subsequent grinding/ milling. The smaller the kernels, the more care and concern required in handling. Incomplete kernel fill and unexpected weather conditions may contribute to small diameter values.

RESULTS

  • Kernel diameter averaged 2.54 mm for Early Harvest sorghum in 2015, a typical value for any sorghum samples.
  • The kernel diameter values for the 2015 Early Harvest samples had a standard deviation of 0.10 mm.
  • Kernel diameters for the Early Harvest samples ranged from 2.20 to 2.90 mm in 2015.
  • In 2015, Early Harvest kernel diameters were distributed so that 26% of the samples had kernel diameters of 2.7 mm or greater, 54% were between 2.5 and 2.69 mm, and 20% were less than 2.5 mm.

2. 1000-Kernel Weight

1000-kernel (1000-k) weight is the weight for a fixed number of kernels. Kernel volume (or size) can be inferred from 1000-k weight, since as 1000-k weight increases or decreases, kernel volume will proportionally increase or decrease. Kernel volume affects drying rates. As kernel volume increases, the volume-to-surface-area ratio for the kernel becomes greater, and drying time to a desired moisture takes longer. Kernel weights tend to be higher for specialty varieties of sorghum that have high amounts of hard (vitreous) endosperm.

RESULTS

  • 1000-k weights averaged 25.97 g for Early Harvest sorghum in 2015, a value on the lower end of typical 1000-k weight values in literature for U.S. sorghum hybrids.
  • The 1000-k weight values for the 2015 Early Harvest samples had a standard deviation of 2.32 g.
  • 1000-k weights for the Early Harvest samples ranged from 19.50 to 32.10 g in 2015.
  • In the 2015 Early Harvest samples, 1000-k weights were distributed so that 14% of the samples had 1000-k weights of 30.00 g or greater, 64% had between 24.00 and 29.99 g, and 22% less than 24 g.

3. Kernel Volume

Kernel volume (or size) is directly related to kernel diameter and often indicative of growing conditions. If conditions are dry, kernels may be small due to stunted development. If drought hits later in the season, kernels may have lower fill. Small kernels are more difficult to handle and, due to their having a greater surface-area-to-volume ratio than large kernels, greater amounts of endosperm are removed during decortication, reducing yield of endospermderived products.

RESULTS

  • Kernel volume averaged 19.22 mm3 for Early Harvest sorghum in 2015, a typical value for any sorghum samples.
  • The kernel volume values for the 2015 Early Harvest samples had a standard deviation of 1.61 mm3.
  • Kernel volumes for the Early Harvest samples ranged from 14.56 to 23.46 mm3 in 2015.
  • In the 2015 Early Harvest samples, kernel volumes were distributed so that 26% of the samples had kernel volumes of less than 18.0 mm3, 64% were between 18.0 and 21.99 mm3, and 10% equal to or greater than 22.0 mm3.

4. Kernel True Density

Kernel true density (kernel weight per kernel volume) is a relative indicator of kernel hardness, which is useful during size reduction operations. Genetics of the sorghum hybrid and the growing environment affect kernel true density. Sorghum with higher density is typically less susceptible to breakage in handling than lower-density sorghum. Most feed sorghum has true density values ranging from 1.330 to 1.400 g/cm3. Sorghum with density greater than 1.315 g/cm3 is judged suitable for processing to brewers’ grits and stiff porridge whereas sorghum with density less than 1.315 g/cm3 is suitable for processing into soft bread flour and starch.

RESULTS

  • Kernel true density averaged 1.350 g/cm3 for U.S. Early Harvest sorghum in 2015.
  • The true density values for the 2015 Early Harvest samples had a standard deviation of 0.015 g/cm3.
  • True densities for the 2015 Early Harvest samples ranged from 1.295 to 1.382 g/cm3 in 2015.
  • In the 2015 Early Harvest samples, kernel true densities were distributed so that 8% of the samples were below 1.315 g/cm3, 10% between 1.315 and 1.329 g/cm3, and 82% greater than or equal to 1.330 g/cm3 and less than 1.390 g/cm3.

5. Kernel Hardness Index

Kernel hardness affects resistance to molds and insects, size reduction behavior and the end use of sorghum. Sieving behavior, size reduction energy consumption, particle size distribution of ground material and yield of kernel components depend on hardness. Harder sorghum produces coarser or larger particles than softer sorghum and requires more energy per mass of sorghum to achieve similar particle size distribution during size reduction. Grinding/milling for optimum particle size for livestock or poultry feed may be costlier for harder sorghum than for softer sorghum. Test weight and kernel density correlate with hardness. Kernel hardness index is a dimensionless number with increasing value indicating kernels increasing in physical hardness.

RESULTS

  • Kernel hardness index averaged 68.5 for Early Harvest sorghum in 2015, a typical value for any sorghum sample.
  • The kernel hardness index values for the 2015 Early Harvest samples had a standard deviation of 6.9.
  • Kernel hardness index for the Early Harvest samples ranged from 37.1 to 84.0 in 2015.
  • In the 2015 Early Harvest samples, kernel hardness indices were distributed so that 6% of the samples had kernel hardness indices of 80.0 or greater, 92% had 40.0 to 79.99, and 2% had less than 40.