2015/2016 Sorghum Harvest and Export Quality Report

IV. HARVEST QUALITY TEST RESULTS

A. Grade Factors

The U.S. Department of Agriculture’s Federal Grain Inspection Service (FGIS) has established numerical grades, definitions, and standards for grains. The attributes that determine the numerical grades for sorghum are test weight, broken kernels and foreign material (BNFM), foreign material, total damage, and heat damage. The table for “U.S. Sorghum Grades and Grade Requirements” is provided on page 83 of this report.

SUMMARY: GRADE FACTORS AND MOISTURE

  • Average U.S. Harvest Aggregate test weight in 2015 was 58.9 lb/bu (75.9 kg/hl), with 84.5% of the samples at or above the factor limit for U.S. No. 1 grade and 97% of the samples at or above the limit for U.S. No. 2 grade (55.0 lb/bu or 70.8 kg/hl).
  • Average U.S. Harvest Aggregate broken kernels and foreign material (BNFM) in the 2015 samples (1.7%) was well below the maximum for U.S. No. 1 grade (3.0%), with 99% of the samples at or below the maximum for U.S. No. 2 grade (6.0%) and 91% of the samples also at or below the maximum for U.S. No. 1 grade.
  • Foreign material in the U.S. Harvest Aggregate samples averaged 0.6% in 2015, well below the maximum value of 1.0% for U.S. No. 1 grade. 98% of the samples were at or below the maximum foreign material allowable for U.S. No. 2 grade (2.0%).
  • Total damage in the 2015 U.S. Harvest Aggregate samples was distributed with 99% of the samples having 2% or less damaged kernels (the maximum allowable for U.S. No. 1 grade), and 99.5% having 5% or less (the maximum allowable for U.S. No. 2 grade).
  • There was no heat damage observed in any of the 2015 U.S. Harvest Aggregate samples.
  • The U.S. Harvest Aggregate moisture contents recorded at the elevator in the 2015 samples averaged 14.1%, with a minimum value of 10.1% and a maximum value of 17.9%.

1. Test Weight

Test weight (kernel weight per standard container volume) is a measure of bulk density and is often used as a general indicator of overall quality and as a gauge of endosperm hardness for size reduction and value-added processing. High test weight sorghum takes up less storage space than the same weight of sorghum with a lower test weight. Test weight is initially impacted by genetic differences in the structure of the kernel. However, it is also affected by moisture content, method of drying, physical damage to the kernel (broken kernels and scuffed surfaces), foreign material in the sample, kernel size, stress during the growing season, and microbiological damage. When sampled and measured at the point of delivery from the farm at a given moisture content, high test weight generally indicates high quality, high percent of hard (or vitreous) endosperm, and sound, clean sorghum. Test weight is highly correlated with kernel true density and reflects kernel hardness and kernel maturity1.

RESULTS

  • Average U.S. Harvest Aggregate test weight in 2015 was 58.9 lb/bu (75.9 kg/hl), above the minimum for U.S. No. 1 grade (57.0 lb/bu or 73.4 kg/hl).
  • The test weight values for the 2015 average U.S. Harvest Aggregate samples had a standard deviation of 1.68 lb/bu (2.16 kg/hl).
  • The 2015 U.S. Harvest Aggregate test weight values were distributed with 84.5% of the samples at or above the factor limit for U.S. No. 1 grade and 97.1% of the samples at or above the limit for U.S. No. 2 grade (55.0 lb/bu or 70.8 kg/hl).
  • Late Harvest average test weight (59.5 lb/bu or 76.6 kg/hl) in 2015 was slightly higher than Early Harvest average test weight (57.8 lb/bu or 74.4 kg/hl), which may be attributable to the more favorable weather conditions for grain fill in the Late Harvest Area compared to the Early Harvest Area.

1Buffo, R.A., C.L. Weller and A.M. Parkhurst. 1998. Relationship among grain sorghum quality factors. Cereal Chemistry 75(1):100-104.

2. Broken Kernels and Foreign Material (BNFM)

Broken kernels and foreign material (BNFM) is an indicator of the amount of clean, sound sorghum available for feed and processing. The lower the percentage of BNFM, the less foreign material and/or fewer broken kernels are in a sample. Higher levels of BNFM in farmoriginated samples generally stem from combine settings and/or weed seeds in the field. BNFM levels will normally increase during drying and handling, depending on the methods used and the soundness of the kernels. Stress crack formation during dry down or during mechanical drying after harvest will also result in an increase in broken kernels and BNFM during subsequent handling.

RESULTS

  • U.S. Harvest Aggregate average BNFM in the 2015 samples (1.7%) was well below the maximum for U.S. No. 1 grade (3.0%).
  • The BNFM values for the 2015 U.S. Harvest Aggregate samples had a standard deviation of 0.93%. Of the 2015 U.S. Harvest Aggregate samples, 99% were at or below the maximum for U.S. No. 2 grade (6.0%), with 90.8% of the samples also at or below the maximum for U.S. No. 1 grade.
  • The 2015 sorghum crop condition rated higher than the average of the previous five crop years throughout most of the growing season. These high crop ratings were reflected in the U.S. Harvest Aggregate BNFM values all being at or below the maximum for U.S. No. 2 grade (6%). In addition, 92% of the samples were at or below the maximum for U.S. No. 1 grade (3%).

3. Foreign Material

Foreign material, a subset of BNFM, is of importance because it has little feed or processing value. It is also generally higher in moisture content than the sorghum itself, and therefore creates a potential for deterioration of sorghum quality during storage. Foreign material also contributes to the spout-line and has the possibility of creating more quality problems and damage because of its higher moisture level, as mentioned above.

RESULTS

  • Foreign material in the U.S. Harvest Aggregate samples averaged 0.6% in 2015, well below the maximum value of 1.0% for U.S. No. 1 grade.
  • The foreign material values for the 2015 U.S. Harvest Aggregate samples had a standard deviation of 0.41%.
  • In the 2015 U.S. Harvest Aggregate samples, 97.6% were at or below the maximum foreign material allowable for U.S. No. 2 grade (2.0%).
  • Late Harvest average foreign material (0.7%) in 2015 was slightly higher than Early Harvest average foreign material (0.5%), which may be attributable to pest pressure differences in the growing areas of the samples.

4. Total Damage

Total damage is the percentage of kernels and pieces of kernels that are visually damaged in some way, including badly ground-damaged, badly weather-damaged, diseased, frostdamaged, germ-damaged, heat-damaged, insect-bored, mold-damaged, sprout-damaged, or otherwise materially damaged. Most of these types of damage result in some sort of discoloration or change in kernel texture. Damage does not include broken pieces of grain that are otherwise normal in appearance. Mold damage is usually associated with higher than desired moisture contents and temperatures during growth and/or in storage. Mold damage and the associated potential for development of mycotoxins are the damage factors of greatest concern. Mold damage can occur prior to harvest as well as during temporary storage at high moisture and high temperature levels before delivery.

RESULTS

  • Average U.S. Harvest Aggregate total damage was 0.1% in 2015, well below the limit for U.S. No. 1 grade (2%).
  • The total damage values for the 2015 U.S. Harvest Aggregate samples had a standard deviation of 0.13%.
  • Total damage in the 2015 U.S. Harvest Aggregate samples was distributed with 99% of the samples having 2% or less damaged kernels (the maximum allowable for U.S. No. 1 grade), and 99.5% having 5% or less (the maximum allowable for U.S. No. 2 grade).
  • No damage was observed in Late Harvest samples, whereas the observed levels for Aggregate samples can be attributed to the damage observed in Early Harvest samples. The absence of damage in the Late Harvest samples may have been due to lack of weather and pest problems, along with good harvesting conditions and rapid transit to the elevator.

5. Heat Damage

Heat damage is a subset of total damage and has separate allowances in the U.S. Grade Standards. Heat damage can be caused by microbiological activity in warm, moist grain or by high heat applied during drying. Heat damage is seldom present in sorghum delivered at harvest directly from farms.

RESULTS

  • There was no heat damage observed in any of the 2015 U.S. Harvest Aggregate samples.
  • The absence of heat damage likely was due in part to recently-harvested samples coming directly from farm to elevator with minimal prior drying.