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United States Department of Agriculture

Agricultural Research Service

Research Project: Systems to Assess, Monitor, and Preserve Peanut Quality and Safety

Location: Peanut Research

2012 Annual Report


1a.Objectives (from AD-416):
OBJECTIVE: 1. Determine spectral response characteristics (near infrared, visible, ultraviolet, and radio spectra) of in-shell and shelled peanuts related to various quality parameters such as oil chemistry, maturity, moisture content, protein. a. Develop a low cost NIR instrument utilizing discrete wavelengths in the near infrared, visible, or ultraviolet electromagnetic spectrum to measure oil chemistry, moisture content, protein, and maturity of in-shell and shelled peanuts. b. Develop techniques to utilize the dissipation of radio frequency energy of in-shell and shelled peanuts to determine pod density in damaged and undamaged peanut kernels. c. Develop techniques using ultrasound for blanching peanuts and predicting their maturity. 2. Develop sensors, instrumentation, and equipment to measure peanut quality throughout post harvest processing from the farm to final product. a. Develop and test a prototype meter to measure kernel moisture content of intact in-shell peanuts. b. Compare a prototype x-ray imaging system to conventional grading methods to determine foreign material, loose shelled kernels, and kernel size distribution of farmer stock grade samples. 3. Develop peanut curing, handling, and storage systems to preserve peanut quality and reduce operating costs. a. Measure energy costs of current peanut curing systems. b. Determine feasibility of catalytic infrared drying systems for use in curing farmer stock peanuts. c. Investigate the use of flexible hermetic storage containers for short term storage of farmer stock peanuts. 4. Reduce post harvest processing costs of peanuts for small-scale edible oil/biodiesel production. a. Develop appropriate scale shelling equipment for use with 130 kg/hr oil expeller. b. Optimize peanut kernel pre-processing to optimize oil expeller capacity, oil extraction, and subsequent transesterfication.


1b.Approach (from AD-416):
Using standard chemical and/or gravimetric procedures, moisture content (MC), total oil content (TOC), protein, and density of the unshelled peanut pods and shelled peanut kernels will be determined. Reflectance and absorbance of individual peanut pods and kernels in the NIR, visible, UV spectra will be measured using a spectrometer. Transmission of radio frequency (RF) individual and bulk samples of pods and kernels will be measured for comparison to density data. Statistical methods such as principal component analysis will be used to select appropriate wavelengths from the NIR, visible, UV, and RF spectra responsive to the desired properties. Calibration equations will be developed. In separate testing, peanut kernels manually sorted into the current peanut maturity groups will be subjected to ultrasound to determine the feasibility of objectively measuring peanut maturity. Collaborative research with commercial partners will be conducted to develop an in-shell moisture meter and to reference data and test an x-ray imaging system for non-destructive peanut grading. Peanut samples of all market types will be obtained from across the U.S. peanut production region. Samples will be processed through the prototype instruments and the predicted moisture content and other grade factors will be predicted. The samples will then be processed using procedures accepted by the Federal-State Inspection Service to determine accepted grade factors, and the moisture content determined using an accepted gravimetric oven method. Measured grade factors including moisture content will be compared to the those determined using the x-ray imaging system and the in-shell moisture meter. Wagon and semi-trailer dryers at a commercial drying facility will be instrumented to measure dryer performance. Data will be analyzed comparing the performance of the conventional wagons to the semi-trailer dryers. Other methods of curing may be more efficient than the conventional forced air methods used above. Peanuts will be cured using laboratory-scale forced air dryers to approximate conventional practice and a conveyor belt equipped catalytic infrared heaters. Energy consumption, drying time, and the resulting single kernel moisture variation, milling quality, and seed germination will be measured and compared. Storage tests will be conducted by placing conventionally grown, harvested, and cured peanuts in 1/10-scale farmer stock warehouses and in commercially available hermetic storage containers. Peanut grade factors, aflatoxin content, and seed germination will be measured before and after storage. The change in these peanut quality factors due to the storage type will be compared. Farmer stock peanuts will be processed in the pilot-scale NPRL Biodiesel Facility to determine the unit costs of on-farm production of biodiesel from peanut. Tests to combine unit operations, such as harvesting, cleaning, and shelling or develop small-scale in-line cleaning and shelling equipment to match the oil expeller capacity will be conducted to minimize the cost of processing peanuts for on-farm biodiesel production.


3.Progress Report:
Techniques using near infrared reflectance and absorbance were developed to measure oil content and oil chemistry of whole peanut seed without destroying the seed. Traditional chemical methods require that the seed be destroyed to determine the oil content and the oil chemistry making it impossible for peanut breeders to test seed from the single seed of a first generation. This allows peanut breeders to confirm the presence of desired oil chemistry traits in the first generation of peanut breeding and then plant the seed to continue development of the new variety. Cooperative Research and Development Agreement partner developed a sensor to measure in-shell peanut kernel moisture content. However, delays in the development and assembly of the sensor prevented deployment and in-field testing during the 2011 harvest. Tests were conducted at a commercial peanut drying facility using the laboratory prototype collaborator during the 2011 harvest confirmed previous research. A nationwide pilot project was conducted during the 2011 peanut harvest using Prototype X-ray imaging systems to grade farmer stock peanuts at nine peanut buying facilities from North Carolina to New Mexico. Grade factors (percent foreign material, loose shelled kernels, and kernel size distribution), measured using the x-ray imaging system were not significantly different than those measured using conventional grading methods. Machine to machine variation was unacceptable and remedies implemented in preparation for tests during the 2012 harvest. Data was collected at cooperating commercial peanut drying facilities to comparing temperature control strategies to reduce fossil fuel consumption for drying peanuts. These data will provide base line information for comparisons of new instrumentation and control methods in the future. Two shellers were tested for the purpose of in-line removal of peanut hulls immediately preceding the oil expeller. Both shellers performed satisfactorily in shelling the peanuts. One of the shellers had a 2000 lb/hour capacity that far exceeded the 300 lb/hr capacity of the oil expeller.


4.Accomplishments
1. Non-destructive measurement of single peanut seed oil content. The first generation of a new peanut variety consists of a single seed which may or may not have the desired oil chemistry. Traditional techniques require destructive testing to determine the oil chemistry meaning that the new variety must be propagated for a second year without knowing whether or not the new variety contains the desired trait. ARS agricultural engineers at Dawson, GA developed a method to measure the oil content and the ratio of oleic to linoleic fatty acids that leaves the seed intact. If the seed contains the desired trait, it may then be used to propagate the new variety with the desired oil chemistry trait eliminating a year from the 8-10 years normally required to bring a new peanut variety to the market. This method also eliminates the time and labor required to grow enough seed without the desired oil characteristics for traditional testing.

2. Prototype in-shell moisture meter developed. Peanut moisture is critical to proper drying, safe storage, and optimal processing and consumes considerable time and labor throughout post harvest processing. Commercial partners and ARS engineers developed a prototype sensor to measure peanut kernel moisture without shelling the sample. Following field calibrations during the fall 2011 peanut harvest, the sensor enables continuous measurement of peanuts during the drying process eliminating the time required to retrieve and shell a sample from the drying trailer for moisture measurement.

3. Drying and shelling equipment for use in developing nations. Poor moisture control and hand processing in developing countries such as Haiti leads to losing as much as 50% of a peanut crop that is desperately needed for food. ARS engineers in Dawson, GA and a peanut equipment manufacturer in Ashburn, GA developed and tested a small scale peanut dryer and peanut sheller that is suitable for use in remote areas of Haiti. The dryer consists of a small electric blower and propane burner, and collapsible bins to dry from 100 lb to 1500 lb of peanuts overnight in lieu of the traditional drying on a pad eliminating the exposure to inclement weather and subsequent mold growth. The sheller has a shelling capacity of up to 1 ton/hr replacing the tedious hand labor currently used. These pieces of equipment reduce the cost and losses in producing a peanut butter based ready to use therapeutic food (RUTF) for the treatment of malnutrition in Haiti.


Review Publications
Sundaram, J., Kandala, C., Butts, C.L., Chen, C.Y., Sobolev, V. 2011. Nondestructive NIR reflectance spectroscopic method for rapid fatty acid analysis of peanut seeds. Peanut Science. 38(2):85-92.

Kandala, C., Sundaram, J., Govindarajan, K., Subbiah, J. 2011. Nondestructive analysis of in-shell peanuts for moisture content using a custom built NIR Spectrometer. Journal of Food Engineering. 2:1-7.

Kandala, C., Sundaram, J. 2012. Determination of moisture content using NIR Reflectance Spectroscopty with single calibration for both Valencia and Virginia in-shell peanuts. Transactions of the ASABE. 55:2.

Kandala, C., Settaluri, V., Sundaram, J. 2012. Nondestructive measurement of moisture content of different types of wheat using a single calibration with a parallel-plate capacitance sensor. Transactions of the ASABE. 55(4).

Last Modified: 9/10/2014
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