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United States Department of Agriculture

Agricultural Research Service

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Research Project: Optical and Mechanical Instrumentation for Quality Assessment of Small Grains

Location: Food Quality Laboratory

2012 Annual Report


1a.Objectives (from AD-416):
(1) Develop spectroscopic imaging procedures (hyperspectral or multispectral) that can be used to assess quality of small grains (emphasizing wheat, rice, and barley) and oilseeds in bulk for grade, class, foreign material, and damage (mold, black point, heat, frost, and insect). (1a). Develop hyperspectral image analysis algorithms for determination of the level of mold damage from Fusarium Head Blight on wheat kernels. This will involve the development of image processing routines that identify the infected kernels in representative samples of intact wheat kernels and determine the regions of Fusarium damage within each infected kernel. (1b) Develop hyperspectral image analysis algorithms for identification of wheat kernels damaged by heat, frost, black point, and insects, as defined by official inspection criteria. (1c) Develop hyperspectral image analysis algorithms for the prediction of flour yield and break flour yield in soft red winter wheat. (2) Develop optical and mechanical methods and instrumentation for grain quality measurement that are applicable at points of sale, such as elevators, terminals, and mills. (2a) Develop rapid and objective optical methods for prediction of starch quality indicators in wheat, such as the ratio of amylose-to-amylopectin, and the identification of wheat into three states of waxiness: waxy, partial waxy, and wild type. (2b) Develop a near-infrared (NIR) spectroscopy procedure for wheat gluten quality determination for use in commerce.


1b.Approach (from AD-416):
Fusarium-inoculated hard red spring and hard red winter wheat samples will be imaged using an in-house near-IR hyperspectral system. Image analysis will be a multistep process. First, for each kernel a mask will be created from one of images whose wavelength creates a strong contrast between kernel and background. The mask will be applied to the images at all other wavelengths in order to remove the background. Principal component analysis (PCA) loadings from images of damaged and normal regions will be examined to identify the wavelengths at local minima and maxima, which inherently possess the greatest contrast between Fusarium damage and healthy endosperm.

Hyperspectral image analysis will also be used to examine three wheat milling properties: milling yield (% straight grade flour) defined as the percent by mass of all flour fractions recovered through a 94-mesh screen; solvent retention capacity in 50% (w/w) sucrose solution, a measure of the water affinity of the macro-polymers (starch, arabinoxylans, gluten, and gliadins); and solvent retention capacity in 5% (w/w) lactic acid, an indicator of gluten strength.

Near-IR spectroscopy will explored as a method for measuring the degree of waxiness in hexaploid wheat. Wild type, partial waxy (waxy null alleles in one or two genomes), and waxy samples (null alleles in all genomes), drawn from breeders' advanced lines of hexaploid wheat, will be used. Gel electrophoresis will be used to identify the waxy protein (granule bound starch synthase, GBSS) in each sample.

Lastly, a near-IR procedure for wheat gluten quality will be developed in conjunction with a rheological procedure. The wheat samples consist of approximately 50 lines grown in field replicated (3x) plots over three consecutive seasons. Half of these lines are transgenic, in which the gene construct modifies the length of the central repeat region within the high molecular weight (HMW) glutenin subunits. Different levels of gene expression, hence, level of glutenin protein, are represented as a function of the transgenic ancestor. Thus, this set will contain a much wider range in the ratio of glutenin-to-gliadin than naturally encountered. Flour from these samples will be evaluated for glutenin and gliadin contents by SE-HPLC another ARS laboratory. At Beltsville, the flour will be scanned in the NIR and FT-mid-IR regions. Rheological properties, such as the recovery response for a gluten specimen subjected to a controlled regiment of compressive force and hold time, will be measured at a third laboratory. Spectral calibrations for glutenin and gliadin concentrations, as well as calibrations for the rheological parameters (percent recovery and recovery time constant), will be developed using partial least squares regression. Additionally, classification algorithms (PLS discriminant analysis and SVM) algorithms will be developed that will identify the genetically modified lines based on their spectral response.


3.Progress Report:
A study was completed on the use of near-infrared spectroscopic imaging (also known as hyperspectral imaging, or HSI) to estimate soft wheat milling quality properties. With HSI, both spectral and physical (shape, size, and texture) information is gathered simultaneously on a layer of intact grain. In the study, conventional quality tests and HSI were performed on approximately 120 common varieties and advanced lines of U.S. soft wheat. Spectral image processing routines were developed for determining five properties of kernel shape (area, length, width, volume, and slenderness) and three spectrally based (principal component) properties. The eight were examined for their relationships to flour quality properties routinely used in variety evaluation, namely flour yield, softness equivalent, and sucrose solvent retention capacity (SRC). If successful, HSI technology offers the possibility of substantially reducing the need for conducting laborious pilot milling tests.

It has only been in the past decade that HSI has developed to the point where it can be used outside of research laboratories. Therefore, a review of first principles of quantum mechanics, light scatter, vibrational spectroscopy, and statistical regression was completed and described in a book chapter for the purpose of expanding this technology to agricultural food quality and safety inspection.

An on-the-fly digital imaging system was designed and fabricated that captures images of freefalling wheat kernels for inspection of defects. The novel aspects of this system include the simultaneous capture of three viewing angles of the object at very short exposure times (~1/30,000 sec) which yields freeze-frame style images that each collectively cover approximately 80% of the whole seed surface. Processing routines were developed that characterize each viewing angle of the kernel by its morphology (size and shape), texture (surface roughness), and boundary silhouette irregularity. The system was tested using a set of weather-damaged breeders samples of hard red and white wheat from a 2011 harvest. Damage conditions included moldy (Fusarium-infected) kernels, kernels with black tip, and sprouted kernels. The image features were subsequently fed into traditional classification algorithms that attempted to distinguish damaged kernels from sound ones. This real time imaging system is to be used in inspection operations and its principles may eventually be applied to online operations in flour mills for removing damaged and diseased kernels from the mainstream.


4.Accomplishments
1. Improvements to single grain defect assessment. Wheat inspection is traditionally reliant on human visual analysis for recognition of defects from mold, weather, disease, and storage. Although several attempts have been made over the decades to develop instrument based alternatives, inspection still remains a challenge. ARS researchers at Beltsville have developed a digital imaging system that captures images of individual seeds in freefall. The design is intended to be coupled with rapid image processing feature analysis to assess the soundness of the seed for inspection purposes and eventually for application in high speed sorting. This work will benefit the wheat trading and milling industries.


Review Publications
Morris, C.F., Delwiche, S.R., Bettge, A.D., Mabille, F., Abecassis, J., Pitts, M.J., Dowell, F.E., Deroo, C., Pearson, T.C. 2011. Collaborative analysis of wheat endosperm compressive material properties. Cereal Chemistry. 88:391-396.

Delwiche, S.R., Morris, C.F., Mabille, F., Abecassis, J. 2012. Influence of instrument rigidity and specimen geometry on calculations of compressive strength properties of wheat endosperm. Cereal Chemistry. 89(1):24-29.

Last Modified: 10/31/2014
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