Location: Food Quality Laboratory
Title: Limitations of single kernel near-infrared hyperspectral imaging of soft wheat for milling quality Authors
Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 2013
Publication Date: April 1, 2013
Citation: Delwiche, S.R., Souza, E.J., Kim, M.S. 2013. Near-infrared hyperspectral imaging for milling quality of soft wheat. Biosystems Engineering. 115:260-273. Interpretive Summary: Wheat variety development in the United States involves several years of greenhouse and field evaluation, with testing for milling and baking quality occurring just before release. For soft wheat, which prevails in the eastern half of the continent, quality is typically assessed by a series of physical and chemical tests. Physical tests typically measure milling flour yield and softness equivalent (a gauge of how easily the endosperm detaches from the kernel upon milling). A common chemical test measures the amount of aqueous solution (of sucrose in our case) absorbed by flour and gives an indication of dough processing characteristics. Unfortunately, both physical and chemical testing procedures are labor intensive and equipment intensive. A relatively new technique called hyperspectral imaging (HSI) was studied as an alternative method for soft wheat quality evaluation. With HSI, both spectral and physical (shape, size, and texture) information are gathered simultaneously on a layer of non-touching kernels. In our study, conventional quality tests and HSI were performed on approximately 120 varieties of soft wheat. Five properties of kernel shape (area, length, width, volume, and slenderness), and three spectrally derived properties were examined for their correlations to flour yield, softness equivalent, and sucrose solvent retention capacity (SRC). HSI properties were most closely correlated to softness equivalent and just slightly correlated to flour yield and sucrose SRC. We conclude that although HSI may become a supplemental tool for wheat quality evaluation, it is doubtful that it can replace conventional methodology. Beneficiaries of this research include plant breeders and the wheat milling and baking industries.
Technical Abstract: Soft wheat milling quality assessment typically begins in the later stages of wheat breeding programs and continues after cultivar release in commercial milling and processing operations. Performed as a combination of physical tests such as pilot scale milling for endosperm extraction efficiency and ash determination, and chemical tests such as solvent retention capacity for functionality evaluation, these evaluations are both equipment and labor intensive. Near-infrared (NIR) hyperspectral image analysis, a technique that is gaining interest in food and pharmaceutical inspection research, was explored as an alternative procedure for milling quality evaluation. Three quality properties were studied, flour yield (the weight fraction of flour to whole grain), softness equivalent (a gauge of how easily flour is released from the kernel during break), and sucrose solvent retention capacity (related to arabinoxylans, which influence water absorption during dough mixing) because of their high degree of heritability and influence on soft wheat quality. NIR hyperspectral (HS) reflectance images (1000-1700 nm) of non-touching kernels were collected on more than 120 pure cultivars or advanced lines of soft red and white wheat. Five morphological properties (area, elliptical eccentricity and major and minor axis lengths, and ellipsoidal volume) and three spectral properties (principal component scores 1 through 3) were exhaustively examined in multiple linear regression models for each quality property. Results indicated that softness equivalent exhibited the highest correlation with HS properties, while sucrose SRC had the lowest correlation. The combination of morphological and spectral properties produced better models than either property group alone. However, because of the inherent chemical and physical complexities of wheat, HS imaging will probably not be sufficient for replacing actual pilot milling procedures.