Near-Infrared Transmission and Reflectance Spectroscopy for the Determination of Dietary Fiber in Barley Cultivars

viscous fibers such as -glucan, is associated with lowering of blood cholesterol levels and normalizing blood Dietary fiber is an important quality parameter of barley (Hordeum glucose and insulin, making foods containing these fivulgare L.) but is extremely laborious to measure. Near-infrared (NIR) transmission and reflectance spectroscopy were investigated bers an important part of dietary strategies to minimize as rapid screening tools to evaluate the total dietary fiber content of cardiovascular disease and type-2 diabetes (American barley cultivars. The Foss Grainspec Rice Analyzer and NIR Systems Dietetic Association, 2002). 6500 spectrometer were used to obtain transmission and reflectance In contrast to its benefits in food, fiber is detrimental spectra, respectively, of polished grains and ground barley. Total diduring malting and brewing. In brewing, a high soluble etary fiber was determined for each cultivar by AOAC Method 991.43. fiber content, particularly of -glucan, causes blocking Modified PLS models developed for predicting total dietary fiber, of filters and reduced recovery of fermentable sugars using transmission spectra (850–1048 nm) of polished grains, had a (see review by Bamforth, 1985). Furthermore, high -glustandard error of cross validation (SECV) of 10.4 (range 58–197) g kg 1 can content can lead to colloidal instability and haze and R 2 of 0.82 indicating sufficient accuracy for selecting or rejecting formation in the final product. The major components high dietary fiber cultivars. NIR reflectance spectroscopy (1104–2494 nm) of ground barley samples resulted in a model with SECV of 5.2 of barley are protein, fiber, and starch; however, there (range 58–197) g kg 1 and R 2 0.96, indicating a high degree of precision appears to be a wide range in genetic variation of these in the prediction of total dietary fiber. The increased accuracy of the components (Oscarsson et al., 1996; Bhatty, 1999; Anreflectance model may be due in part to more information available dersson, 1999). Globally, covered or hulled barley is the in the wavelength region used. The precision, low cost per sample most widely produced and is the traditional barley used and speed of measurement of the technique allow making dietary for malting and brewing. Alternatively, naked or hullfiber selection decisions for large numbers of progeny in barley breedless barley is most often used for food since it does not ing programs. require processing to remove the hull, and thus nutrients and bioactive components are retained. The fiber content of plant material is measured as D fiber is an important quality parameter for total dietary fiber (AOAC, 1992), which, by definition, barley cultivars. High fiber content is undesirable includes plant nonstarch polysaccharides, oligosacchain cultivars used for brewing and animal feed and desirrides, fructans, resistant starch, and lignin (AACC, 2001). able in barley cultivars used for food production. The This is in contrast to crude fiber, acid detergent fiber, primary use of barley is for production of malt or germiand neutral detergent fiber methods, which do not meanated barley used as a source of fermentable sugars for sure all of the individual components (Dreher, 1987). the production of beer and whiskey. Other uses include Conventional dietary fiber analysis is extremely time feed for animals in northern climates where corn (Zea consuming and labor intensive. The procedures used for mays L.) cannot be grown, as a staple for human food, total, soluble, and insoluble dietary fiber are enzymatic– and for the production of waxy starch used in food gravimetric methods or enzymatic chromatographic methprocessing (Andersson, 1999). Fiber extracted from barods that take 2 to 3 d to perform and are labor intensive ley has potential in functional and fortified foods such (e.g., AOAC, 1992, Englyst et al., 1982). It would be beneas snack bars and beverages. Additional food uses of ficial in breeding programs to have a rapid method that barley in Japan include barley tea, shochu, miso, and would allow evaluating the fiber content of hundreds of as a rice extender. samples per day. Although to date the production of barley for human NIR spectroscopy is an analytical technique that is food has been minor, the fact that some cultivars contain rapid, requires very little labor once a calibration is considerable quantities of fiber, particularly soluble fiobtained, and does not require chemicals or, therefore, ber, present primarily in the form of -glucan (Fincher, create chemical waste. The technique has extensive ap1975), makes barley of greater interest as a source of plication for the analysis of constituents of agricultural dietary fiber. High dietary fiber intake, particularly of crops, feeds, and foods (Williams and Norris, 1987, 2001; Marten et al., 1989; Osborne et al., 1993; Roberts et al., 2004). Previous work has demonstrated the potential of S.E. Kays and F.E. Barton II, USDA-ARS-RRC, P.O. Box 5677, Athens, GA 30604-5677; N. Shimizu and K. Ohtsubo, National Food NIR spectroscopy for the rapid evaluation of neutral Research Institute, Incorporated Administrative Agency, 2-1-12 Kandetergent fiber, total dietary fiber, and the components nondai, Tsukuba, Ibaraki, 305-8642, Japan. Received 6 Jan. 2005. of dietary fiber in wheat bran mixtures, oat bran, and *Corresponding author ([email protected]). diverse cereal products (Baker , 1983; Horváth et al., Published in Crop Sci. 45:2307–2311 (2005). Crop Breeding, Genetics & Cytology Abbreviations: NIR, near-infrared; PLS, partial least squares; R 2, coefficient of determination; r 2, multiple coefficient of determination; doi:10.2135/cropsci2005.0013 © Crop Science Society of America SD, standard deviation; SEC, standard error of calibration; SECV, standard error of cross validation; TDF, total dietary fiber. 677 S. Segoe Rd., Madison, WI 53711 USA 2307 Published online September 23, 2005