Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/17/2005
Publication Date: 12/31/2005
Citation: Kim, Y., Singh, M., S.E. Kays. 2006. Near-infrared spectroscopy for measurement of total dietary fiber in homogenized meals. Journal of Agricultural and Food Chemistry. 54:292-298. Interpretive Summary: Mixed meals are packaged foods that contain two or more food groups and are available to the consumer as ready-to-eat or ready-to-heat and eat meals. As packaged products U.S. nutrition labeling regulations require total dietary fiber (TDF) to be reported on the nutrition labels of mixed meals. Traditional TDF analysis for monitoring mixed meals requires a minimum of 4 days processing time, is labor intensive, and generates chemical waste. Near infrared (NIR) spectroscopy is a technique that measures the amount of light energy reflected by a substance in a specific region of the electromagnetic spectrum and relates the energy to a measured component of the substance by mathematical modeling. NIR presents a rapid, inexpensive, accurate, and environmentally benign method for the analysis of a variety of components in foods. Based on the success of NIR spectroscopy for rapid measurement of TDF in low moisture food products such as cereal foods and dehydrated vegetables with no or little sample preparation, this study was conducted to evaluate the feasibility of NIR spectroscopy for prediction of TDF in mixed meals. Models were developed for a wide variety of meals using samples at three preparation levels: homogenized only (HO); homogenized and dried (HD); and homogenized, dried and defatted (HDF). Performing spectroscopic analysis with the dried and defatted samples reduced the analysis time from 4 days for conventional analysis to 2 days. The accuracy of prediction was greatest for the HDF model followed by the HD model. NIR spectroscopy has utility for the screening of samples for TDF in mixed meals by agencies responsible for monitoring nutrition labeling accuracy.
Technical Abstract: Near infrared (NIR) spectroscopy was investigated as a method for prediction of total dietary fiber (TDF) in mixed meals. Meals were prepared for spectral analysis by homogenization only (HO), homogenization and drying (HD), and homogenization, drying and de-fatting (HDF). The NIR spectra (400-2498 nm) were obtained with a dispersive NIR spectrometer. TDF was determined in HDF samples by an enzymatic-gravimetric assay (AOAC 991.43) and values calculated for HD and HO samples. Using multivariate analysis software and optimum processing, PLS models (n=114) were developed to relate NIR spectra to the corresponding TDF values. The HO, HD, and HDF models predicted TDF in independent validation samples (n=37) with SEP of 0.93 (range 0.7-8.4) %, 1.90 (range 2.2-18.9) %, and 1.45 (range 2.8-23.3) % and the coefficient of determination of 0.89, 0.92 and 0.97, respectively. Compared with traditional analysis of TDF in mixed meals, which takes a minimum of 4 days, NIR spectroscopy provides a faster method for screening samples for TDF. The accuracy of prediction was greatest for the HDF model followed by the HD model.