Abstract
The chemical method for the determination of the resistant starch (RS) content in grains is time-consuming and labor intensive. Near-infrared (NIR) and attenuated total reflectance mid-infrared (ATR-MIR) spectroscopy are rapid and nondestructive analytical techniques for determining grain quality. This study was the first report to establish and compare these two spectroscopic techniques for determining the RS content in wheat grains. Calibration models with four preprocessing techniques based on the partial least squares (PLS) algorithm were built. In the NIR technique, the mean normalization + Savitzky–Golay smoothing (MN + SGS) preprocessing technique had a higher coefficient of determination (Rc2 = 0.672; Rp2 = 0.552) and a relative lower root mean square error value (RMSEC = 0.385; RMSEP = 0.459). In the ATR-MIR technique, the baseline preprocessing method exhibited a better performance regarding to the values of coefficient of determination (Rc2 = 0.927; Rp2 = 0.828) and mean square error value (RMSEC = 0.153; RMSEP = 0.284). The validation of the developed best NIR and ATR-MIR calibration models showed that the ATR-MIR best calibration model has a better RS prediction ability than the NIR best calibration model. Two high grain RS content wheat mutants were screened out by the ATR-MIR best calibration model from the wheat mutant library. There was no significant difference between the predicted values and chemical measured values in the two high RS content mutants. It proved that the ATR-MIR model can be a perfect substitute in RS measuring. All the results indicated that the ATR-MIR spectroscopy with improved screening efficiency can be used as a fast, rapid, and nondestructive method in high grain RS content wheat breeding.
Highlights
Resistant starch (RS) is the starch that cannot be converted into glucose when passing through the healthy small intestine [1]
Chemical Measured Wheat Grain RS Content. e RS content in whole wheat grain flour samples was measured by the AOAC method in the calibration set ranged from 0.220% to 3.348% with the mean content 1.011% (Table 1); while the RS content in the validation set ranged from 0.267% to 2.842% with the mean content 1.285% (Table 2). e standard deviation (SD) in the calibration set and validation set is 0.679 and 0.697, respectively. e coefficient of variation (CV) in the calibration set and validation set is 67.086% and 53.846%, respectively
Region has strong absorption peaks and belongs to the fundamental molecular vibration modes. e peaks between 3600 and 3000 cm−1 were assigned to hydrogen bonded water (O-H stretching vibration). e weak band detected at 1652 cm−1 was responsible for C O vibration of the decarboxylated groups. e region between 1200 and 950 cm−1 was attributed to the O-C stretch vibrations of the glucose ring [37, 38]. 1146 cm−1 and 1047 cm−1 are the stretching vibrations linked to the primary and secondary alcohol hydroxyl groups in glucose, and 1002 cm−1 is the C-O stretching vibration of the pyranose ring
Summary
Resistant starch (RS) is the starch that cannot be converted into glucose when passing through the healthy small intestine [1]. RS can increase satiety and reduce calorie intake, which could reduce postprandial blood glucose levels [2], regulate the intestinal metabolism [3], reduce colon cancer risk [4], control bodyweight [5], and absorb minerals [6]. E improvement of the RS content in grains is an important goal for breeding. A few high RS content grain varieties, such as RS111 [10], the hulless barley variety Himalaya 292 [11], and durum wheat [12], have been released to the public. While, they still cannot satisfy the growing demand. A simple, fast, and nondestructive method for screening mutants with millions of mutants becomes vital for breeding
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