Association between the nutritional and fermentation profiles with protein-related molecular structure using fourier transformed infrared spectroscopy of snowbird faba bean seeds. Effects of steam pressure toasting duration

Abstract

Heat processing alters the physicochemical structure of feed and food, modifying the degradation and the total nutrient supply. The objective of this study was to determine the extent of molecular structure modifications related to steam pressure toasting (SPT) time (0–120 min) in Faba bean seeds (FBS, Vicia faba cv. Snowbird). Whole FBS (n = 3 years) were autoclaved at 121°C and analyzed with Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy in the mid-infrared (mid-IR) region. The amide to total carbohydrates (TC) area ratio decreased quadratically from 0.77 to 0.67 absorbance units (AU; P < 0.01), as well as the structural carbohydrates (STC) to TC area ratio (P < 0.01). Conversely, the cellulosic compounds (CEC) to STC area ratio increased quadratically from raw to 120 min of SPT (P = 0.01). The peak absorbance for amide I, II, β-sheet, and α-helix decreased quadratically with increasing SPT time (P < 0.01). Based on the multivariate analysis, T30, T60, and T90 did not share similar molecular spectra in the amide I area at ca. 1715–1584 cm⁻¹ (PC-1 =92 %). The rumen undegraded crude protein (BCP_DVE, g/kg DM) had an inverse relationship with α-helix (r = -0.66; P = 0.01), β-sheet (r = -0.56; P = 0.03), and amide and amide I areas (r = -0.61; P = 0.02). Similarly, the intestinal digestible crude protein (IADP, g/kg CP), the total metabolizable protein (g/kg DM), and the feed milk value (FMV, kg milk/kg DM feed) presented a negative correlation with all the protein-related molecular profiles (P < 0.05). The analysis of FTIR data allowed us to detect differences between the experimental treatments. The AU in areas and heights of amide I and II, α-helix and β-sheet heights, and the area ratio of amide to TC were lower with increasing SPT time. Moreover, a positive correlation between the EDCP and all the spectral profiles was observed.