Ultrastructural-chemical makeup of yellow-seeded (Brassica rapa) and brown-seeded (Brassica napus) canola within cellular dimensions, explored with synchrotron reflection FTIR microspectroscopy

Abstract

Synchrotron-based FTIR micro spectroscopy, developed recently as a novel, rapid and non-destructive analytical technique, could reveal chemical information of the intrinsic microstructures of biological tissues at ultra-spatial resolution. The objective of this study was to use synchrotron reflection FTIR microspectroscopy to explore chemical makeup (functional group and bonding characteristics) of ultrastructural tissues within cellular dimensions (10 µm × 10 µm) of yellow-seeded (Brassica rapa ‘Klondike’) and brown-seeded (Brassica napus ‘Bounty’) canola. The results showed that the ratios of total CH2:CH3, CH3-asymmetric:CH3-symmetric, CH2-asymmetric:CH2-symmetric and total CH-asymmetric:CH-symmetric were 1.06 and 1.13, 1.28 and 1.26, 2.90 and 3.08, 1.82 and 1.78, for the yellow-seeded and brown-seeded canola, respectively. There were no differences between the two canola types in the content and ratios of CH groups (CH2 and CH3) of the scanned areas, indicating that lipid chain length and branching are similar between the two seed types. There were significant differences in amide I and total CHO, indicating different microstructural protein (peptide C=O bonding) and carbohydrate makeup between the two canola types. The results also show differences in the ratios of total NH and OH:CHO (2.85 vs. 3.84, P < 0.01), total CH:total CHO (0.23 vs. 0.32, P < 0.01), amide I:NH and OH (0.48 vs. 0.37, P = 0.07), amide I:hemiceullulose (P = 0.09), hemicellulose:total CHO (0.039 vs. 0.059, P < 0.001), CHO:amide I (1.11 vs. 0.84, P = 0.051) between the yellow-seeded and brown-seeded canola, and indicate that the chemical makeup of the microstructure differs between the yellow-seeded (Brassica rapa) and brown-seeded (Brassica napus) canola type. In conclusion, this study indicates that synchrotron-based reflection FTIR microspectroscopy can be used to identify microstructural-chemical features of canola tissue. More detailed study is required to define the extent of differences that exist between the yellow-seeded (Brassica rapa) vs. dark-brownseeded (Brassica napus) canola. Such information on the microstructural-chemical features can be used by canola breeding programs to select superior varieties of canola for special purposes, and for predicting canola quality and nutritive value for humans and animals. Key words: Synchrotron, reflection infrared microspectroscopy, functional groups, chemical makeup, ultrastructure, canola, feed structure and chemistry