Investigations of Native and Resistant Starches and Their Mixtures Using Near-Infrared Spectroscopy

Resistant starches (RS) play important roles in our nutrition; therefore, the investigation of these starches is notably important. In our study, two native starches (maize and wheat) and two resistant starches (Hi-maize™260, high amylose maize starch as RS2 and Fibersym™70, phosphorylated wheat starch as RS4) were investigated as is and in their physical mixtures (samples containing 20%, 40%, 60% and 80% RS) using near-infrared (NIR) spectroscopy. The aim of our study was to examine the spectra of resistant starches and to differentiate the resistant starch components in different ratios by NIR spectroscopy. The differences of samples were presented in two characteristic absorption bands for carbohydrate: carbohydrate II (2,080–2,130 nm) and carbohydrate III (2,275–2,290 nm) regions. Additionally, principal component analysis (PCA) for all samples was carried out. It was shown that the increasing amount of amylose can be sensitively followed up in carbohydrate II region. The phosphorylated RS4 is not so characteristic probably due to the reduced mobility of amorphous chains; however, the RS4 addition can be observed. Additionally, it was proven that the carbohydrate III region is sensitive for the changes of amylose–amylopectin ratio as well. The wheat-based RS4 addition causes linear changes in maize-based mixtures; thus the botanical origin is determining in this region. The global PCA analysis justified that the RS2 addition can be sensitively followed up independent on the medium; however, the increasing amount of RS4 cannot be detected in the PCA plot. The loading spectra of PC1 component attribute great significance to the carbohydrate III region.