Effect of radio frequency energy on buckwheat quality: An insight into structure and physicochemical properties of protein and starch.

Radio frequency (RF) heating as an emerging technology is widely used to improve cereal-based food quality. To further investigate effects of RF treatment on buckwheat quality, structures and physicochemical properties of protein and starch in buckwheat were evaluated under various temperatures (80, 90, and 100 °C) and holding times (0, 5, and 10 min). Results showed that protein-starch complexes were reaggregated with the increases of RF heating temperature and time, as well as the values of R1047/1022, crystallinity, random coil, and α-helix significantly decreased, and the values of ß-sheet obviously increased. Moreover, viscosities and rheological properties of buckwheat were reduced by the raised RF treatment intensity. Besides, the RF processing had a mostly positive effect on swelling power at low temperature of 30 °C, but contrary effect at high temperatures of 60 °C and 90 °C. However, changes of water solubility index, emulsifying capacity, and emulsion stability depended on the RF processing intensity. These results of the study suggested that buckwheat quality was affected by multiple RF treatment conditions, which can be tailored to develop a RF process having the potential to improve the function of buckwheat flour.

Isolated Pea Resistant Starch Substrates with Different Structural Features Modulate the Production of Short-Chain Fatty Acids and Metabolism of Microbiota in Anaerobic Fermentation In Vitro.

Resistant starches (RSs) with different structural features were isolated from both native and pullulanase-debranched and acid-hydrolyzed pea starches. Their microscopic changes, short-chain fatty acids (SCFA) composition, microbiota communities, and structural characteristics of the corresponding fermenta residues by the end of 24 h of the in vitro fermentation period were investigated. The microbial fermentation clearly caused numerous cracks and erosion on the RS granule surface. In comparison to the positive control, significantly higher levels of butyrate, propionate, and total SCFA were produced after 24 h of in vitro fecal fermentation when resistant starches were used as substrates. The RS substrates with different structural characteristics enabled varying growth of Bifidobacterium spp., Eubacterium spp., and Faecalibacterium spp. The discrepancy in microbiota communities associated with the differences in SCFA from the fermentation of RS with different structural features would be critical toward the rational design of foods containing resistant starch with targeted health benefits.

The retrogradation characteristics of pullulanase debranched field pea starch: Effects of storage time and temperature.

The structural changes and retrogradation behavior of the processed pea starch stored at 4 °C and 25 °C for different length of time (6, 12, 24, 48, and 72 h) was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), solid-state 13C nuclear magnetic resonance spectroscopy (13CNMR), Fourier transform infrared spectroscopy (FT-IR), and small angle X-ray scattering (SAXS), their corresponded physicochemical properties were studied by rapid visco-analyzer (RVA). A mixture of B- and V-type crystalline polymorph was observed by XRD for all processed and retrograded pea starch. A continuous increase in the following parameters was observed during the initial retrogradation of pea starch for 6-48 h at 4 °C and for 6-24 h at 25 °C, followed by a decreased trend during the subsequent storage time from 48 h to 72 h at 4 °C, and from 24 h to 72 h at 25 °C, including the values of relative crystallinity, degree of order, and degree of double helix measured by XRD, 13CNMR, and FT-IR, respectively. The results of this study would provide useful information for better designing of starch-based food ingredients with improved functional and health benefits.