Effects of dynamic high-pressure microfluidization treatment on the functional and structural properties of potato protein isolate and its complex with chitosan.

In our previous work, dynamic high-pressure microfluidization (DHPM) treatment was shown to promote the interaction between chitosan (CS) and potato protein isolate (PPI), but the modification mechanism of DHPM treatment (6 k-12 k psi) on PPI and its complex with CS remains to be elucidated. Here, moderate DHPM treatment (≤9k psi) was found to decrease the particle size, increase the surface charge, and improve the solubility of PPI and its emulsifying and foaming properties. The PPI functional properties were further improved by CS addition followed by DHPM treatment. The ultraviolet and fluorescence spectral results showed that DHPM treatment could destroy the PPI molecularstructure, while CS addition could provide a protective mechanism against PPI damage, which was also proved by the surface hydrophobicity. The circular dichroism spectral analysis exhibited that DHPM treatment could convert different types of secondary structures by disrupting the PPI intermolecular hydrogen bonds, while CS addition could promote the formation of hydrogen bonds in the system, which was also demonstrated by infrared spectroscopy. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) results exhibited that DHPM treatment (≤12 k psi) was not sufficient to reduce the PPI molecular mass, while DHPM treatment (6 k-12 k psi) could destroy the structure of CS/PPI complex. The thermodynamic analysis showed that the PPI thermodynamic stability could be improved by DHPM treatment, but decreased by CS addition plus DHPM treatment. These results showed that DHPM treatment has a good potential to modify the PPI and CS/PPI complex.

Effects of granule size on physicochemical and digestive properties of potato powder.

BACKGROUND: Potato powder, a rich source of high-quality protein and starch, plays an important role in the production of functional foods. In this study, ball-mill processed potato powders with different particle sizes (278, 208, 129, and 62 µm) were analyzed in terms of physicochemical, pasting, rheological, and digestive properties. RESULTS: Scanning electron microscopy and laser diffraction analysis of the samples revealed mono-model particle-size distributions. X-ray diffraction analysis confirmed structure destruction of starch pellets. Proximate composition and physical property analysis showed an increase in the water, ash, protein, and starch content. Meanwhile, the water solubility index and swelling power values were found to increase with decreasing grain size, and so were the brightness (L*) and redness (b*) values of the potato powders. With particle size reduced to 129 µm, large changes were observed in gelatinization properties, such as peak viscosity, trough viscosity, breakdown viscosity, and final viscosity. Oscillatory rheology results also showed that, with the decrease in particle size, the storage modulus (G') and loss modulus (G″) improved, with highest storage modulus (G') observed in the 129 µm particle size. The hydrolysis rate and glycemic index also increased in the 129 µm potato powder. CONCLUSION: The results provide information that could be useful for improving quality characteristics by using specific grain sizes in the development of potato-based products such as gluten-free products and ethnic food products with particular functional and rheological properties. © 2020 Society of Chemical Industry.

The formation mechanism and thermodynamic properties of potato protein isolate-chitosan complex under dynamic high-pressure microfluidization (DHPM) treatment.

The objective of the study was to explore the formation mechanism and thermodynamic properties of chitosan (CS)-potato protein isolate (PPI) complex under DHPM treatment. The transmission electron microscopic (TEM) results showed the formation of a complex between CS and PPI. Meanwhile, particle size and zeta-potential were shown to increase with increasing CS concentration, further confirming the formation of the complex. The surface hydrophobicity results showed CS was bound to PPI by hydrogen bond. The ultraviolet and fluorescence spectral analysis exhibited CS formed a protective mechanism against PPI destruction, preventing the exposure of tyrosine and tryptophan residues. Infrared spectrum and circular dichroism spectral analysis revealed no occurrence of chemical reaction between CS and PPI under DHPM treatment, further indicating that they are bound by hydrogen bond and hydrophobic interaction. Moreover, CS addition was shown to enhance the intermolecular interaction and promote the formation of intermolecular hydrogen bond network. Differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) revealed that CS addition could improve the thermal stability of PPI. These results have shed light on the formation mechanism and thermodynamic properties of the CS/PPI complex and facilitate its application in food industry.