Effects of Electrospun Potato Protein-Maltodextrin Mixtures and Thermal Glycation on Trypsin Inhibitor Activity

Abstract

Fibers of potato protein and polysaccharides were obtained by needleless electrospinning. Mixtures of maltodextrin DE2 (dextrose equivalent) (0.8 g/mL), DE21 (0.1 g/mL), and different concentrations of potato protein (0.05, 0.1, 0.15, and 0.2 g/mL) were used for fiber production. Glycation was performed via the Maillard reaction after thermal treatment (0/6/12/24/48 h, 65 °C, 75% relative humidity). The effects of electrospinning and heating on trypsin inhibitor activity (IA) were studied. The results of the IA assay showed that electrospinning and glycation caused significant differences in IA among blends, heating times, and the interaction of blend and heating time (p < 0.001). The higher the protein content in the fibers, the higher the IA. The lowest IA was found in the mixture with the lowest protein content after 48 h. In other blends, the minimum IAs were found between 6 and 12 h of heating. The determination of the free lysine groups showed a nonsignificant decrease after heating. However, higher free lysine groups per protein (6.3−9.5 g/100 g) were found in unheated fibers than in the potato protein isolate (6.0 ± 0.5 g/100 g). The amide I and amide II regions, detected by the Fourier transform infrared spectra, showed only a slight shift after heating.

Keywords: free lysine groups; glycation; glycoconjugates; maltodextrin; needleless electrospinning; potato protein; trypsin inhibitor.

Figure 1

(A) Average concentration of lysine (mg/g fiber) and (B) concentration of lysine in the protein content over heating times for the different ratios (MD DE 2:MD DE 21:PP)(A (80:10:5), B (80:10:10), C (80:10:15), and D (80:10:20)) with standard deviation (different letters indicate significant differences (A) between heating times at the same blend and (B) between blends at the same heating time (p < 0.05)).

Figure 2

(A) Measurement of the trypsin inhibitory effect of pure potato protein (absorbance measurement at 450 nm over the quantity of potato protein in the assay), (B) positive control without potato protein, and (C) trypsin inhibitory activity of all fibers (MD DE 2:MD DE 21:PP—A (80:10:5), B (80:10:10), C (80:10:15), and D (80:10:20)) vs. heating time (different letters indicate significant differences between heating times (lower case) or blends (upper case) (p < 0.05)).

Figure 3

FTIR spectra (700−1800 cm⁻¹) of all fibers with different ratios (MD DE 2:MD DE 21:PP)—(A) (80:10:5), (B) (80:10:10), (C) (80:10:15), (D) (80:10:20), and (E) maltodextrins DE 21, DE 2, and potato protein.

Figure 4

PCA of the different FTIR spectra of (A) different blends (MD DE 2:MD DE 21:PP—A (80:10:5), B (80:10:10), C (80:10:15), and D (80:10:20)) and (B) different heating times. (Labelled spectra are outliers, and the confidence ellipsoids represent in each case a probability of 95%).

Figure 5

Schematic illustration of the study with respect to the addition of different concentrations of potato protein and the effects of electrospinning and thermal treatment on trypsin inhibitor activity.