No abstract

Undaria pinnatifida insoluble dietary fibre (UIDF) was modified by alkali (NaOH solution) and complex enzyme (xylanase and cellulase) to improve the physicochemical properties. Scanning electron microscopy revealed that the surface structure after modification was rough and loose. The characteristic absorption peaks in Fourier transfer infrared spectrometry and X-ray diffraction patterns showed that enzymes can further hydrolyse the UIDF than alkali mainly in amorphous region, and increased the soluble dietary fibre content to 16.31%. The alkaline and complex enzymatic modification both resulted in higher water retention capacity, water swelling capacity, oil absorption capacity, glucose adsorption capacity and the inhibition ability towards α-amylase. The complex enzymatic modification exhibited better features in almost all properties, and the modification did not change the inhibiting mechanism on α-amylase (noncompetitive type). Overall, both two modifications could effectively improve the properties of UIDF, which may promote its use in food applications.

Ascorbyl palmitate (AP) is an amphiphilic molecule due to its structure (a hydrophobic hydrocarbon chain and a hydrophilic ascorbyl group) (Palma, Lo Nostro, Manzo, & Allemandi, 2002). The antioxidant capacity is similar to other natural reducing compounds due to the entire ascorbyl group (Ullio Gamboa, Benedini, Schulz, & Allemandi, 2016). It has been used in the food, pharmaceutical, and

The alkaline method is used to form the complex between starch and ascorbyl palmitate (AP) in this study. Normal maize starch (NMS) and high amylose maize starch (HAMS) are screened to investigate the effects of AP concentrations (0%, 2.5%, 5.0%, 10.0%, 20.0%) on the properties of complexes at 60 °C. HAMS can bind more AP than NMS because of more amylose content. Comparing the endothermic peaks in DSC analysis, 5% and 10% AP levels are sufficient to interact with NMS and HAMS, respectively. The disappeared or weakened AP characteristic absorption peaks in FTIR spectra prove the formation of V‐amylose structure. The XRD analyses reveal that the inclusion complexes are formed with AP with six glucose units per turn due to the steric hindrance of AP, and the self‐aggregation of AP in the complexes is also detected. The self‐aggregation of AP do not affect the indigested ordered helical chain segments of starch in in vitro digestion. The 5% and 10% AP levels are enough to decrease the rate and extent of starch digestion in NMS and HAMS complexes, respectively. The formation of starch‐AP inclusion complexes also appear to enhance the stability of AP against light, heat, and oxidation.

No abstract