New insights into in vivo gastroduodenal digestion of oil-in-water emulsions: gastric stability and in vitro digestion modeling.

In this paper, effect of emulsion stability on gastroduodenal emptying/secretion was reviewed and differentiated. Moreover, novel perspectives on physiology of gastric lumen, duodenum, and gall bladder were achieved using mathematical models, being useful for designing artificial digestive systems. In this regard, numerical data for dynamic gastric emptying/secretion were offered for gastric-stable and gastric-unstable emulsion intakes. It was shown that alterations in human gastric and duodenal volume follow, respectively, linear and sinusoidal curves, with high correlation coefficients (r2 > 0.93). For both emulsions, about 30-40 mL ingesta discharged rapidly from stomach upon ingestion; However, further gastric emptying was regulated for the rest of digestion period, so that 0.1 mL/min oil was passing through duodenum. Intragastric evacuation of both emulsions started with a lag phase during which stomach stored secretions incrementally by slow gastric discharge. Lag phase ended with fat layering, when emptying considerably enhanced. This reduction was gradual for stable emulsion while unstable emulsion experienced a rapid emptying before slow declining trend. Along with initial gastric emptying, 87% of gallbladder content discharged into duodenum, prolonged up to the gradual reduction phase of stomach. Supplementary investigations are needed to quantify gastroduodenal secretions, particularly pepsin and pancreas in response to emulsion ingesta.

pH-Induced structural transitions in whey protein isolate and ultrasonically solubilized Persian gum mixture.

The present work evidently reports that ultrasonic depolymerization strongly enhanced complex coacervation between Persian gum (PG) and whey protein isolate (WPI). PG was sonicated at 60 °C, operating frequency of 20 kHz and nominal power output of 800 W for various times followed by mixing with WPI. Acid-induced interaction between the two biopolymers was studied by turbidity, light scattering, zeta potential and viscosity measurements over a wide pH range. Sonication of intact PG (IPG) for 10 min considerably reduced the molecular weight from 4.12 × 106 to 0.76 × 106 g/mol. Besides, ultrasonic fragmentation of water insoluble fraction of PG drove protein containing chains into the soluble phase. Sonicated PG (SPG) was shown to be more flexible with higher number of carboxyl groups available for electrostatic interaction with WPI, such that the complete neutralization did not occur even at protein to polysaccharide ratio of 50: 1. Additionally, scattered light intensity and viscosity measurements revealed two maxima in the pH ranges of 4.4-4.85 and 3.27-4.0, being highly intense for the gum sonicated for 10 min and longer. Considering the pH-behavior of WPI components, the former peak was related to interpolymer complex formation between ß-lactoglobulin and long chain fraction of SPG, while the latter was attributed to intrapolymer association of α-lactalbumin with the short chain oligosaccharides arising from ultrasonic degradation of PG.

Ultrasonic degradation of Persian gum and gum tragacanth: Effect on chain conformation and molecular properties.

The present study introduces the ultrasonic modification of two Iranian native gum exudates, Persian gum (PG) and gum tragacanth (GT) for the first time. They were sonicated at a constant frequency of 20 kHz and temperature of 60 °C for various times (0, 2, 5, 10, 20, 30 and 40 min) and the changes in their molecular properties were investigated using oven drying, gel permeation chromatography-multiangle laser-light scattering (GPC-MALLS), rheometery and FTIR analysis. Results indicated that the soluble dry mass of both hydrocolloids was extensively enhanced (from less than 10% at time zero to more than 90% at the end of treatment time) by sonication. Moreover, the molecular weight and viscosity of gums dispersions were decreased with the increase of the treatment time. Fracture in polysaccharide chains was confirmed by analysis of the molecular weight parameters. Calculation of chain breaks and polydispersity index (PDI) revealed that scissions occurred at the backbone as well as the side branches. PG, owing to its higher molecular weight, displayed more extensive and faster degradation than GT. However, the chain rupture of GT was twice more than that of PG at the end of sonication time. The specific volume for gyration (SVg) and molecular density (ρ) showed that intact PG contains compactly packed molecules with greater number of cross-linked bonds compared to GT. Furthermore, the conformational changes into semi-flexible chains and worm-like coils were determined for both gums after 40 min sonication. Variation of the molecular density along with the results of FTIR analysis demonstrated that ultrasonication broke C-O-C bonds in both PG and GT leading to more flexible chains.