Impact of elderly gastrointestinal alterations on gastric emptying and enzymatic hydrolysis of skim milk: An in vitro study using a dynamic stomach system.

This study aimed to evaluate gastric emptying and enzymatic hydrolysis of skim milk using a dynamic in vitro gastrointestinal system mimicking digestive conditions in young adult and elderly individuals. The gastric emptying half-time was 22.5 and 26.5 min in the young adult and elderly models, respectively. The degree of proteolysis at 120 min reached 42.3 % under adult digestion, significantly higher than that for the elderly (37.2 %). Moreover, milk proteins, particularly ß-lactoglobulin, was more resistant to hydrolysis throughout elderly digestion. The slowed gastric emptying and impaired proteolysis were supported by the formation of more large clusters and protein aggregates under elderly digestion particularly between 60 and 120 min. This was attributed to the decreased gastric contractions and lowered digestive secretions in the elderly model that would impede the flow and breakdown of protein aggregates. This study is meaningful for future development of milk products that are more suitable for the elderly.

In vitro gastric digestion of cooked white and brown rice using a dynamic rat stomach model.

The changes in physical, rheological and enzyme-digestive behaviours of cooked white and brown rice, with similar amylose content, were investigated using a dynamic in vitro rat stomach (DIVRS) model and a static soaking method. The brown rice had a higher resistance on disintegration and lower gastric emptying rate with 53% of the brown rice particles retained in the stomach at the end compared to 32% for the white rice. Furthermore, the release rate of maltose from the starch hydrolysis was higher in the white rice throughout the digestion suggesting the lower glycemic potency of the brown rice. These differences could be contributed from the rigid bran layer in the brown rice which would inhibit the moisture absorption into rice kernels, limit textural degradation, and generate higher gastric digesta viscosity leading to lower mixing and mass transfer efficiency. This study suggests that the structural difference could affect physiochemical properties during gastric digestion.

Reversible absorption of SO2 by amino acid aqueous solutions.

Six water-soluble amino acids (glycine, l-α-alanine, dl-alanine, ß-alanine, proline and arginine) aqueous solutions were applied to remove SO(2) from SO(2)-N(2) system in this report. All the tested amino acids solutions were found to be excellent absorbents for SO(2) removal, and SO(2) saturation uptake of ß-alanine solution was the highest under the same experimental conditions. The effects of amino acid concentration, SO(2) concentration, absorption temperature, desorption temperature and initial pH value of the absorbent on the removal of SO(2) were investigated with ß-Ala solution. The experimental results showed that SO(2) saturation uptake increased with the increase in ß-alanine solution and SO(2) concentration. Room temperature (20-30°C) was found to be optimal for SO(2) absorption. Additionally the SO(2) desorption capacity increased with increasing desorption temperature. The neutral environment pH value of 6.8 was found to be optimal for SO(2) removal. Ten continuous absorption-desorption cycles showed that the absorbent had an excellent regeneration performance. (13)C NMR and ultraviolet analyses offer ample evidence to speculate that the bonding between SO(2) and ß-alanine was not covalent but some weak interactive forces, such as dispersion force, induction force, dipole-dipole force and hydrogen bond.

Reversible removal of SO2 at low temperature by Bacillus licheniformis immobilized on γ-Al2O3.

Bacillus licheniformis R08 biomass was immobilized on γ-Al2O3 and the effects of R08 biomass loading, SO2 concentration, water vapor, oxygen and temperature on removal of SO2 were investigated. The experimental results indicated that SO2 saturation capacity increased with increasing R08 biomass loading and SO2 concentration, but decreased with increasing adsorption temperature. Water vapor activated the adsorbent and promoted SO2 removal. An increase in oxygen concentration from 5 to 10% had little effect on SO2 removal. FTIR analysis revealed that the R08 biomass bound to γ-Al2O3 mainly by forming R-CO-O-Al bonds. X-ray photoelectron spectroscopy analysis indicated that γ-Al2O3 reacted with SO2 and formed aluminum sulfate in the presence of oxygen when R08 biomass loading was 13.8%, but that amido groups of the R08 biomass reacted with SO2 and formed sulfite when biomass loading was 32.4%. Ten continuous adsorption-desorption cycles showed that the adsorbent had an excellent regeneration performance.