Stability, bifurcation, and chaos in a class of scalar quartic polynomial delay systems.

In this paper, a class of scalar quartic polynomial delay systems is investigated. We found rich dynamics in this system through numerical simulation, including chaotic attractors, chaotic saddles, and intermittent chaos. Moreover, this chaotic quartic system may serve as an approximation, through Taylor expansion, for a wide class of scalar delay differential equations. Thus, these nonlinear systems may exhibit chaotic behaviors, and the studies in our paper may provide an insight into the emergence of chaos in other time-delay nonlinear systems. We also conduct a detailed theoretical analysis of the system, including the stability of equilibria and Hopf bifurcation analysis based on the theory of normal form and center manifold. Additionally, a numerical analysis is provided to give numerical evidence for the existence of chaos.

Comparison of intestinal absorption of soybean protein isolate-, glutenin- and peanut protein isolate-bound Nε-(carboxymethyl) lysine after in vitro gastrointestinal digestion.

Advanced glycation end products (AGEs), a heterogeneous compound existed in processed foods, are related to chronic diseases when they are accumulated excessively in human organs. Protein-bound Nε-(carboxymethyl) lysine (CML) as a typical AGE, is widely determined to evaluate AGEs level in foods and in vivo. This study investigated the intestinal absorption of three protein-bound CML originated from main food raw materials (soybean, wheat and peanut). After in vitro gastrointestinal digestion, the three protein-bound CML digests were ultrafiltered and divided into four fractions: less than 1 kDa, between 1 and 3 kDa, between 3 and 5 kDa, greater than 5 kDa. Caco-2 cell monolayer model was further used to evaluate the intestinal absorption of these components. Results showed that the absorption rates of soybean protein isolate (SPI)-, glutenin (Glu)-, peanut protein isolate (PPI)-bound CML were 30.18%, 31.57% and 29.5%, respectively. The absorption rates of components with MW less than 5 kDa accounted for 19.91% (SPI-bound CML), 22.59% (Glu-bound CML), 23.64% (PPI-bound CML), respectively, and these samples were absorbed by paracellular route, transcytosis route and active route via PepT-1. Taken together, these findings demonstrated that all three protein-bound CML digests with different MW can be absorbed in diverse absorption pathways by Caco-2 cell monolayer model. This research provided a theoretical basis for scientific evaluation of digestion and absorption of AGEs in food.

Effects of Hydroxypropyl Methylcellulose on Physicochemical Properties and Microstructure of κ-Carrageenan Film.

We investigated the effects of different proportions of hydroxypropyl methylcellulose (HPMC) on the properties of κ-carrageenan film. Biodegradable κ-carrageenan/HPMC films (κCHM film) were prepared by the solution casting method and their physicochemical properties were evaluated. The results show that the addition of HPMC enhanced oxygen barrier capacity, mechanical properties (tensile strength and elongation at break) and thermal stability. Notably, when the addition of HPMC increased to 6% of κ-carrageenan (w:w), the κCHM-6 film not only effectively improved water resistance, including lower water solubility, water vapor permeability and higher water contact angle, but also made the structure of the κCHM-6 film more compact. Moreover, rheological measurement and atomic force microscopy characterization showed that κ-carrageenan had suitable compatibility with HPMC. Attenuated total reflection-Fourier transform infrared spectroscopy analysis further confirmed the enhancement of hydrogen bond interactions. This finding could contribute to promoting the potential application of κCHM film in food packaging.

Absorption and transport of myofibrillar protein-bound Nɛ-(carboxymethyl)lysine in Caco-2 cells after simulated gastrointestinal digestion.

This study aimed to investigate the absorption and transport of myofibrillar protein-bound Nɛ-(carboxymethyl)lysine (MP-bound CML) in Caco-2 cells after simulated gastrointestinal digestion. Four kinds of MP-bound CML hydrolysates with molecular weights (MWs) less than 1 kDa, 1-3 kDa, 3-5 kDa and greater than 5 kDa, were obtained by ultrafiltration; their absorption and transport were studied in Caco-2 cells. Peptide-bound CML in hydrolysates with MWs less than 1 kDa was absorbed by 6.58 % and might transport across Caco-2 cells monolayer through paracellular pathway; peptide-bound CML in hydrolysates with MWs 1-3 kDa was absorbed by 12.8 % and might transport across Caco-2 cells monolayer through paracellular pathway and transcytosis route; peptide-bound CML in hydrolysates with MWs 3-5 kDa was absorbed by 14.66 % and might be through active route via PepT-1 transport across Caco-2 cells monolayer; whereas protein-bound CML in hydrolysates with MWs greater than 5 kDa was only absorbed by 1.02 %, which was hardly transported into Caco-2 cells. In conclusion, MP-bound CML could be absorbed by 35.06 % into Caco-2 cells after simulated gastrointestinal digestion and is transported across Caco-2 cells through paracellular pathway, transcytosis route and active route via PepT-1.