Role of conformation transition of high acyl gellan in the design of double network hydrogels.

Double network hydrogels (DNs) with excellent strength and toughness have been preliminarily applied in the preparation of artificial foods. To evaluate the effect of conformation transition of ductile polymers on the physicochemical properties of DNs, we firstly prepared agarose (AR)/high acyl gellan (HAG) DNs and investigated their mechanical properties, and then calcium ion (Ca2+) was introduced into optimized AR/HAG DNs to regulate the conformation of ductile chains (HAG) for further increasing their mechanical properties. The mechanical strength of the optimized AR/HAG gel is 5 times and 2 times that of AR and HAG gel, respectively. Compared with adding Ca2+ method, immersing Ca2+ solution endowed optimized DNs with 5-fold increase in mechanical strength, outstanding textural properties and lower swelling ratio, which was attributed to the extended conformation of ductile chains. Furthermore, the obtained DNs were reminiscent of beef omasum based on their physicochemical properties. Optimized AR/HAG DNs after immersing in 2 wt% CaCl2 solution exhibited comparable texture properties with beef omasum by three correlation analysis methods and sensory evaluation, providing a new strategy to fabricate biomimetic food with high chewiness by regulating the conformation of ductile polymers in DNs.

Fabrication of agarose/fish gelatin double-network hydrogels with high strength and toughness for the development of artificial beef tendons.

Agarose/fish gelatin (AR/FGA) double-network hydrogels (DNs) were fabricated via a one-step heating-cooling method. The structure, mechanical and textural properties, water-holding capacity, swelling behavior and sensory characteristics of the DNs were analyzed and compared with the corresponding single-network hydrogels (SNs) and beef tendons. An increase in FGA concentration (10-40 wt%) significantly enhanced the mechanical strength and toughness of DNs, while a moderate increase in AR concentration (0.5-1.5 wt%) only improved their mechanical strength. The 1.5 wt% AR/40 wt% FGA DNs attained excellent fracture stress and strain compared with the single AR and single FGA gels. This can be attributed to the energy dissipation effect, intermolecular hydrogen bond interactions and higher entanglement density of molecule chains. Furthermore, AR/FGA DNs attained a higher hardness, water holding capacity and lower swelling rate compared with SNs. The principal component analysis and correlation analysis showed that the 1.5 wt% AR/30 wt% FGA DNs displayed the most comparable correlation with beef tendons, which was consistent with the results of the sensory evaluation, showing great potential as artificial beef tendons. Our findings provide guidance for the modulation of gel properties and development of artificial foods.

Concentrations and health risks of inorganic arsenic and methylmercury in shellfish from typical coastal cities in China: A simultaneous analytical method study.

Shellfish consumption is an important pathway for coastal residents exposure to inorganic arsenic (iAs) and methylmercury (MeHg). An integrated method had been developed for simultaneous determination of iAs and MeHg in shellfish with microwave-assisted extraction and high performance liquid chromatography-inductively coupled plasma mass spectrometry identification. The limits of detection were 0.0520, 0.1003 and 0.0015 mg/kg (dry weight) for AsIII, AsV and MeHg, respectively. The proposed method was applied to evaluate the contents and health risks of iAs and MeHg in shellfish from the typical coastal cities (Lianyungang and Yantai) in China. The concentrations of iAs and MeHg in fresh shellfish were 0.10-1.69 mg/kg and 0.46-6.38 µg/kg, respectively. The target hazard quotient and target cancer risk values of iAs were the highest for the children and adults in Lianyungang, and were respectively larger than 1 and 1 × 10-4, indicating both non-carcinogenic and carcinogenic risks of iAs exposure were significant in this area.

The Correlation Between In Vitro Antioxidant Activity and Immunomodulatory Activity of Enzymatic Hydrolysates from Selenium-Enriched Rice Protein.

The antioxidant and immunomodulatory activities of selenium-enriched rice protein hydrolysates (Se-PH) were evaluated by a cellular antioxidant activity test and macrophage proliferation and phagocytosis assays, respectively. The results showed that trypsin hydrolysate provided the highest proliferation rate of 60.91% at a concentration of 100 µg/mL. Moreover, a remarkable rise in the phagocytosis rates for trypsin hydrolysate (64.1%) and pepsin-trypsin hydrolysate (54.5%) was observed when the sample concentrations were increased to 50 µg/mL. A positive correlation was found between the phagocytic ability of macrophages and both the selenium concentration and the degree of hydrolysis of Se-PH, and the correlation coefficients R obtained were 0.792 and 0.930 (P < 0.05), respectively. The capacity of Se-PH to inhibit the oxidation of dichlorodihydrofluorescein had a significant negative correlation with the phagocytic ability of macrophages (R = -0.840, P < 0.05). In conclusion, a positive correlation was found between the antioxidant activity and the immunomodulatory activity of Se-PH, which could be used as potential functional food additives for improving human health.