Preparation, investigation and storage application of thymol-chitooligosaccharide complex with enhanced antioxidant and antibacterial properties.

BACKGROUND: Thymol (Thy) is a natural bioactive agent which possesses various properties and has been widely used in medicine and food industries. However, its poor bioavailability can limit its application. RESULTS: In this study, Thy was interacted with chitooligosaccharide (COS) as Thy-COS complex via an ionic crosslinking method using sodium tripolyphosphate as a crosslinker. The characteristics and thermal stability of Thy-COS were evaluated by ultraviolet-visible (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1 H-NMR) and thermogravimetric analysis, and its antioxidant and antibacterial properties were also evaluated. The highest loading capacity of Thy (52.3%) in Thy-COS formed at mass ratio of 1:5. Results indicated the Thy-COS complex was formed mainly by hydrophobic interactions and hydrogen bonds. Upon complexation, the thermal stability, antioxidant and antibacterial activity of Thy were significantly improved. Thy-COS complex was made into a coated film for Nanguo pears and greatly improved its storage quality. Thy-COS delayed the weight loss and softening of Nanguo pears and kept more vitamin-C content (2.12 mg (100 g)-1 ). CONCLUSION: In conclusion, Thy-COS was successfully prepared and improved antioxidant and antibacterial properties of Thy, which has great potential in the food industry. © 2021 Society of Chemical Industry.

Applications of nuclear magnetic resonance spectroscopy to the evaluation of complex food constituents.

Due to a number of unparalleled advantages such as fastness, accuracy, intactness, nuclear magnetic resonance spectroscopy (NMR) has fulfilled a significant role in determining structures and dynamics of various physical, chemical and biological systems in the field of food analysis. This study introduced the principle of NMR, key NMR techniques such as 1H NMR, DOSY, NOESY, HSQC, etc., and the knowledge of NMR applications on the evaluation of complex food system, especially the interactions of food components. The reviewed research work provides sufficient evidence that NMR spectroscopy has been an invaluable tool and will play an increasingly important role in specific technical support for food assessment. In addition, NMR combined with various other technologies could give a complete picture of the mechanism of the performance of functional food compounds, which are vital for human health and influence the intrinsic food properties during processing, storage and transportation at the molecular level.

Natural Dissociation Ratio of Carboxyl Group Controlled Highly Dispersed Silver Nanoparticles on PSA Microspheres and Their Catalytic Performance.

The highly dispersed silver nanoparticle-loaded poly(styrene-co-acrylic acid) nanocomposites (nAg@PSA) were prepared and characterized by transmission electron microscopy and thermogravimetry. The amount and distribution of colloidal silver per particle were related to the dissociation ratio of carboxyl groups in the PSA sphere. The amount of carboxyl groups was evaluated by a conductivity titration curve. However, the dissociation of carboxyl groups on PSA is difficult to determine accurately via existing methods because the dissociation ratio will increase with increasing impurity ions during titration. We developed a technique to determine the dissociation ratio of PSA without impurity ions. This employs a novel distance-variable parallel electrode system. Thus, the relationship between nano silver distribution and natural dissociation of carboxyl groups on the surface of the PSA spheres was investigated for the first time. Accurately measuring and controlling the dissociation facilitated the production of PSA spheres containing highly dispersed silver nanoparticles. The catalytic performance of as-prepared nAg@PSA catalysts was studied by reduction of 4-nitrophenol. By controlling the amount of natural dissociation ratio of carboxyl group on PSA sphere, dispersion of silver nanoparticles can be designed and attained controllably. They offer easy synthesis, high catalytic performance, and good recyclability.

Enhancement of the water solubility and antioxidant activity of hesperidin by chitooligosaccharide.

BACKGROUND: Hesperidin is a natural product and a strong antioxidant with potential applications in various food and pharmaceutical products. However, its poor water solubility greatly limits its applications. RESULTS: In this study, chitooligosaccharide (COS) was applied to prepare a stable complex with hesperidin (Hesp-COS) via the spray-drying method at 100 °C for 20 min. The resultant complex was characterized by Fourier transformation infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and proton nuclear magnetic resonance spectroscopy. It was demonstrated that the aromatic rings of hesperidin interacted with COS through hydrogen bonding and formed Hesp-COS complex. As a result, both the water solubility and antioxidant activity of Hesp-COS were higher than that of the free hesperidin. CONCLUSION: The preparation conditions of Hesp-COS in this study were efficient and produced an increment in both the water solubility and antioxidant activity of hesperidin. © 2017 Society of Chemical Industry.