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.

Preparation, Evaluation and Characterization of Rutin-Chitooligosaccharide Complex.

Rutin possesses a wide range of application prospects with various bioactivities. However, its bitter and water-insoluble properties restrict its application in the field of functional foods. A new complex of rutin and chitooligosaccharide (Rutin-COS) was prepared via spray-drying method (100 °C, 1 L/h) and freeze-drying method (-80 °C, 24 h), respectively. The water solubility, bitterness, antioxidant and antibacterial activities of Rutin-COS were evaluated, and the complexation of Rutin-COS was characterized by SEM, 1H-NMR and ROESY. Compared to freeze-drying method, spray-drying method was more effective for preparing stable Rutin-COS complex. The spray-dried Rutin-COS showed increased water solubility, weakened bitterness, enhanced antioxidant and antibacterial activity compared to rutin. The Rutin-COS complex was demonstrated to be formed through hydrogen bonds between the A, B rings of rutin and COS.

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.

Functional enrichment of mannanase-treated spent brewer yeast.

In this study, the effect of Bacillus amyloliquefaciens-produced ß-mannanase on the nutrient diffusion (release) and antioxidant activity of spent brewer yeast (SBY) was investigated. Three pretreatments were performed: (1) autolysis at 50°C for 24 h; (2) autolysis at 50°C for 24 h, with the addition of ß-mannanase during the autolysis; (3) autolysis at 50°C for 24 h, and the ß-mannanase was added for another 12 h treatment. The pretreatments with the addition of ß-mannanase caused significant cell wall degradation, markedly increased the yield of SBY extracts. More importantly, this study found that polysaccharides were degraded to be oligosaccharides with a considerable reduction in molecular weights. Meanwhile, pretreatment with the enzyme also exhibited a higher antioxidant activity in SBY extract compared to autolysis itself. The current study indicated that pretreatment (3) had a better effect than pretreatment (2) in terms of improving in antioxidant activity in SBY extract. These improved characteristics of SBY extracts isolated through enzymatic treatment appear to show promising features for their prospective use as natural functional agents.

NMR spectroscopic and quantum mechanical analyses of enhanced solubilization of hesperidin by theasinensin a.

PURPOSE: The use of hesperidin in the pharmaceutical field is limited by its aqueous insolubility. The effects of natural compounds in tea on the solubility of hesperidin were evaluated and the underlying mechanism was investigated by nuclear-magnetic resonance (NMR) and quantum mechanical calculations. METHODS: The solubility of hesperidin was measured by liquid chromatography time-of-flight mass spectrometry; the structure of the hesperidin/theasinensin A complex was characterized by (1)H-NMR, diffusion-ordered NMR spectroscopy, and rotating frame NOE spectroscopy, as well as theoretically by quantum mechanical calculations. RESULTS: Among the natural compounds in tea, theasinensin A was the most effective in improving hesperidin solubility. The complexation of hesperidin with theasinensin A led to changes in the chemical shift of protons in hesperidin (Δδ: 0.01-0.27 ppm) and diffusion coefficient (ΔD: 0.66-1.32 × 10(-10) m(2)/s) of hesperidin. ROE correlation signals between hesperidin and theasinensin A and quantum mechanical calculations revealed that two hesperidin molecules formed a stable complex with theasinensin A (2:1 complex) with a ΔG energy of -23.5 kJ/mol. CONCLUSIONS: This is the first study that provides insight into the enhanced solubility of hesperidin through interactions with theasinensin A via a 2:1 complex formation between hesperidin and theasinensin A.

Effect of Frozen Treatment on the Sensory and Functional Quality of Extruded Fresh Noodles Made from Whole Tartary Buckwheat.

Extruded noodles made from whole Tartary buckwheat are widely known as healthy staple foods, while the treatment of fresh noodles after extrusion is crucial. The difference in sensory and functional quality between frozen noodles (FTBN) and hot air-dried noodles (DTBN) was investigated in this study. The results showed a shorter optimum cooking time (FTBN of 7 min vs. DTBN of 17 min), higher hardness (8656.99 g vs. 5502.98 g), and less cooking loss (5.85% vs. 21.88%) of noodles treated by freezing rather than hot air drying, which corresponded to better sensory quality (an overall acceptance of 7.90 points vs. 5.20 points). These effects on FTBN were attributed to its higher ratio of bound water than DTBN based on the Low-Field Nuclear Magnetic Resonance results and more pores of internal structure in noodles based on the Scanning Electron Microscopy results. The uniform water distribution in FTBN promoted a higher recrystallization (relative crystallinity of FTBN 26.47% vs. DTBN 16.48%) and retrogradation (degree of retrogradation of FTBN 34.67% vs. DTBN 26.98%) of starch than DTBN, strengthening the stability of starch gel after noodle extrusion. FTBN also avoided the loss of flavonoids and retained better antioxidant capacity than DTBN. Therefore, frozen treatment is feasible to maintain the same quality as freshly extruded noodles made from whole Tartary buckwheat. It displays significant commercial potential for gluten-free noodle production to maximize the health benefit of the whole grain, as well as economic benefits since it also meets the sensory quality requirements of consumers.

Synthesis and biophysical analysis of Naringin-Chitooligosaccharide complex.

In this study, new complexes of Naringin and Chitooligosaccharide (Nari-COS) at different mole ratios (1:1, 1:5, 1:10) were prepared by spray-drying method so as to enhance the water solubility and weaken the bitterness of naringin. At the same time, the antioxidant and the antibacterial properties of this complex were evaluated. SEM, FTIR, 1H NMR analysis confirmed the successful synthesis of Nari-COS formed through hydrogen bonds between the A, B rings of naringin and COS. Nari-COS exhibited significantly better water solubility, reduced bitterness, stronger antioxidant capacity, and enhanced antibacterial property in comparison to pure naringin, benefitting the extensive application of natural products in foods.

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.

Effect of freezing treatment of soybean on soymilk nutritional components, protein digestibility, and functional components.

Soymilk is a popular beverage in many countries owing to its nutrition and health effects. To increase household consumption of soymilk, instant soybeans were developed by freezing and subsequent drying pretreatment, which overcome the time-consuming need of soaking during soymilk preparation for home making. However, compared with the traditional soymilk making, the nutritional quality and functional properties of this soymilk made from the soybean by direct grinding in water without soaking are not clear yet. Soymilk made from untreated soybeans, soaked soybeans, and soaking, freezing, and air-drying soybeans (FADTS) were compared on their properties including nutritional components, in vitro protein digestibility, and functional components. It was found that FADTS was the best at extracting lipid and Ca, good at extracting of protein, carbohydrate, oligosaccharides, Fe, phytic acids, and tannins, and in producing soymilks with highest in vitro protein digestibility. The soluble protein and protein digestibility of FADTS (4 day) increased significantly from 44.4% and 78.5% of control to 56.2% and 85.0%, respectively. Soymilk from 4 days FADTS contained similar protein content and higher Fe content (4.40 mg/kg) compared to soaked sample (3.82 mg/kg). The results revealed that FADTS performed better at producing soymilk than untreated and soaked soybeans.

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.

Application of diffusion ordered-1H-nuclear magnetic resonance spectroscopy to quantify sucrose in beverages.

This work focuses on a quantitative analysis of sucrose using diffusion ordered-quantitative (1)H-nuclear magnetic resonance spectroscopy (DOSY-qNMR), where an analyte can be isolated from interference based on its characteristic diffusion coefficient (D) in gradient magnetic fields. The D value of sucrose in deuterium oxide at 30°C was 4.9 × 10(-10)m(2)/s at field gradient pulse from 5.0 × 10(-2) to 3.0 × 10(-1)T/m, separated from other carbohydrates (glucose and fructose). Good linearity (r(2)=0.9999) was obtained between sucrose (0.5-20.0 g/L) and the resonance area of target glucopyranosyl-α-C1 proton normalised to that of cellobiose C1 proton (100.0 g/L, as an internal standard) in 1D sliced DOSY spectrum. The DOSY-qNMR method was successfully applied to quantify sucrose in orange juice (36.1 ± 0.5 g/L), pineapple juice (53.5 ± 1.1g/L) and a sports drink (24.7 ± 0.6g/L), in good agreement with the results obtained by an F-kit method.

Quantitative analysis of D-(+)-glucose in fruit juices using diffusion ordered-1H nuclear magnetic resonance spectroscopy.

This study works on D-(+)-glucose quantitative analysis using diffusion ordered-quantitative (1)H nuclear magnetic resonance spectroscopy (DOSY-qNMR), by which an analyte could be distinguished from interferences based upon a characteristic diffusion coefficient (D) in gradient magnetic fields. The D value of D-(+)-glucose in deuterium oxide at 30°C was 5.6 × 10(-10) m(2)/s at a field gradient pulse of between 5.0 × 10(-2) and 3.0 × 10(-1) T/m, distinguished from fructose, sucrose and starch. Good linearity (r(2) = 0.9998) was obtained between D-(+)-glucose (0.5-20.0 g/L) and the ratio of the resonance area of α-C1 proton (5.21 ppm) in D-(+)-glucose to that of the ß-C1 proton (5.25 ppm) in D-glucuronic acid (50.0 g/L) as an internal standard. The DOSY-qNMR method was successfully applied to quantify D-(+)-glucose in orange juice (18.3 ± 1.0 g/L), apple juice (26.3 ± 0.4 g/L) and grape juice (45.6 ± 0.6 g/L); the values agreed well with a conventional F-kit glucose method.