Mannitol and oligosaccharides as new criteria for determining cold tolerance in sugarcane varieties

Sugarcane can be very susceptible to damage by freezes. Freeze-deteriorated cane can cause problems in processing and sometimes leads to a factory shut-down. This study was undertaken during the 2000/2001 harvest season to assess the cold tolerance performance of six commercial sugarcane varieties and to establish new and more sensitive criteria to measure cold tolerance. Two varieties CP 70-321 and CP 79-318, with known cold tolerance, were planted in the study as controls. The other varieties included LHo 83-153, LCP 85-384, HoCP 85-845 and HoCP 91-555. Freezing temperatures occurred on 20 December 2000 when the min. field temperature was −4.4 °C, and again on 21 December, 30 December through 5 January 2001, 9–10 January and 20–21 January. The lowest field temperature recorded was −5.6 °C on 4 January. Freezing conditions prevailed for 8–15 h during each freeze incident. Stalks of all varieties were frozen to the ground following the initial freeze, with freeze cracks evident only after the 4 January freeze. For this study, samples were taken on the date of the first freeze, 20 December, and subsequently again at 7, 14, 22 and 30 days after the first freeze. Criteria used to measure overall stalk cold-tolerance included changes in pH, Brix, dextran (ASI-II method), sucrose, glucose, and fructose concentrations. Mannitol, ethanol and the oligosaccharides, palatinose, leucrose, iso-maltotriose and 1-kestose, were simultaneuously measured using IC-IPAD. Marked differences were observed in most criteria for all varieties, particularly 22 and 30 days after the first freeze. Mannitol was strongly correlated (r²=0.84) with dextran, confirming its use as an indicator for cane dextran deterioration. In comparison, ethanol was only weakly correlated (r²=0.55) with dextran and did not always predict cane dextran deterioration. Iso maltotriose was the most sensitive oligosaccharide indicator of freeze deterioration, although both leucrose and palatinose could be used to confirm whether severe dextran formation (>1500 ppm/Brix) has occurred in cane. Isomaltotriose was strongly correlated (r²=0.89) with dextran and pH (r²=−0.83); pH was also a strong indicator of both dextran (r²=−0.85) and mannitol (r²=−0.92) formation. Four of the varieties, CP 79-318, LCP 85-384, HoCP 85-845 and HoCP 91-555, were shown to be susceptible to other sources of microbial and enzymic deterioration as well as dextran deterioration from Leuconostoc bacteria, especially 30 days after the first freeze. This was indicated by increased glucose/fructose ratios, ethanol formation, changes in 1-kestose concentration, and further sucrose losses.     

Effect of dextran glycation on nanofibril assembly of soya β‐conglycinin at pH 2.0 and the pH stability of nanofibrils

In this study, we investigated the effects of dextran glycation on soya β‐conglycinin self‐assembly into nanofibrils at 85 °C and pH 2.0, as well as their stability at pH 2.0–10.0. Although the hydrolysis rate of β‐conglycinin decreased, glycation significantly increased the structural change rate in the initial stage of nanofibril formation and the growth of nanofibril. It is suggested that the glycation of three subunits (α′, α, β) in β‐conglycinin may promote fibril assembly because the extension regions of α′ and α subunits play an important role in affecting the rate of structural changes in fibril formation. At neutral pH, conjugate nanofibrils are highly dispersible and transparent and remained greater structural stability compared with mixture. The improvement stability of conjugate nanofibrils may be contributed to dextran which provides some steric hindrance to prevent the aggregation of nanofibrils; this would also facilitate the application of soya β‐conglycinin nanofibrils in food industry.     

Roberts铜盐法测定蔗汁葡聚糖含量的热效应——淀粉对受热蔗汁葡聚糖测定的影响

作者从研究中发现:用Roberts铜盐法测定蔗汁样本葡聚糖含量时,所得结果与蔗汁的受热有关,受热蔗汁的测定值高于真实值,作者将这种现象暂称为Roberts铜盐法测定蔗汁样本葡聚糖含量的热效应。研究表明:蔗汁中的淀粉是引起热效应的重要因素。本文最后提出了一种由淀粉引起的热效应的可行校正方法。     

Preparation and characterization of magnetite/dextran nanocomposite used as a precursor of magnetic fluid

Magnetic nanoparticles were synthesized by the co-precipitation of Fe²⁺ and Fe³⁺ using ammonium hydroxide (NH₄OH). The obtained nanoparticles were characterized by X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer. In order to prepare a biocompatible water-based magnetic fluid, the nanoparticles were modified by dextran through a two-step method. The influences of dextran molecular weight on the size, morphology, coating efficiency and magnetic property of magnetite/dextran nanocomposite were investigated. The magnetite/dextran nanocomposite was dispersed in water to form a magnetic fluid by ball milling. The rheological property of magnetic fluids was investigated using a rotating rheometer.     

High-intensity ultrasound processed acerola juice containing oligosaccharides and dextran promotes Lacticaseibacillus casei NRRL B-442 growth

In the present study, a prebiotic acerola juice containing gluco-oligosaccharides and dextran was produced and processed by high-intensity ultrasound (HIUS). After a simulated in vitro digestion, the gluco-oligosaccharides and dextran maintained 90% and 80% of their initial concentration in all prebiotic’s juices. At the same time, Vitamin C and phenolic compounds concentration increased significantly by 19% and 7% (P < 0.05). After the in vitro digestion, the prebiotic juice HIUS processed by 10 min showed the highest increase in gluco-oligosaccharides and bioactive compound concentrations. The HIUS processing imparted some dextran hydrolysis and improved its fermentability by Lacticaseibacillus casei. Gluco-oligosaccharides were extensively consumed as substrate in simulated intestinal conditions, promoting the L. casei NRRL B-442 growth and production of organic acids and short-chain organic acids. The prebiotic juice HIUS processed for 6 min showed the best responses regarding the metabolism of L. casei NRRL B-442. The results showed high-intensity ultrasound processed acerola juices containing gluco-oligosaccharides and dextran as a prebiotic food.     

Degradation kinetics of fluorouracil-acetic-acid-dextran conjugate in aqueous solution

The degradation kinetics of fluorouracil-acetic-acid-dextran conjugate (FUAC-dextran) was investigated in various buffer solutions with different pH value and physiological saline solution at 60°C and 37°C, respectively. The hydrolytic reaction displayed pseudo-first-order degradation kinetics. Hydrolytic rate constant obtained was the function of pH value and independent of species of buffering agents. The smallest rate constant was observed at pH round 3.00. The activation energy of the hydrolytic reaction was estimated from Arrhenius equation as 88.73 ± 6.00 kJ·mol^-1. The special base catalytic degradation of the conjugate was observed from acidic to slight alkaline condition and the special base catalytic rate constants were calculated. The conjugate was more stable in physiological saline than that in buffer solution at pH 7.00 or 9.00 at 37°C. The results revealed that the conjugate was stable in acidic condition and will degrade in alkaline condition.     

大鼠原位肠肝血管灌流模型的优化及完善

目的: 对大鼠原位肠肝血管灌流模型的灌流液组成成分进行优化,以获取最佳灌流液配方。方法: 对灌流条件进行优化,分别对Krebs-Ringer(K-R)液加牛血清白蛋白和甘露醇、K-R液加牛血清白蛋白和右旋糖酐T-40二者进行对比,找出最佳的灌流介质。然后对最佳的灌流介质中牛血清白蛋白的含量进行了优化。结果: K-R液加牛血清白蛋白和右旋糖酐T-40组优于K-R液加牛血清白蛋白和甘露醇组;5%牛血清白蛋白的灌流液是一个较为经济理想的灌流液。结论: 在灌流介质中5%牛血清白蛋白是一个较为理想和经济的比例。     

Production and structural characterisation of dextran from an indigenous strain of Leuconostoc mesenteroides BA08 in Whey

In this work, the production of dextran was carried out in whey‐supplemented media using Leuconostoc mesenteroides BA08. Different growth and nutritional parameters were optimised to maximise the dextran production. Batch production in whey‐based media under optimised nutritional and growth conditions yielded a dextran concentration of 17.25 g/L. Structural analysis of the purified polymer by FT‐IR, 1D ¹H and ¹³C nuclear magnetic resonance methodology revealed that polymer was a linear dextran having 93% α‐(1→6) linkage in the main chain. The morphology of the dried dextran and dextran‐producing cells was also studied by scanning electron microscope which showed a granular and porous or weblike structure, respectively. The results obtained showed that the industrial whey supplemented with nutrients such as sucrose, yeast extract and K₂HPO₄ can serve as an ideal growth medium for dextran production. The optimised fermentation and nutritional parameters can be further scaled up to establish the potential for the commercial production of food‐grade dextran from whey as part of a novel cost‐effective and environment‐friendly approach.     

Degradation Kinetics of Fluorouracil-Acetic-Acid-Dextran Conjugate in Aqueous Solution

ABSTRACT

The degradation kinetics of fluorouracil-acetic-acid-dextran conjugate (FUAC-dextran) was investigated in various buffer solutions with different pH value and physiological saline solution at 60°C and 37°C, respectively. The hydrolytic reaction displayed pseudo-first-order degradation kinetics. Hydrolytic rate constant obtained was the function of pH value and independent of species of buffering agents. The smallest rate constant was observed at pH round 3.00. The activation energy of the hydrolytic reaction was estimated from Arrhenius equation as 88.73 ± 6.00 kJ·mol^?1. The special base catalytic degradation of the conjugate was observed from acidic to slight alkaline condition and the special base catalytic rate constants were calculated. The conjugate was more stable in physiological saline than that in buffer solution at pH 7.00 or 9.00 at 37°C. The results revealed that the conjugate was stable in acidic condition and will degrade in alkaline condition.     

Improvement of functional properties of peanut protein isolate by conjugation with dextran through Maillard reaction

Reaction mixtures containing peanut protein isolate (PPI) and dextran (1:1 weight ratio) were dry-heated at 60 °C and 79% relative humidity for 7 days. SDS-PAGE analysis indicated that PPI had become complexed with dextran to form conjugates of higher molecular weight. Arachin, accounting for 50% of peanut proteins, was hard to glycosylate with dextran, which might limit the extent of glycosylation of PPI. The thermal stability of PPI was remarkably improved by mixture/conjugation with dextran. Proteins in mixtures/conjugates might have a more compacted tertiary conformation than PPI. The protein solubility of conjugates at pH 4.5-6.0 was remarkably increased compared with the PPI/mixture. Mixture with dextran could significantly improve the emulsifying and foaming properties of PPI (p < 0.05). Conjugation with dextran could further enhance emulsifying and foaming properties of PPI.