Aqueous Sugar Solutions Research Articles

Thermal Properties of Freeze-Concentrated Sugar-Phosphate Solutions

In order to understand the effect of phosphate salts on the freeze-concentrated glass-like transition temperature (T g′) of aqueous sugar solutions, two types of sugar (glucose and maltose) and five types of phosphate salts (Na3PO4, Na4P2O7, Na5P3O10, K3PO4, and K4P2O7) were employed, and the thermal properties of various sugar-phosphate aqueous systems were investigated using differential scanning calorimetry. The T g′ of glucose increased with increasing sodium phosphates up to a certain phosphate ratio, decreasing thereafter. The maximum T g′ value was slightly higher in the order of Na3PO4 > Na4P2O7 ≥ Na5P3O10. Maltose-sodium phosphate also showed a similar trend as glucose-sodium phosphate samples. However, the degree of T g′-rise of maltose systems was much less than that of glucose. It is thought that the T g′ elevated by the molecular interaction between sugar and phosphate ions will be reduced by hydrated sodium ions. In comparisons between potassium phosphate and sodium phosphate, it was found that sugar-potassium phosphates showed the lower maximum T g′ at a lower phosphate ratio than sugar-sodium phosphates. In addition, the T g′ of potassium phosphates dropped sharply in comparison with sodium phosphates at the high phosphate ratio. These results suggest that potassium phosphates are lower T g′ than sodium phosphates, and that potassium ion plays a better plasticizer than sodium ion. A certain amount of sodium phosphates (Na3PO4 and Na4P2O7) caused devitrification. Potassium phosphates, however, did not show devitrification which can be explained by the fact that potassium ion can be dynamically restricted by sugar.

Polarizable Empirical Force Field for Hexopyranose Monosaccharides Based on the Classical Drude Oscillator

A polarizable empirical force field based on the classical Drude oscillator is presented for the hexopyranose form of selected monosaccharides. Parameter optimization targeted quantum mechanical (QM) dipole moments, solute–water interaction energies, vibrational frequencies, and conformational energies. Validation of the model was based on experimental data on crystals, densities of aqueous-sugar solutions, diffusion constants of glucose, and rotational preferences of the exocylic hydroxymethyl of d-glucose and d-galactose in aqueous solution as well as additional QM data. Notably, the final model involves a single electrostatic model for all sixteen diastereomers of the monosaccharides, indicating the transferability of the polarizable model. The presented parameters are anticipated to lay the foundation for a comprehensive polarizable force field for saccharides that will be compatible with the polarizable Drude parameters for lipids and proteins, allowing for simulations of glycolipids and glycoproteins.

A new hydrogen bonding local composition based model in obtaining phase behavior of aqueous solutions of sugars

In this research, the local composition based model proposed by Pazuki et al. is developed to consider the hydrogen bonding effect by using the molecular surface area parameter. The proposed model has two terms which account for the combinatorial and residual effects. The Freed-FV model is used for the combinatorial term while the model proposed by Pazuki et al. is developed for the residual term along with hydrogen bonding effects. The interaction parameters of the model are obtained from the experimental data of water activity. Also, the model is used to correlate and predict thermophysical properties of aqueous sugar solutions (glucose, sucrose, fructose, maltose, mannose, maltotriose, xylose and galactose) such as water activity, density, solubility, osmotic coefficient, vapor pressure and boiling point. A comparison between the results obtained from the model and UNIQUAC model shows that the proposed model can successfully predict thermophysical properties of sugar–water systems in various conditions.

Ratiometric fluorescence sensing of sugars via a reversible disassembly and assembly of the peptide aggregates mediated by sugars

An amphiphilic dipeptide (1) bearing pyrene and phenylboronic acid was demonstrated as a unique example of a ratiometric sensing system for sugars by reversibly converting the peptide aggregates into the monomer form of the complex with sugars in aqueous solutions.

粘度測定による糖やアミノ酸の水和および高分子間相互作用の解析

粘度測定による糖やアミノ酸の水和および高分子間相互作用の解析

H-Bond activated glycosylation of nucleobases: implications for prebiotic nucleoside synthesis

Glycosylation of nucleobases is achieved by heating metal free aqueous solution of nucleobase and sugar. It seems that abstraction of N9/N1 H by C1′-OH promotes N9/N1(nucleobase)-C1′ (sugar) covalent bond formation.

Conversion of sugars to ethylene glycol with nickel tungsten carbide in a fed-batch reactor: high productivity and reaction network elucidation

Bifunctional nickel tungsten carbide catalysis was used for the conversion of aqueous sugar solutions into short-chain polyols such as ethylene glycol. It is shown that very concentrated sugar solutions, viz. up to 0.2 kg L−1, can be converted without loss of ethylene glycol selectivity by gradually feeding the sugar solution. Detailed investigation of the reaction network shows that, under the applied reaction conditions, glucose is converted via a retro-aldol reaction into glycol aldehyde, which is further transformed into ethylene glycol by hydrogenation. The main byproducts are sorbitol, erythritol, glycerol and 1,2-propanediol. They are formed through a series of unwanted side reactions including hydrogenation, isomerisation, hydrogenolysis and dehydration. Hydrogenolysis of sorbitol is only a minor source of ethylene glycol. To assess the relevance of the fed-batch system in biomass conversions, both the influence of the catalyst composition and the reactor setup parameters like temperature, pressure and glucose addition rate were optimized, culminating in ethylene glycol yields up to 66% and separately, volume productivities of nearly 300 gEG L−1 h−1.

A mutarotation mechanism based on dual proton exchange in the amorphous d-glucose

It is a well known fact that carbohydrates have unusual chemical and physical properties when they approach the glassy state during the cooling process. Differences between sugar aqueous solutions and their pure anhydrous states are caused mainly by the different intermolecular interactions related to the different hydrogen bond patterns. The mutarotation, a specific reaction in the saccharides, was recently investigated in the supercooled liquid and the glassy state of D-glucose. It was shown that the activation energy of this process in the supercooled liquid state is twice as low as for the same process in aqueous solution. In contrast, the activation energy in the glassy state is twice as high as in the aqueous solution. Herein, we present possible explanations for this phenomenon and propose a universal mechanism for the mutarotation process in the amorphous state of matter. In this work, for the first time, a double proton exchange mechanism in carbohydrates is proposed.

General nature of liquid–liquid transition in aqueous organic solutions

The presence or absence of a liquid-liquid transition in water is one of the hot topics in liquid science, and while a liquid-liquid transition in water/glycerol mixtures is known, its generality in aqueous solutions has remained elusive. Here we reveal that 14 aqueous solutions of sugar and polyol molecules, which have an ability to form hydrogen bonding with water molecules, exhibit liquid-liquid transitions. We find evidence that both melting of ice and liquid-liquid transitions in all these aqueous solutions are controlled solely by water activity, which is related to the difference in the chemical potential between an aqueous solution and pure water at the same temperature and pressure. Our theory shows that water activity is determined by the degree of local tetrahedral ordering, indicating that both phenomena are driven by structural ordering towards ice-like local structures. This has a significant implication on our understanding of the low-temperature behaviour of water.

Cookie- Versus Cracker-Baking—What's the Difference? Flour Functionality Requirements Explored by SRC and Alveography

The many differences between cookie- and cracker-baking are discussed and described in terms of the functionality, and functional requirements, of the major biscuit ingredients—flour and sugar. Both types of products are similar in their major ingredients, but different in their formulas and processes. One of the most important and consequential differences between traditional cracker and cookie formulas is sugar (i.e., sucrose) concentration: usually lower than 30% in a typical cracker formula and higher than 30% in a typical cookie formula. Gluten development is facilitated in lower-sugar cracker doughs during mixing and sheeting; this is a critical factor linked to baked-cracker quality. Therefore, soft wheat flours with greater gluten quality and strength are typically preferred for cracker production. In contrast, the concentrated aqueous sugar solutions existing in high-sugar cookie doughs generally act as an antiplasticizer, compared with water alone, so gluten development during dough mixing and starch gelatinization/pasting during baking are delayed or prevented in most cookie systems. Traditional cookies and crackers are low-moisture baked goods, which are desirably made from flours with low water absorption [low water-holding capacity (WHC)], and low levels of damaged starch and water-soluble pentosans (i.e., water-accessible arabinoxylans). Rheological (e.g., alveography) and baking tests are often used to evaluate flour quality for baked-goods applications, but the solvent retention capacity (SRC) method (AACC 56-11) is a better diagnostic tool for predicting the functional contribution of each individual flour functional component, as well as the overall functionality of flours for cookie- and/or cracker-baking.

Measuring the sugar consumption of larvae in bumblebee micro-colonies: a promising new method for tracking food economics in bees

The consumption of sugar is an important part of the energy intake of social insect. Its monitoring provides information regarding the costs and efficiency of energy flow in a colony. This study aims at tracking the sugar flow from a sugar source to artificial bumblebee micro-colonies and at quantifying the amount of sugar consumed by the larvae. We developed a new method of sugar tracking that utilises an inert lanthanide complex (GdDOTA) dissolved in an aqueous sugar solution. The delayed defecation of bee larvae enabled the collection of all faeces from a cocoon. The amount of digested sugar corresponded to the amount of the lanthanide in the faeces, which was quantified using inductively coupled plasma spectrometric techniques. We highlight the possibility of the novel developed method to be extended for tracking the energy flow within a colony using up to 15 different metal markers without the necessity of killing individuals.

유체의 점성이 원심펌프 성능에 미치는 영향

원심펌프 작동유체의 점도변화에 따른 성능특성을 실험적인 방법으로 연구하였다. 비교적 비속도가 낮은 소형 원심펌프에 뉴턴유체인 설탕수용액과 글리세린수용액을 사용하여 작동유체의 점도를 변화시켜 가며 펌프성능시험을 수행한 후 전양정, 축동력 및 펌프의 효율을 청수의 경우와 비교·분석하여 얻은 결과는 다음과 같았다. (1) 전양정은 작동유체의 점도를 변화시킬 경우 청수에 비해 점도가 높아짐에 따라서 차단점에서의 양정은 극히 적은 변화를 보였으나, 유량이 증가함에 따라 양정의 감소하는 폭이 크게 나타났다. 따라서 유량-양정곡선(H-Q 곡선)의 기울기가 급해짐을 알 수 있었다. (2) 축동력은 작동유체의 점도가 청수에 비해 클수록 증가하였으며 차단점에서는 소요동력이 열로 소산되어 차이가 거의 없었으나, 유량이 증가할수록 축동력의 증가하는 폭이 커짐을 알 수 있었다.

Effects of Sugars on the Formation of Nanometer‐Sized Droplets of Vegetable Oil by an Isothermal Low‐Energy Emulsification Method

Effects of sugars on the formation of nanometer-sized oil droplets induced by the addition of vegetable oil to aqueous dispersions of polyoxyethylene sorbitan monooleate (MOPS, Tween 80) at 25°C without the application of intensive mechanical energy were investigated. Phase diagrams were constructed using polarized light microscopy and small angle X-ray scattering (SAXS) to elucidate the relationship between the type of phases involved in the process of emulsification and the droplet size in the resulting emulsions. Nanometer-sized oil droplets as small as 220 nm in diameter were obtained when the sponge phase (L3 ) was formed at first, followed by the phase transition to coexisting multiple phases including the micellar cubic phase (I1 ) with increasing vegetable oil content. Sugars expanded the area of the sponge phase toward lower MOPS contents, enabling the formation of nano-emulsions from a wider range of the initial composition. The area of the sponge phase increased in the order of d-fructose ≈ d-glucose < sucrose < d-maltose, consistent with the order of the literature value of the mean number of equatorial hydroxyl groups per sugar molecule and that of the hydration number of sugar that represents the average number of water molecules forming a complex with a single molecule of sugar in aqueous solution. The present results confirm that sugars facilitate the formation of nano-emulsions using the isothermal low-energy emulsification method, presumably due to their abilities to shift the effective hydrophile-lipophile balance (HLB) of the surfactant toward the hydrophobic side.

Recovering bioethanol from olive bagasse fermentation by nanofiltration

The aim of this manuscript was the study of the recovery of bioethanol produced by the fermentation of the lignocellulosic biomass (olive bagasse) by nanofiltration. In terms of downstream processing, the nanofiltration permeate stream was expected to be comprised mostly of water and ethanol, and as such, ethanol may be further recovered by conventional distillation. Different nanofiltration membranes (NF90 and NF270) were tested for their efficiency in the separation of bioethanol. Model aqueous solutions of ethanol and sugars, and real liquors were processed by nanofiltration focusing on flux and rejection performance. The results shown that the more complex medium of a real liquor interacts with the membrane and lower the rejection to target solutes. Generally, both membranes tested were suitable for separating and recovering ethanol from a fermentation medium. The diafiltration mathematical model developed in this work shown to be capable of describing experimental results, which may be considered extremely important for process design and scaling up purposes.

Optimization of the Effect of Process Parameters and Study of Quality Characteristics of Osmotic Dehydrated Amla Slices

The osmotic dehydration technique not only enables the storage of the fruits for a longer period, but also preserves flavour, nutritional characteristics and prevents microbial spoilage. Osmotic Dehydration is done by immersing Vegetable & Fruits, whether in pieces or whole, in salt or sugar aqueous solution of high osmotic pressure. The amla (Phyllanthus emblica) is an effective source of Vitamin C. The ascorbic acid (Vitamin C) content in the amla fruit is one of the highest contents of all plants. The amla plant has been used in Indian medicine for years. In Ayurvedic medicine, the amla plant is used to treat minor hemorrhage and to help foster cardiovascular health. The study conducted for Amla slices during osmotic dehydration followed by tray drying and the influence of process variables on the quality characteristics. The samples were osmodehydrated at in combination of sugar (25- 60°Brix) and salt (5%, 7.5% and 10%) solution at temperature of 30°C in 4:1 and 8:1 ratio. The treated sample slices were spread on stainless steel trays of the tray dryer and they were dried in tray dryer at temperature 50 0 C. The samples were weighed at an interval of 30 minutes. The sample took around 2 to 3 hours depending on the drying temperature to reach equilibrium moisture content. It was observed that the weight reduction, solid gain and weight loss increased with increase of the parameters like time, concentration of the sugar solution and ratio of the solution to sample. The quality parameters such as reducing sugars and ash content were determined.

A continuous‐effect membrane distillation process based on hollow fiber AGMD module with internal latent‐heat recovery

A continuous‐effect membrane distillation (CEMD) process was developed by equipping air gap membrane distillation (AGMD)‐based and strictly‐parallel hollow fiber module with internal heat recovery. Its performance was indicated by flux, performance ratio and evaporation efficiency. Two kinds of CEMD modules made from different membrane fibers were tested. A face‐centered central composite experimental design was conducted to investigate the influences of operating variables including cold‐feed temperature, hot‐feed temperature, and feed‐in flow rate on the performance. Within the studied experimental range, the maximum PR of 13.8 was obtained. A theoretical model based on governing transport equations was established to predict the process performance, and the model described the experimental data fairly well. In light of the model, possible ways to further increase PR were predicted. The dilute aqueous sugar solution was successfully concentrated 12‐fold to a final concentration of about 20 wt % by using CEMD process with a final PR of 8.2. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1278–1297, 2013

An experimental investigation on heat transfer for different parameters in centripetally located boiling agitation vessels

In this study, the effects of blade size, agitation speed and the gap between the blade and the bottom surface on heat transfer rate in centripetally located boiling agitation vessels are aimed to investigate by experimentally. Aqueous sugar solutions at constant pressure and different temperatures were used for boiling experiments. The experiments were performed using 3 different agitator speeds, 2 different gaps and 3 different sized blades. It was seen that the heat transfer rate is depending on sugar concentration, agitator speed and the gap. Also, the process time and the capacity variations depending on the radius for boiling vessels were examined for the half-sphere heating surface.

Solubility and physical properties of sugars in pressurized water

In this study, the solubility, density, and refractive index of glucose and lactose in water as a function of temperature were measured. For solubility of sugars in pressurized water, experimental data were obtained at pressures of (15 to 120) bar and temperatures of (373 to 433)K using a dynamic flow high pressure system. Density data for aqueous sugar solutions were obtained at pressures of (1 to 300)bar and temperatures of (298 to 343)K. The refractive index of aqueous sugar solutions was obtained at 293K and atmospheric pressure. Activity coefficient models, Van Laar and the Conductor-like Screening Model-Segment Activity Coefficient (COSMO-SAC), were used to fit and predict the experimental solubility data, respectively. The results obtained showed that the solubility of both sugars in pressurized water increase with an increase in temperature. However, with the increase of pressure from 15 bar to 120 bar, the solubility of both sugars in pressurized water decreased. The Van Laar model fit the experimental aqueous solubility data with deviations lower than 13 and 53% for glucose and lactose, respectively. The COSMO-SAC model predicted qualitatively the aqueous solubility of these sugars.

Probing the general time scale question of boronic acid binding with sugars in aqueous solution at physiological pH

The boronic acid group is widely used in chemosensor design due to its ability to reversibly bind diol-containing compounds. The thermodynamic properties of the boronic acid–diol binding process have been investigated extensively. However, there are few studies of the kinetic properties of such binding processes. In this report, stopped-flow method was used for the first time to study the kinetic properties of the binding between three model arylboronic acids, 4-, 5-, and 8-isoquinolinylboronic acids, and various sugars. With all the boronic acid–diol pairs examined, reactions were complete within seconds. The kon values with various sugars follow the order of d-fructose>d-tagatose>d-mannose>d-glucose. This trend tracks the thermodynamic binding affinities for these sugars and demonstrates that the ‘on’ rate is the key factor determining the binding constant.

Fluid flow beneath a semipermeable membrane during drying processes

The dynamic interactions between a semipermeable membrane and a long, thin layer of liquid beneath it are investigated in the context of drying processes. The membrane separates two aqueous solutions of sugar, and the transport of water across the membrane is driven by concentration and pressure gradients across it. A model is formulated using a long-wave approximation that includes the effects of volume loss due to water transport across the membrane, the incompressibility and bending stiffness of the membrane, and the dynamical effects that arise owing to the viscous stresses generated by the fluid flow. This model is first applied to study the desiccation of a sessile vesicle that is clamped to a rigid substrate and then also to study the behavior of blisters on laminated substrates. For each problem, equilibrium membrane shapes are obtained and their bifurcation structures are described as the sugar concentration above the membrane is varied. It is demonstrated that a wrinkled membrane coarsens to lessen the frequency of wrinkles and that if the membrane is clamped symmetrically so that it meets the substrate at a nonzero angle, then the membrane favors an asymmetric shape as water is drawn out through it.