Apparent Specific Volume Research Articles

Apparent specific volumes and tastes of cyclamates, other sulfamates, saccharins and acesulfame sweeteners

Measurements of apparent specific volume (ASV) for a series of alternative sweeteners (cyclamates, sulfamates, saccharins, acesulfames and anilinomethanesulfonates) have been made. Taste data have been obtained for many of the new compounds unless the toxicity of the associated metals precluded this. Apparent molar volume (AMV), isentropic specific (IASC) and isentropic molar (IAMC) compressibilities were also measured. Sixteen metallic cyclamates cyc-C 6H 11NHSO 3M and two phenylsulfamates ArNHSO 3Na, namely 3,5-dimethyl- and 3,4-dimethoxyphenylsulfamates have been examined. When the ASVs for these are combined with those for 15 aliphatic, aromatic and alicyclic sulfamates from a previous study, many of the values are seen to fall into the region that was previously identified as being the “sweet area”, i.e. the ASVs lay between ∼0.5 and ∼0.7 (a few sweet compounds fall below this range and it is suggested that it could be extended slightly to accommodate these). Interestingly, the anilinomethanesulfonates, ArNHCH 2SO 3Na (Ar=C 6H 5-, 3-MeC 6H 4- and 3-ClC 6H 4-) lie clearly in the sweet region but only one of them shows slight sweetness showing that the molecular structural change made (compared with the ‘parent’ sulfamate–NHSO 3 −) cannot be accommodated at the receptor site.

Volumetric Study of Lysozyme in Dimethyl Sulfoxide + Water Solution at 298.15 K

The densities, d, and fluorescence spectra of ternary mixtures of water (1) + dimethyl sulfoxide (2) + lysozyme (3) were measured, and the partial specific volumes of lysozyme, v̄°, were determined as the extrapolated values of the apparent partial specific volumes at an infinitely dilute concentration of lysozyme at 298.15 K. A binary mixture of water + dimethyl sulfoxide has a minimum excess volume when the mole fraction of dimethyl sulfoxide (x2) is in the range 0.25 to 0.42, and lysozyme unfolds and aggregates within this range. This indicates that the strong interaction between water and dimethyl sulfoxide might influence the conformation of lysozyme by interfering water−lysozyme interactions. In the range x2 > 0.8, lysozyme was in a disaggregated−denatured state, having a partial specific volume of (0.706 ± 0.002) cm3·g-1, which was smaller than that in the native state, (0.712 ± 0.001) cm3·g-1, probably because the unfolding led to a decreased cavity volume of lysozyme in the solvent.

Volumetric properties of aqueous solutions of some cyclohexylsulfamates at 25.0 °C

The densities of aqueous solutions of some salts of cyclohexylsulfamic acid (lithium, potassium, ammonium and tetramethylammonium, synthesized in our laboratory) and of the commercially available sodium and calcium cyclohexylsulfamate, were measured in the concentration range from 0.003 to 1.000 mol kg −1 at a temperature of 25.0 °C. The apparent and partial molar volumes of the solutes studied were determined as a useful tool in elucidating the structural interactions (e.g. ion–ion and ion–solvent) occurring in solution. The apparent molar volumes mainly show small negative deviations from the Debye–Hückel's limiting law, though in some cases no deviations were observed. The concentration dependence of the apparent molar volumes was expressed in the form of a polynomial of second degree; the empirical constant B v which can be used as a direct measure of the ion–ion interactions, equals zero or it is negative for the solutes investigated. Additionally, the partial molar ionic volume of the cyclohexylsulfamate anion was calculated and also the apparent specific volume of the solutes; in general the latter is closely associated with the taste quality. It was found that the values of the apparent specific volumes of the solutes investigated lie on the borderline between the values reported for sweet and bitter substances.

Volumetric Properties, Compressibilities and Volume Fluctuations in Phospholipid-Cholesterol Bilayers

Abstract We conducted detailed measurements of the apparent specific volume of dipalmitoylphosphatidylcholine (DPPC)–cholesterol mixtures in excess water as a function of pressure up to 70MPa (700bar) at 20, 38 and 50°C. The volumetric properties and the isothermal compressibility κ T of the lipid vesicles were determined at cholesterol concentrations, χchol, ranging up to 50 mol. The thermodynamic data are compared with other physico-chemical properties of phospholipid–cholesterol mixtures. Furthermore, the thermodynamic properties of the system are discussed in the light of the various T, χchol–phase diagrams and computer simulation studies published in the literature.

Role of water in sweet taste chemoreception

Abstract The mechanistic understanding of sweet taste chemoreception has been advanced by the microscopic and macroscopic studies of sweetener­water interactions. This approach has led to the concept of water mobility as a key to interpreting sweetness. The apparent specific volume of a solution is a determinant of its taste quality, as sweetness is known to be confined to the range 0.51­0.71 cm3 g-1. Thus, the "ideal" quality of the sugars is presumed to be due to their occupancy of the center of this range (i.e., 0.618 cm3 g-1). Most sweeteners elicit off-tastes and flavors and exhibit different apparent specific volumes. This leads to the conclusion that taste quality is broadly determined by the packing characteristics of sweet molecules among water molecules and the compactness of their hydration shells, expressed as their apparent specific isentropic compressibilities. The role of water can, therefore, be applied in modern attempts to optimize sweet taste quality, and different food salts can be explored as useful taste modifiers. Salts interact more strongly with water structure than do any other taste solutes, and it emerges that the ionic charge density is an important criterion. Such studies show how sweetener formulations are likely to improve within the next decade.

Hydration properties and the role of water in taste modalities of sucrose, caffeine, and sucrose-caffeine mixtures.

Solution properties of sapid molecules are informative on their type of hydration (hydrophobic or hydrophilic) and on the extent of the hydration layer. Physicochemical properties (intrinsic viscosity and apparent specific volume) and nuclear magnetic resonance (NMR) relaxation rates R(1) and R(2) for pure sucrose, bitter molecule caffeine, and their mixture were found to be relevant in the interpretation of the effects of these solutes on water mobility. Likewise, surface tension, contact angles with a hydrophobic surface, and the adhesion forces to this type of surface of the aqueous solutions of sapid molecules were found to discriminate between their effects on water cohesion and also between their taste qualities. The interpretation of the two sets of independent experimental results, namely physicochemical and spectroscopic data, helps in the elucidation of the role of water in sweet and bitter taste chemoreception.

DEEP FAT FRYING OF POTATO STRIPS—QUALITY ISSUES

Moisture loss and oil adsorption kinetics, structural properties (apparent density, true density, specific volume and internal porosity), color changes and viscoelastic behavior (compression tests, crispness) were investigated during deep fat frying of french fries. The effect of frying conditions (oil temperature, sample thickness and oil type), drying pretreatment and osmotic dehydration pretreatment on the above properties was also examined. The results showed that oil temperature and thickness of potato strips have a significant effect on oil uptake, moisture loss and color parameters of french fries, while the use of hydrogenated oil in the frying medium does not affect these properties. The porosity of french fries increases with oil temperature increases and sample thickness and it is higher for products fried with hydrogenated oil. Maximum stress and maximum strain increase during frying, while crispness of potato strips is higher for hydrogenated oil, and lower for refined oil. Air drying and osmotic pretreatment increase porosity of fried potatoes but decrease their oil and moisture content. A negative effect on color development with drying time was also observed. Pre-fry drying as well as osmotic pre-treatment increases the maximum stress and maximum strain of french fries during frying. Air drying pre-treatment increases the crispness of potato strips while osmotic pre-treatment does not affect it, with the exception of sugar solutions.

Effect of osmotic dedydration pretreatment on quality of french fries

Osmotic dehydration as a pretreatment before frying in order to produce low-fat french fries was examined. A relationship between frying kinetics and the type of solution used for osmotic dehydration before frying of french fries has been developed. The effect of osmotic dehydration on the structural properties (apparent density, true density, specific volume and internal porosity) and color parameters (lightness, a, b) of french fries was also investigated. Four types of solutions (sugar, NaCl, maltodextrine 12 and maltodextrine 21) were used. The results showed that osmotic pretreatment has a significant effect on oil uptake and moisture loss of french fries, as well as on the structural properties and color parameters of french fries. Osmotic dehydration pretreatment decreases oil and moisture content of french fries, while the porosity and intermit of color increased.

Effect of pre-drying on quality of french fries

The effect of duration of pre-drying on structural properties (apparent density, true density, specific volume and internal porosity) and color parameters (lightness, a, b) of fried potatoes was also investigated. The results showed that pre-drying pre-treatment had a significant effect on oil uptake and moisture loss, as well as structural properties and color parameters of french fries. Air drying decreased the oil and moisture contents of french fries, while the porosity increased. A negative effect on color development with drying time was also observed. A relationship between frying kinetics and drying time before frying of french fries has been developed.

Volume, expansivity and isothermal compressibility changes associated with temperature and pressure unfolding of staphylococcal nuclease

We have characterized the temperature- and pressure-induced unfolding of staphylococcal nuclease (Snase) using high precision densitometric measurements. The changes in the apparent specific volume, expansion coefficient and isothermal compressibility were determined by these measurements. To our knowledge, these are the first measurements of the volume and isothermal compressibility changes of a protein undergoing pressure-induced unfolding. In order to aid in interpreting the temperature and pressure dependence of the apparent specific volume of Snase, we have also carried out differential scanning calorimetry under the solution conditions which are used for the volumetric studies. We have seen that large compensating volume and compressibility effects accompany the temperature and pressure-induced protein unfolding. Measurements of the apparent specific volume and thermal expansion coefficient of Snase at ambient pressure indicate the formation of a pre-transitional, molten globule type of intermediate structure about 10°C below the actual unfolding temperature of the protein. Compared to the folded state, the apparent specific volume of the unfolded protein is about 0.3-0.5 % smaller. In addition, we investigated the pressure dependence of the apparent specific volume of Snase at a number of different temperatures. At 45°C we calculate a decrease in apparent specific volume due to pressure-induced unfolding of −3.3 10−3 cm3 g−1 or −55 cm3 mol−1. The threefold increase in compressibility between 40 and 70 MPa reflects a transition to a partially unfolded state, which is consistent with our results obtained for the radius of gyration of the pressure-denatured state of Snase. At the lower temperature of 35°C, a significant increase in compressibility around 30 MPa is indicative of the formation of a pressure-induced molten globule-like intermediate. Changes in the apparent volume, expansion coefficient and isothermal compressibility are discussed in terms of instrinsic, hydrational and thermal contributions accompanying the unfolding transition.

Hydration properties of Na, K, Mg gluconates and gluconate/sucrose mixtures and their possible taste effect

Abstract Density and ultrasonic velocity were measured in aqueous solutions of sodium, potassium and magnesium gluconate as a function of increasing concentration. Apparent molar volume (AMV), apparent specific volume (ASV), isentropic apparent molar (IAMC) compressibility and hydration numbers were calculated from the experimental data. The results show that AMV and ASV increase as the concentration of gluconates is increased. This is interpreted on the basis of molecular interaction between solute and solvent molecules. These measurements were repeated by adding Na, K and Mg gluconates to 10 and 20% sucrose solution with the aim of understanding the influence of gluconates on water association in sucrose solutions. The results show that the values of IAMC decrease as the concentration is increased. Moreover, Mg gluconate shows more negative IAMC than Na and K gluconates. The observed results are explained on the basis of the hydration of gluconates in the sucrose-water system. NMR relaxation rates (R 1 and R 2 ) show an increase as the concentration of the gluconate is increased. On the other hand, the results of Na, K and Mg gluconate in 10 and 20% sucrose solutions demonstrated that the effect of Mg gluconate enhances the hydration properties of sucrose water mixtures more than Na and K gluconate. The overall results show the importance of water interactions with sapid molecules and this can lead to a better understanding of their tastes.

Effect of frying conditions on shrinkage and porosity of fried potatoes

Apparent density, true density, specific volume and internal porosity were investigated during deep fat frying of french fries. The effect of frying conditions (oil temperature, sample thickness and oil type) on the above properties was examined. A simple mathematical model was used to correlate the above properties with oil and moisture content. Five parameters with physical meaning were incorporated into the model: the enclosed water density ρ w, the enclosed oil density ρ L, the dry solids density ρ s, the dry solids bulk density ρ bo and the volume shrinkage coefficient β ′. Moisture and oil content during deep fat frying and consequently all the examined properties are affected by frying conditions. The results showed that the porosity of french fries increases with oil temperature increases and sample thickness and it is higher for products fried with hydrogenated oil.

Studies on the physicochemical properties of inulin and inulin oligomers

Inulin, Raftiline® ST, Raftilose® P and oligofructose in aqueous solutions were investigated at 2.5, 5, 10, 15, 17.5, 20 and 25 g of solute in 100 g of water by physicochemical measurements in order to obtain molecular weights, reducing activities, apparent specific volumes, isentropic apparent specific compressibilities, and 1H-NMR pulse relaxation times ( T 1 values). Molecular weights have been found to range from 340 to 4620 g mol −1. Raftilose® P is the only sample which shows reducing capacity and may be expected to be susceptible to the Maillard reaction. Apparent specific volumes lie within the sweet range 0.60–0.64 cm 3 g −1 and increase with degree of polymerisation (DP); this behaviour describes increasing displacement of water as molecular weight increases. Isentropic apparent specific compressibilities increase as concentration of solute, molecular weight and DP increase, showing reduced solute–water affinity. T 1 values decrease with increasing molecular weight and concentration as a result of increased order of protons and reduced water mobility.

A study of the solution properties of selected binary mixtures of bulk and intense sweeteners in relation to their psychophysical characteristics

The solution properties of binary mixtures of two bulk sweeteners (sucrose and maltitol) and three intense sweeteners (acesulfame K, aspartame and sodium cyclamate) were studied. The parameters measured were apparent specific volumes, isentropic compressibilities and compressibility hydration numbers. An attempt has been made to correlate the solution properties of some of the mixtures with their sweetness responses. Both specific volume and isentropic compressibility data have been used to interpret the possibility of synergism or suppression in the mixtures in terms of the affinity of the solutes for the surrounding solvent structure, and hence the effectiveness of transport of the molecules to their appropriate receptor sites. However, an understanding of the nature and stereochemistry of the individual components in the mixtures is necessary for predicting the packing characteristics of molecules in water and their accession to receptor sites. The intense sweeteners seem to play an important role in modifying the structure of water in solution. Although there is no clear proof of how this affects perception, fine differences in solution behaviour can be observed with isentropic apparent specific compressibility measurements. The study supports the idea that receptors lie at different depths in the lingual epithelium, and also that in two-component systems, one species may alter the packing efficiency of the other in solution sufficiently to effect a change in taste quality or intensity.

Solution properties of ethanol in water

The packing propensity of ethanol in aqueous solution is very unusual, yet ethanol finds extensive use both in the food and the pharmaceutical industry. An analysis of the solution properties of increasing concentrations of ethanol in water at 20° and 37°C reveals valuable information about its packing characteristics. Apparent molar and specific volumes provide information about the interaction of ethanol with surrounding water structure. Isentropic apparent molar and specific compressibilities indicate the extent to which the hydration layer around the ethanol molecules can be compressed. Compressibility hydration numbers show the number of water molecules that are displaced by the introduction of the ethanol to water. The enhanced packing efficiency of ethanol in water at low concentrations, is affected by the formation of cage-like structures around the hydrophobic end of the molecule. At high concentrations, however, linear chains or rings of ethanol molecules are formed which change its mode of packing within the three-dimensional structure of water. These effects may be used to help explain the mechanism of action of ethanol in food, pharmaceutical and other applications.

Some taste molecules and their solution properties.

The solution properties of a variety of different sapid substances from all four basic taste modalities, namely, sweet (n = 24), salty (n = 7), sour (n = 11) and bitter (n = 2), have been investigated. Some multisapophoric molecules, i.e. molecules exhibiting more than one taste, have also been included in the study in an attempt to define their properties in relation to the tastes they exhibit; eight sweet-bitter and three salty-bitter molecules were used. The density and sound velocity of their solutions in water have been measured and their apparent volumes, apparent compressibilities and compressibility hydration numbers calculated and compared. Apparent molar volumes (phi(v)) and apparent specific volumes (ASV) reflect the state of hydration of the molecules, and thus their extent of interaction with water structure. The range of ASVs reported are 0.13-0.49 cm3/g for salty molecules, 0.55-0.68 cm3/g for sweet molecules, 0.53-0.88 cm3/g for sweet-bitter molecules and a much wider range (0.16-0.85 cm3/g) for sour molecules. Isentropic apparent specific compressibilities range from -2.33 x 10(-5) to -8.06 x 10(-5) cm3/g x bar for salty molecules, -3.38 x 10(-7) to -2.34 x 10(-5) cm3/g x bar for sweet molecules, +6.35 x 10(-6) to -2.22 x 10(-5) cm3/g x bar for sweet-bitter molecules and +6.131 x 10(-6) to -2.99 x 10(-5) cm3/g x bar for sour molecules. Compressibility hydration numbers are also determinable from the measurements of isentropic compressibilities and these reflect the number of water molecules that are disturbed by the presence of the solutes in solution. This study also shows that it is possible to group isentropic apparent molar compressibility values by the taste quality exhibited by the molecules in the same order as for ASV.

The volume and compressibility changes of lysozyme associated with guanidinium chloride and pressure-assisted unfolding

The apparent specific volumes and isentropic compressibilities of hen egg white lysozyme were measured in aqueous guanidinium chloride solutions at 25 °C by means of a vibrational densimeter and a sing-around ultrasonic velocimeter. Little transition attributable to a protein unfolding was detected in the partial specific volume, while the partial specific isentropic compressibility decreased slightly around the transition region. The pressure-assisted unfolding was also investigated in aqueous guanidinium chloride solutions by means of ultraviolet spectroscopy. Assuming a two-state transition model, it was found that the free energy change of unfolding depends almost linearly on pressure and the unfolding reaction is accompanied by a small decrease in volume. The compressibility behavior is in conflict with the notion that a protein structure is almost completely unfolded by guanidinium chloride and most of the amino acid residues in the protein interior are exposed to solvent. These results support the current view that globular proteins have some residual structures even in the unfolded state induced by a strong denaturant.

Solution properties and sweetness response of selected bulk and intense sweeteners.

Two bulk sweeteners (sucrose and maltitol) and four intense sweeteners (acesulfame K, aspartame, sodium cyclamate, and sodium saccharin) are used in this study. Densities and sound velocity values of the sweeteners in solution are measured at 20 degrees C, and their apparent molar and specific volumes, their isentropic apparent molar and specific compressibilities, as well as their compressibility hydration numbers are calculated and reported. The introduction of solute molecules in water results in a volume change of the solvent as a result of attractive forces exerted by the solute molecules; such forces are in the form of electrostrictive or hydrogen-bonding forces, or charge-dipole attraction. Changes of molar volumes with increasing concentration give an indication of the extent of solute-solute interaction, whereas isentropic compressibilities give a direct measurement of the state of hydration of the solute molecules. The compressibility hydration numbers reported give an indication of the number of water molecules disturbed by the presence of each solute molecule in solution. Isentropic compressibilities seem to be a more sensitive parameter for distinguishing the bulk sweeteners from the artificial sweeteners. The sweetness response of the sweeteners is then explained in terms of their solution behaviors.

Sweet–bitter interactions and the solution properties of chlorinated sugars

Among chlorinated sugars, some are intensely sweet, some are bitter and others are tasteless. Although chlorination of sugars provokes an increase in lipophilicity, a certain hydrophilic/lipophilic balance is needed for sweeteners to be perceived. Two chlorinated sugars, sucralose (trichlorogalactosucrose) and methyldichlorogalactoside, respectively known for their enhanced sweetness (650×) and inhibitory effect on the sweetness of sucrose, are studied. Their sapid properties are interpreted on the basis of their physicochemical properties (intrinsic viscosity, apparent specific volume, surface tension, contact angle and vibrational spectra). It is particularly shown that the perturbation of the structure of water by these molecules, compared with that by simple sugars, helps in understanding their taste mechanism.

On the Solubility of Gas Molecules in Glassy Polymers and the Nonequilibrium Approach

The recent nonequilibrium approach of Doghieri and Sarti for the solubility of gases in glassy polymers is reexamined. Analytical expressions for the equilibrium and nonequilibrium contributions to the chemical potential of the penetrant are presented. Volume dilation of the glassy matrix is explicitly taken into consideration. The role of the apparent partial molar or specific volume of the sorbed gas is also examined. The model is tested against the experimental data of Fleming and Koros for the solubility of CO2 in Bisphenol A polycarbonate.