Analysis of the sugar content of fruit juices and drinks using ultrasonic velocity measurements

The use of ultrasound to determine the sugar content of fruit juices and drinks has been assessed. The velocity of ultrasound and the density were measured in solutions of D-glucose, D-fructose, and sucrose at various concentrations (0–40% w/v) and temperatures (10–30°C). The velocity of ultrasound was measured in 50:50wt:wt mixed solutions of sucrose and D-glucose over the same range of concentrations and temperatures. Measurements of the velocity of ultrasound, the density and the refractive index were made on various fruit juices and drinks at 20°C. The sugar content of the juices and drinks was determined by enzymatic assay. Ultrasonic measurements are shown to predict sugar contents in pure sugar solutions to within 0.2% w/v and in mixed sugar solutions to within 0.5% w/v. The ultrasonic measurements were sensitive to sugar species. It is shown that ultrasound compares well with other techniques for sugar content determination in fruit juices and drinks, and has the advantage that the equipment can be used for on-line process control. Applications for this ultrasonic technique are proposed.     

Measurement,prediction and correlation of density,viscosity, surface tension and ultrasonic velocity of different honey types at different temperatures

The aim of this study is to investigate the influence of temperature (20, 25, 30, 35, 40, 45 and 50 °C) and concentration on the evolution of different physical properties (density, viscosity, ultrasonic velocity and surface tension) of honeys. Temperature influences negatively all the physical properties of honey. A good correlation between density, viscosity, ultrasonic velocity and surface tension using linear and polynomial equations was observed. Also a good correlation between density, ultrasonic velocity and surface tension for all the honey samples (R² = 0.954) was obtained. The correlation between surface tension and viscosity was made using the Pelofsky model and an exponential model; the latter one describes better the correlation between surface tension and viscosity.     

Impact of cosolvents (polyols) on globular protein functionality: Ultrasonic velocity, density, surface tension and solubility study

The objective of this study was to understand how cosolvents influence the molecular and functional properties of globular proteins in aqueous solutions. The ultrasonic velocity, density and adiabatic compressibility of cosolvent solutions (0–50 wt% sorbitol or glycerol) were measured in the absence and presence of a globular protein (1 wt% β-lactoglobulin) at 30 °C. These measurements were used to calculate the partial specific apparent volume and adiabatic compressibility of the protein. The protein's volume decreased and its compressibility increased in the presence of high cosolvent concentrations, which were attributed to changes in the properties of the protein interior and solvation layer. Sorbitol was more effective than glycerol at decreasing the protein volume at high cosolvent concentrations, which may be because glycerol has some surface activity and may therefore accumulate around hydrophobic regions on the protein surface. Our data were used to account for the observation that sorbitol is more effective than glycerol at increasing the thermal stability and self-association of the β-lactoglobulin. A better understanding of the influence of protein–cosolvent–solvent interactions on the functionality of globular proteins may facilitate the design of protein-based products.     

Depletion Flocculation of Beverage Emulsions by Gum Arabic and Modified Starch

ABSTRACT: The creaming velocity, apparent viscosity, and ultrasonic attenuation spectra (1 to 50 MHz) of 5 wt% n hexadecane oil-in-water emulsions containing different droplet radii (r = 0.15 - 0.7 μm), biopolymer types (gum arabic or modified starch), and biopolymer concentrations (0 to 2.5 wt%) were measured. Depletion flocculation was observed in the emulsions when the nonabsorbed biopolymer concentration exceeded a critical concentration (CFC). The CFC increased with decreasing droplet radius for both biopolymers because the magnitude of the depletion attraction increases with droplet size. The CFC was lower for gum arabic than modified starch because it has a higher effective volume in solution. Depletion flocculation led to an increase in creaming instability and apparent viscosity of the emulsions. Flocculation could be nondestructively monitored by measuring the decrease in ultrasonic attenuation of the emulsions. These results show that depletion flocculation by gum arabic and modified starch can have an adverse effect on the stability of beverage emulsions.     

Ultrasonic velocity measurements on some liquids under thermal cycle: Ultrasonic velocity hysteresis

This study was performed to determine the existence of hysteresis during ultrasonic velocity measurements on methanol, ethanol, distilled water, processed water and glycerol under thermal cycle (5–50 °C). The ultrasonic velocity of the liquids were measured with 1.0 MHz transducers using a through transmission ultrasonic system. Statistical analyses results showed that there were ultrasonic velocity hystereses on the liquid samples under thermal cycle. The study of liquids undergoing thermal cycle is useful for determining the temperature effects on ultrasonic velocity and will help developing precise control applications in food industry by reducing the uncertainties in ultrasonic velocity measurements.     

Measurement of solid fat content by ultrasonic reflectance in model systems and chocolate

A series of confectionery coating fat (CCF) and cocoa butter (CB) dispersions in corn oil were prepared and tempered to a range of temperatures (10, 12 and 15 °C and 26, 27.5 and 29 °C respectively) to produce samples with solid fat contents (SFC) between 0 and 9%. The ultrasonic velocity in the CCF samples increased with increasing SFC and decreased with temperature, however the CB samples were too attenuating to allow velocity measurements. The ultrasonic reflectance at the surface of both sets of dispersions decreased linearly with SFC but at the same level of solids was less for CB than CCF suggesting some dependence on other aspects of fat structure. The microstructures and thermal properties of the fat systems are compared in an attempt to understand these structural differences. Finally ultrasonic reflectance is shown to respond to changes in a chocolate melt during tempering.     

Ultrasonic characterization of lactose dissolution

The ultrasonic properties (at 2.25 MHz) of lactose solutions and suspension of lactose crystals (d ∼ 50 μm) were measured as a function of concentration (0–40 wt.%). Ultrasonic velocity increased linearly with concentration regardless of the state of dissolution of the lactose crystals while ultrasonic attenuation was low and concentration-independent when the lactose was dissolved and increased approximately linearly with the concentration of suspended crystals. Therefore the amount of lactose present and the state of dissolution can be determined simultaneously with single ultrasonic sensor. A sensor based on this principle was applied to a stirred tank and used to measure the time taken to mix powdered lactose into a solution and the time for the added lactose to dissolve.     

Ultrasonic velocity measurements in ethanol–water and methanol–water mixtures

In this study, ultrasonic velocity measurements were used to estimate the alcohol type and volume concentration in water–alcohol binary mixtures. Varying mixtures of ethanol in water and methanol in water were prepared and the ultrasonic velocities for each concentration level were measured between 10 and 50 °C. Results of the statistical analyses indicated that ultrasonic velocity measurements can be used to distinguish between ethanol and methanol in a water–alcohol binary mixture and to estimate the alcohol concentration level. The results were validated by testing three commercial liquids with a known ethanol concentrations and one commercial liquid with known methanol concentration.     

超声波对糖溶液物化特性的研究

研究了果糖、葡萄糖、蔗糖、麦芽糖、乳糖五种糖溶液的声速-浓度关系,结果表明:糖溶液中声速与浓度呈极显著正相关,得到的二次回归方程的回归系数大于0.9970。同时比较了声参量和密度对糖类型的辨别性,结果表明:超声检测方法对糖的种类具有更好的辨别性。探讨了声特性与糖分子结构以及糖分子与水分子的水合作用与超声参量之间的关系,表明超声参量可用于对糖溶液物化特性的研究。     

Composition assessment of raw meat mixtures using ultrasonics

The use of ultrasonic velocity measurements to determine the composition of dry fermented sausages was assessed. Mixtures of ground lean and fatty tissues were prepared to cover a wide range of fat (2–90 wt.%), moisture (7–76 wt.%), and protein (2–21 wt.%) contents. The ultrasonic velocity in fat decreased on average 5.6 ms⁻¹ per °C increase in temperature, due to the negative temperature coefficient for fat and the fat melting, which is observed in (DSC) differential scanning calorimetry analysis. The ultrasonic velocity temperature dependence allowed the determining of the fat, moisture and protein+others content, by measuring the ultrasonic velocity in the mixtures at 4 and 25°C and using a semi-empirical equation. The explained variance was 99.6% for fat, 98.7% for moisture and 85.4% for protein+others. The results obtained show the feasibility of using ultrasonic velocity measurement to assess the composition of meat products such as dry fermented sausages, rapidly and non-destructively.     

Prediction of Proximate Fish Composition from Ultrasonic Properties: Catfish, Cod, Flounder, Mackerel and Salmon

The ultrasonic velocity within Atlantic cod (Gadus morhua), Atlantic mackerel (Scomber sombrus), Atlantic salmon (Salmo salar), Channel catfish (Ictalurus punctatus), and Sole flounder (Pseudopleuronectes americanus) fillets was measured over a range of temperatures (5 to 35°C) using an ultrasonic pulse-echo technique (～3.5 MHz). Lipid, protein, moisture and ash content of fillets were determined by standard methods. Ultrasonic velocity-temperature profiles were dependent on fish composition and could be predicted reasonably well using a semi-empirical equation developed in a previous study. Ultrasonic velocity measurements show potential for analyzing fish composition.     

Ultrasonic Spectroscopy Study of Salad Dressings

Ultrasonic velocity and attenuation spectra (1 to 100 MHz) of salad dressings with different disperse phase volume fractions (φ= 0 to 0.394) and mean droplet radii (0.3 to 0.6 μm) were measured at 25 °C. There were significant differences between the experimental measurements and theoretical predictions due to droplet flocculation. The measured attenuation coefficient was lower than expected at low frequencies because of thermal overlap effects, but it was greater than expected at high frequencies because of scattering. These deviations could be accounted for using an effective medium theory. Results suggest that ultrasonic velocities at 14 MHz were independent of droplet size and could be used to measure droplet concentration of salad dressings.     

Evaluation of High-Pressure Thermophysical Parameters of the Diacylglycerol (DAG) Oil Using Ultrasonic Waves

Modeling of high-pressure technological processes in the food industry requires knowledge of thermophysical parameters of processed foodstuffs in a broad range of pressures and temperatures. However, the high-pressure thermophysical parameters of foodstuffs are very rarely published in the literature. Therefore, further research is necessary to achieve a deeper insight into the biophysical and thermophysical phenomena under pressure to provide better control of technological processes and optimize the effects of pressure. The essential goal of this work is to evaluate the impact of high pressure and temperature on the thermophysical parameters of liquid foodstuffs on the example of diacylglycerol (DAG) oil (which attracted recently a considerable attention from research and industrial communities due to its remarkable benefits for health), using ultrasonic wave velocity and density measurements. Isotherms of adiabatic and isothermal compressibility, isobaric thermal expansion coefficient, internal pressure, and thermal pressure coefficient versus pressure were evaluated, based on the measurement of the compressional ultrasonic wave velocity and density of DAG oil at high pressures (up to 500 MPa) and at various temperatures. The adiabatic compressibility is affected mostly by the changes of pressure, i.e., it grows about four times when the pressure increases from the atmospheric pressure (0.1 MPa) to 400 MPa at a temperature of 50 °C. By contrast, the internal pressure is a pronounced function of the temperature, i.e., it increases six times when the temperature rises from 20 to 50 °C at a pressure of a 200 MPa. To perform numerical calculations, it was convenient to introduce a Tammann–Tait type equation of state to approximate the measured density isotherms of the investigated DAG oil. The results obtained in this paper can be applied in modeling and optimization of high-pressure technological processes and processing of foodstuffs. Evaluation of high-pressure isotherms of the considered thermophysical parameters of the DAG oil is an original authors’ contribution to the state-of-the-art.     

Using reflectance spectroscopy to predict beef tenderness

A study was conducted to determine if reflectance measurements made in the near-infrared region of the spectrum were additive to reflectance measurements made in the visible region of the spectrum for predicting Warner–Bratzler shear force (WBSF) values. Eighty seven strip loins were collected following fabrication over 3 d at a commercial beef processing facility from heifer carcasses with Slight or Traces marbling scores. Spectroscopic measurements were made at approximately 50 h postmortem using a Hunter-Lab UltraScan. Subsequently, all strip loins were aged for 14 d, cooked to an internal temperature of 70 °C, and sheared to obtain WBSF values. Reflectance measurements obtained in the near-infrared region of the spectrum were correlated with WBSF values, however, these measurements were not additive to the predictive ability of reflectance measurements (R² values did not differ) made in the visible portion of the spectrum when the use of broad-band wavelength filters were simulated. It was therefore determined, that both the visible and near-infrared spectra measure reflectance and that both methods are acceptable methods of tenderness prediction.     

Ultrasonic monitoring of lard crystallization during storage

This work addresses the use of ultrasonics as a non-destructive technique with which to monitor lard crystallization during cooling and storage. The ultrasonic velocity was measured during both the isothermal crystallization of lard (at 0, 3, 5, 7, 10 and 20 °C) and during the non-isothermal crystallization. In addition, lard crystallization was also studied through Differential Scanning Calorimetry (DSC) and instrumental texture analysis (penetration tests). The measurement of the ultrasonic velocity allowed the bulk crystallization to be detected. The evolution of the ultrasonic velocity and the textural measurements during isothermal crystallization showed two steep increases, which may be explained by the two fractions of triglycerides found in DSC thermograms. At 7, 10 and 20 °C the second fraction did not crystallize within the first 11 days of storage. A two-step crystallization model based on the Avrami model was used to properly describe (% var > 99.9 and RMSE < 1.99 m s^− 1) the relationship between the ultrasonic velocity and the isothermal crystallization time. In addition, a model was developed to estimate the percentage of solid fat content during isothermal crystallization. Therefore, it may be pointed out that ultrasonic techniques could be useful to monitor the crystallization pattern of complex fats during long periods of storage.     

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

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 (R₁ and R₂) 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.     

Compressibility and density of select liquid and solid foods under pressures up to 700 MPa

Compressibility and density were measured at 25 °C and pressures up to 700 MPa with a variable volume piezometer for sucrose solutions (2.5–50%), soy protein solutions (2.5–10%), soybean oil, chicken fat, clarified butter, chicken breast, ham, cheddar cheese, carrot, guacamole, apple juice, and honey. Compressibility of sucrose and soy protein solutions decreased as a function of concentration (p < 0.01). For equal mass concentrations, protein solutions were less compressible (p < 0.04) than sucrose solutions at pressures greater than 200 MPa. Relative to water, fats showed high compressibility to 100 MPa, similar compressibility from 100 to 300 MPa, and less compressibility from 300 to 700 MPa. Chicken breast, ham, cheddar cheese, carrot and guacamole showed relatively large compressibility from 0.1 to 100 MPa. Honey showed the smallest volume decrease over 700 MPa. Density of all samples increased with pressure, at a decreasing rate.     

Use of Ultrasound to Determine Cod Fillet Composition

The relationships between the composition and ultrasonic properties of Atlantic cod (Gadus morhua) fillets were examined. The lipid, protein, moisture and ash contents of cod fillets were determined by official methods. The ultrasonic velocity and attenuation coefficient of the fillets were measured using a pulse-echo technique. The ultrasonic velocity of the fillets varied between 1575 and 1595 m s^?1, decreasing linearly with increasing moisture content (r² > 0.8 for 26 samples). No systematic relationship was observed between the attenuation coefficient and moisture content. Our experiments highlight the potential of using ultrasonic velocity measurements to rapidly and nondestructively determine the moisture content of cod fillets (and possibly their protein content by deduction).     

Ultrasonic assessment of the melting behaviour in fat from Iberian dry-cured hams

The feasibility of using ultrasounds to characterize the melting properties of fat from Iberian dry-cured hams was evaluated. Differential Scanning Calorimetry (DSC) and ultrasonic measurements were used to characterize the fat melting. The ultrasonic velocity in fat decreased with the increase in temperature, showing four different sections (0–4 °C, 4–10 °C, 10–20 °C and 20–24 °C). Ultrasonic velocity was related (R² = 0.99) to the percentage of melted fat (%MEF) showing an increase of 5.4 ms⁻¹ for 1% increase of melted fat (%MEF above 60%). The thermal history did not affect the ultrasonic measurements from 10 to 25 °C and, consequently, this range was the most suitable for classifying Iberian dry-cured products with different genetics and feeding backgrounds. Ultrasonic measurements could be a reliable technique to estimate the %MEF and subsequently the related sensory attributes in Iberian dry-cured ham at 10–25 °C, which is the common temperature range for the consumption of Iberian dry-cured products.     

Ultrasonic Monitoring of Powder Dissolution

Sucrose (20 wt%) and lactose (10 wt%) powders were mixed with water (at 2, 20, and 40 °C) and allowed to dissolve. The proportion of an ultrasonic pulse reflecting at the interface between a polymer delay line and the dissolving sugars decreased during the dissolution process, and the magnitude of this signal, normalized to the echo from pure water, was proportional to only the dissolved portion. Ultrasonic reflectance is thus an appropriate sensor to monitor powder dissolution since it can distinguish dissolved and undissolved fractions without prior separation. The kinetics of sucrose dissolution were modeled using a cube‐root equation and the rate constant of the process increased with temperature.