牛奶脂肪含量对超声波检测参数的影响

探测了不同温度下不同脂肪含量牛奶的超声特性参数———声速与衰减系数,分析了脂肪含量与超声参数间的关系以及温度对此关系的影响。结果表明:在温度10.9～39.1℃内,声速随脂肪含量的变化不大,其在39.1℃表现出来的最大变化率仅为0.164%,声速/温度随脂肪含量的变化稍大,其表现的变化率为4.29%;而衰减随脂肪含量的增加显著,在39.1℃时,衰减随脂肪含量变化的变化率最大,为113.2%,衰减/温度随脂肪含量变化的变化率为40.4%。这表明衰减随脂肪含量的变化趋势最明显,且温度对衰减的影响也相对较小,因此利用衰减系数作为测定牛奶脂肪含量的主要指标比其他参数更易于检测出脂肪含量上的差异。     

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).     

Amino Acid and Vitamin Composition of Raw and Cooked Horse Mackerel

Amino acid, vitamin (A, E, B₁, B₂, B₃ and B₆), and proximate composition were determined in raw and cooked horse mackerel. The changes in amino acid, vitamin, and proximate content were found to be significant for all cooking methods (frying, grilling, and steaming). Cooking did in general significantly increase the contents of essential, semi-essential, and other amino acids compared to raw fish species. Amino acid contents of grilled mackerel were significantly higher (p < 0.05) than those found in fried and steamed mackerel. The A, E, B₂, and B₆ vitamin content of fried horse mackerel was found to be significantly (p < 0.05) higher than the grilled and steamed samples. The B₁ content of steamed and B₃ content of grilled were found higher than the other cooked samples. Moisture, protein, fat, ash, and carbohydrate contents of cooked fish ranged between 56.52% to 61.34%, 20.79% and 23.93%, 13.44% and 19.61%, 1.70% and 2.47%, and 1.02% and 4.36 %, respectively. Fried fish had intermediate fat values, while grilled and steamed fishes had a comparatively low value.     

α-Relaxation in honey study versus moisture content: High frequency ultrasonic investigation around room temperature

Ultrasonic longitudinal attenuation and velocity have been measured for various frequencies between 0.5 and 13.5 MHz versus temperature, in honeys with moisture contents between 15% and 19%. With the help of attenuation measurements, the temperature of the alpha transition T_α (associated with the glass transition) has been deduced versus moisture content and ultrasonic frequency. Regarding the high sensitivity of T_α towards moisture content, one can distinguish two honeys with moisture contents difference less than 0.1%. Considering the fact that the experiments are not difficult to perform and are carried out at around room temperature, this technique could be useful for honey quality control or more generally for aqueous polymers study.     

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.     

Characterisation of frozen orange juice by ultrasound and wavelet analysis

Ultrasound technology was used to analyse the freezing behaviour of orange juice. The ultrasonic properties of orange juice, specifically velocity and attenuation coefficient, were characterised as the temperature was decreased from 20 to ?50 °C. The results were compared with NMR free induction decay data and correlated with the amount of unfrozen water present in the frozen sample. The velocities of longitudinal waves (P‐wave) and shear waves (S‐wave) in frozen orange juice were measured, yielding values of around 4000 and 2000 m s^?1 respectively. They were related to the amount of unfrozen water in the frozen sample. The elastic moduli of the samples at different temperatures were obtained from the measured ultrasonic velocities. Significant changes in the attenuation of the ultrasonic waves propagated through the frozen sample were observed as a result of ice nucleation and growth. Information about the spectral behaviour of the ultrasound signal was obtained by means of wavelet analysis. The analysis provided a direct measure of the spectral content of the ultrasonic waves over time and showed the variation in the ultrasonic velocity dispersion with temperature. Significant velocity dispersions occurred for frequencies less than 1 MHz. Copyright © 2004 Society of Chemical Industry     

Ultrasonic Velocity in Cheddar Cheese as Affected by Temperature

The ultrasonic velocity in Cheddar cheese is temperature dependent. This relationship can be used to make corrections when determining ultrasonic texture or to determine mean temperatures in cooling/heating processes. At 0 < T < 35 °C ultrasonic velocity was 1590 to 1696 m/s, at 0 and 35 °C, respectively. Differential Scanning Calorimetry thermograms linked the temperature dependence of ultrasonic velocity to fat melting. Three parts are distinguished in the curve as a consequence of the fat melting and the appearance of free oil. The most reliable temperature interval to carry out ultrasonic measurements in Cheddar cheese is identified as 0 to 17 °C.     

Low Frequency Ultrasonics for Texture Measurements in Cooked Carrots (Daucus carota L.)

The use of low frequency ultrasound for texture evaluation of carrots cooked at 100°C for 0 to 15 min was examined. Uniaxial compression, microscopy and analyses of density and dry matter were used to provide comparative results for evaluating relationships between texture and ultrasonic parameters. During the first minutes of cooking the sound velocity (v) decreased and a positive correlation was found between compressive Young's modulus (E_cy) and sound velocity (v). During extended heating, sound velocity (v) increased and attenuation (α) decreased as a result of changes in mechanical properties and air and water content of the tissue.     

CHARACTERIZATION OF RECONSTITUTED MILK POWDER BY ULTRASOUND SPECTROSCOPY

When instant milk powder (IMP) is reconstituted with water, the product should resemble fresh milk. However, undissolved particles were found at the surface and in the bulk of the product. A visual reconstitution test (RT) is made on IMP to determine the reconstituted quality of the product. This test is directly linked to the presence of the undissolved particles. The particles found at the surface are formed by clustered liquid‐fat aggregates, which rise to the top of the milk and may give an impression of spoiled milk. The particles found in the bulk are small particles in the solution mostly composed of a protein gel. Because the repeatability and precision of the RT are very poor, a quantitative analytical technique is desirable. In this study we investigated five different quality milk powders by an ultrasound spectroscopy technique. The ultrasonic velocity and attenuation parameters were measured with a frequency scanning pulse echo reflectometer. We found that the ultrasonic velocity cannot be correlated to RT because the predominant phenomenon that affects the ultrasonic velocity is the physical state of the different components of the milk matrix (liquid fat, crystalline fat and lactose crystals), and this physical state is not a significant factor in powder quality. However, the ultrasonic attenuation coefficient is well correlated with RT. This is because, between two different quality powders, the most important factor that causes variation in the attenuation is scattering, correlated to particle size and to volume fraction rather than by the composition or physical state of the matrix and the same particle size factor, and volume fraction factor characterizes the powder reconstitution's quality.     

Study of butter fat content in milk on the inactivation of Listeria innocua ATCC 51742 by thermo-sonication

Ultrasound combined with heat treatment has yielded favorable results in the inactivation of microorganisms; however, the composition of food influences the rate of microbial inactivation. The objective of this research was to study the effect of butter fat content in milk on the inactivation of Listeria innocua and compositional parameters after thermo-sonication. Four butter fat contents in milk were evaluated at 63 °C for 30 min of sonication (Hielscher® UP400S, 400 W, 24 kHz, 120 μm amplitude). Results showed that inactivation of Listeria cells occurs first in fat free milk, and that the rate of inactivation decreases with increasing fat content. No degradation of protein content or color variation was observed after the treatments. The pH dropped to 6.22, and lactic acid content showed an increase of 0.015% after the treatment; solids-non-fat, density and freezing point decreased. During storage life, growth of mesophiles was retarded with sonication.Industrial relevanceUltrasound is an emerging technology that has shown positive effects in milk processing. Listeria monocytogenes represent one of the main foodborne pathogenic microorganisms in the food industry. Results of this research show that thermo-sonication is a viable technology capable of inactivating Listeria cells in milk and extending shelf-life without significant nutritional or physicochemical changes.     

Insight in ultrasonic shear reflection parameters by studying temperature and limonene influence on cocoa butter crystallization

In this study an inverse model was developed to derive relevant ultrasonic parameters from ultrasonic shear reflectometry measurements. The inverse model includes four variable parameters: t_ind (induction time), K (crystallization rate), v_s2 (shear ultrasonic velocity) and a_s2 (shear ultrasonic attenuation coefficient). Both the temperature effect and the effect of a minor component limonene (in different concentrations) on the isothermal crystallization of cocoa butter were studied with the ultrasonic shear reflectometry technique and associated inverse model. Subsequently, the ultrasonic parameters were compared with results of conventional techniques to monitor fat crystallization (DSC, PLM). The study shows that t_ind and K provide information on the kinetics of the microstructure development. The parameter v_s2 is related with the equilibrium SFC, while a_s2 is both influenced by the SFC and the organization of the crystals in the network, yielding information about the microstructure of the crystallized samples.Industrial relevanceThe microstructure of crystallized fat determines to a large extent the macroscopic properties of fat rich products, such as texture, mouthfeel,… Hence, monitoring the crystallization behavior (including not only the primary crystallization but also the microstructural development) during the production process is of utmost importance in order to obtain high quality end products. The ultrasonic shear reflectometry technique is a fast non-destructive technique which provides quantitative data about the crystallization process based on an inverse model. The simplicity of the technique offers potential for inline control. This may be beneficial to evaluate the crystallization process under different process conditions and to stimulate product innovation as more insight can be obtained in the microstructure development of new products.     

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.     

Ultrasonic assessment of fresh cheese composition

Fresh cheese composition was assessed by measuring ultrasonic velocity in cheese and cheese blends at different temperatures. Twenty types of commercial, fresh cheeses with fat contents ranging from 0.2% to 17.6% w.b. were analyzed. Ultrasonic velocity was not only heavily dependent on the composition of the cheese but also on its structure. Based on the different effect temperature has on velocity in water and fat, a semi-empirical model was used to estimate the cheese composition from velocity measurements at six temperatures ranging from 3 to 29 °C. The model provided good results for the assessment of the fat (R² = 0.984/0.996; RMSE = 4.6/1.1 for whole and blended cheese, respectively) and water (R² = 0.964/0.995; RMSE = 6.5/0.7 for whole and blended cheese, respectively) content. The ultrasonic measurements could be carried out during the cooling process that takes place after curdling and used as a quality control tool to detect process anomalies in-line.     

Ultrasonic cutting of cheese: Composition affects cutting work reduction and energy demand

Eight cheese varieties with different moisture (357–488 g kg^?1), fat (183–335 g kg^?1) and protein content (202–292 g kg^?1) were subjected to ultrasonic cutting using a 40 kHz guillotine sonotrode. Cutting force curves were evaluated with respect to ultrasound-induced cutting work reduction and energy demand of the sonotrode. With cutting velocity and ultrasonic amplitude set to 2500 mm min^?1 and 12 μm, respectively, composition had a significant effect on the response of the cheeses. Whereas cutting work reduction was mainly determined by fat-in-dry matter, the energy demanded by the sonotrode to maintain vibration was inversely interrelated to the ratio of moisture to solids-non-fat. Three selected cheeses were subjected to cutting experiments with systematically varied cutting velocity and amplitude. The results indicate that the cheeses respond differently to the cutting parameters, and that their careful adjustment is helpful for a target-orientated design of the process.     

Application of Ultrasonic Waves to Detect Sealworms in Fish Tissue

The potential of employing ultrasonic waves to detect sealworms embedded deep in the fish musculature was demonstrated. Images were made of sealworm-infested cod by using both the scanning laser acoustic microscopic technique, as well as the pulse-echo technique at 10 MHz. Also, attenuation of ultrasound in the frequency range from 1.0 to 12.25 MHz was studied in Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), ocean catfish (Anarhichas lupus), and the parasitic sealworm (Phocanema decipiens). The difference in the attenuation of ultrasound in sealworms and in fish tissue increased as a function of frequency. The differences between ultrasonic properties (attenuation and backscatter) of fish tissue and seal-worms was attributable to the high collagen content of the sealworms. The differences were sufficiently large at 10 MHz that sealworms could be detected in over 4 cm thickness of fish tissue.     

Dual-energy photon attenuation for soft tissue analysis

The mass attenuation coefficients σ_I and σ_A of collimated low energy gamma radiation emitted from point sources of ¹²⁵I and ²⁴¹Am have been measured in components of lean beef and fatty tissue. The ratio R = σ_I/σ_A for comminuted fatty tissue/muscle mixtures was approximately linearly related to the extractable fat content determined by the standard method of soxhlet extraction and a least squares analysis gave a residual standard deviation of ±2% extractable fat. R was unaffected by fluctuations in sample temperature over the range 20 to ? 10°C and could be measured without knowledge of the sample thickness or packing density. Comparative measurements of attenuation relative to that of water were more reproducible than absolute values. Factors influencing the attenuation in soft tissues were assessed by adopting a three-component mixture model: that the soft tissues were composed of extractable fat (R/R_W = 0.759 ± 0.004), fat-free dry solids (R/R_W = 1.089 ± 0.008) and water (R/R_W = 1). The likely effects of variations in the fatty acid composition of the fat, and of variations in the protein and mineral contents of the dry solids, are discussed.     

Effects of Four Cooking Methods on the Proximate, Mineral and Fatty Acid Composition of Fish Fillets

The effects of baking, broiling, deep frying and cooking in a microwave oven on the proximate, mineral and fatty acid composition of grouper (Epinephelus morio), red snapper (Lutjanus campechanus), Florida pompano (Trachinotus carolinus) and Spanish mackerel (Scomberomorus maculatus) were determined. The lipid content of low fat species was not significantly changed by cooking, but lipid was lost from fatty fillets during cooking. The fatty acid composition of all fillets was not significantly changed by baking, broiling or microwave cooking. Deep fried fillets absorbed the major fatty acids in the cooking medium, and as the fillet lipid content increased the extent of absorption of fatty acids from the cooking medium decreased. Sodium, potassium and magnesium levels were decreased when low fat species were cooked, but these minerals were not lost when raw fillets containing higher lipid levels were cooked. Cooking did not significantly affect the concentration of the microelements, zinc, copper, iron and manganese.     

Rapid evaluation of frying oil degradation using ultrasonic technology

The quality of frying oils covering a wide range of oil degradation and degree of unsaturation was analyzed using ultrasonic techniques. Ultrasonic velocity and attenuation decreased with temperature, and the average velocity temperature coefficients were −3.59 and −3.51 m s⁻¹ °C⁻¹ for monounsaturated (MUO) and polyunsaturated (PUO) oils, respectively. Velocity was linearly related to viscosity, showing higher values for PUO than for MUO. Velocity was also related to the percentage of polar compounds (R² = 0.77 and 0.86 for PUO and MUO, respectively) and polymers (R² = 0.86 for PUO and MUO together). The use of velocity and viscosity in a single prediction model allowed to classify 97.5% of the samples correctly, according to the 25% polar compounds limit. Therefore, ultrasonic techniques can be used to characterize thermal degradation of oils when subjected to different frying conditions, which could be useful for frying operators or inspection services.     

Stability of n-3 fatty acids in fish particles during processing by impingement jet

Impingement jet systems have been identified as an alternative to conventional drying and freezing methods. Due to a high gas-particle relative velocity, which enhance heat transfer, product quality is improved. Surface heat transfer coefficients, drying and freezing times of fish particles (mackerel, Trachurus murphyi) were determined under several operation conditions (gas velocity and temperature, particle geometry, material load) using impingement jet. Heat transfer coefficients were estimated in the range of 100–300 W/m² K and a correlation of Nusselt and Reynolds numbers were established. Drying and freezing time was significantly influenced by gas temperature and particle geometry. The susceptibility of n-3 fatty acids of fish particles to oxidation during drying and freezing was determined by GC analyses of methyl esters of fatty acids, and results were compared with those obtained by alternative conventional methods. As freezing and drying time increased, n-3 fatty acids losses increased. This suggests that a lower gas temperature with short freezing time would yield a higher quality of fish particle (i.e. with minimal n-3 fatty acids losses) and a higher gas temperature with short drying time would yield a higher quality of product.     

牛奶中主要成分超声特性及温度影响的研究

用超声波测量牛奶中主要成分含量的方法是基于超声特性参数与溶液组分的关系,这种关系还受到温度的较大影响。本实验研究了超声波的速度(衰减)与牛奶中主要成分含量以及温度的关系。结果表明,在温度为30～50℃范围内,牛奶中的声速随温度升高先增加后减小,衰减则随温度升高而增加;在同一温度下,声速和衰减随时间无显著改变。根据实验结果计算出牛奶中脂肪和蛋白质与声速(衰减)之间的关系,为完善检测方法和检测系统提供了参考。