The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Todor Vasiljevic - One of the best experts on this subject based on the ideXlab platform.
-
lactose hydrolysis in milk as affected by Neutralizers used for the preparation of crude β galactosidase extracts from lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, P JelenAbstract:Three different Neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the enzyme deactivation occurred within 1–1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P<0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses.
-
Lactose hydrolysis in milk as affected by Neutralizers used for the preparation of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, Piotr JeleńAbstract:Three different Neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P < 0.05) higher enzyme activity of the CEE than that obtained using NaOH or KOH. The kinetic parameters, kcat and Km, of the Michaelis-Menten model were determined for lactose hydrolysis in skim milk using 1% (v/v) addition of a CEE. There was no significant (P > 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the enzyme deactivation occurred within 1-1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P < 0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses. © 2002 Elsevier Science Ltd. All rights reserved.
P Jelen - One of the best experts on this subject based on the ideXlab platform.
-
lactose hydrolysis in milk as affected by Neutralizers used for the preparation of crude β galactosidase extracts from lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, P JelenAbstract:Three different Neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the enzyme deactivation occurred within 1–1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P<0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses.
Piotr Jeleń - One of the best experts on this subject based on the ideXlab platform.
-
Lactose hydrolysis in milk as affected by Neutralizers used for the preparation of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842
Innovative Food Science and Emerging Technologies, 2002Co-Authors: Todor Vasiljevic, Piotr JeleńAbstract:Three different Neutralizers (NaOH, KOH, NH4OH) were employed for pH maintenance during the growth of Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, used as a source of β-galactosidase extracts. The crude enzymatic extract (CEE) was obtained by bead milling of the cell paste, collected from the cultivation of the source microorganism in skim milk at 43 °C and constant pH. Lactose hydrolysis kinetics in skim milk and proteolytic activity during the hydrolysis were evaluated. The use of NH4OH as a neutralizer resulted in significantly (P < 0.05) higher enzyme activity of the CEE than that obtained using NaOH or KOH. The kinetic parameters, kcat and Km, of the Michaelis-Menten model were determined for lactose hydrolysis in skim milk using 1% (v/v) addition of a CEE. There was no significant (P > 0.05) difference in kcat among the different extracts, with a clear temperature dependence following Arrhenius kinetics. The rate of lactose hydrolysis was dependent on the initial enzyme activity and temperature. The highest initial rate was observed at 65 °C; however, the enzyme deactivation occurred within 1-1.5 h. The proteolytic activity determined by HPLC peptide mapping was significantly (P < 0.05) higher in the moderate temperature range (20 and 37 °C) than at 7 or 55 °C. Industrial relevance: Since lactose intolerance affects a large proportion of the world's population, an economically feasible and effective process with a cheap source of β-galactosidase may have a substantial potential. The use of crude β-galactosidase extracts from Lactobacillus bulgaricus 11842 appears to be a promising approach for development of a technologically feasible process of lactose hydrolysis for food or non-food uses. © 2002 Elsevier Science Ltd. All rights reserved.
A K Singh - One of the best experts on this subject based on the ideXlab platform.
-
detection of calcium based Neutralizers in milk and milk products by aas
Journal of Food Science and Technology-mysore, 2015Co-Authors: R Sowmya, K P Indumathi, Simran Kaur Arora, Vivek Sharma, A K SinghAbstract:Current study was carried out with the intent to standardize detection and estimation method for calcium (Ca) based Neutralizers in milk and milk based indigenous products (khoa and paneer) using atomic absorption spectroscopy (AAS). Neutralized milk, khoa and paneer samples were prepared using milk with developed acidity to which calculated quantity of neutralizer (Ca based) was added. Rosalic acid test results get masked at times due to developed acidity which neutralizes the alkalinity imparted by neutralizer and hence gives false result with time in neutralizer added samples. Atomic absorption spectroscopy proved to be an accurate estimate which could detect the abnormal rise in mineral concentration even with slight addition of Neutralizers in comparison with control milk and milk products. Formalin, which is a commonly used preservative in milk samples for chemical analysis, did not have any significant impact on estimation of calcium in the neutralized milk during storage.
M J Brennan - One of the best experts on this subject based on the ideXlab platform.
-
The characteristics of a nonlinear vibration neutralizer
Journal of Sound and Vibration, 2012Co-Authors: M J Brennan, Gianluca GattiAbstract:Abstract This paper concerns an investigation into the use of cubic nonlinearity in a vibration neutralizer to improve its effectiveness. It is assumed that the frequency of the harmonic excitation is well above the resonance frequency of the machine to which the neutralizer is attached, and that the machine acts as a simple mass. It is also assumed that the response of the system is predominantly at the harmonic excitation frequency of the machine. The harmonic balance method is used to analyze the system. It is shown how the nonlinearity has the effect of shifting the resonant peak to a higher frequency away from the tuned frequency of the neutralizer so that the device is robust to mistune. In a linear neutralizer this can only be achieved by adding mass to the neutralizer, so the nonlinearity has a similar effect to that of adding mass. Some characteristic features are highlighted, and the effects of the system parameters on the performance are discussed. It is shown that, for a particular combination of the system parameters, the effect of the nonlinearity is also to increase the bandwidth of the device compared to the linear neutralizer with similar mass and damping. Some approximate expressions are derived, which facilitate insight into the parameters which influence the dynamics of the system. The results are validated by some experimental work.
-
On the optimization of a nonlinear vibration neutralizer
2010Co-Authors: M J Brennan, Gianluca Gatti, Ivana KovacicAbstract:This paper concerns an investigation into the use of cubic nonlinearity in a vibration neutralizer to improve its effectiveness. It is assumed that the excitation frequency is well above the resonance frequency of the machine to which the neutralizer is attached, and that the machine acts as a simple mass. It is also assumed that the response of the system is predominantly at the harmonic excitation frequency of the machine. The harmonic balance method is used to analyze the system. It is shown that the nonlinearity has the effect of shifting the resonant peak to a higher frequency away from the tuned frequency of the neutralizer so that the device is robust to mistune. In a linear neutralizer this can only be achieved by adding mass to the neutralizer, so the nonlinearity has the same effect as adding mass. An optimum value of nonlinearity is determined. A minimum value of the damping in the neutralizer is also determined such that the response of the machine is single valued for all frequency. In this case the effect of the nonlinearity is to increase the bandwidth of the device compared to the linear neutralizer with similar mass and damping.
-
Real-time control of both stiffness and damping in an active vibration neutralizer
Smart Materials and Structures, 2001Co-Authors: M. R. F. Kidner, M J BrennanAbstract:Recent improvements to the vibration neutralizer have involved the incorporation of a variable-stiffness device so that the natural frequency can be adjusted. The device can then track an excitation frequency that is varying slowly with time. This paper describes a neutralizer where both damping and stiffness in the neutralizer are adjustable, so that the performance of the device can be improved in addition to its tracking capability. An experimental investigation is described in which the feasibility of real-time control of both stiffness and damping properties was assessed. A fuzzy controller was designed to adjust the resonance frequency of a beamlike neutralizer by changing its geometry, and to adjust the gain in a velocity feedback loop to reduce the damping in the device. The dot product of the complex velocity vectors of the neutralizer and host structure was used as an indicator of the tuning error. Damping was controlled by a fuzzy rule base, which used the rms level of neutralizer and host structure velocities as errors. Significant improvements in the vibration attenuation of a host structure were achieved compared with a passive neutralizer.
-
Optimum tuning of a vibration neutralizer for global vibration control
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2001Co-Authors: Jedol Dayou, M J BrennanAbstract:This paper is concerned with optimization of the natural frequency of a vibration neutralizer to minimize the global vibration of a structure at a single frequency. The optimization is carried out using a quadratic minimization technique to determine the dynamic stiffness of the control device that is required, and then the optimum resonance frequency of the neutralizer is determined. It is shown that, with the exception of very low frequencies, an optimally adjusted vibration neutralizer can be as effective as an active device at a single frequency. Simulations are presented with a single neutralizer on a beam to facilitate insight into the mechanisms of control.
-
Varying the Stiffness of a Beam-Like Neutralizer Under Fuzzy Logic Control
Journal of Vibration and Acoustics, 2001Co-Authors: M. R. F. Kidner, M J BrennanAbstract:Vibration Neutralizers are effective vibration control devices at a single frequency. If they can compensate for drift in the excitation frequency by adjusting their stiffness the performance can be improved, and the range of problems to which they can be applied is broadened. This paper considers a beam-like adaptive vibration neutralizer, and it is shown that the stiffness of the device and hence its natural frequency can be significantly altered by varying the beam cross-section. Several different beam configurations are investigated and the rate of change of stiffness as a function of beam separation is calculated for each configuration. The results are validated by some simple experiments. Real-time stiffness control of a beam-like tuneable neutralizer is also demonstrated both by computer simulation and experiment. The neutralizer is subjected to swept sine excitation over a six-second period and the tuned condition is maintained throughout the excitation period. The efficacy of using a nonlinear fuzzy logic controller is compared with the use of a simple proportional controller.