J. Inst. Brew. 111(3), 282-289, 2005 � -Glucanase from barley malt is known to be thermolabile bu... more J. Inst. Brew. 111(3), 282-289, 2005 � -Glucanase from barley malt is known to be thermolabile but important in the mashing process. Therefore, the potential of increasing the thermostability of � -glucanase in ACES buffer (0.1 M, pH 5.6) by high hydrostatic pressure has been invest- tigated. Inactivation of the enzyme as well as changes of the conversion rate in
The impact of high hydrostatic pressure and temperature on the stability and catalytic activity o... more The impact of high hydrostatic pressure and temperature on the stability and catalytic activity of alpha-amylase from barley malt has been investigated. Inactivation experiments with alpha-amylase in the presence and absence of calcium ions have been carried out under combined pressure-temperature treatments in the range of 0.1-800 MPa and 30-75 degrees C. A stabilizing effect of Ca(2+) ions on the enzyme was found at all pressure-temperature combinations investigated. Kinetic analysis showed deviations of simple first-order reactions which were attributed to the presence of isoenzyme fractions. Polynomial models were used to describe the pressure-temperature dependence of the inactivation rate constants. Derived from that, pressure-temperature isokinetic diagrams were constructed, indicating synergistic and antagonistic effects of pressure and temperature on the inactivation of alpha-amylase. Pressure up to 200 MPa significantly stabilized the enzyme against temperature-induced ina...
Pressures currently used in the food industry range from tens of MPa in common homogenizers or su... more Pressures currently used in the food industry range from tens of MPa in common homogenizers or supercritical fluid extractors to up to 400 or 800 MPa in ultra high pressure homogenizers or high pressure (HP) pasteurization units, respectively. Laboratory sized HP research units ...
The compression heating of water and water/propylene-glycol mixtures during high-pressure process... more The compression heating of water and water/propylene-glycol mixtures during high-pressure processing was studied using a purpose-designed experimental setup allowing for near-adiabatic conditions. The fluids were pressurised in a Stansted ISO-LAB FPG11501 HPP 3 L unit up to 750 MPa. Pressure/temperature profiles at varying initial temperatures (5-90°C) were recorded and numerically evaluated to obtain pressure and temperature dependent compression heating properties of water/glycol mixtures at 0%, 25%, 50%, 75% and 100% glycol concentration. A further step was implemented in the numerical routine to derive the compression heating properties as function of pressure, temperature and glycol concentration.
The effect of high pressure-thermal processing (HPTP), in the range of 0.1-600 MPa and 100-140°C ... more The effect of high pressure-thermal processing (HPTP), in the range of 0.1-600 MPa and 100-140°C for up to 60 min, on colour change and proteolysis of reconstituted skim milk (10% w/w) was investigated. The kinetic results showed that colour change (DE ab ) and proteolysis (determined by chromatography) increased with both increasing temperature and pressure. The apparent reduction of free amino groups in skim milk, indicating sugar conjugation to milk proteins/peptides, was accelerated with increasing temperature, but decelerated with increasing pressure (at constant temperature) at higher temperature. The milk's colour changed drastically at 400 MPa where most of the milk proteins formed coagulates and left the solutions nearly translucent. Mathematical models describing the kinetics of colour change, proteolysis, and free amino acids reduction as a function of pressure and temperature are proposed.
There is an increasing demand to tailor the functional properties of mixed biopolymer systems tha... more There is an increasing demand to tailor the functional properties of mixed biopolymer systems that find application in dairy food products. The effect of static high pressure processing (HPP), up to 600MPa for 15min at room temperature, on milk-gelatin mixtures with different solid concentrations (5%, 10%, 15% and 20% w/w milk solid and 0.6% w/w gelatin) was investigated. The viscosity remarkably increased in mixtures prepared with high milk solid concentration (15% and 20% w/w) following HPP at 300MPa, whereas HPP at 600MPa caused a decline in viscosity. This was due to ruptured aggregates and phase separation as confirmed by confocal laser scanning microscopy. Molecular bonding of the milk-gelatin mixtures due to HPP was shown by Fourier-transform infrared spectra, particularly within the regions of 1610-1690 and 1480-1575cm(-1), which reflect the vibrational bands of amide I and amide II, respectively.
During the last decades pulsed electric field (PEF) processing received considerable attention du... more During the last decades pulsed electric field (PEF) processing received considerable attention due to its potential to enhance food products or create alternatives to conventional methods in food processing. It is generally acknowledged that PEF processing can deliver safe and chill-stable fruit juices with fresh-like sensory and nutritional properties. Relatively low-processing temperature and short residence times can achieve highly effective inactivation of microorganisms while retaining product quality. A first commercial application of PEF for preservation of fruit juices was launched in 2006 in the United States. Since then, industrial-scale processing equipment for liquid and solid products were developed and, in Europe in 2009, an industrial juice preservation line was installed using 20 kV/cm pulses at 40 to 50 • C to extend the chill-stability of fruit juices, including citrus juices and smoothies, from 6 to 21 d. The related PEF processing costs are in the range of US $0.02 to 0.03 per liter and are justified due to access to new markets and reduced return of spoiled product. However, despite its commercial success there are still many unknown factors associated with PEF processing of fruit and citrus juices and many conflicting reports in the literature. This literature review, therefore, aims to provide a comprehensive overview of the current scientific knowledge of PEF effects on microbial, enzymatic, nutritional, and sensory quality and stability of orange juices.
ABSTRACT Consumer demand and current market conditions warrant investigation of dairy processing ... more ABSTRACT Consumer demand and current market conditions warrant investigation of dairy processing technologies that can deliver improved product quality and stability and reduced energy use during processing, without compromising product and process safety. One candidate technology for the extension of shelf-life in dairy products is pulsed electric field (PEF) processing. PEF is considered to be an effective, non-thermal intervention that appears to hold some promise. Research on the application of PEF to control spoilage and pathogenic microorganisms and enzyme systems in dairy products spans a wide array of processing equipment and reaction conditions. PEF has been reported to effectively reduce the numbers of both pathogens and spoilage organisms in milk; however, there is a high degree of variability between studies. The application of PEF in combination with lower temperature thermal processing can deliver comparable reductions in microbial load without significant detrimental effects to the sensory and physico-chemical properties of food products.
ABSTRACT This review highlights the current knowledge on gelation of hydrocolloids induced by hig... more ABSTRACT This review highlights the current knowledge on gelation of hydrocolloids induced by high pressure processing (HPP) of dairy products. Pressure-induced gelation of single systems (casein rich, whey protein rich, gelatin, and polysaccharide solutions) as well as rheological and thermo-mechanical effects of HPP on mixture systems are discussed. The mechanism of dairy protein gelation under pressure, their properties and microstructure, and potential application of HPP to improve physical properties of dairy products (cheese, yoghurt, and ice cream) are included. HPP is a promising tool for future manufacturing of structured dairy products with unique sensorial properties.
ABSTRACT Pulsed electric field (PEF) treatment at 49 kV/cm for 19.36 μs (up to 70 °C) was perform... more ABSTRACT Pulsed electric field (PEF) treatment at 49 kV/cm for 19.36 μs (up to 70 °C) was performed on reconstituted skim milk (10 wt%). The milk condition was varied either by pH adjustment (pH 6.7–8.0) or by the addition of ethylenediaminetetraacetic acid (EDTA) (up to 30 mM). Except for milks at pH ⩾ 7.5, PEF treatment did not affect size and ξ-potential of the milk particles, the amounts of protein in the serum or the state of the whey proteins. For milks at pH ⩾ 7.5, a decrease in the size of the milk particles and an increase in the amount of proteins in the serum were measured. Sodium dodecyl sulphate – polyacrylamide gel electrophoresis (SDS–PAGE) measurements showed that the amount of caseins in the serum increased, while the whey proteins were not affected. This indicates that the decrease of the size of the milk proteins is due to the dissociation of the casein micelles. Further, this study demonstrates that the PEF effects on milks at pH ⩾ 7.5 is due to ohmic heating during the PEF treatment.
The curcuminoid-carrying potential of oat fiber was examined as a potential route to overcome the... more The curcuminoid-carrying potential of oat fiber was examined as a potential route to overcome the low aqueous solubility of curcuminoids. Aqueous dispersions of oat fiber were mixed with curcuminoids solubilized in ethanol to obtain curcuminoids−oat fiber (1% w/w) dispersions in aqueous ethanol (2% v/v). Centrifugation of the curcuminoids−oat fiber dispersions resulted in a supernatant (95.3% w/w: 0.11% w/w protein, 0.17% w/w β-glucan) and precipitate (4.74% w/w: 0.18% w/w protein, 0.11% w/w β-glucan) with the curcuminoids being almost equally partitioned into both fractions. Curcuminoids solubility in the supernatant was markedly greater than that in aqueous ethanol and water. The curcuminoids were in the amorphous state in the precipitated fraction and were more stable to degradation than the curcuminoids in the supernatant. These studies show the potential of oat fiber as a carrier for curcuminoids into functional foods.
The preservation of low-acid canned food to achieve non-refrigerated, shelf-stable products requi... more The preservation of low-acid canned food to achieve non-refrigerated, shelf-stable products requires the elimination of vegetative microbial cells as well as the inactivation of bacterial endospores capable of growing in the product at the conditions prevailing during distribu-tion and ...
Approximations of the electric field strength and specific energy input of continuous pulsed elec... more Approximations of the electric field strength and specific energy input of continuous pulsed electric field (PEF) systems often assume parallel plate configurations. However, it is known that actual electric field strengths and specific energy inputs can be significantly different from this simplistic approach. A systematic study of more than 150 dimensions and various insulator geometries of pilot-scale PEF treatment chambers
ABSTRACT The application of high pressure for processing fish muscles has showed a great potentia... more ABSTRACT The application of high pressure for processing fish muscles has showed a great potential on improving the physicochemical, microbial and sensory quality of fish muscles. High pressure results in the inactivation of micro-organisms and autolytic enzymes and lead to an extension of fish muscles shelf life. High pressure inhibits the formation of putrefactive compounds and maintains the hardness of fish muscles, resulting in higher sensory quality compared to untreated muscle over storage time. However, the discolouration, cooked appearance and lipid oxidation are the drawbacks that could limit the application of high pressure on fish muscles. Besides, pressure-induced gelling and high-pressure freezing/thawing of fish muscles are the main areas being investigated intensively to obtain the benefits of high-pressure processing on fish muscles.
J. Inst. Brew. 111(3), 282-289, 2005 � -Glucanase from barley malt is known to be thermolabile bu... more J. Inst. Brew. 111(3), 282-289, 2005 � -Glucanase from barley malt is known to be thermolabile but important in the mashing process. Therefore, the potential of increasing the thermostability of � -glucanase in ACES buffer (0.1 M, pH 5.6) by high hydrostatic pressure has been invest- tigated. Inactivation of the enzyme as well as changes of the conversion rate in
The impact of high hydrostatic pressure and temperature on the stability and catalytic activity o... more The impact of high hydrostatic pressure and temperature on the stability and catalytic activity of alpha-amylase from barley malt has been investigated. Inactivation experiments with alpha-amylase in the presence and absence of calcium ions have been carried out under combined pressure-temperature treatments in the range of 0.1-800 MPa and 30-75 degrees C. A stabilizing effect of Ca(2+) ions on the enzyme was found at all pressure-temperature combinations investigated. Kinetic analysis showed deviations of simple first-order reactions which were attributed to the presence of isoenzyme fractions. Polynomial models were used to describe the pressure-temperature dependence of the inactivation rate constants. Derived from that, pressure-temperature isokinetic diagrams were constructed, indicating synergistic and antagonistic effects of pressure and temperature on the inactivation of alpha-amylase. Pressure up to 200 MPa significantly stabilized the enzyme against temperature-induced ina...
Pressures currently used in the food industry range from tens of MPa in common homogenizers or su... more Pressures currently used in the food industry range from tens of MPa in common homogenizers or supercritical fluid extractors to up to 400 or 800 MPa in ultra high pressure homogenizers or high pressure (HP) pasteurization units, respectively. Laboratory sized HP research units ...
The compression heating of water and water/propylene-glycol mixtures during high-pressure process... more The compression heating of water and water/propylene-glycol mixtures during high-pressure processing was studied using a purpose-designed experimental setup allowing for near-adiabatic conditions. The fluids were pressurised in a Stansted ISO-LAB FPG11501 HPP 3 L unit up to 750 MPa. Pressure/temperature profiles at varying initial temperatures (5-90°C) were recorded and numerically evaluated to obtain pressure and temperature dependent compression heating properties of water/glycol mixtures at 0%, 25%, 50%, 75% and 100% glycol concentration. A further step was implemented in the numerical routine to derive the compression heating properties as function of pressure, temperature and glycol concentration.
The effect of high pressure-thermal processing (HPTP), in the range of 0.1-600 MPa and 100-140°C ... more The effect of high pressure-thermal processing (HPTP), in the range of 0.1-600 MPa and 100-140°C for up to 60 min, on colour change and proteolysis of reconstituted skim milk (10% w/w) was investigated. The kinetic results showed that colour change (DE ab ) and proteolysis (determined by chromatography) increased with both increasing temperature and pressure. The apparent reduction of free amino groups in skim milk, indicating sugar conjugation to milk proteins/peptides, was accelerated with increasing temperature, but decelerated with increasing pressure (at constant temperature) at higher temperature. The milk's colour changed drastically at 400 MPa where most of the milk proteins formed coagulates and left the solutions nearly translucent. Mathematical models describing the kinetics of colour change, proteolysis, and free amino acids reduction as a function of pressure and temperature are proposed.
There is an increasing demand to tailor the functional properties of mixed biopolymer systems tha... more There is an increasing demand to tailor the functional properties of mixed biopolymer systems that find application in dairy food products. The effect of static high pressure processing (HPP), up to 600MPa for 15min at room temperature, on milk-gelatin mixtures with different solid concentrations (5%, 10%, 15% and 20% w/w milk solid and 0.6% w/w gelatin) was investigated. The viscosity remarkably increased in mixtures prepared with high milk solid concentration (15% and 20% w/w) following HPP at 300MPa, whereas HPP at 600MPa caused a decline in viscosity. This was due to ruptured aggregates and phase separation as confirmed by confocal laser scanning microscopy. Molecular bonding of the milk-gelatin mixtures due to HPP was shown by Fourier-transform infrared spectra, particularly within the regions of 1610-1690 and 1480-1575cm(-1), which reflect the vibrational bands of amide I and amide II, respectively.
During the last decades pulsed electric field (PEF) processing received considerable attention du... more During the last decades pulsed electric field (PEF) processing received considerable attention due to its potential to enhance food products or create alternatives to conventional methods in food processing. It is generally acknowledged that PEF processing can deliver safe and chill-stable fruit juices with fresh-like sensory and nutritional properties. Relatively low-processing temperature and short residence times can achieve highly effective inactivation of microorganisms while retaining product quality. A first commercial application of PEF for preservation of fruit juices was launched in 2006 in the United States. Since then, industrial-scale processing equipment for liquid and solid products were developed and, in Europe in 2009, an industrial juice preservation line was installed using 20 kV/cm pulses at 40 to 50 • C to extend the chill-stability of fruit juices, including citrus juices and smoothies, from 6 to 21 d. The related PEF processing costs are in the range of US $0.02 to 0.03 per liter and are justified due to access to new markets and reduced return of spoiled product. However, despite its commercial success there are still many unknown factors associated with PEF processing of fruit and citrus juices and many conflicting reports in the literature. This literature review, therefore, aims to provide a comprehensive overview of the current scientific knowledge of PEF effects on microbial, enzymatic, nutritional, and sensory quality and stability of orange juices.
ABSTRACT Consumer demand and current market conditions warrant investigation of dairy processing ... more ABSTRACT Consumer demand and current market conditions warrant investigation of dairy processing technologies that can deliver improved product quality and stability and reduced energy use during processing, without compromising product and process safety. One candidate technology for the extension of shelf-life in dairy products is pulsed electric field (PEF) processing. PEF is considered to be an effective, non-thermal intervention that appears to hold some promise. Research on the application of PEF to control spoilage and pathogenic microorganisms and enzyme systems in dairy products spans a wide array of processing equipment and reaction conditions. PEF has been reported to effectively reduce the numbers of both pathogens and spoilage organisms in milk; however, there is a high degree of variability between studies. The application of PEF in combination with lower temperature thermal processing can deliver comparable reductions in microbial load without significant detrimental effects to the sensory and physico-chemical properties of food products.
ABSTRACT This review highlights the current knowledge on gelation of hydrocolloids induced by hig... more ABSTRACT This review highlights the current knowledge on gelation of hydrocolloids induced by high pressure processing (HPP) of dairy products. Pressure-induced gelation of single systems (casein rich, whey protein rich, gelatin, and polysaccharide solutions) as well as rheological and thermo-mechanical effects of HPP on mixture systems are discussed. The mechanism of dairy protein gelation under pressure, their properties and microstructure, and potential application of HPP to improve physical properties of dairy products (cheese, yoghurt, and ice cream) are included. HPP is a promising tool for future manufacturing of structured dairy products with unique sensorial properties.
ABSTRACT Pulsed electric field (PEF) treatment at 49 kV/cm for 19.36 μs (up to 70 °C) was perform... more ABSTRACT Pulsed electric field (PEF) treatment at 49 kV/cm for 19.36 μs (up to 70 °C) was performed on reconstituted skim milk (10 wt%). The milk condition was varied either by pH adjustment (pH 6.7–8.0) or by the addition of ethylenediaminetetraacetic acid (EDTA) (up to 30 mM). Except for milks at pH ⩾ 7.5, PEF treatment did not affect size and ξ-potential of the milk particles, the amounts of protein in the serum or the state of the whey proteins. For milks at pH ⩾ 7.5, a decrease in the size of the milk particles and an increase in the amount of proteins in the serum were measured. Sodium dodecyl sulphate – polyacrylamide gel electrophoresis (SDS–PAGE) measurements showed that the amount of caseins in the serum increased, while the whey proteins were not affected. This indicates that the decrease of the size of the milk proteins is due to the dissociation of the casein micelles. Further, this study demonstrates that the PEF effects on milks at pH ⩾ 7.5 is due to ohmic heating during the PEF treatment.
The curcuminoid-carrying potential of oat fiber was examined as a potential route to overcome the... more The curcuminoid-carrying potential of oat fiber was examined as a potential route to overcome the low aqueous solubility of curcuminoids. Aqueous dispersions of oat fiber were mixed with curcuminoids solubilized in ethanol to obtain curcuminoids−oat fiber (1% w/w) dispersions in aqueous ethanol (2% v/v). Centrifugation of the curcuminoids−oat fiber dispersions resulted in a supernatant (95.3% w/w: 0.11% w/w protein, 0.17% w/w β-glucan) and precipitate (4.74% w/w: 0.18% w/w protein, 0.11% w/w β-glucan) with the curcuminoids being almost equally partitioned into both fractions. Curcuminoids solubility in the supernatant was markedly greater than that in aqueous ethanol and water. The curcuminoids were in the amorphous state in the precipitated fraction and were more stable to degradation than the curcuminoids in the supernatant. These studies show the potential of oat fiber as a carrier for curcuminoids into functional foods.
The preservation of low-acid canned food to achieve non-refrigerated, shelf-stable products requi... more The preservation of low-acid canned food to achieve non-refrigerated, shelf-stable products requires the elimination of vegetative microbial cells as well as the inactivation of bacterial endospores capable of growing in the product at the conditions prevailing during distribu-tion and ...
Approximations of the electric field strength and specific energy input of continuous pulsed elec... more Approximations of the electric field strength and specific energy input of continuous pulsed electric field (PEF) systems often assume parallel plate configurations. However, it is known that actual electric field strengths and specific energy inputs can be significantly different from this simplistic approach. A systematic study of more than 150 dimensions and various insulator geometries of pilot-scale PEF treatment chambers
ABSTRACT The application of high pressure for processing fish muscles has showed a great potentia... more ABSTRACT The application of high pressure for processing fish muscles has showed a great potential on improving the physicochemical, microbial and sensory quality of fish muscles. High pressure results in the inactivation of micro-organisms and autolytic enzymes and lead to an extension of fish muscles shelf life. High pressure inhibits the formation of putrefactive compounds and maintains the hardness of fish muscles, resulting in higher sensory quality compared to untreated muscle over storage time. However, the discolouration, cooked appearance and lipid oxidation are the drawbacks that could limit the application of high pressure on fish muscles. Besides, pressure-induced gelling and high-pressure freezing/thawing of fish muscles are the main areas being investigated intensively to obtain the benefits of high-pressure processing on fish muscles.
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