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Research paper thumbnail of High Hydrostatic Pressure Processing at High Temperature: Impact on Quality Attributes and Future Outlook from Consumers’ Perspective

Research paper thumbnail of Pulsed Electric Field processing: Its technological opportunities and consumer perception. In: Food Processing Technologies: Impact on Product Attributes

Papers by Farnaz Faridnia

Research paper thumbnail of Effects of Pulsed Electric Fields on Selected Quality Attributes of Beef Outside Flat (Biceps femoris

Pulsed electric field (PEF) processing is a non-thermal food processing technology that applies b... more Pulsed electric field (PEF) processing is a non-thermal food processing technology that applies brief (µs) electrical pulses of high voltage to food products placed between two electrodes. Depending on the process intensity, the process affects cell membrane permeability due to localised structural changes. There are few reports on the use of PEF for the processing of solid foods like meat. Therefore, the current project was designed to assess the impact of PEF processing on beef muscles and its potential use to reduce meat ageing time and cost. Post rigor Biceps femoris (a low value beef muscle) cuts were exposed to PEF (electric field strength of 1.7-2.0 kV/cm and pulsed electrical energy of 185 kJ/kg) processing and sampled after aging at 4 o C for 3, 7, 14 or 21 days. Samples were assessed for temperature increases, electrical conductivity, pH, purge loss, cooking loss, tenderness and colour stability. The microstructure of PEF treated and untreated meat samples were also investigated. Our results showed that temperature, electrical conductivity, and pH were significantly (P<0.05) affected by PEF treatment conditions. Tenderness, as indicated by a reduced shear force value, significantly (P<0.05) increased following PEF treatment compared to the untreated samples. Cooking loss was not affected by PEF treatment, whilst purge loss significantly (P<0.05) increased after PEF treatment and during ageing. The PEF treated meat samples showed a dramatic increase in the number of myofibrils ruptured along the z-lines compared to the untreated samples during ageing. This resulted in beef muscle with a more porous structure compared to the untreated samples and accounts for the observed increase in electrical conductivity and purge loss. These results suggest that PEF induces changes in the microstructure and texture of meat and could potentially be used to improve tenderness, decrease ageing time or to alter functional properties.

Research paper thumbnail of Innovative approach to determine the effect of pulsed electric fields on the microstructure of whole potato tubers: Use of cell viability, microscopic images and ionic leakage measurements

The aim of this study was to gain an in-depth understanding of the effect of pulsed electric fiel... more The aim of this study was to gain an in-depth understanding of the effect of pulsed electric fields (PEF) on the microstructure of potato tubers. The effect of peeling prior to PEF was also studied. Whole potato tubers were subjected to PEF at a constant frequency of 50 Hz, over a range of electric field strengths (0.2 to 1.1 kV/cm) and energy levels (1 to 10 kJ/kg). To determine the uniformity of the PEF effect across the potato tuber, cell viability was assessed using tetrazolium salt staining. To evaluate the effectiveness of PEF processing the leakage of ionic species from the tubers was measured using atomic absorption spectrophotometry and FESEM-EDS analysis. In addition the influence of PEF on cell disruption and microstructural damage was assessed using scanning electron microscopy (Cryo-SEM). As the electric field strength and energy increased potassium ion leakage and electrical conductivity of the medium increased. The orientation of the tuber towards the electrodes and the presence of the skin greatly affected the impact of PEF on cell disruption and viability. At electric field strengths of 0.3 kV/cm and above, potato cells located in the pith (inner medulla) showed more damage and had a higher proportion of cell death compared to cells located in the outer medulla. This is the first study to provide visual evidence that the application of electric fields to solid, living foods, such as potato tubers, results in an uneven distribution of cell damage and death owing to the presence of vascular bundles and cells that vary in their resistance to electric fields.

Research paper thumbnail of Pulsed Electric Field processing: Its technological opportunities and consumer perception

Research paper thumbnail of Pulsed Electric Field processing: Its technological opportunities and consumer perception

Research paper thumbnail of ijfs12532-sup-0001-FigS1

Research paper thumbnail of ijfs12532-sup-0003-FigS3a

Research paper thumbnail of ijfs12532-sup-0004-FigS3b

Research paper thumbnail of ijfs12532-sup-0002-FigS2

Research paper thumbnail of Combined Effects of Pulsed Electric Fields and Ageing on Selected Quality Attributes of Beef Outside Flat (Biceps femoris)

Pulsed electric field (PEF) processing is a nonthermal food processing technology that applies br... more Pulsed electric field (PEF) processing is a nonthermal food processing technology that applies brief (µs) electrical pulses of high voltage to food products placed between two electrodes. Depending on the process intensity, the process affects cell membrane permeability due to localised structural changes. There are few reports on the use of PEF for the processing of solid foods like meat. Therefore, the current project was designed to assess the impact of PEF processing on beef muscles and its potential use to reduce meat ageing time and cost. Post rigor Biceps femoris (a low value beef muscle) cuts were exposed to PEF (electric field strength of 1.7 -2.0 kV/cm and pulsed electrical energy of 185 kJ/kg) processing and sampled after aging at 4 o C for 3, 7, 14 or 21 days. Samples were assessed for temperature increases, electrical conductivity, pH, purge loss, cooking loss, tenderness and colour stability. The microstructure of PEF treated and untreated meat samples were also investigated. Our results showed that temperature, electrical conductivity, and pH were significantly (P<0.05) affected by PEF treatment conditions. Tenderness, as indicated by a reduced shear force value, significantly (P<0.05) increased following PEF treatment compared to the untreated samples. Cooking loss was not affected by PEF treatment, whilst purge loss significantly (P<0.05) increased after PEF treatment and during ageing. The PEF treated meat samples showed a dramatic increase in the number of myofibrils ruptured along the z-lines compared to the untreated samples during ageing. This resulted in beef muscle with a more porous structure compared to the untreated samples and accounts for the observed increase in electrical conductivity and purge loss. These results suggest that PEF induces changes in the microstructure and texture of meat and could potentially be used to improve tenderness, decrease ageing time or to alter functional properties.

Research paper thumbnail of <i>In vitro</i> binding of mutagenic heterocyclic aromatic amines by <i>Bifidobacterium pseudocatenulatum</i> G4

Beneficial Microbes, 2010

Consumption of probiotics has been associated with decreased risk of colon cancer and reported to... more Consumption of probiotics has been associated with decreased risk of colon cancer and reported to have antimutagenic/anti-carcinogenic properties. One possible mechanism for this effect involves physical binding of the mutagenic compounds, such as heterocyclic amines (HCAs), to the bacteria. Therefore, the objective of this study was to examine the binding capacity of bifidobacterial strains of human origin on mutagenic heterocyclic amines which are suspected to play a role in human cancers. In vitro binding of the mutagens Trp-p-2, IQ, MeIQx, 7,8DiMeIQx and PhIP by three bacterial strains in two media of different pH was analysed using high performance liquid chromatography. Bifidobacterium pseudocatenulatum G4 showed the highest decrease in the total HCAs content, followed by Bifidobacterium longum, and Escherichia coli. pH affects binding capacity; the highest binding was obtained at pH 6.8. Gram-positive tested strains were found to be consistently more effective than the gram-negative strain. There were significant decreases in the amount of HCAs in the presence of different cell concentrations of B. pseudocatenulatum G4; the highest decrease was detected at the concentration of 10 10 cfu/ml. The results showed that HCAs were able to bind with all bacterial strains tested in vitro, thus it may be possible to decrease their absorption by human intestine and increase their elimination via faeces.

Research paper thumbnail of Effect of freezing as pre-treatment prior to pulsed electric field processing on quality traits of beef muscles

Innovative Food Science & Emerging Technologies, 2014

The purpose of this research was to study the effects of freezing as pre-treatment prior to pulse... more The purpose of this research was to study the effects of freezing as pre-treatment prior to pulsed electric field (PEF) on the quality of beef semitendinosus muscles. Fresh and frozen-thawed samples were treated using square -wave bipolar pulses at electric field strength 1.4 kV/cm, pulse width 20 μs, frequency 50 Hz and total specific energy 250 kJ/kg. PEF caused significant microstructural changes of meat tissue compared to freezing. Combined freezing-thawing and PEF resulted in improved tenderness indicated by reduced shear force, but not PEF alone. PEF significantly increased purge loss but not cooking loss. A two log-unit increase in aerobic microbial counts during log phase of frozen-thawed PEF-treated samples was positively associated with increased purge loss. PEF itself did not affect the ratios of polyunsaturated/saturated fatty acids and omega 6/omega 3 nor the free fatty acid profiles. Freezing with and without PEF greatly affected the volatile profile of meat. Industrial relevance: PEF treatment provides an alternative to mechanical, thermal and enzymatic cell disintegration of animal raw materials, providing a short duration (milliseconds) and energy efficient treatment. In this study, the possible relationship between freezing prior to PEF and changes in beef tissue microstructure that influence storage stability and safety was investigated. The results of this study contribute toward understanding how PEF induced changes in beef microstructure influence the important quality attributes of beef.

Research paper thumbnail of Impact of pulsed electric fields and post-mortem vacuum ageing on beef longissimus thoracis muscles

International Journal of Food Science & Technology, 2014

The impact of pulsed electric field (PEF) processing (0.2-0.6 kV cm À1 , 1-50 Hz, 20 ls) followed... more The impact of pulsed electric field (PEF) processing (0.2-0.6 kV cm À1 , 1-50 Hz, 20 ls) followed by vacuum ageing (1 and 3 days) on the quality traits of beef longissimus thoracis (LT) was assessed. The results show that pH, colour stability (L*, a* and R630/580 values) and cooking loss were unaffected by PEF treatments, whilst moisture content significantly (P < 0.05) decreased by 0.7-3.6%. No significant (P > 0.05) difference was found in shear force between PEF treated and untreated samples. However, the shear force values significantly reduced in response to ageing times regardless of the PEF treatments. After 3 days post-treatment ageing, the shear force decreased by 20-22% compared to 1 day ageing for all samples. Furthermore, Cryo-SEM results suggest that PEF treatments have led to more porous tissue structure leading to more water loss. Protein profile was unchanged by PEF treatments applied.

Research paper thumbnail of High Hydrostatic Pressure Processing at High Temperature: Impact on Quality Attributes and Future Outlook from Consumers’ Perspective

Research paper thumbnail of Pulsed Electric Field processing: Its technological opportunities and consumer perception. In: Food Processing Technologies: Impact on Product Attributes

Research paper thumbnail of Effects of Pulsed Electric Fields on Selected Quality Attributes of Beef Outside Flat (Biceps femoris

Pulsed electric field (PEF) processing is a non-thermal food processing technology that applies b... more Pulsed electric field (PEF) processing is a non-thermal food processing technology that applies brief (µs) electrical pulses of high voltage to food products placed between two electrodes. Depending on the process intensity, the process affects cell membrane permeability due to localised structural changes. There are few reports on the use of PEF for the processing of solid foods like meat. Therefore, the current project was designed to assess the impact of PEF processing on beef muscles and its potential use to reduce meat ageing time and cost. Post rigor Biceps femoris (a low value beef muscle) cuts were exposed to PEF (electric field strength of 1.7-2.0 kV/cm and pulsed electrical energy of 185 kJ/kg) processing and sampled after aging at 4 o C for 3, 7, 14 or 21 days. Samples were assessed for temperature increases, electrical conductivity, pH, purge loss, cooking loss, tenderness and colour stability. The microstructure of PEF treated and untreated meat samples were also investigated. Our results showed that temperature, electrical conductivity, and pH were significantly (P<0.05) affected by PEF treatment conditions. Tenderness, as indicated by a reduced shear force value, significantly (P<0.05) increased following PEF treatment compared to the untreated samples. Cooking loss was not affected by PEF treatment, whilst purge loss significantly (P<0.05) increased after PEF treatment and during ageing. The PEF treated meat samples showed a dramatic increase in the number of myofibrils ruptured along the z-lines compared to the untreated samples during ageing. This resulted in beef muscle with a more porous structure compared to the untreated samples and accounts for the observed increase in electrical conductivity and purge loss. These results suggest that PEF induces changes in the microstructure and texture of meat and could potentially be used to improve tenderness, decrease ageing time or to alter functional properties.

Research paper thumbnail of Innovative approach to determine the effect of pulsed electric fields on the microstructure of whole potato tubers: Use of cell viability, microscopic images and ionic leakage measurements

The aim of this study was to gain an in-depth understanding of the effect of pulsed electric fiel... more The aim of this study was to gain an in-depth understanding of the effect of pulsed electric fields (PEF) on the microstructure of potato tubers. The effect of peeling prior to PEF was also studied. Whole potato tubers were subjected to PEF at a constant frequency of 50 Hz, over a range of electric field strengths (0.2 to 1.1 kV/cm) and energy levels (1 to 10 kJ/kg). To determine the uniformity of the PEF effect across the potato tuber, cell viability was assessed using tetrazolium salt staining. To evaluate the effectiveness of PEF processing the leakage of ionic species from the tubers was measured using atomic absorption spectrophotometry and FESEM-EDS analysis. In addition the influence of PEF on cell disruption and microstructural damage was assessed using scanning electron microscopy (Cryo-SEM). As the electric field strength and energy increased potassium ion leakage and electrical conductivity of the medium increased. The orientation of the tuber towards the electrodes and the presence of the skin greatly affected the impact of PEF on cell disruption and viability. At electric field strengths of 0.3 kV/cm and above, potato cells located in the pith (inner medulla) showed more damage and had a higher proportion of cell death compared to cells located in the outer medulla. This is the first study to provide visual evidence that the application of electric fields to solid, living foods, such as potato tubers, results in an uneven distribution of cell damage and death owing to the presence of vascular bundles and cells that vary in their resistance to electric fields.

Research paper thumbnail of Pulsed Electric Field processing: Its technological opportunities and consumer perception

Research paper thumbnail of Pulsed Electric Field processing: Its technological opportunities and consumer perception

Research paper thumbnail of ijfs12532-sup-0001-FigS1

Research paper thumbnail of ijfs12532-sup-0003-FigS3a

Research paper thumbnail of ijfs12532-sup-0004-FigS3b

Research paper thumbnail of ijfs12532-sup-0002-FigS2

Research paper thumbnail of Combined Effects of Pulsed Electric Fields and Ageing on Selected Quality Attributes of Beef Outside Flat (Biceps femoris)

Pulsed electric field (PEF) processing is a nonthermal food processing technology that applies br... more Pulsed electric field (PEF) processing is a nonthermal food processing technology that applies brief (µs) electrical pulses of high voltage to food products placed between two electrodes. Depending on the process intensity, the process affects cell membrane permeability due to localised structural changes. There are few reports on the use of PEF for the processing of solid foods like meat. Therefore, the current project was designed to assess the impact of PEF processing on beef muscles and its potential use to reduce meat ageing time and cost. Post rigor Biceps femoris (a low value beef muscle) cuts were exposed to PEF (electric field strength of 1.7 -2.0 kV/cm and pulsed electrical energy of 185 kJ/kg) processing and sampled after aging at 4 o C for 3, 7, 14 or 21 days. Samples were assessed for temperature increases, electrical conductivity, pH, purge loss, cooking loss, tenderness and colour stability. The microstructure of PEF treated and untreated meat samples were also investigated. Our results showed that temperature, electrical conductivity, and pH were significantly (P<0.05) affected by PEF treatment conditions. Tenderness, as indicated by a reduced shear force value, significantly (P<0.05) increased following PEF treatment compared to the untreated samples. Cooking loss was not affected by PEF treatment, whilst purge loss significantly (P<0.05) increased after PEF treatment and during ageing. The PEF treated meat samples showed a dramatic increase in the number of myofibrils ruptured along the z-lines compared to the untreated samples during ageing. This resulted in beef muscle with a more porous structure compared to the untreated samples and accounts for the observed increase in electrical conductivity and purge loss. These results suggest that PEF induces changes in the microstructure and texture of meat and could potentially be used to improve tenderness, decrease ageing time or to alter functional properties.

Research paper thumbnail of <i>In vitro</i> binding of mutagenic heterocyclic aromatic amines by <i>Bifidobacterium pseudocatenulatum</i> G4

Beneficial Microbes, 2010

Consumption of probiotics has been associated with decreased risk of colon cancer and reported to... more Consumption of probiotics has been associated with decreased risk of colon cancer and reported to have antimutagenic/anti-carcinogenic properties. One possible mechanism for this effect involves physical binding of the mutagenic compounds, such as heterocyclic amines (HCAs), to the bacteria. Therefore, the objective of this study was to examine the binding capacity of bifidobacterial strains of human origin on mutagenic heterocyclic amines which are suspected to play a role in human cancers. In vitro binding of the mutagens Trp-p-2, IQ, MeIQx, 7,8DiMeIQx and PhIP by three bacterial strains in two media of different pH was analysed using high performance liquid chromatography. Bifidobacterium pseudocatenulatum G4 showed the highest decrease in the total HCAs content, followed by Bifidobacterium longum, and Escherichia coli. pH affects binding capacity; the highest binding was obtained at pH 6.8. Gram-positive tested strains were found to be consistently more effective than the gram-negative strain. There were significant decreases in the amount of HCAs in the presence of different cell concentrations of B. pseudocatenulatum G4; the highest decrease was detected at the concentration of 10 10 cfu/ml. The results showed that HCAs were able to bind with all bacterial strains tested in vitro, thus it may be possible to decrease their absorption by human intestine and increase their elimination via faeces.

Research paper thumbnail of Effect of freezing as pre-treatment prior to pulsed electric field processing on quality traits of beef muscles

Innovative Food Science & Emerging Technologies, 2014

The purpose of this research was to study the effects of freezing as pre-treatment prior to pulse... more The purpose of this research was to study the effects of freezing as pre-treatment prior to pulsed electric field (PEF) on the quality of beef semitendinosus muscles. Fresh and frozen-thawed samples were treated using square -wave bipolar pulses at electric field strength 1.4 kV/cm, pulse width 20 μs, frequency 50 Hz and total specific energy 250 kJ/kg. PEF caused significant microstructural changes of meat tissue compared to freezing. Combined freezing-thawing and PEF resulted in improved tenderness indicated by reduced shear force, but not PEF alone. PEF significantly increased purge loss but not cooking loss. A two log-unit increase in aerobic microbial counts during log phase of frozen-thawed PEF-treated samples was positively associated with increased purge loss. PEF itself did not affect the ratios of polyunsaturated/saturated fatty acids and omega 6/omega 3 nor the free fatty acid profiles. Freezing with and without PEF greatly affected the volatile profile of meat. Industrial relevance: PEF treatment provides an alternative to mechanical, thermal and enzymatic cell disintegration of animal raw materials, providing a short duration (milliseconds) and energy efficient treatment. In this study, the possible relationship between freezing prior to PEF and changes in beef tissue microstructure that influence storage stability and safety was investigated. The results of this study contribute toward understanding how PEF induced changes in beef microstructure influence the important quality attributes of beef.

Research paper thumbnail of Impact of pulsed electric fields and post-mortem vacuum ageing on beef longissimus thoracis muscles

International Journal of Food Science & Technology, 2014

The impact of pulsed electric field (PEF) processing (0.2-0.6 kV cm À1 , 1-50 Hz, 20 ls) followed... more The impact of pulsed electric field (PEF) processing (0.2-0.6 kV cm À1 , 1-50 Hz, 20 ls) followed by vacuum ageing (1 and 3 days) on the quality traits of beef longissimus thoracis (LT) was assessed. The results show that pH, colour stability (L*, a* and R630/580 values) and cooking loss were unaffected by PEF treatments, whilst moisture content significantly (P < 0.05) decreased by 0.7-3.6%. No significant (P > 0.05) difference was found in shear force between PEF treated and untreated samples. However, the shear force values significantly reduced in response to ageing times regardless of the PEF treatments. After 3 days post-treatment ageing, the shear force decreased by 20-22% compared to 1 day ageing for all samples. Furthermore, Cryo-SEM results suggest that PEF treatments have led to more porous tissue structure leading to more water loss. Protein profile was unchanged by PEF treatments applied.