Assessment of milk fatty acids has been proposed to support farm management practices including a... more Assessment of milk fatty acids has been proposed to support farm management practices including adjustment of feeding regimes and monitoring animal status. This study assessed the performance of a miniaturised near infrared (NIR) sensor for assessment of fatty acids in milk. Samples (n = 483) were from 114 farms, varying in lactation stages within two production seasons and included different dairy breeds. The fatty acids (C4:0, C6:0, C14:0, C16:0, C18:1 c9, SFA, MUFA, SCFA, BCFA) showed Ratio of performance to deviation values higher than two. The performance was equivalent to other independent studies utilising NIR. However, in this study, we used a low‐cost NIR spectrophotometer suitable for on‐the‐farm use.
This research paper aimed to locate protein modifications caused by treatment of milk and determi... more This research paper aimed to locate protein modifications caused by treatment of milk and determine if the modification locations were consistent. The majority of milk for consumption is homogenised using pressure and heat, and this causes changes in the location of proteins in the milk as well as protein modifications. To investigate these proteomic changes, raw milk was pasteurised (72°C, 15 s), then, to separate the treatment for homogenisation, heated at these different pressures and temperatures: 45°C without no pressure applied, 45°C with 35 MPa, 80°C without pressure applied and 80°C, with 35 MPa. Proteomic analysis was done after separating the milk into three fractions: whey, casein and cream. Protein modifications in each fraction were examined and we found Maillard products as well as oxidation to be of interest. The proteins were also further identified and characterised to compare protein modification sites and differences in proteins present in the cream resulting from...
A complexation study between blackcurrant pectin (BCP) and whey protein (WP) was carried out to i... more A complexation study between blackcurrant pectin (BCP) and whey protein (WP) was carried out to investigate the impact of bound anthocyanins on pectin–protein interactions. The effects of pH (3.5 and 4.5), heating (85 °C, 15 min), and heating sequence (mixed-heated or heated-mixed) were studied. The pH influenced the color, turbidity, particle size, and zeta-potential of the mixtures, but its impact was mainly significant when heating was introduced. Heating increased the amount of BCP in the complexes—especially at pH 3.5, where 88% w/w of the initial pectin was found in the sedimented (insoluble) fraction. Based on phase-separation measurements, the mixed-heated system at pH 4.5 displayed greater stability than at pH 3.5. Heating sequence was essential in preventing destabilization of the systems; mixing of components before heating produced a more stable system with small complexes (<300 nm) and relatively low polydispersity. However, heating WP before mixing with BCP prompted...
Abstract Structural manipulation of β-lactoglobulin through processes such as heat treatment and ... more Abstract Structural manipulation of β-lactoglobulin through processes such as heat treatment and complexation with other molecules has proven fruitful in industrial formulations. To fully appreciate the ramifications of such methods on protein interfacial adsorption we have investigated assemblies of β-lactoglobulin at oil/water interfaces predominantly at pH 3 and at different conditions of ionic strength, salt type and temperature. These parameters were tuned to vary the relative amounts of two native species, namely, monomer and its smallest aggregate, the dimer, while the interface was monitored using rheology and tensiometry. Unfolding of β-lactoglobulin at the interface triggers the formation of disulfide linkages between the free thiol groups of two monomers which are located at cys121. In this way, monomers pair up to form discrete assemblies of two β-lactoglobulin molecules (non-native dimers) that are not interconnected further and this is reflected in the absence of a viscoelastic layer in solutions with high monomer concentrations. Native dimers however form primary particles capable of forming two thiol bonds allowing the formation of extended networks. A higher concentration of dimers increases the final interfacial elastic strength of the network. This fundamental relation between the quaternary structure of β-lg and its subsequent interfacial network suggests a possible interfacial role in its biological function.
Microencapsulation helps to improve bioavailability of a functional whey protein, lactoferrin (Lf... more Microencapsulation helps to improve bioavailability of a functional whey protein, lactoferrin (Lf), in adults. Herein, we report the Lf loading capacity (LC) and retention efficiency (RE) in the microparticles of surface-reacted calcium carbonate (SRCC) of different types and compare them to those of widely used vaterite microparticles. The LCs and REs are analyzed in connection to the total surface area and the volume of intraparticle pores. The best performing SRCC3 demonstrates Lf LC of 11.00 wt% achieved in a single absorption step and 74% RE after two cycles of washing with deionized water. A much larger surface area of SRCC templates and a lower pH required to release Lf do not affect its antitumor activity in MCF-7 assay. Layer-by-Layer assembly of pepsin-tannic acid multilayer shell around Lf-loaded microparticles followed by acidic decomposition of the inorganic core produces microencapsulated Lf with a yield ~36 times higher than from vaterite templates reported earlier, while the scale of encapsulated Lf production is ~12,000 times larger. In vitro digestion tests demonstrate the protection of ~65% of encapsulated Lf from gastric digestion. The developed capsules are prospective candidates for functional foods fortified with Lf.
Abstract Milk processing affects the molecular and supramolecular characteristics of milk. While ... more Abstract Milk processing affects the molecular and supramolecular characteristics of milk. While many of these changes have been studied extensively, the effect of homogenisation on volatile components and lipids at different pressures and temperatures is still poorly understood. The aim of this study was to determine the effect of homogenisation pressure (0, 150, 250 and 350 bar) at different temperatures (45 °C, 60 °C and 80 °C) on the content of individual milk volatile components, phospholipids and triacylglycerols. The results demonstrated the importance of temperature and pressure (P > 0.001) on the formation of 2-heptanone. Temperature was the most important factor for significant (P > 0.05) loss of the milk fat globule membrane lipid phosphatidyletholamine (PE) from the milk serum. Moreover, a significant increase (P > 0.001) in the level of all triacylglycerols groups in the serum phase of homogenised milk was observed, independent of the temperature of the homogenisation process.
International journal of food microbiology, Jan 16, 2016
Due to technical simplicity and strong inhibition against the growth of psychrotrophic bacteria i... more Due to technical simplicity and strong inhibition against the growth of psychrotrophic bacteria in milk, CO2 treatment has emerged as an attractive processing aid to increase the storage time of raw milk before downstream processing. However, it is yet to be adopted by the industry. In order to further explore the suitability of CO2 treatment for raw milk processing, the bacterial populations of carbonated raw milk collected locally from five different sources in Australia were analysed with next-generation sequencing. Growth inhibition by CO2 was confirmed, with spoilage delayed by at least 7days compared with non-carbonated controls. All non-carbonated controls were spoiled by Gammaproteobacteria, namely Pseudomonas fluorescens group bacteria, Serratia and Erwinia. Two out of the five carbonated samples shared the same spoilage bacteria as their corresponding controls. The rest of the three carbonated samples were spoiled by the lactic acid bacterium (LAB) Leuconostoc. This is con...
Valorisation of acid whey (AW) is a challenge for the dairy industry largely due to processing di... more Valorisation of acid whey (AW) is a challenge for the dairy industry largely due to processing difficulties associated with the inability of lactose to crystallise in the presence of lactic acid (LA), which can require removal of LA from AW prior to further processing. The aim of the present study was to compare the performance of three commercially available nanofiltration (NF) membranes in the processing of AW. NF membrane types HL, DL and DK, were assessed under industrially relevant conditions including adjusted pH levels (3, 4.5 or 7.3) and two processing temperatures (25 or 40 °C). Additionally, nano-diafiltration (NDF) was employed at 25 °C. In both NF and NDF, higher permeate fluxes were obtained with HL membranes. Lactose retention appeared temperature dependent only, while LA transmission depended on pH, membrane type and temperature. Both, pH and temperature influenced the divalent and phosphate ion transmissions. Formation of calcium complexes with phosphates and lactates, which may consequently induce attraction with proteins, was responsible for the pH and temperature effects on transmission of components. NF with the HL membrane at 40 °C and adjusted pH 3.0 showed the highest permeate transmission (∼50%) for LA and was able to retain ∼93% lactose. This system also had the highest flux (average of 60 L/m2/h). In contrast, NDF showed only ∼34% LA transmission while ∼97% lactose was retained. Thus removal of almost half of the LA content of AW was possible in the best case, which indicates that NF may have a useful role to play in the valorisation of this industrial by-product.
Assessment of milk fatty acids has been proposed to support farm management practices including a... more Assessment of milk fatty acids has been proposed to support farm management practices including adjustment of feeding regimes and monitoring animal status. This study assessed the performance of a miniaturised near infrared (NIR) sensor for assessment of fatty acids in milk. Samples (n = 483) were from 114 farms, varying in lactation stages within two production seasons and included different dairy breeds. The fatty acids (C4:0, C6:0, C14:0, C16:0, C18:1 c9, SFA, MUFA, SCFA, BCFA) showed Ratio of performance to deviation values higher than two. The performance was equivalent to other independent studies utilising NIR. However, in this study, we used a low‐cost NIR spectrophotometer suitable for on‐the‐farm use.
This research paper aimed to locate protein modifications caused by treatment of milk and determi... more This research paper aimed to locate protein modifications caused by treatment of milk and determine if the modification locations were consistent. The majority of milk for consumption is homogenised using pressure and heat, and this causes changes in the location of proteins in the milk as well as protein modifications. To investigate these proteomic changes, raw milk was pasteurised (72°C, 15 s), then, to separate the treatment for homogenisation, heated at these different pressures and temperatures: 45°C without no pressure applied, 45°C with 35 MPa, 80°C without pressure applied and 80°C, with 35 MPa. Proteomic analysis was done after separating the milk into three fractions: whey, casein and cream. Protein modifications in each fraction were examined and we found Maillard products as well as oxidation to be of interest. The proteins were also further identified and characterised to compare protein modification sites and differences in proteins present in the cream resulting from...
A complexation study between blackcurrant pectin (BCP) and whey protein (WP) was carried out to i... more A complexation study between blackcurrant pectin (BCP) and whey protein (WP) was carried out to investigate the impact of bound anthocyanins on pectin–protein interactions. The effects of pH (3.5 and 4.5), heating (85 °C, 15 min), and heating sequence (mixed-heated or heated-mixed) were studied. The pH influenced the color, turbidity, particle size, and zeta-potential of the mixtures, but its impact was mainly significant when heating was introduced. Heating increased the amount of BCP in the complexes—especially at pH 3.5, where 88% w/w of the initial pectin was found in the sedimented (insoluble) fraction. Based on phase-separation measurements, the mixed-heated system at pH 4.5 displayed greater stability than at pH 3.5. Heating sequence was essential in preventing destabilization of the systems; mixing of components before heating produced a more stable system with small complexes (<300 nm) and relatively low polydispersity. However, heating WP before mixing with BCP prompted...
Abstract Structural manipulation of β-lactoglobulin through processes such as heat treatment and ... more Abstract Structural manipulation of β-lactoglobulin through processes such as heat treatment and complexation with other molecules has proven fruitful in industrial formulations. To fully appreciate the ramifications of such methods on protein interfacial adsorption we have investigated assemblies of β-lactoglobulin at oil/water interfaces predominantly at pH 3 and at different conditions of ionic strength, salt type and temperature. These parameters were tuned to vary the relative amounts of two native species, namely, monomer and its smallest aggregate, the dimer, while the interface was monitored using rheology and tensiometry. Unfolding of β-lactoglobulin at the interface triggers the formation of disulfide linkages between the free thiol groups of two monomers which are located at cys121. In this way, monomers pair up to form discrete assemblies of two β-lactoglobulin molecules (non-native dimers) that are not interconnected further and this is reflected in the absence of a viscoelastic layer in solutions with high monomer concentrations. Native dimers however form primary particles capable of forming two thiol bonds allowing the formation of extended networks. A higher concentration of dimers increases the final interfacial elastic strength of the network. This fundamental relation between the quaternary structure of β-lg and its subsequent interfacial network suggests a possible interfacial role in its biological function.
Microencapsulation helps to improve bioavailability of a functional whey protein, lactoferrin (Lf... more Microencapsulation helps to improve bioavailability of a functional whey protein, lactoferrin (Lf), in adults. Herein, we report the Lf loading capacity (LC) and retention efficiency (RE) in the microparticles of surface-reacted calcium carbonate (SRCC) of different types and compare them to those of widely used vaterite microparticles. The LCs and REs are analyzed in connection to the total surface area and the volume of intraparticle pores. The best performing SRCC3 demonstrates Lf LC of 11.00 wt% achieved in a single absorption step and 74% RE after two cycles of washing with deionized water. A much larger surface area of SRCC templates and a lower pH required to release Lf do not affect its antitumor activity in MCF-7 assay. Layer-by-Layer assembly of pepsin-tannic acid multilayer shell around Lf-loaded microparticles followed by acidic decomposition of the inorganic core produces microencapsulated Lf with a yield ~36 times higher than from vaterite templates reported earlier, while the scale of encapsulated Lf production is ~12,000 times larger. In vitro digestion tests demonstrate the protection of ~65% of encapsulated Lf from gastric digestion. The developed capsules are prospective candidates for functional foods fortified with Lf.
Abstract Milk processing affects the molecular and supramolecular characteristics of milk. While ... more Abstract Milk processing affects the molecular and supramolecular characteristics of milk. While many of these changes have been studied extensively, the effect of homogenisation on volatile components and lipids at different pressures and temperatures is still poorly understood. The aim of this study was to determine the effect of homogenisation pressure (0, 150, 250 and 350 bar) at different temperatures (45 °C, 60 °C and 80 °C) on the content of individual milk volatile components, phospholipids and triacylglycerols. The results demonstrated the importance of temperature and pressure (P > 0.001) on the formation of 2-heptanone. Temperature was the most important factor for significant (P > 0.05) loss of the milk fat globule membrane lipid phosphatidyletholamine (PE) from the milk serum. Moreover, a significant increase (P > 0.001) in the level of all triacylglycerols groups in the serum phase of homogenised milk was observed, independent of the temperature of the homogenisation process.
International journal of food microbiology, Jan 16, 2016
Due to technical simplicity and strong inhibition against the growth of psychrotrophic bacteria i... more Due to technical simplicity and strong inhibition against the growth of psychrotrophic bacteria in milk, CO2 treatment has emerged as an attractive processing aid to increase the storage time of raw milk before downstream processing. However, it is yet to be adopted by the industry. In order to further explore the suitability of CO2 treatment for raw milk processing, the bacterial populations of carbonated raw milk collected locally from five different sources in Australia were analysed with next-generation sequencing. Growth inhibition by CO2 was confirmed, with spoilage delayed by at least 7days compared with non-carbonated controls. All non-carbonated controls were spoiled by Gammaproteobacteria, namely Pseudomonas fluorescens group bacteria, Serratia and Erwinia. Two out of the five carbonated samples shared the same spoilage bacteria as their corresponding controls. The rest of the three carbonated samples were spoiled by the lactic acid bacterium (LAB) Leuconostoc. This is con...
Valorisation of acid whey (AW) is a challenge for the dairy industry largely due to processing di... more Valorisation of acid whey (AW) is a challenge for the dairy industry largely due to processing difficulties associated with the inability of lactose to crystallise in the presence of lactic acid (LA), which can require removal of LA from AW prior to further processing. The aim of the present study was to compare the performance of three commercially available nanofiltration (NF) membranes in the processing of AW. NF membrane types HL, DL and DK, were assessed under industrially relevant conditions including adjusted pH levels (3, 4.5 or 7.3) and two processing temperatures (25 or 40 °C). Additionally, nano-diafiltration (NDF) was employed at 25 °C. In both NF and NDF, higher permeate fluxes were obtained with HL membranes. Lactose retention appeared temperature dependent only, while LA transmission depended on pH, membrane type and temperature. Both, pH and temperature influenced the divalent and phosphate ion transmissions. Formation of calcium complexes with phosphates and lactates, which may consequently induce attraction with proteins, was responsible for the pH and temperature effects on transmission of components. NF with the HL membrane at 40 °C and adjusted pH 3.0 showed the highest permeate transmission (∼50%) for LA and was able to retain ∼93% lactose. This system also had the highest flux (average of 60 L/m2/h). In contrast, NDF showed only ∼34% LA transmission while ∼97% lactose was retained. Thus removal of almost half of the LA content of AW was possible in the best case, which indicates that NF may have a useful role to play in the valorisation of this industrial by-product.
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