TY - BOOK

T1 - Interactions between milk protein ingredients and other milk components during processing

AU - Liu, Guanchen

PY - 2016

Y1 - 2016

N2 - Microparticulated whey protein (MWP) are colloidal particles usually formed by combined heatingand shearing of whey protein concentrates (WPC), and typically have particle sizes ranging from1.0 to 10 μm. Nanoparticulated whey protein (NWP) have a smaller particle size (100 to 990 nm).Previous research in our group shown that, both MWP and NWP can give a higher viscosity anddenser microstructure compared to WPC when used as fat replacer in low-fat yoghurt. In the thesis,we investigated how these two types of commercial whey protein particles interact with other milkcomponents and how these interactions affect final acidified milk products.By detecting the properties of the whey protein aggregates, MWP and NWP showed low nativewhey protein content, low free thiol content and high surface hydrophobicity and were relativelystable at high temperature in the 5 % pure dispersions. When MWP and NWP were added to non-fatmilk model systems (5% protein in total) and processed into chemically (glucono-delta-lactone)acidified milk gels, the formation of disulfide-linked structures was closely related to the increasedparticle size of heated milk model systems and the rheological behavior of the acidified gels. MWPenriched systems produced weak protein networks during acidification and required the addition ofwhey protein isolate (WPI) to increase gel strength. However, systems containing NWP exhibitedpronounced increase in particle size and higher firmness of acidified gels through both covalent andnon-covalent interactions. NWP could self-associate above pH 5.5 and then further interactionsbetween caseins, NWP or casein/whey protein complexes took place at lower pH. Not only declineof electrostatic repulsion but other interactions, such as hydrophobic interaction, play an importantrole in contributing to the early self-association of NWP.For the textural properties, rheology and microstructure of final acidified gels, NWP provided acidgels with higher firmness and viscosity, lower syneresis and a denser microstructure. On thecontrary, MWP appeared to only weakly interact with other proteins present and resulted in aprotein network with low connectivity in the resulting gels. Increasing the casein/whey protein ratiodid not decrease the gel strength in the acidified milk model systems with added whey proteinaggregates.The results of this study highlighted the influences of interactions between added whey proteiningredients and other milk components on final acidified dairy products. The properties and theinteractions of whey protein aggregates with other milk proteins during processing are crucial forfinal texture and structure of acidified milk gels. The knowledge obtained from these results isexpected to provide input for producing tailor-made whey protein aggregates to achieve a desiredfunctionality in dairy products, especially in acidified milk products

AB - Microparticulated whey protein (MWP) are colloidal particles usually formed by combined heatingand shearing of whey protein concentrates (WPC), and typically have particle sizes ranging from1.0 to 10 μm. Nanoparticulated whey protein (NWP) have a smaller particle size (100 to 990 nm).Previous research in our group shown that, both MWP and NWP can give a higher viscosity anddenser microstructure compared to WPC when used as fat replacer in low-fat yoghurt. In the thesis,we investigated how these two types of commercial whey protein particles interact with other milkcomponents and how these interactions affect final acidified milk products.By detecting the properties of the whey protein aggregates, MWP and NWP showed low nativewhey protein content, low free thiol content and high surface hydrophobicity and were relativelystable at high temperature in the 5 % pure dispersions. When MWP and NWP were added to non-fatmilk model systems (5% protein in total) and processed into chemically (glucono-delta-lactone)acidified milk gels, the formation of disulfide-linked structures was closely related to the increasedparticle size of heated milk model systems and the rheological behavior of the acidified gels. MWPenriched systems produced weak protein networks during acidification and required the addition ofwhey protein isolate (WPI) to increase gel strength. However, systems containing NWP exhibitedpronounced increase in particle size and higher firmness of acidified gels through both covalent andnon-covalent interactions. NWP could self-associate above pH 5.5 and then further interactionsbetween caseins, NWP or casein/whey protein complexes took place at lower pH. Not only declineof electrostatic repulsion but other interactions, such as hydrophobic interaction, play an importantrole in contributing to the early self-association of NWP.For the textural properties, rheology and microstructure of final acidified gels, NWP provided acidgels with higher firmness and viscosity, lower syneresis and a denser microstructure. On thecontrary, MWP appeared to only weakly interact with other proteins present and resulted in aprotein network with low connectivity in the resulting gels. Increasing the casein/whey protein ratiodid not decrease the gel strength in the acidified milk model systems with added whey proteinaggregates.The results of this study highlighted the influences of interactions between added whey proteiningredients and other milk components on final acidified dairy products. The properties and theinteractions of whey protein aggregates with other milk proteins during processing are crucial forfinal texture and structure of acidified milk gels. The knowledge obtained from these results isexpected to provide input for producing tailor-made whey protein aggregates to achieve a desiredfunctionality in dairy products, especially in acidified milk products

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122823601105763

M3 - Ph.D. thesis

BT - Interactions between milk protein ingredients and other milk components during processing

PB - Department of Food Science, Faculty of Science, University of Copenhagen

ER -