Gels made from six experimental whey protein concentrate (WPC) processes using chemical pretreatment, ultrafiltration and microfiltration (MF) of Swiss cheese whey, and three commercial WPC, were compared for rheological, microstructural and sensory properties. Based on relations between shear stress (ST) and total sulthydryl levels, we contirmed that disulfide bonding is important in gelation. Other components, i.e., lipids, lactose, calcium and sodium, interacting simultaneously, affected gel formation. Gel water holding capacity (WHC) was related to microstructure but not to ST. WHC was useful to characterize the 3-dimensional gel structure formations. Light microscopy showed the strongest gel had a fine-stranded, solvent-retaining structure.
Chemical pretreatment, microfiltration (MF) and ultrafiltration (UF) were applied to produce delipidized whey protein concentrates (WPC). Processes including both chemical pretreatment and MF resulted in WPC with <0.5% lipids. Low-pH UF and isoelectric point (PI) precipitation were more effective for lipid removal than chemical pretreatment by thermocalcic aggregation. Protein permeation ratios in MF processes were improved by UF preconcentration of whey. Protein permeation and flux were different between the two MF membranes used. Isoelectric point precipitation increased S-Lg contents, but not u-La, in the resulting WPC (B). Minor proteins exhibited lower concentrations in WPC B and MF WPC products.
The ability of whey protein concentrates (WPC) to form highly expanded and stable foams is critical for food applications such as whipped toppings and meringue-type products. The foaming properties were studied on six experimental and three commercial WPC, manufactured by membrane fractionation processes to contain reduced lipids and calcium. Lipidreduced WPC had excellent foaming properties. Experimental delipidized WPC MF 0.45 and commercial delipidized WPC E had higher (P < 0.05) foam expansion than egg white protein (EWP). However. WPC B made bv low-DH UF and isoelectric orecinitation did not form a foam. Lipids -and ash were the main facto; aeecting foaming properties.
Rheological and microstructural properties of five dialyzed whey protein concentrate (WPC) gels were investigated. Maximum WPC gel hardness as determined by shear stress (ST) was observed at 2.7-4.5 mM Ca and 0.6-1.1 mM Ca 2+ concentrations with a Ca ionization of 20-25%. Gel cohesiveness by shear strain (SN) correlated with total lipid and phospholipid (PLP) concentrations and percent of lipid unsaturation. Microstructural characteristics of the gels, as determined by light microscopy (LM), confirmed their water holding capacity (WHC) and rheological properties.
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