Dispersions (4%, w/w, protein) of reconstituted milk protein concentrate (MPC) powders varying in protein content (35-90% protein on dry matter basis) were standardized to a lactose content that was either unadjusted, 5.6 or 11.2% (w/w) and then heated at 90 °C for 10 min at pH 6.7. Protein interactions in heated milk and rheological properties and microstructure of acid gels formed by the addition of glucono-delta-lactone (GDL) were studied. Heat-induced dissociation of κ-casein was influenced by the lactose content of dispersions made from high protein MPC powders. A decrease in elastic moduli (G') of acid gels at pH 4.6 with increasing MPC protein content was offset by lactose standardization of the dispersions. An increase in gelation pH and in water holding capacity of acid gels was observed with lactose standardization of dispersions. Confocal microscopy revealed a decrease in porosity of acid gels with increasing lactose content of MPC dispersions.
Bibliographical noteFunding Information:
The authors would like to acknowledge the financial support of the Midwest Dairy Foods Research Center (Brookings, SD, USA), the Agricultural Utilization Research Institute (St.Paul, MN, USA) (3X5738) and the Agricultural Experiment Station (South Dakota State University, SD, USA) ( HATCH3ADP12-328100 ).
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