High pressure throttling of acidified pectin-casein dispersions from 310 MPa to atmospheric pressure

HPT is a potential processing treatment for beverages containing pectin and casein. The L values and OD650 remain high and are not greatly affected by treatment or storage time. In LMP-casein and HMP-casein dispersions, appar ent viscosity was about 2 times lower after HPT treatment. HPT treatment of dispersions of HMP-casein resulted in more Newtonian behavior and 5 times lower consistency values compared to control dispersions. The L values and OD650 changed slightly with storage time suggesting some rearrangement or r eassociation processes. Most likely, some changes in pectin-casein interact ions of the HPT treated dispersions are occurring during storage. However, these changes did not negatively impact on viscosity or stability of the di spersions. If dissociation of caseins and formation of smaller casein parti cles occurs during HPT treatment as reported for hydrostatic pressure treat ment, then the decrease in viscosity may result from the formation of small er aggregates of casein particles and pectin. Alternatively, the viscosity decrease could be due to depolymerization or disaggregation of pectin. Proc essing problems associated with acidified beverages include determining the minimum amounts of pectin to stabilize acidified milks depending on proces s parameters and casein micelle characteristics. Clearly, one advantage of HPT to 310 MPa of pectin-casein dispersions is the reduction of viscosity e ven at high pectin levels.