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ABSTRACT

The effects of ultrahigh pressure (UHP)-treated whey protein on firmness, meltability and microstructure of process cheese and process cheese foods were investigated. Cheese base was made with reconstituted nonfat dry milk (NFDM) and cream. Commercial full fat process cheese (CFF), commercial low fat process cheese food (CLF) and control low fat process cheese food prepared from cheese base and Cheddar cheese without the addition of whey protein (CLC) were selected or prepared as control-process cheese and process cheese foods. Experimental low fat process cheese foods were prepared from cheese base and Cheddar cheese with the addition of 5% (w/w) untreated whey protein (LWP) or 5% (w/w) whey protein treated at 690 MPa for 5 min (LHP). The firmness of LHP was equivalent to that of CLF. Meltability of LWP and LHP was acceptable as specified with a Schreiber melt-test score greater than four. The Schreiber melt-test scores for LHP were greater than those for CFF, CLF and LWP. The greater meltability of LHP was attributed to the addition of UHP-treated whey protein to LHP. The uninterrupted protein matrices observed in the microstructures of CLC, LWP and LHP were attributed to reduced fat contents and increased protein contents. The microstructures of CFF, CLF, CLC and LWP exhibited a smooth protein matrix while that of LHP had a rough protein matrix. The unfolding of whey protein during UHP treatment may contribute to a rough protein matrix in the microstructure of LHP. This study demonstrates that the addition of UHP-treated whey protein to low fat process cheese foods may lead to low fat process cheese food with acceptable firmness and meltability, but result in the production of low fat process cheese food with undesirable sandy or grainy texture.