The effect of pH at renneting on the microstructure, composition and texture of Cheddar cheese

Abstract

The effect of milk pH at renneting on the microstructure, composition and texture of Cheddar cheese was investigated. Four different Cheddar cheeses were made by the addition of rennet to milk pre-acidified to pH 6.7, pH 6.5, pH 6.3 or pH 6.1. The gel renneted at pH 6.1 showed a dense protein network when observed using confocal laser scanning microscopy and cryo scanning electron microscopy. This structure became more compact after cooking, forming an irregular and coarse matrix with lower porosity than in other treatments. There was less fat lost to the whey during the draining of curd after cooking and higher fat lost to the whey during pressing in samples made from milk renneted at a lower pH. The texture of the Cheddar cheese made using milk renneted at pH 6.1 was altered, with lower chewiness, gumminess, cohesiveness and springiness when compared to cheese made using milk renneted at pH 6.7 or pH 6.5. The yield in dry matter of cheese renneted at pH 6.1 or pH 6.3 was 11–13% higher than for cheese renneted at pH 6.7. These results indicate that the pH of milk at renneting is a process variable that can be used to increased yield and alter the texture of Cheddar cheese.