Microstructure of pasteurized process cheese manufactured from vacuum condensed and ultrafiltered milk

Abstract

Milk standardized to 45 g·kg-1 protein (UF1 and CM1) and 60 g·kg-1 protein (UF2 and CM2) using ultrafiltered milk (150 g·kg-1 protein) or vacuum condensed milk (120 g·kg -1 protein) was used for manufacturing Cheddar cheese. Pasteurized Process cheeses were manufactured using a 1:1 blend of 18-week and 30-week Cheddar cheese. The moisture content of the Process cheeses ranged from 393 to 402 g·kg-1. Fat content was the highest in the control cheese (350 g·kg-1) and the lowest in UF2 (316 g·kg -1). Microstructure of cheeses was observed using cryo-scanning electron microscopy. Fat globules of different sizes embedded in the continuous protein network were observed. Whereas, a porous structure with relatively large pores was noted in the control cheese, more compact protein masses were observed in cheeses made from concentrated milk. Fat globules in all cheeses were surrounded by cavities. Firmness of cheese was associated with less porous (compact) protein network. Large areas of dense highly fused protein were observed in UF2 cheeses, which showed the highest resistance to compression (highest firmness). Fractures in the protein network were observed as the firmness of cheese increased. Such fractures reduced the ability of protein network to entrap fat and increased the level of free oil. Appendages connecting fat globules to protein network were seen in cheese containing low amounts of free oil which indicated good emulsifying properties. The continuous less rigid protein structure with good emulsifying properties (the presence of appendages connecting protein network to fat globules) produced cheese with increased meltability. This study shows that the application of concentrated milks for Cheddar cheese-making influences Process cheese functionality and structure. © INRA, EDP Sciences, 2006.