The effect of fat content on the rheology, microstructure and heat-induced functional characteristics of Cheddar cheese

Cheddar cheeses with the different fat contents were made in triplicate and ripened at 4 degrees C for 30 d and at 7 degrees C for the remainder of the 180-d investigation period. The cheeses were designated: full-fat (FFC) 300 g kg(-1); reduced-fat (RFC), 219 g kg(-1); half-fat (HFC) 172 g kg(-1); and low-fat (LFC), 71.5 g kg(-1). A decrease in the fat content from 300 to less than or equal to 172 g kg(-1) resulted in significant (P < 0.05) decreases in contents of moisture in non-fat substance and pH 4.6 soluble N (expressed as % total N), and increases in the contents of moisture, protein, intact casein and free amino acids. Reduction in fat content resulted in an increase in the volume fraction of the casein matrix and a decrease in the extent of fat globule clumping and coalescence. The mean values of fracture stress and firmness for the FFC were significantly lower than those of the RFC and HFC, which had similar values; the values for the LFC exceeded the limits of the test and were markedly higher than those of the other cheeses at all times. On baking the cheese, reduction in fat content resulted in significant increases in the mean melt time (time required for shred fusion) and apparent viscosity and a decrease in the mean flowability of the melted cheese. The stretchability of the FFC increased most rapidly and, at approximately 15 and 30 d, attaining mean values which were significantly higher than those of the other cheeses. Thereafter the stretchability of the FFC decreased progressively to values that were significantly (i.e., at 150 d) or numerically (i.e., at 180 d) lower than those of the RFC and HFC. At ripening times greater than or equal to 15 and less than or equal to 90 d, the stretchability of the LFC was significantly lower than that of the RFC, and significantly or numerically lower than the HFC.