Impact of controlling the lactose to casein ratio of concentrated milks on the properties of cheddar cheese

Abstract Text: Final pH value in cheese is determined by the amount of lactic acid in the curd, as well as, its buffering properties, which is determined by concentration of casein and residual insoluble calcium phosphate. The use of concentrated milks requires adjustment of cheesemaking parameters to achieve similar cheese composition and pH values compared with unconcentrated milks. We believe that the final pH value of cheese made from concentrated milk could be better controlled by maintaining a constant lactose-to-casein (L:CN) ratio in the milk. The objective of this study was to investigate the effect of three casein concentrations (2.3, 2.9 and 3.2%) in milks, that were standardized to a constant L:CN ratio of 1.3, on the composition, texture, functionality and sensory properties of milled-curd Cheddar cheese through 9 months of ripening. Whole milk was concentrated by ultrafiltration and the composition was standardized by combining retentate, permeate and/or water to obtain appropriate CN levels while maintaining a constant L:CN ratio. Preliminary work demonstrated that increasing the CN content of milk resulted in cheeses with lower moisture content (P < 0.05). To keep the moisture contents similar between all CN levels, modifications to  cheese manufacturing procedure (such as increasing curd particle size, depth of the milled-curd and the salting regimen) were necessary for the milks containing higher CN levels. Cheese functionality during ripening was assessed using texture profile analysis and dynamic low-amplitude oscillatory rheology. Sensory Spectrum^® and Quantitative Descriptive Analysis was conducted with 9 trained panelists to evaluate texture and flavor attributes using a 15-point scale. Increasing the CN content of milks resulted in cheeses with lower pH, higher buffering capacity, higher residual lactose and lactic acid concentrations (P < 0.05). Hardness obtained from texture profile analysis showed no differences between treatments; however, treatments made from milks with higher CN contents exhibited lower maximum loss tangent (meltability). Sensory results indicated that acidity was higher in cheeses made with increased CN (P < 0.05). This study suggested that to maintain similar pH values in cheeses made from concentrated milks, the L:CN ratio would need to be varied. Adjustment of the L:CN ratio of milk is a promising technique to improve the control of the final pH in cheeses made from concentrated milks.

Keywords: higher casein milk, lactose, Cheddar cheese functionality