Hardness of Butter. I. Influence of Season and Manufacturing Method

Hardness was measured on weekly samples of conventionally churned and continuously made butter, -~ taken over a period of 1 yr.Penetrometer and sectility methods were used at 17 and 12 ° C., respectively.The continuously made butters were consistently harder than the conventionally churned butters.Similar seasonal variations were found for both butters and were greater than differences between the two butter types at 17 ° C. Hardness maxima occurred sinmltaneously with softening-point minima, as determined previously.Hardness of conventional butter was less influenced by the experimental temperature difference than was that of the continuous type butter.The hardness of the continuous type butter decreased as gas was added and, therefore, gas content may be a partial cause of the hardness differences between the two butter types.A major portion of the setting of the continuous butter occurred during the first 3 hr.after manufacture and was attributed to crystallization, which was still in progress.The hardening taking place after this first period was attributed to thixotropic changes.Extensive hardness increase, assmned to be caused by thixotropie changes, occurred in conventional butter and extended over approximately 1 wk.Setting was prevented in both butters during storage at low temperature (--20 ° C.), but resumed a normal course on subsequent removal of the butter to higher storage temperatures.A permanent hardness decrease was imparted to both butter types by storage at 20-22.50 C.