Milk coagulation cut-time determination using ultrasonics

A nondestructive method of determining milk coagulation cut-time was investigated. Velocity and attenuation of ultrasonic waves through coagulating skim milk were measured after rennet addition. The ultrasonic attenuation measurements were found suitable for distinguishing the effect of different experimental variables (three levels of temperature, rennet and CaCl2). Based on the rate of change of attenuation during coagulation, a turning point was defined at which the attenuation rate change was -0.1 neper/m/min. The cut-time was proposed to be 20 min from the time the turning point was observed. The cut-times predicted by this criterion were statistically similar to those predicted by the manual method currently used in the industry.