Firmness of Enzymatically-Formed Milk Gels Measured by Resistance to Oscillatory Deformation

Firmness of milk gels formed with rennet extract and a mixture of rennet and porcine pepsin (Chymoset) was measured with an apparatus developed by CSIRO, Australia. The device consisted of two juxtapositioned diaphragms; one oscillated and sent pulses through the milk gel to a receiving diaphragm. The extent of pulses or deformations transmitted through the gel was proportional to gel firmness. Variability in rates of firming was greater between replicate samples treated with pepsin-rennet than between replicate samples treated with rennet. The apparatus was used successfully to monitor curd firmness under commercial cheese-making conditions. The equipment is simple, sturdy, easily cleaned, does not distrub the gel structure, and yields accurate, reproducible data.