Potential and restrictions of photocentrifugation for determining the emulsion stability of melted spreadable processed cheese
A previous study had shown that the method of photocentrifugation could be adapted to monitor emulsion stability of melted spreadable processed cheese (PC) with low content of emulsifying salts (ES). The present study continued the experiments with higher ES content exploring the potential and restrictions of this new approach. The PC containing 40% fat in dry matter and 1.0 or 1.9% w/w ES was manufactured for 5–19 min at 82 °C and three different rotational speeds of the cutter. Light transmission was measured during centrifugation of the melted PC in thin cuvettes at 60 °C. The transmission profiles were used to characterize emulsion stability. Fat distribution was measured for better interpretation of the centrifugation results. An increase in transmission to ≥20% occurred after different periods of centrifugation at 1200×g. Samples with 1.0% w/w ES showed different particle movements during centrifugation for 150 min. Polydisperse creaming, sedimentation, and distinct zone sedimentation were identified, the latter allowing the calculation of characteristic sedimentation velocities. The PC with 1.9% w/w ES manufactured at a cutter speed of 3000 rpm for 5 min required the maximum acceleration of 2150×g to achieve measurable transmission after 195 min, corresponding to 291 days under normal gravity. These results show the high sensitivity of photocentrifugation proving even little physical changes of the PC matrix. However, this sensitivity restricts the applications to melted spreadable and suboptimal emulsified products.