The Effect of Long-term Freezing on Renneting Properties of Sarda Sheep Milk

Abstract

Summary Cold storage is a well-known strategy to limit concerns about seasonality for sheep dairy productions. Th e aim of this study was to investigate the eff ect of long-term freezing on milk renneting properties from the Sarda sheep, an autochthonous breed from Italy. Two-hundred milk samples from 50 pluriparous Sarda ewes were collected at monthly intervals throughout the lactation from April to July. Each sample of fresh milk was analysed for composition and subsamples were obtained and frozen for one, three and fi ve months. Renneting properties, both from the fresh and frozen subsamples, were achieved using the Formagraph instrument and results were submitted to a mixed model statistical analysis. Th e storage eff ect signifi cantly aff ected (P<0.01) the renneting parameters. A large amount of non coagulating subsamples was registered aft er a long-term frozen storage. Furthermore, milk clotting time was longer in frozen subsamples and curd fi rmness diminished aft er a freezing period of fi ve months. In conclusion, the remarkable decreasing of sheep milk renneting characteristics aft er frozen storage can predict a worse yield and quality of cheese-making and suggests that freezing of Sarda raw milk should be limited to shorter periods.