Effect of thermal, physical and chemical treatments on FFA contents in Awassi sheep milk

Abstract

The influence of cooling (5 °C); heating (20 ° or 50 °C); pasteurization (71 °C for 15 s); agitation (5 or 10 min); boiling (100 °C); pH changes and certain chemicals (copper sulphate, lead nitrate, silver nitrate, and sodium chloride) on lipolysis in Awassi sheep milk and local cow milk stored at 5 °C for 24 h was investigated. Lipolysis in the control Awassi sheep milk (0.49 μeq FFA ml −1) was significantly different than in the control local cow milk (0.36 μeq FF A ml −1). Lipolysis in cooled Awassi sheep milk (0.23 μeq FFA ml −1) was significantly different compared with cow milk (0.13 μeq FFA ml −1). Pasteurization and boiling caused a decrease in lipolysis in sheep milk as compared with fresh sheep and cow milk examined at 37 °C and stored for 24 h at 5 °C. Agitation resulted in slightly higher lipolysis in sheep milk than in cow milk. Addition of chemicals resulted in significant increase in lipolysis. Lipolysis in acidified sheep milk (0.14 μeq FFA ml −1) was significantly different than in acidified cow milk (0.11 μeq FFA ml −1). It was also significantly different in sheep milk (0.57 μeq FFA ml −1) than in cow milk (0.74 μeq FFA ml −1) to which a NaOH solution was added. It was observed that lipolysis in Awassi sheep and local cow milk could be significantly reduced by boiling or pasteurizing.