| Abstract: | Electron Microscopic Investigations of the Influence of Temperature and Feeding Conditions on the Crystal Structure of Fat Globules in Cream Electron microscopy can provide informations on crystal formations in fat globules of cream depending on temperature and feeding conditions. When cooling cream from barn-fed animals to 15°C, frequently globules occur with and without a peripheral crystalline shell (Types 4 and 2, respectively) and with numerous crystalline aggregates and little oil in the interior. In summer cream rich in oleic acid as well as in cream from underfed cows, however, only globules without a crystalline shell (Type 2) occur more frequently. Under all feeding conditions, globules with and without a crystalline shell (Types 1 and 3, respectively) and with a completely fluid interior are less frequently observed. The simultaneous existence of different fat globule types in cream is mainly caused by super-cooling phenomena, while in bulk milk it also result partly from variations in the fatty acid composition of different globules. The abundance of the different globule types can independently of the fat composition be influenced by carefully controlling the cream ripening temperature. Thus, the spreadability and oiling-off behaviour of butter as well as the quality of whipping cream of whipped cream (plug formation and serum separation) can significantly be influenced. Quality variations in milk products caused by fat fractionation, crystal displacements, crystal nucleus formation and membrane destabilization can therefore be explained with the aid of electron microscopy. |
