Food Structure


Nonfat dry milk and buttermilk solids used as ingredients in meat binders can be differentiated by transmission electron microscopy. The meat binders are suspended in water and coarser ingredients such as wheat and mustard flours are separated from the milk solids by low-speed centrifugation (415 g for 30 min). The milk solids thus purified are concentrated by ultracentrifugation (8 x 104 g for 90 min) and the resulting pellets are embedded in a resin, thin-sectioned, stained, and examined by transmission electron microscopy. Buttermilk solids are revealed by the presence of fat globule membrane fragments. In the absence of buttermilk solids only casein micelles are found in the pellets. Sensitivity of this technique is 1 part of buttermilk solids in 20 parts of milk solids, i. e. 5% of buttermilk (w/w).

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