Method to assess the ability of rough surfaces to eliminate slip in food viscometry

In squeezing flow viscometry the presence or absence of friction between th e specimen and the plates has a dramatic effect on the flow curve character istics. It is therefore proposed that the method can be used to test whethe r a given surface, with a particular rough finish, is effective to eliminat e slip of a given self-lubricating food. The concept is demonstrated with e xperimental data of commercial samples of mayonnaise and mustard, which wer e pressed between pairs of parallel polished and rough metal plates in an i mperfect squeezing flow array, and their force height relationship was reco rded. In all the cases, the absolute magnitude of slope of the log-force ve rsus log height plot was smaller than one. This shows that these two produc ts are self-lubricating to such an extent that roughening of the plates sur face, at least to the extent used in this work, can be an ineffective means to avoid slip. Similar results have been previously reported in three diff erent kinds of tomato products, which suggests that the problem may not be limited to food emulsions.