Imperfect squeezing flow viscosimetry for commercial refried beans

The imperfect squeezing flow patterns of almost intact canned fat free and vegetarian refried beans of two national brands were determined using all T eflon and grooved metal sensors. The force versus height curves were remark ably reproducible and characteristic of the products and brands irrespectiv e of the upper plate's diameter and the sensor's finish. Both types of prod uct had a very high degree of plasticity but those of one brand were more s ensitive to the deformation rate. The consistency of the corresponding prod ucts of the two brands could be compared in terms of an apparent stress at a predetermined height (1.5 and 2.5 mm), and their yield stress in terms of an apparent residual stress, or percent force drop, after a given time (60 and 120 s). At a deformation rate of 6 mm/min the apparent stress at a hei ght of 1.5 mm was in the order of 9-11 or 15-19 kPa for the fat free produc ts and 14-15 versus 18-20 kPa for the vegetarian products. After 120 s of r elaxation, the stress decayed to about 30 to 60% of its initial level depen ding on the product and brand. The residual stress level was generally high er when determined with the grooved metal sensors. The products with relati vely higher stresses at a given height also showed a relatively slower rela xation pattern suggesting that consistency and apparent yield stress may be related rather than independent properties of refried beans.