Imperfect squeezing flow viscosimetry for commercial refried beans / Viscosimetría de extensión biaxial imperfecta de frijoles refritos

The imperfect squeezing flow patterns of almost intact canned fat free and vegetarian refried beans of two national brands were determined using all Teflon and grooved metal sensors. The force versus height curves were remarkably reproducible and characteristic of the products and brands irrespec tive of the upper plate's diameter and the sensor's finish. Both types of product had a very high degree of plasticity but those of one brand were more sensitive to the deformation rate. The consis tency of the corresponding products 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 height of 1.5 mm was in the order of 9-11 or 15-19 kPa for the fat free products and 14-15 versus 18-20 kPa for the vegetarian products. After 120 s of relaxation, the stress decayed to about 30 to 60% of its initial level depending on the product and brand. The re sidual stress level was generally higher when determined with the grooved metal sensors. The prod ucts with relatively higher stresses at a given height also showed a relatively slower relaxation pat tern suggesting that consistency and apparent yield stress may be related rather than independent properties of refried beans.