2.3. Physical measurements — viscosity
Four 175 g containers of each of treatments were tested for viscosity. Samples were removed from frozen storage at −28°C and transferred to a warmer freezer set at −18°C the afternoon prior to the day of testing. On the morning of the test, the samples were transferred from the −18°C freezer to a 4°C cooler and held for 4 h prior to conducting the rheological tests. The step-wise tempering routine was necessary to ensure gradual sample warming and to retain as much of the original frozen foam structure as possible. Samples were then loaded into the cup (27.5 mm internal diameter) of a Bohlin VOR Rheometer (Lund, Sweden). The bob (37.5 mm high with a diameter of 25 mm) was lowered into the sample creating a gap width of 2.5 mm. The amount of sample loaded varied from 8.5 to 15 g, due to variations in the original overrun of the sample. The temperature of ice cream upon loading ranged from between −3 and −6°C. A constant temperature of 30°C was maintained by the rheometer for all apparent viscosity, flow behaviour index and consistency coefficient measurements.