An Okonomi sauce and a Yakisoba sauce, both commercially available, were analyzed for the rheological properties with a cone-and-plate type viscometer and a rotational viscometer B in order to find how temperature changes their rheological properties and to study how temperature affects their flavor.
(1)An analysis with the cone-and-plate type viscometer revealed non-Newtonian fluidity expressed as s = K(D)n for both sauces. Apparent viscosity (na = s/D) decreased with shear rate increase and na at a constant shear rate tended to decrease with temperature increase. The Okonomi sauce was higher in apparent viscosity than the Yakisoba sauce; it was 2.3-2.8 times as high at 10℃, 2.6-3.2 times as high at 20℃, and 2.8-3.7 times as high at 30℃. The Yakisoba sauce seems to be prepared for a lower viscosity than the Okonomi sauce because it needs to mix evenly with the “noodle” at cooking.
(2)Measurement with the rotational viscometer B showed that torque increased with increase in rotor rpm at a constant temperature for both sauces. Torque was also found to decrease with temperature increase.
(3)A sensory evaluation was performed for the flavor of the Okonomi sauce kept at 20℃ or 40℃. The level of consistency was evaluated to be higher at 20℃ as was the case with viscosity measurements. However, the Okonomi sauce had a more preferred consistency when it was kept at 40℃ and lower in viscosity. Sweetness was more intensely perceived at 40℃ and sourness was perceived more intenseluy at 20℃. Also, temperature was not found to affect the intensity of hot taste and saltiness stimuli. The taste of Okonomi sauce was more preferred at 40℃. An overall evaluation gave a significantly higher (significance level, 5%) preference score to the Okonomi sauce at 40℃.