Heat-activated time-temperature integrator indicating instant cup noodle doneness

Abstract

A time-temperature integrator (TTI) to indicate the doneness of instant cup noodles in hot water was developed based on assessment of amylase activity by starch-iodine complex degradation. The substrate for the TTI color reaction was a starch-iodine complex that was rendered heat-resistant by the addition of NaCl. The catalyst was amylase immobilized in agar beads. The use of low-melting agar beads allowed the TTI to be activated by hot water. The noodle doneness was determined by measurement of the water content of the noodles during the reconstitution. The water content at which the sensory score was the highest in preference tests was determined to be the doneness point (57.8%, w/w). The environmental conditions of consumption were modeled in 12 cases, TTI endpoints were adjusted to be equivalent to the noodle doneness points in representative three cases (case 1, 7, 12). The enzyme contents of the TTIs for these three cases were found to not be identical. The three TTIs were, therefore, tested further for all cases, resulting in the finding that the endpoints for the TTI prepared based on case 7 matched the noodle doneness in most of the cases. In this evaluation, the differences in water content in the range of 56.8%–58.7% at TTI endpoints from the optimal value of 57.8% were found to be tolerable based on sensory testing of preference. As a result, a new TTI for instant cup noodle doneness was successfully developed.