5.1 The purpose of time-intensity measurements is to establish the pattern of development and decline of a particular sensory characteristic over time. TI evaluations are applicable when measurements at a single time point (an averaging process) are not sufficient to distinguish products that have very different temporal characteristics.

5.2 TI has applications for a variety of products. Examples include: food products, ranging from short-term sweetness in a beverage to long-term elasticity in chewing gum; personal care products, measuring the development and longevity of shampoo lather and the residual skin feel of a skin cream; household care products, monitoring the intensity of scents over time; pharmaceuticals, monitoring skin cooling after application of a topical analgesic. Auditory signals or visual changes in products can also be evaluated by the TI technique.

1.1 This guide covers procedures for conducting and analyzing time-intensity (TI) evaluations of products or other sensory stimuli. Time-intensity is the measurement of the intensity of a single sensory sensation over time in response to a single exposure to a product or other sensory stimulus. Simultaneous evaluations of multiple sensory attributes are possible, although are outside of the scope of this document. See Reference List for more information.

1.2 This guide utilizes a specially trained panel to measure the intensity of a single continuous sensation during the time from initial exposure:

1.2.1 To its extinction,

1.2.2 To a specified intensity, or

1.2.3 To a predetermined limit of time.

1.3 Applications not covered in this guide include measuring:

1.3.1 Multiple sensations,

1.3.2 Multiple exposures within a single measurement, and

1.3.3 Qualitative or hedonic changes in the perceived sensation.

1.4 This guide includes protocols for the selection and training of judges, descriptions and use of physical data collection devices, and methods of data handling, summarization, and statistical analysis. An example, with data handling and analysis approaches, is included in the appendix.

1.5 This guide is not applicable to measure product shelf life or stability.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.