A New Subjective Softness Evaluation Method for Hygiene Paper

Hygiene paper belongs to a category of consumer products whose properties need to be evaluated subjectively by users. For hygiene paper (e.g., tissues and towels), softness, absorbency, and strength are the three most important attributes. These attributes are most frequently evaluated by Sensory Panel Tests (SPTs). Subjective evaluation methods employ ranking, rating, and/or the percentage (%) of the preferences between two products in collecting the data. However, none of these methods provides linear and continuous scale values such as physical measurements which have many benefits. Such a linear and continuous scale is also referred to as the Thurstone interval scale. When more than two products are to be compared, a round-robin paired-comparison test would be required for each pair. In the present study, several subjective tests had been conducted with 100 panelists. They were not trained and minimal instruction was provided for evaluating softness of seven commercial bathroom tissues. Each panelist was asked to rank and rate the seven tissue samples and to select the softer on between two samples in paired-comparison tests. The results showed that the paired-comparison test method was the most discriminating. The method, however, has also the problem that it does not generate linear-scale numbers and the required number of round-robin tests increases dramatically as the number of products for testing increases. To solve this problem, a new SPT (NSPT) was developed. It was concluded that the NSPT would be much easier and faster than the conventional SPT while being more relevant to the consumers. The NSPT is expected to play a critical role in developing an objective test method which can be used to predict subjective tissue softness evaluation.