Formalization of at-line Human Evaluations to Monitor Product Changes during Processing: The Concept of Sensory Indicator

Abstract

Sensory characteristics of food products are essential for consumers. It is a challenge for firms to maintain these characteristics constant, with as few variations in quality as possible. The control of quality properties and in particular sensory ones can be carried out using reliable process control strategies. Nevertheless, classical control approaches can rarely be used in food processes due in particular to the lack of real-time, reliable instrumental sensors, which limits available information on the product, and to poor understanding of the interactions between food and process. The scarcity of suitable on-line sensors is closely related to the variability of the raw material, the complexity of the biological phenomena during processing and the severe constraints that sensors must satisfy, such as hygiene, high humidity, and so on. As a consequence, some food product properties are very difficult to be quantified during food manufacture [11]. However, various solutions have been explored to overcome this problem: sensor design and adaptation, off-line measurements, software sensors [21]. Moreover, human evaluation is widely accepted as a tool for the evaluation of the quality of food products: operators play a major role in process control, since they take into account not only the information from sensors but also that from their own senses [20]. They can detect small changes in product characteristics such as cookie color after baking [12] thanks to their process knowledge and experience.