Sensory texture and fundamental rheology of agar and agarose gels

Texture properties of foods are an important component of food quality perception and acceptability. In order to design specific textures with predictable sensory attributes, a molecular understanding of food structures and their corresponding texture is necessary. Fundamental rheological methods are valuable tools for investigating structural mechanisms because they are based on physical and chemical theory, and when combined with descriptive sensory analysis, structure-function relationships can be established. The overall objective of this research was to utilize model food systems to further elucidate how physical properties of foods relate with the dynamic sensory perception of texture.; Agar and agarose gels were used as model food gel systems. Rheological profiles of agarose gels were developed, including linear, non-linear and fracture properties. A mathematical model was proposed to reliably describe and quantify non-linear behavior. Descriptive analysis was used to quantify the perceived hand texture characteristics of agarose gels, and results were compared with rheological profiles to determine if structure-function relationships could be established. Significant correlations between sensory hand texture and rheological properties were reported. Small-strain rheological tests could not distinguish gels as sensitively as fracture properties, indicating that fracture properties relate to sensory texture better than small-strain rheology.; Descriptive sensory analysis and large-strain rheological methods were also used to investigate texture characteristics of agar gels. Significant correlations between sensory mouth texture and rheological properties were reported. First bite and chew-down sensory terms highly correlated with each other and with fracture properties. Additionally, the sensory properties that contribute to perception of strain-hardening were determined, and were found to behave in a similar manner as non-linear rheological behavior, which is an important first step in understanding how non-linearity influences sensory perception of texture. These findings clearly demonstrate that fundamental large-strain rheological properties give valuable information toward the understanding of sensory perception of physical properties of foods.