Instrumental and sensory characterization for a texture profile analysis of fluid foods

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Title: Instrumental and sensory characterization for a texture profile analysis of fluid foods
Author: Pollen, Noel Robert
Advisors: Christopher Daubert, Committee Chair
Abstract: Texture is a criterion by which quality is judged and an important factor when selecting or rejecting products. Therefore, an understanding of food texture is paramount to deliver foods that adhere to consumer expectations. Texture profile analysis, a method of quantifying textural attributes, has successfully been employed for solid foods, however the texture profile analysis procedure for solids is not easily applied to fluid foods. Characterization of fluid foods has primarily focused on viscosity as the primary textural property of interest. Unfortunately, viscosity alone can not describe the myriad of fluid food textural properties. Processing, preparation, and swallowing subjects fluid foods to different stresses that influence flow behavior. Some fluids possess a complex set of intrinsic material properties, such as viscoelastic and time - dependent properties. These materials can respond differently depending on the type and magnitude of stress. In this research project, fluid foods were exposed to a variety of rheological methods, exerting different stresses to invoke unique flow behaviors. Rheological methods included measurements for shear viscosity, biaxial extensional viscosity, an empirical stringiness index, and yield stress. These tests were evaluated at different rates to examine properties other than viscosity as possible textural attributes of fluid foods. Principal component and correlation analysis identified stringiness and yield stress to be separate rheological properties from viscosity; whereas biaxial extensional viscosity was interrelated with shear viscosity. Therefore, the most appropriate conditions for these instrumental methods were selected so as to determine viscosity, stringiness, and yield stress as independent rheological properties. Reference materials as well as terminology and definitions have been established for viscosity sensory methods. However, fluid foods possess rheological properties in addition to viscosity that may contribute to texture. Therefore, a sensory protocol involving model systems was developed to investigate the contribution of stringiness and yield stress on fluid food texture. Principal component and correlation analysis specified definitions and procedures, along with model systems, to individually assess sensory responses to stringiness, yield stress, and viscosity as textural attributes of fluid foods. Texture clearly ties together several intrinsic attributes, like structure, with a set of human interaction variables, like chewing and handling, to result in a complicated process of many stimuli working in combination. Therefore, texture lends itself to both rheological and sensory evaluation. Appropriate instrumental and sensory methods to evaluate viscosity, stringiness, and yield stress as separate attributes of fluid foods were developed, however it was not known if these techniques quantified similar textural attributes. The relationship between instrumental and sensory evaluation of fluid food texture was examined to determine if these methods were related. In addition, since stringiness, viscosity, and yield stress were separate rheological and sensory attributes, a visual representation of the textural "pattern" of these properties was developed, called a texture map. Results showed correlation between instrumental and sensory methods, suggesting these methods evaluated similar textural characteristics. Texture mapping was an adequate tool for visually evaluating the texture of fluid foods based on selected instrumental and sensory methods. There are many benefits to the food scientist from this experiment. Due to the limited amount of research on the textural importance of stringiness and yield stress, the instrumental and sensory protocol in this experiment offers a tool to evaluate these properties as textural attributes, whereas traditionally viscosity has been the primary property of interest. Furthermore, texture mapping provides a technique to visually compare and differentiate fluid foods on a fundamental basis. Also, the mapping procedure provides a tool to assess new ingredient functionality in a food or to track ingredient performance as a function of temperature, storage conditions, and shelf life. This profiling technique provides the food industry with a protocol to rapidly quantify the textural behavior of fluid foods.
Date: 2002-08-27
Degree: MS
Discipline: Food Science
URI: http://www.lib.ncsu.edu/resolver/1840.16/2152


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