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Abstract 059

Human visual perception of haze and relationships with instrumental measurements of turbidity. Thresholds, magnitude estimation and sensory descriptive analysis of haze in model systems

Food Quality and Pref. 10 (6): 421-436, 1999

A. Carrasco and K. J. Siebert

Spherical polymer beads (0.769, 2.600, and 10.300 µm diameter) were suspended in clear, yellow and red liquids. The samples were measured by turbidimetry and assessed by panelists. Thresholds were determined by the Ascending Method of Limits and ranged from 0.384 to 0.815 NTU. The results were influenced by both particle size and solution color. Visual intensity (assessed by Magnitude Estimation) rose linearly with particle concentration until it reached a plateau. A regression model was developed that expressed visual haze intensity as a function of particle concentration and size, and liquid color (R2=0.949). A relationship between visual and instrumental responses was also developed (R2=0.870); when particle size was included, this improved to R2=0.978. Turbidimeter response could be predicted from particle concentration and size (R2=0.986). Principal Components Analysis was applied to Descriptive Analysis results and showed that two factors accounted for 99% of the observed variation. Suspensions of large particles at intermediate concentrations appeared non-homogeneous.

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