The sensory responses of a young adult population were compared to one over age 60. Using a central composite design, sweetness and flavor intensity, flavor quality, overall acceptability, perceived thirst quenching and flavor identification were evaluated using an artificially flavored cherry beverage varying in sucrose, flavor, and color. The mean data were modeled to a response surface as a function of sucrose, color, and flavor. In both populations the measures were responsive to factors manipulated in the design. Color had specific unique effects on overall acceptance, flavor quality, and intensity in each of the populations. The older population was more sensitive to visual cues and less sensitive to changes in flavor concentration.

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Mayonnaise samples, which belong to oil-in-water emulsions, were plant-scale products, which contained either 70% oil (normal products, samples 1-12) or 30% oil (type Light, which are also considered as mayonnaises according to the Czech legislation, samples 13-17). Refined rapeseed oil was used as oil phase in all cases, and all samples contained 2.0% egg yolk (in agreement with the Czech legislation), and the same amount of modified starch. Different viscosities were obtained by changing mechanical processes in the preparation of mayonnaise. An increase in energy input and in the processing temperature yields emulsions of smaller droplet size, and thus of higher values of steady state viscosity, as was observed in the preparation of salad dressing emulsions [6]. Methods Rheological procedureSamples of mayonnaise were measured in a computercontrolled rotational rheometer Rotovisco RT 10 (Gebrüder Haake GmbH, Karlsruhe, Germany) at 10 and 25°C, equipped with a vane rotor FL 20 and a Coaxial Cylinder Sensor System (Cylinder Sensors Z 43/S and Z 38/S), which was ripped to reduce slipping. The temperature was equilibrated for 15 min. The yield value τ o [Pa] and the apparent viscosity η A [Pa × s] were determined as described in 3.2.(see Figs. 1 and 2). Rheological properties and sensory texture of mayonnaiseMayonnaises are viscoplastic oil-in-water emulsions, in which rheological properties have important influences on functional properties and the sensory quality. A set of 17 samples of both traditional and light mayonnaises were tested at 10 and 25°C, using a rheoviscometer Rotovisco RT 10. Nonlinear relations were observed between the yield value and the apparent viscosity. The yield value was correlated with several sensory characteristics rated after manipulation with a spoon, but not in oral testing. No relations were obtained between the apparent viscosity and sensory characteristics. The yield value and the texture acceptability were related significantly to the flavour acceptability. Multivariate statistical techniques were found advantageous for improving the prediction of the texture acceptance.

Abstract:The changes in viscosity and normal stress difference during the ageing of concentrated aqueous solutions of poly(vinyl alcohol) prepared at 80 ~ and the effect of the procedure used in the preparation of solutions on the course of these changes are described. The results are interpreted by means of shear compliance ]e and relaxation time 3~Key words: Polyvinylalcohol, ageing, concentrated solutions, non-Newtonian viscosity, normal stress.Aqueous solutions ofpoly(vinyl alcohol) (PVA) undergo the process of ageing, reflected predominantly in a rise in their viscosity with time which in concentrated solutions is followed by gel formation. This effect has been known for a long time and is the cause underlying the formation of aggregated supermolecular structures [1][2][3]. The formation of such structures is affected by the tacticity of the polymer and by the content of residual acetate groups [4]. These structures are supposedly formed also in dilute solutions [5] and contain amorphous and paracrystalline parts [5][6][7], the mutual ratio of which depends on experimental conditions during the preparation of solutions, and predominantly on the dissolution temperature. On the other hand, however, the process of ageing is affected not only by the dissolution temperature, but also by the temperature at which the ageing takes place, by the temperature prehistory of solutions, by the polymer concentration in solution and by the kind of the solvent [8][9][10][11]. In the existing studies dealing with the / problem of ageing of PVA solutions partial results are mostly presented in a descriptive manner, which does not lead to a more general and deeper characterization of theological changes in the supermolecular structures which arise during ageing. The only attempt at a quantitative explanation of the rheological behaviour of concentrated PVA solutions has been made by Nakagaki and Nishii [12]. Their interpretation is based on Rouse's theory of elasticity which holds for linear K 955 aggregates and intermolecular aggregation. In addition to a rise of viscosity with time, the formation of supermolecular structures during the ageing of concentrated PVA solutions is also reflected in their non-Newtonian behaviour [13]. So far, this effect has not been studied in greater detail, which made us use it, along with the measurement of normal stress, in a detailed investigation of the process of ageing.The objective of our investigations of concentrated aqueous PVA solutions consists in a systematic study of rheological properties during their ageing as a function of temperature, the experimental conditions during dissolution of the polymer and of the polymer concentration. In the present study we have combined viscosity and normal stress measurements. The quantitative interpretation of the results of our measurements was based on the values of shear compliance calculated from the measured values of the first normal stress difference, and of the relaxation time To calculated from the experimental dependence of r//r/o on ...

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