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Affiliation(s)

Facultad de Ciencias Químicas, Universidad Veracruzana, Lomas del Estadio S/N, Xalapa, Veracruz 91000, México

ABSTRACT

Temperature effect was evaluated over the viscosity of commercial carrot puree in the range 30 to 60 °C, using a Brookfield viscometer, model 4535, Lab-Line instruments. In order to perform the viscosity tests, 28 specimens of carrot puree from a local market were used. Totally, 72 tests (each one with a couple replicas) were performed during five minutes, using four temperatures (30, 40, 50 and 60 °C), six shear rates (0.26, 0.52, 1.05, 2.09, 5.24 and 10.47 s-1) and three spindles (4, 5 and 6). Statistical analysis was performed using LSD and Duncan tests with a confidence interval of 95% (p value of 0.05). In the current study, it was observed that an increase in the temperature triggers a reduction in the viscosity of the carrot specimens analyzed, although the samples tested at 60 °C were deviated from this trend, which may be due to denaturation of the starch containing carrot samples at such temperature. Multiple biochemical and micro-structural changes inside the food specimens may begin to occur below and over the physiological range (20-45 °C). Experimental data were analyzed with Power Law model in order to obtain the best fitted parameters as a function of shear rate: It was observed that the consistent index (k) decreased with an increment in the temperature; while all the values of parameter “n” lesser than one, which means that the puree samples behaved as a pseudo-plastic fluid. Besides that, an Arrhenius model was used to fit the parameters as a function of temperature: Parameter A was lower using the experimental data at shear rates of 10.47 s-1. The modeling performed may be helpful for the appropriate selection of some process variables, as the shear rate and operation temperature, used for the production of carrot puree; all this is in order to obtain the finished product with the desired consistency.

KEYWORDS

Food rheology, viscosity, temperature, carrot puree.

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