Temperature effect was evaluated over the viscosity of commercial carrot puree in the range 30 to 60 ℃, using aBrookfield viscometer, model 4535, Lab-Line instruments. In order to perform the viscosity tests, 28 spec...Temperature effect was evaluated over the viscosity of commercial carrot puree in the range 30 to 60 ℃, using aBrookfield viscometer, model 4535, Lab-Line instruments. In order to perform the viscosity tests, 28 specimens of carrot puree froma local market were used. Totally, 72 tests （each one with a couple replicas） were performed during five minutes, using fourtemperatures （30, 40, 50 and 60 ℃）, six shear rates （0.26, 0.52, 1.05, 2.09, 5.24 and 10.47 s1） 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 currentstudy, 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℃ were deviated from this trend, which may be due to denaturation of the starch containing carrotsamples at such temperature. Multiple biochemical and micro-structural changes inside the food specimens may begin to occur belowand over the physiological range （20-45 ℃）. Experimental data were analyzed with Power Law model in order to obtain the bestfitted parameters as a function of shear rate： It was observed that the consistent index （k） decreased with an increment in thetemperature; while all the values of parameter ＂n＂ lesser than one, which means that the puree samples behaved as a pseudo-plasticfluid. Besides that, an Arrhenius model was used to fit the parameters as a function of temperature： Parameter A was lower usingtheexperimental data at shear rates of 10.47 s-1. The modeling performed may be helpful for the appropriate selection of some processvariables, as the shear rate and operation temperature, used for the production of carrot puree; all this is in order to obtain the finishedproduct with the desired consistency.展开更多
文摘Temperature effect was evaluated over the viscosity of commercial carrot puree in the range 30 to 60 ℃, using aBrookfield viscometer, model 4535, Lab-Line instruments. In order to perform the viscosity tests, 28 specimens of carrot puree froma local market were used. Totally, 72 tests （each one with a couple replicas） were performed during five minutes, using fourtemperatures （30, 40, 50 and 60 ℃）, six shear rates （0.26, 0.52, 1.05, 2.09, 5.24 and 10.47 s1） 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 currentstudy, 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℃ were deviated from this trend, which may be due to denaturation of the starch containing carrotsamples at such temperature. Multiple biochemical and micro-structural changes inside the food specimens may begin to occur belowand over the physiological range （20-45 ℃）. Experimental data were analyzed with Power Law model in order to obtain the bestfitted parameters as a function of shear rate： It was observed that the consistent index （k） decreased with an increment in thetemperature; while all the values of parameter ＂n＂ lesser than one, which means that the puree samples behaved as a pseudo-plasticfluid. Besides that, an Arrhenius model was used to fit the parameters as a function of temperature： Parameter A was lower usingtheexperimental data at shear rates of 10.47 s-1. The modeling performed may be helpful for the appropriate selection of some processvariables, as the shear rate and operation temperature, used for the production of carrot puree; all this is in order to obtain the finishedproduct with the desired consistency.
