Rheological characterization of tomato products is important not only for design of unit operations, but also to optimizeprocesses and guarantee high quality of food products. Time dependence is related with structura...Rheological characterization of tomato products is important not only for design of unit operations, but also to optimizeprocesses and guarantee high quality of food products. Time dependence is related with structural changes due to shear rate. Thus,rheological characterization as a function of time is extremely important to understand the changes that occurred in food productsduring commercial processes. However, these characterizations are rare in the literature for tomato products. Those rheologicalproperties depend of several parameters, such as agronomic, structural and process parameters. In this study, the effect of shear rateon the viscosity at room temperature （22 ~C） of two kinds of tomato sauce （homemade and commercial） is analyzed; using aBrookfield viscometer model 4535, Lab-Line Instruments. Homemade sauce was prepared with fresh saladette tomatoes from a localmarket. Rheological analysis was performed at shear rates from 0.05 to 10.47 sl; using all the spindles available. Statistical analysiswas made using LSD and Duncan tests with a confidence interval of 95% （p-value of 0.05）. It was demonstrated that homemade andcommercial tomato sauce behaved as a thixotropic fluid, due to the typical decrease on viscosity samples observed when testing timewas increased. When tomato sauce is at rest, it has a gelled tridimensional structure; and, as soon as a shear stress is applied, themovement generates an alignment of tomato constituent chains in flow direction, breaking physic entanglements and thus causing adecrease in viscosity as a function of time. Furthermore, it was discovered that the viscosity of homemade sauce was higher than theviscosity of commercial sauce. The latter may be due to the pre-thermal treatment. During this unit operation, polymeric chains oflycopene most likely break into smaller chains of isoprene, causing the observed decrease in viscosity. Besides, commercial saucecontains additives, seasonings, preservatives and thickeners that are not in a homemade sauce.展开更多
文摘Rheological characterization of tomato products is important not only for design of unit operations, but also to optimizeprocesses and guarantee high quality of food products. Time dependence is related with structural changes due to shear rate. Thus,rheological characterization as a function of time is extremely important to understand the changes that occurred in food productsduring commercial processes. However, these characterizations are rare in the literature for tomato products. Those rheologicalproperties depend of several parameters, such as agronomic, structural and process parameters. In this study, the effect of shear rateon the viscosity at room temperature （22 ~C） of two kinds of tomato sauce （homemade and commercial） is analyzed; using aBrookfield viscometer model 4535, Lab-Line Instruments. Homemade sauce was prepared with fresh saladette tomatoes from a localmarket. Rheological analysis was performed at shear rates from 0.05 to 10.47 sl; using all the spindles available. Statistical analysiswas made using LSD and Duncan tests with a confidence interval of 95% （p-value of 0.05）. It was demonstrated that homemade andcommercial tomato sauce behaved as a thixotropic fluid, due to the typical decrease on viscosity samples observed when testing timewas increased. When tomato sauce is at rest, it has a gelled tridimensional structure; and, as soon as a shear stress is applied, themovement generates an alignment of tomato constituent chains in flow direction, breaking physic entanglements and thus causing adecrease in viscosity as a function of time. Furthermore, it was discovered that the viscosity of homemade sauce was higher than theviscosity of commercial sauce. The latter may be due to the pre-thermal treatment. During this unit operation, polymeric chains oflycopene most likely break into smaller chains of isoprene, causing the observed decrease in viscosity. Besides, commercial saucecontains additives, seasonings, preservatives and thickeners that are not in a homemade sauce.
