EFFECT OF POTATO STARCH AND AGAR ON THE RHEOLOGICAL BEHAVIOUR OF TOMATO KETCHUP

Mircea-Adrian OROIAN, Gheorghe GUTT

Abstract

Two different type of hydrocolloids (potato starch and agar) were added, at different levels (for agar 0, 0,25, 0,5 and 1 g/100 g (w/w), and for potato starch 0, 0,5, 1, 2, 4g/100 g (w/w)), to a tomato ketchup which was a homemade one, having total soluble solid (TSS) content of 10 g/100 g (w/w). The intrinsic viscosity of the tomato ketchup is leading from the pectic substances which normal occurs in fruits. The effect of these two hydrocolloids used, was investigated by a rotational viscometer, Brookfield viscometer (Brookfield Engineering Inc, Model RV- DV I Prime) at 6 rpm with RV spindles. The Brookfield viscometer DV I Prime with disk spindles represents an easily and cheap method for rheological characterization of non-Newtonian fluids, in this case of tomato ketchup. Both   biopolymers increased the viscosity of tomato ketchup; however, the agar generated the maximum increase of the apparent viscosity of tomato sausage. The highest viscosity was obtained for the sample where 1 g agar / 100 g tomato ketchup was added. The tomato ketchup viscosity of the samples with potato starch has a linear evolution with the increasing of the concentration, while the viscosity of the sample with agar increases exponentially with the increasing of agar concentration

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