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

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