3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures
3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures
3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures
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Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology<br />
Fig. 2. Viscosity curves of the studied ketchup samples at shear<br />
rate 10–1,000 s –1 and temperature 25 ± 1 °C<br />
small viscosity sensitivity between refrigerator and room<br />
temperature 6 . The smallest change in the apparent viscosity<br />
about 11.4 % was found in sample A1 with pH <strong>3.</strong>5.<br />
Conclusions<br />
Rheological properties are next to colour and flavour the<br />
important criterion of sensory evaluation of the food product<br />
and its acceptation by consumer. The necessity to set the flow<br />
behaviour of product so that their characteristics, standard<br />
and quality would be maintained during transportation, storage<br />
and application is important from aesthetical and practical<br />
point too.<br />
Three samples of the formulated ketchup with different<br />
pH level were investigated. The pH level of analysed tomato<br />
ketchups varied from <strong>3.</strong>5 to 4.5, the most common pH range<br />
in ketchups.<br />
The results indicated that studied samples of tomato<br />
ketchup behave as non-newtonian fluids with pseudoplastic<br />
characteristics. The apparent viscosity was decreased with<br />
increasing pH level of tomato ketchups samples at all tem-<br />
s788<br />
Fig. <strong>3.</strong> Effect of temperature on viscosity of the studied ketchup<br />
samples at shear rate D = 10 s –1 and temperature range<br />
from 5 ± 1 °C to 90 ± 1 °C<br />
perature range from 5 °C to 90 °C and at all shear rate range<br />
from 10 s –1 to 1,000 s –1 .<br />
This work has been supported by APVT No. 20-002904.<br />
REFEREnCES<br />
1. Valencia C., Sánchez M. C., Ciruelos A., Latorre A.,<br />
Madiedo J. M., Gallegos C.: Food Res. Int. 36, 911<br />
(2003).<br />
2. Sharoba A., Senge B., El-Mansy H., Bahlol H., Blochwitz<br />
R.: Eur. Food Res. Tech. 220, 142 (2005).<br />
<strong>3.</strong> Rao M. A.: Rheology of fluid and semisolid foods: principles<br />
and applications. Aspen Publishers Inc., Gaithersburg,<br />
Maryland 1999.<br />
4. Štern P., Hojerová J.: Bull Food Res. 39, 167 (2000).<br />
5. Valencia C., Sánchez M. C., Ciruelos A., Gallegos C.:<br />
Food Sci. Tech. Int. 10, 95 (2004).<br />
6. Hojerová J., Štern P., Zsemlye R.: Bull Food Res. 44, 83<br />
(2005).
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